Merge pull request #52 from MisterWil/enhanced_logging

Added auth and standard logging with templating and file rolling
2019-05-01 15:44:23 +01:00 · 2019-05-01 15:44:23 +01:00 · 93b7d31332
commit 93b7d31332
parent 46a0d7ca54 9eaa9fdcbf
24 changed files with 823 additions and 223 deletions
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -2,6 +2,21 @@

 ## Changes since v3.2.0

+- [#52](https://github.com/pusher/oauth2_proxy/pull/52) Logging Improvements (@MisterWil)
+  - Implement flags to configure file logging
+    - `-logging-filename` Defines the filename to log to
+    - `-logging-max-size` Defines the maximum
+    - `-logging-max-age` Defines the maximum age of backups to retain
+    - `-logging-max-backups` Defines the maximum number of rollover log files to retain
+    - `-logging-compress` Defines if rollover log files should be compressed
+    - `-logging-local-time` Defines if logging date and time should be local or UTC
+  - Implement two new flags to enable or disable specific logging types
+    - `-standard-logging` Enables or disables standard (not request or auth) logging
+    - `-auth-logging` Enables or disables auth logging
+  - Implement two new flags to customize the logging format
+    - `-standard-logging-format` Sets the format for standard logging
+    - `-auth-logging-format` Sets the format for auth logging
+
 - [#111](https://github.com/pusher/oauth2_proxy/pull/111) Add option for telling where to find a login.gov JWT key file (@timothy-spencer)

 # v3.2.0
--- a/Gopkg.lock
+++ b/Gopkg.lock
@ -190,6 +190,14 @@
  revision = "836bfd95fecc0f1511dd66bdbf2b5b61ab8b00b6"
  version = "v1.2.11"

+[[projects]]
+  digest = "1:11c58e19ff7ce22740423bb933f1ddca3bf575def40d5ac3437ec12871b1648b"
+  name = "gopkg.in/natefinch/lumberjack.v2"
+  packages = ["."]
+  pruneopts = ""
+  revision = "a96e63847dc3c67d17befa69c303767e2f84e54f"
+  version = "v2.1"
+
 [[projects]]
  digest = "1:be4ed0a2b15944dd777a663681a39260ed05f9c4e213017ed2e2255622c8820c"
  name = "gopkg.in/square/go-jose.v2"
@ -222,6 +230,7 @@
    "google.golang.org/api/admin/directory/v1",
    "google.golang.org/api/googleapi",
    "gopkg.in/fsnotify/fsnotify.v1",
+    "gopkg.in/natefinch/lumberjack.v2",
  ]
  solver-name = "gps-cdcl"
  solver-version = 1
--- a/Gopkg.toml
+++ b/Gopkg.toml
@ -38,3 +38,7 @@
 [[constraint]]
  branch = "master"
  name = "golang.org/x/crypto"
+
+[[constraint]]
+  name = "gopkg.in/natefinch/lumberjack.v2"
+  version = "2.1.0"
--- a/README.md
+++ b/README.md
@ -270,6 +270,8 @@ An example [oauth2_proxy.cfg](contrib/oauth2_proxy.cfg.example) config file is i
 Usage of oauth2_proxy:
  -acr-values string:  optional, used by login.gov (default "http://idmanagement.gov/ns/assurance/loa/1")
  -approval-prompt string: OAuth approval_prompt (default "force")
+  -auth-logging: Log authentication attempts (default true)
+  -auth-logging-format string: Template for authentication log lines (see "Logging Configuration" paragraph below)
  -authenticated-emails-file string: authenticate against emails via file (one per line)
  -azure-tenant string: go to a tenant-specific or common (tenant-independent) endpoint. (default "common")
  -basic-auth-password string: the password to set when passing the HTTP Basic Auth header
@ -298,6 +300,12 @@ Usage of oauth2_proxy:
  -htpasswd-file string: additionally authenticate against a htpasswd file. Entries must be created with "htpasswd -s" for SHA encryption
  -http-address string: [http://]<addr>:<port> or unix://<path> to listen on for HTTP clients (default "127.0.0.1:4180")
  -https-address string: <addr>:<port> to listen on for HTTPS clients (default ":443")
+  -logging-compress: Should rotated log files be compressed using gzip (default false)
+  -logging-filename string: File to log requests to, empty for stdout (default to stdout)
+  -logging-local-time: If the time in log files and backup filenames are local or UTC time (default true)
+  -logging-max-age int: Maximum number of days to retain old log files (default 7)
+  -logging-max-backups int: Maximum number of old log files to retain; 0 to disable (default 0)
+  -logging-max-size int: Maximum size in megabytes of the log file before rotation (default 100)
  -jwt-key string: private key in PEM format used to sign JWT, so that you can say something like -jwt-key="${OAUTH2_PROXY_JWT_KEY}": required by login.gov
  -jwt-key-file string: path to the private key file in PEM format used to sign the JWT so that you can say something like -jwt-key-file=/etc/ssl/private/jwt_signing_key.pem: required by login.gov
  -login-url string: Authentication endpoint
@ -316,7 +324,7 @@ Usage of oauth2_proxy:
  -redeem-url string: Token redemption endpoint
  -redirect-url string: the OAuth Redirect URL. ie: "https://internalapp.yourcompany.com/oauth2/callback"
  -request-logging: Log requests to stdout (default true)
-  -request-logging-format: Template for request log lines (see "Logging Format" paragraph below)
+  -request-logging-format: Template for request log lines (see "Logging Configuration" paragraph below)
  -resource string: The resource that is protected (Azure AD only)
  -scope string: OAuth scope specification
  -set-xauthrequest: set X-Auth-Request-User and X-Auth-Request-Email response headers (useful in Nginx auth_request mode)
@ -327,6 +335,8 @@ Usage of oauth2_proxy:
  -skip-oidc-discovery: bypass OIDC endpoint discovery. login-url, redeem-url and oidc-jwks-url must be configured in this case
  -skip-provider-button: will skip sign-in-page to directly reach the next step: oauth/start
  -ssl-insecure-skip-verify: skip validation of certificates presented when using HTTPS
+  -standard-logging: Log standard runtime information (default true)
+  -standard-logging-format string: Template for standard log lines (see "Logging Configuration" paragraph below)
  -tls-cert string: path to certificate file
  -tls-key string: path to private key file
  -upstream value: the http url(s) of the upstream endpoint or file:// paths for static files. Routing is based on the path
@ -457,9 +467,52 @@ following:
 - [rc3.org: Using HMAC to authenticate Web service
  requests](http://rc3.org/2011/12/02/using-hmac-to-authenticate-web-service-requests/)

-## Logging Format
+## Logging Configuration

-By default, OAuth2 Proxy logs requests to stdout in a format similar to Apache Combined Log.
+By default, OAuth2 Proxy logs all output to stdout. Logging can be configured to output to a rotating log file using the `-logging-filename` command.
+
+If logging to a file you can also configure the maximum file size (`-logging-max-size`), age (`-logging-max-age`), max backup logs (`-logging-max-backups`), and if backup logs should be compressed (`-logging-compress`).
+
+There are three different types of logging: standard, authentication, and HTTP requests. These can each be enabled or disabled with `-standard-logging`, `-auth-logging`, and `-request-logging`.
+
+Each type of logging has their own configurable format and variables. By default these formats are similar to the Apache Combined Log.
+
+### Auth Log Format
+Authentication logs are logs which are guaranteed to contain a username or email address of a user attempting to authenticate. These logs are output by default in the below format:
+
+```
+<REMOTE_ADDRESS> - <user@domain.com> [19/Mar/2015:17:20:19 -0400] [<STATUS>] <MESSAGE>
+```
+
+The status block will contain one of the below strings:
+
+- `AuthSuccess` If a user has authenticated successfully by any method
+- `AuthFailure` If the user failed to authenticate explicitly
+- `AuthError` If there was an unexpected error during authentication
+
+If you require a different format than that, you can configure it with the `-auth-logging-format` flag.
+The default format is configured as follows:
+
+```
+{{.Client}} - {{.Username}} [{{.Timestamp}}] [{{.Status}}] {{.Message}}
+```
+
+Available variables for auth logging:
+
+| Variable | Example | Description |
+| --- | --- | --- |
+| Client | 74.125.224.72 | The client/remote IP address. Will use the X-Real-IP header it if exists. |
+| Host  | domain.com | The value of the Host header. |
+| Protocol | HTTP/1.0 | The request protocol. |
+| RequestMethod | GET | The request method. |
+| Timestamp | 19/Mar/2015:17:20:19 -0400 | The date and time of the logging event. |
+| UserAgent | - | The full user agent as reported by the requesting client. |
+| Username | username@email.com | The email or username of the auth request. |
+| Status | AuthSuccess | The status of the auth request. See above for details. |
+| Message | Authenticated via OAuth2 | The details of the auth attempt. |
+
+### Request Log Format
+HTTP request logs will output by default in the below format:

 ```
 <REMOTE_ADDRESS> - <user@domain.com> [19/Mar/2015:17:20:19 -0400] <HOST_HEADER> GET <UPSTREAM_HOST> "/path/" HTTP/1.1 "<USER_AGENT>" <RESPONSE_CODE> <RESPONSE_BYTES> <REQUEST_DURATION>
@ -472,7 +525,43 @@ The default format is configured as follows:
 {{.Client}} - {{.Username}} [{{.Timestamp}}] {{.Host}} {{.RequestMethod}} {{.Upstream}} {{.RequestURI}} {{.Protocol}} {{.UserAgent}} {{.StatusCode}} {{.ResponseSize}} {{.RequestDuration}}
 ```

-[See `logMessageData` in `logging_handler.go`](./logging_handler.go) for all available variables.
+Available variables for request logging:
+
+| Variable | Example | Description |
+| --- | --- | --- |
+| Client | 74.125.224.72 | The client/remote IP address. Will use the X-Real-IP header it if exists. |
+| Host  | domain.com | The value of the Host header. |
+| Protocol | HTTP/1.0 | The request protocol. |
+| RequestDuration | 0.001 | The time in seconds that a request took to process. |
+| RequestMethod | GET | The request method. |
+| RequestURI | "/oauth2/auth" | The URI path of the request. |
+| ResponseSize | 12 | The size in bytes of the response. |
+| StatusCode | 200 | The HTTP status code of the response. |
+| Timestamp | 19/Mar/2015:17:20:19 -0400 | The date and time of the logging event. |
+| Upstream | - | The upstream data of the HTTP request. |
+| UserAgent | - | The full user agent as reported by the requesting client. |
+| Username | username@email.com | The email or username of the auth request. |
+
+### Standard Log Format
+All other logging that is not covered by the above two types of logging will be output in this standard logging format. This includes configuration information at startup and errors that occur outside of a session. The default format is below:
+
+```
+[19/Mar/2015:17:20:19 -0400] [main.go:40] <MESSAGE>
+```
+
+If you require a different format than that, you can configure it with the `-standard-logging-format` flag. The default format is configured as follows:
+
+```
+[{{.Timestamp}}] [{{.File}}] {{.Message}}
+```
+
+Available variables for standard logging:
+
+| Variable | Example | Description |
+| --- | --- | --- |
+| Timestamp | 19/Mar/2015:17:20:19 -0400 | The date and time of the logging event. |
+| File | main.go:40 | The file and line number of the logging statement. |
+| Message | HTTP: listening on 127.0.0.1:4180 | The details of the log statement. |

 ## Adding a new Provider

--- a/api/api.go
+++ b/api/api.go
@ -4,22 +4,22 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
-	"log"
 	"net/http"

 	"github.com/bitly/go-simplejson"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // Request parses the request body into a simplejson.Json object
 func Request(req *http.Request) (*simplejson.Json, error) {
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		log.Printf("%s %s %s", req.Method, req.URL, err)
+		logger.Printf("%s %s %s", req.Method, req.URL, err)
 		return nil, err
 	}
 	body, err := ioutil.ReadAll(resp.Body)
 	resp.Body.Close()
-	log.Printf("%d %s %s %s", resp.StatusCode, req.Method, req.URL, body)
+	logger.Printf("%d %s %s %s", resp.StatusCode, req.Method, req.URL, body)
 	if err != nil {
 		return nil, err
 	}
@ -37,12 +37,12 @@ func Request(req *http.Request) (*simplejson.Json, error) {
 func RequestJSON(req *http.Request, v interface{}) error {
 	resp, err := http.DefaultClient.Do(req)
 	if err != nil {
-		log.Printf("%s %s %s", req.Method, req.URL, err)
+		logger.Printf("%s %s %s", req.Method, req.URL, err)
 		return err
 	}
 	body, err := ioutil.ReadAll(resp.Body)
 	resp.Body.Close()
-	log.Printf("%d %s %s %s", resp.StatusCode, req.Method, req.URL, body)
+	logger.Printf("%d %s %s %s", resp.StatusCode, req.Method, req.URL, body)
 	if err != nil {
 		return err
 	}
--- a/contrib/oauth2_proxy.cfg.example
+++ b/contrib/oauth2_proxy.cfg.example
@ -18,8 +18,18 @@
 #     "http://127.0.0.1:8080/"
 # ]

-## Log requests to stdout
-# request_logging = true
+## Logging configuration
+#logging_filename = ""
+#logging_max_size = 100
+#logging_max_age = 7
+#logging_local_time = true
+#logging_compress = false
+#standard_logging = true
+#standard_logging_format = "[{{.Timestamp}}] [{{.File}}] {{.Message}}"
+#request_logging = true
+#request_logging_format = "{{.Client}} - {{.Username}} [{{.Timestamp}}] {{.Host}} {{.RequestMethod}} {{.Upstream}} {{.RequestURI}} {{.Protocol}} {{.UserAgent}} {{.StatusCode}} {{.ResponseSize}} {{.RequestDuration}}"
+#auth_logging = true
+#auth_logging_format = "{{.Client}} - {{.Username}} [{{.Timestamp}}] [{{.Status}}] {{.Message}}"

 ## pass HTTP Basic Auth, X-Forwarded-User and X-Forwarded-Email information to upstream
 # pass_basic_auth = true
--- a/htpasswd.go
+++ b/htpasswd.go
@ -5,9 +5,9 @@ import (
 	"encoding/base64"
 	"encoding/csv"
 	"io"
-	"log"
 	"os"

+	"github.com/pusher/oauth2_proxy/logger"
 	"golang.org/x/crypto/bcrypt"
 )

@ -67,6 +67,6 @@ func (h *HtpasswdFile) Validate(user string, password string) bool {
 		return bcrypt.CompareHashAndPassword([]byte(realPassword), []byte(password)) == nil
 	}

-	log.Printf("Invalid htpasswd entry for %s. Must be a SHA or bcrypt entry.", user)
+	logger.Printf("Invalid htpasswd entry for %s. Must be a SHA or bcrypt entry.", user)
 	return false
 }
--- a/http.go
+++ b/http.go
@ -2,11 +2,12 @@ package main

 import (
 	"crypto/tls"
-	"log"
 	"net"
 	"net/http"
 	"strings"
 	"time"
+
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // Server represents an HTTP server
@ -86,17 +87,17 @@ func (s *Server) ServeHTTP() {

 	listener, err := net.Listen(networkType, listenAddr)
 	if err != nil {
-		log.Fatalf("FATAL: listen (%s, %s) failed - %s", networkType, listenAddr, err)
+		logger.Fatalf("FATAL: listen (%s, %s) failed - %s", networkType, listenAddr, err)
 	}
-	log.Printf("HTTP: listening on %s", listenAddr)
+	logger.Printf("HTTP: listening on %s", listenAddr)

 	server := &http.Server{Handler: s.Handler}
 	err = server.Serve(listener)
 	if err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
-		log.Printf("ERROR: http.Serve() - %s", err)
+		logger.Printf("ERROR: http.Serve() - %s", err)
 	}

-	log.Printf("HTTP: closing %s", listener.Addr())
+	logger.Printf("HTTP: closing %s", listener.Addr())
 }

 // ServeHTTPS constructs a net.Listener and starts handling HTTPS requests
@ -114,24 +115,24 @@ func (s *Server) ServeHTTPS() {
 	config.Certificates = make([]tls.Certificate, 1)
 	config.Certificates[0], err = tls.LoadX509KeyPair(s.Opts.TLSCertFile, s.Opts.TLSKeyFile)
 	if err != nil {
-		log.Fatalf("FATAL: loading tls config (%s, %s) failed - %s", s.Opts.TLSCertFile, s.Opts.TLSKeyFile, err)
+		logger.Fatalf("FATAL: loading tls config (%s, %s) failed - %s", s.Opts.TLSCertFile, s.Opts.TLSKeyFile, err)
 	}

 	ln, err := net.Listen("tcp", addr)
 	if err != nil {
-		log.Fatalf("FATAL: listen (%s) failed - %s", addr, err)
+		logger.Fatalf("FATAL: listen (%s) failed - %s", addr, err)
 	}
-	log.Printf("HTTPS: listening on %s", ln.Addr())
+	logger.Printf("HTTPS: listening on %s", ln.Addr())

 	tlsListener := tls.NewListener(tcpKeepAliveListener{ln.(*net.TCPListener)}, config)
 	srv := &http.Server{Handler: s.Handler}
 	err = srv.Serve(tlsListener)

 	if err != nil && !strings.Contains(err.Error(), "use of closed network connection") {
-		log.Printf("ERROR: https.Serve() - %s", err)
+		logger.Printf("ERROR: https.Serve() - %s", err)
 	}

-	log.Printf("HTTPS: closing %s", tlsListener.Addr())
+	logger.Printf("HTTPS: closing %s", tlsListener.Addr())
 }

 // tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
--- a/logger/logger.go
+++ b/logger/logger.go
@ -0,0 +1,452 @@
+package logger
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"runtime"
+	"sync"
+	"text/template"
+	"time"
+)
+
+// AuthStatus defines the different types of auth logging that occur
+type AuthStatus string
+
+const (
+	// DefaultStandardLoggingFormat defines the default standard log format
+	DefaultStandardLoggingFormat = "[{{.Timestamp}}] [{{.File}}] {{.Message}}"
+	// DefaultAuthLoggingFormat defines the default auth log format
+	DefaultAuthLoggingFormat = "{{.Client}} - {{.Username}} [{{.Timestamp}}] [{{.Status}}] {{.Message}}"
+	// DefaultRequestLoggingFormat defines the default request log format
+	DefaultRequestLoggingFormat = "{{.Client}} - {{.Username}} [{{.Timestamp}}] {{.Host}} {{.RequestMethod}} {{.Upstream}} {{.RequestURI}} {{.Protocol}} {{.UserAgent}} {{.StatusCode}} {{.ResponseSize}} {{.RequestDuration}}"
+
+	// AuthSuccess indicates that an auth attempt has succeeded explicitly
+	AuthSuccess AuthStatus = "AuthSuccess"
+	// AuthFailure indicates that an auth attempt has failed explicitly
+	AuthFailure AuthStatus = "AuthFailure"
+	// AuthError indicates that an auth attempt has failed due to an error
+	AuthError AuthStatus = "AuthError"
+
+	// Llongfile flag to log full file name and line number: /a/b/c/d.go:23
+	Llongfile = 1 << iota
+	// Lshortfile flag to log final file name element and line number: d.go:23. overrides Llongfile
+	Lshortfile
+	// LUTC flag to log UTC datetime rather than the local time zone
+	LUTC
+	// LstdFlags flag for initial values for the logger
+	LstdFlags = Lshortfile
+)
+
+// These are the containers for all values that are available as variables in the logging formats.
+// All values are pre-formatted strings so it is easy to use them in the format string.
+type stdLogMessageData struct {
+	Timestamp,
+	File,
+	Message string
+}
+
+type authLogMessageData struct {
+	Client,
+	Host,
+	Protocol,
+	RequestMethod,
+	Timestamp,
+	UserAgent,
+	Username,
+	Status,
+	Message string
+}
+
+type reqLogMessageData struct {
+	Client,
+	Host,
+	Protocol,
+	RequestDuration,
+	RequestMethod,
+	RequestURI,
+	ResponseSize,
+	StatusCode,
+	Timestamp,
+	Upstream,
+	UserAgent,
+	Username string
+}
+
+// A Logger represents an active logging object that generates lines of
+// output to an io.Writer passed through a formatter. Each logging
+// operation makes a single call to the Writer's Write method. A Logger
+// can be used simultaneously from multiple goroutines; it guarantees to
+// serialize access to the Writer.
+type Logger struct {
+	mu             sync.Mutex
+	flag           int
+	writer         io.Writer
+	stdEnabled     bool
+	authEnabled    bool
+	reqEnabled     bool
+	stdLogTemplate *template.Template
+	authTemplate   *template.Template
+	reqTemplate    *template.Template
+}
+
+// New creates a new Standarderr Logger.
+func New(flag int) *Logger {
+	return &Logger{
+		writer:         os.Stderr,
+		flag:           flag,
+		stdEnabled:     true,
+		authEnabled:    true,
+		reqEnabled:     true,
+		stdLogTemplate: template.Must(template.New("std-log").Parse(DefaultStandardLoggingFormat)),
+		authTemplate:   template.Must(template.New("auth-log").Parse(DefaultAuthLoggingFormat)),
+		reqTemplate:    template.Must(template.New("req-log").Parse(DefaultRequestLoggingFormat)),
+	}
+}
+
+var std = New(LstdFlags)
+
+// Output a standard log template with a simple message.
+// Write a final newline at the end of every message.
+func (l *Logger) Output(calldepth int, message string) {
+	if !l.stdEnabled {
+		return
+	}
+
+	now := time.Now()
+	file := "???:0"
+
+	if l.flag&(Lshortfile|Llongfile) != 0 {
+		file = l.GetFileLineString(calldepth + 1)
+	}
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.stdLogTemplate.Execute(l.writer, stdLogMessageData{
+		Timestamp: FormatTimestamp(now),
+		File:      file,
+		Message:   message,
+	})
+
+	l.writer.Write([]byte("\n"))
+}
+
+// PrintAuth writes auth info to the logger. Requires an http.Request to
+// log request details. Remaining arguments are handled in the manner of
+// fmt.Sprintf. Writes a final newline to the end of every message.
+func (l *Logger) PrintAuth(username string, req *http.Request, status AuthStatus, format string, a ...interface{}) {
+	if !l.authEnabled {
+		return
+	}
+
+	now := time.Now()
+
+	if username == "" {
+		username = "-"
+	}
+
+	client := GetClient(req)
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.authTemplate.Execute(l.writer, authLogMessageData{
+		Client:        client,
+		Host:          req.Host,
+		Protocol:      req.Proto,
+		RequestMethod: req.Method,
+		Timestamp:     FormatTimestamp(now),
+		UserAgent:     fmt.Sprintf("%q", req.UserAgent()),
+		Username:      username,
+		Status:        fmt.Sprintf("%s", status),
+		Message:       fmt.Sprintf(format, a...),
+	})
+
+	l.writer.Write([]byte("\n"))
+}
+
+// PrintReq writes request details to the Logger using the http.Request,
+// url, and timestamp of the request.  Writes a final newline to the end
+// of every message.
+func (l *Logger) PrintReq(username, upstream string, req *http.Request, url url.URL, ts time.Time, status int, size int) {
+	if !l.reqEnabled {
+		return
+	}
+
+	duration := float64(time.Now().Sub(ts)) / float64(time.Second)
+
+	if username == "" {
+		username = "-"
+	}
+
+	if upstream == "" {
+		upstream = "-"
+	}
+
+	if url.User != nil && username == "-" {
+		if name := url.User.Username(); name != "" {
+			username = name
+		}
+	}
+
+	client := GetClient(req)
+
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.reqTemplate.Execute(l.writer, reqLogMessageData{
+		Client:          client,
+		Host:            req.Host,
+		Protocol:        req.Proto,
+		RequestDuration: fmt.Sprintf("%0.3f", duration),
+		RequestMethod:   req.Method,
+		RequestURI:      fmt.Sprintf("%q", url.RequestURI()),
+		ResponseSize:    fmt.Sprintf("%d", size),
+		StatusCode:      fmt.Sprintf("%d", status),
+		Timestamp:       FormatTimestamp(ts),
+		Upstream:        upstream,
+		UserAgent:       fmt.Sprintf("%q", req.UserAgent()),
+		Username:        username,
+	})
+
+	l.writer.Write([]byte("\n"))
+}
+
+// GetFileLineString will find the caller file and line number
+// taking in to account the calldepth to iterate up the stack
+// to find the non-logging call location.
+func (l *Logger) GetFileLineString(calldepth int) string {
+	var file string
+	var line int
+	var ok bool
+
+	_, file, line, ok = runtime.Caller(calldepth)
+	if !ok {
+		file = "???"
+		line = 0
+	}
+
+	if l.flag&Lshortfile != 0 {
+		short := file
+		for i := len(file) - 1; i > 0; i-- {
+			if file[i] == '/' {
+				short = file[i+1:]
+				break
+			}
+		}
+		file = short
+	}
+
+	return fmt.Sprintf("%s:%d", file, line)
+}
+
+// GetClient parses an HTTP request for the client/remote IP address.
+func GetClient(req *http.Request) string {
+	client := req.Header.Get("X-Real-IP")
+	if client == "" {
+		client = req.RemoteAddr
+	}
+
+	if c, _, err := net.SplitHostPort(client); err == nil {
+		client = c
+	}
+
+	return client
+}
+
+// FormatTimestamp returns a formatted timestamp.
+func (l *Logger) FormatTimestamp(ts time.Time) string {
+	if l.flag&LUTC != 0 {
+		ts = ts.UTC()
+	}
+
+	return ts.Format("2006/01/02 15:04:05")
+}
+
+// Flags returns the output flags for the logger.
+func (l *Logger) Flags() int {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	return l.flag
+}
+
+// SetFlags sets the output flags for the logger.
+func (l *Logger) SetFlags(flag int) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.flag = flag
+}
+
+// SetStandardEnabled enables or disables standard logging.
+func (l *Logger) SetStandardEnabled(e bool) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.stdEnabled = e
+}
+
+// SetAuthEnabled enables or disables auth logging.
+func (l *Logger) SetAuthEnabled(e bool) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.authEnabled = e
+}
+
+// SetReqEnabled enabled or disables request logging.
+func (l *Logger) SetReqEnabled(e bool) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.reqEnabled = e
+}
+
+// SetStandardTemplate sets the template for standard logging.
+func (l *Logger) SetStandardTemplate(t string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.stdLogTemplate = template.Must(template.New("std-log").Parse(t))
+}
+
+// SetAuthTemplate sets the template for auth logging.
+func (l *Logger) SetAuthTemplate(t string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.authTemplate = template.Must(template.New("auth-log").Parse(t))
+}
+
+// SetReqTemplate sets the template for request logging.
+func (l *Logger) SetReqTemplate(t string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.reqTemplate = template.Must(template.New("req-log").Parse(t))
+}
+
+// These functions utilize the standard logger.
+
+// FormatTimestamp returns a formatted timestamp for the standard logger.
+func FormatTimestamp(ts time.Time) string {
+	return std.FormatTimestamp(ts)
+}
+
+// Flags returns the output flags for the standard logger.
+func Flags() int {
+	return std.Flags()
+}
+
+// SetFlags sets the output flags for the standard logger.
+func SetFlags(flag int) {
+	std.SetFlags(flag)
+}
+
+// SetOutput sets the output destination for the standard logger.
+func SetOutput(w io.Writer) {
+	std.mu.Lock()
+	defer std.mu.Unlock()
+	std.writer = w
+}
+
+// SetStandardEnabled enables or disables standard logging for the
+// standard logger.
+func SetStandardEnabled(e bool) {
+	std.SetStandardEnabled(e)
+}
+
+// SetAuthEnabled enables or disables auth logging for the standard
+// logger.
+func SetAuthEnabled(e bool) {
+	std.SetAuthEnabled(e)
+}
+
+// SetReqEnabled enables or disables request logging for the
+// standard logger.
+func SetReqEnabled(e bool) {
+	std.SetReqEnabled(e)
+}
+
+// SetStandardTemplate sets the template for standard logging for
+// the standard logger.
+func SetStandardTemplate(t string) {
+	std.SetStandardTemplate(t)
+}
+
+// SetAuthTemplate sets the template for auth logging for the
+// standard logger.
+func SetAuthTemplate(t string) {
+	std.SetAuthTemplate(t)
+}
+
+// SetReqTemplate sets the template for request logging for the
+// standard logger.
+func SetReqTemplate(t string) {
+	std.SetReqTemplate(t)
+}
+
+// Print calls Output to print to the standard logger.
+// Arguments are handled in the manner of fmt.Print.
+func Print(v ...interface{}) {
+	std.Output(2, fmt.Sprint(v...))
+}
+
+// Printf calls Output to print to the standard logger.
+// Arguments are handled in the manner of fmt.Printf.
+func Printf(format string, v ...interface{}) {
+	std.Output(2, fmt.Sprintf(format, v...))
+}
+
+// Println calls Output to print to the standard logger.
+// Arguments are handled in the manner of fmt.Println.
+func Println(v ...interface{}) {
+	std.Output(2, fmt.Sprintln(v...))
+}
+
+// Fatal is equivalent to Print() followed by a call to os.Exit(1).
+func Fatal(v ...interface{}) {
+	std.Output(2, fmt.Sprint(v...))
+	os.Exit(1)
+}
+
+// Fatalf is equivalent to Printf() followed by a call to os.Exit(1).
+func Fatalf(format string, v ...interface{}) {
+	std.Output(2, fmt.Sprintf(format, v...))
+	os.Exit(1)
+}
+
+// Fatalln is equivalent to Println() followed by a call to os.Exit(1).
+func Fatalln(v ...interface{}) {
+	std.Output(2, fmt.Sprintln(v...))
+	os.Exit(1)
+}
+
+// Panic is equivalent to Print() followed by a call to panic().
+func Panic(v ...interface{}) {
+	s := fmt.Sprint(v...)
+	std.Output(2, s)
+	panic(s)
+}
+
+// Panicf is equivalent to Printf() followed by a call to panic().
+func Panicf(format string, v ...interface{}) {
+	s := fmt.Sprintf(format, v...)
+	std.Output(2, s)
+	panic(s)
+}
+
+// Panicln is equivalent to Println() followed by a call to panic().
+func Panicln(v ...interface{}) {
+	s := fmt.Sprintln(v...)
+	std.Output(2, s)
+	panic(s)
+}
+
+// PrintAuthf writes authentication details to the standard logger.
+// Arguments are handled in the manner of fmt.Printf.
+func PrintAuthf(username string, req *http.Request, status AuthStatus, format string, a ...interface{}) {
+	std.PrintAuth(username, req, status, format, a...)
+}
+
+// PrintReq writes request details to the standard logger.
+func PrintReq(username, upstream string, req *http.Request, url url.URL, ts time.Time, status int, size int) {
+	std.PrintReq(username, upstream, req, url, ts, status, size)
+}
--- a/logging_handler.go
+++ b/logging_handler.go
@ -6,17 +6,11 @@ package main
 import (
 	"bufio"
 	"errors"
-	"fmt"
-	"io"
 	"net"
 	"net/http"
-	"net/url"
-	"text/template"
 	"time"
-)

-const (
-	defaultRequestLoggingFormat = "{{.Client}} - {{.Username}} [{{.Timestamp}}] {{.Host}} {{.RequestMethod}} {{.Upstream}} {{.RequestURI}} {{.Protocol}} {{.UserAgent}} {{.StatusCode}} {{.ResponseSize}} {{.RequestDuration}}"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // responseLogger is wrapper of http.ResponseWriter that keeps track of its HTTP status
@ -92,93 +86,22 @@ func (l *responseLogger) Flush() {
 	}
 }

-// logMessageData is the container for all values that are available as variables in the request logging format.
-// All values are pre-formatted strings so it is easy to use them in the format string.
-type logMessageData struct {
-	Client,
-	Host,
-	Protocol,
-	RequestDuration,
-	RequestMethod,
-	RequestURI,
-	ResponseSize,
-	StatusCode,
-	Timestamp,
-	Upstream,
-	UserAgent,
-	Username string
-}
-
 // loggingHandler is the http.Handler implementation for LoggingHandlerTo and its friends
 type loggingHandler struct {
-	writer      io.Writer
-	handler     http.Handler
-	enabled     bool
-	logTemplate *template.Template
+	handler http.Handler
 }

 // LoggingHandler provides an http.Handler which logs requests to the HTTP server
-func LoggingHandler(out io.Writer, h http.Handler, v bool, requestLoggingTpl string) http.Handler {
+func LoggingHandler(h http.Handler) http.Handler {
 	return loggingHandler{
-		writer:      out,
-		handler:     h,
-		enabled:     v,
-		logTemplate: template.Must(template.New("request-log").Parse(requestLoggingTpl)),
+		handler: h,
 	}
 }

 func (h loggingHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	t := time.Now()
 	url := *req.URL
-	logger := &responseLogger{w: w}
-	h.handler.ServeHTTP(logger, req)
-	if !h.enabled {
-		return
-	}
-	h.writeLogLine(logger.authInfo, logger.upstream, req, url, t, logger.Status(), logger.Size())
-}
-
-// Log entry for req similar to Apache Common Log Format.
-// ts is the timestamp with which the entry should be logged.
-// status, size are used to provide the response HTTP status and size.
-func (h loggingHandler) writeLogLine(username, upstream string, req *http.Request, url url.URL, ts time.Time, status int, size int) {
-	if username == "" {
-		username = "-"
-	}
-	if upstream == "" {
-		upstream = "-"
-	}
-	if url.User != nil && username == "-" {
-		if name := url.User.Username(); name != "" {
-			username = name
-		}
-	}
-
-	client := req.Header.Get("X-Real-IP")
-	if client == "" {
-		client = req.RemoteAddr
-	}
-
-	if c, _, err := net.SplitHostPort(client); err == nil {
-		client = c
-	}
-
-	duration := float64(time.Now().Sub(ts)) / float64(time.Second)
-
-	h.logTemplate.Execute(h.writer, logMessageData{
-		Client:          client,
-		Host:            req.Host,
-		Protocol:        req.Proto,
-		RequestDuration: fmt.Sprintf("%0.3f", duration),
-		RequestMethod:   req.Method,
-		RequestURI:      fmt.Sprintf("%q", url.RequestURI()),
-		ResponseSize:    fmt.Sprintf("%d", size),
-		StatusCode:      fmt.Sprintf("%d", status),
-		Timestamp:       ts.Format("02/Jan/2006:15:04:05 -0700"),
-		Upstream:        upstream,
-		UserAgent:       fmt.Sprintf("%q", req.UserAgent()),
-		Username:        username,
-	})
-
-	h.writer.Write([]byte("\n"))
+	responseLogger := &responseLogger{w: w}
+	h.handler.ServeHTTP(responseLogger, req)
+	logger.PrintReq(responseLogger.authInfo, responseLogger.upstream, req, url, t, responseLogger.Status(), responseLogger.Size())
 }
--- a/logging_handler_test.go
+++ b/logging_handler_test.go
@ -8,6 +8,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/pusher/oauth2_proxy/logger"
 )

 func TestLoggingHandler_ServeHTTP(t *testing.T) {
@ -17,7 +19,7 @@ func TestLoggingHandler_ServeHTTP(t *testing.T) {
 		Format,
 		ExpectedLogMessage string
 	}{
-		{defaultRequestLoggingFormat, fmt.Sprintf("127.0.0.1 - - [%s] test-server GET - \"/foo/bar\" HTTP/1.1 \"\" 200 4 0", ts.Format("02/Jan/2006:15:04:05 -0700"))},
+		{logger.DefaultRequestLoggingFormat, fmt.Sprintf("127.0.0.1 - - [%s] test-server GET - \"/foo/bar\" HTTP/1.1 \"\" 200 4 0.000\n", logger.FormatTimestamp(ts))},
 		{"{{.RequestMethod}}", "GET\n"},
 	}

@ -32,7 +34,9 @@ func TestLoggingHandler_ServeHTTP(t *testing.T) {
 			w.Write([]byte("test"))
 		}

-		h := LoggingHandler(buf, http.HandlerFunc(handler), true, test.Format)
+		logger.SetOutput(buf)
+		logger.SetReqTemplate(test.Format)
+		h := LoggingHandler(http.HandlerFunc(handler))

 		r, _ := http.NewRequest("GET", "/foo/bar", nil)
 		r.RemoteAddr = "127.0.0.1"
--- a/main.go
+++ b/main.go
@ -3,7 +3,6 @@ package main
 import (
 	"flag"
 	"fmt"
-	"log"
 	"math/rand"
 	"net/http"
 	"os"
@ -13,10 +12,11 @@ import (

 	"github.com/BurntSushi/toml"
 	options "github.com/mreiferson/go-options"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 func main() {
-	log.SetFlags(log.Ldate | log.Ltime | log.Lshortfile)
+	logger.SetFlags(logger.Lshortfile)
 	flagSet := flag.NewFlagSet("oauth2_proxy", flag.ExitOnError)

 	emailDomains := StringArray{}
@ -75,8 +75,21 @@ func main() {
 	flagSet.Bool("cookie-secure", true, "set secure (HTTPS) cookie flag")
 	flagSet.Bool("cookie-httponly", true, "set HttpOnly cookie flag")

-	flagSet.Bool("request-logging", true, "Log requests to stdout")
-	flagSet.String("request-logging-format", defaultRequestLoggingFormat, "Template for log lines")
+	flagSet.String("logging-filename", "", "File to log requests to, empty for stdout")
+	flagSet.Int("logging-max-size", 100, "Maximum size in megabytes of the log file before rotation")
+	flagSet.Int("logging-max-age", 7, "Maximum number of days to retain old log files")
+	flagSet.Int("logging-max-backups", 0, "Maximum number of old log files to retain; 0 to disable")
+	flagSet.Bool("logging-local-time", true, "If the time in log files and backup filenames are local or UTC time")
+	flagSet.Bool("logging-compress", false, "Should rotated log files be compressed using gzip")
+
+	flagSet.Bool("standard-logging", true, "Log standard runtime information")
+	flagSet.String("standard-logging-format", logger.DefaultStandardLoggingFormat, "Template for standard log lines")
+
+	flagSet.Bool("request-logging", true, "Log HTTP requests")
+	flagSet.String("request-logging-format", logger.DefaultRequestLoggingFormat, "Template for HTTP request log lines")
+
+	flagSet.Bool("auth-logging", true, "Log authentication attempts")
+	flagSet.String("auth-logging-format", logger.DefaultAuthLoggingFormat, "Template for authentication log lines")

 	flagSet.String("provider", "google", "OAuth provider")
 	flagSet.String("oidc-issuer-url", "", "OpenID Connect issuer URL (ie: https://accounts.google.com)")
@ -110,7 +123,7 @@ func main() {
 	if *config != "" {
 		_, err := toml.DecodeFile(*config, &cfg)
 		if err != nil {
-			log.Fatalf("ERROR: failed to load config file %s - %s", *config, err)
+			logger.Fatalf("ERROR: failed to load config file %s - %s", *config, err)
 		}
 	}
 	cfg.LoadEnvForStruct(opts)
@ -118,9 +131,10 @@ func main() {

 	err := opts.Validate()
 	if err != nil {
-		log.Printf("%s", err)
+		logger.Printf("%s", err)
 		os.Exit(1)
 	}
+
 	validator := NewValidator(opts.EmailDomains, opts.AuthenticatedEmailsFile)
 	oauthproxy := NewOAuthProxy(opts, validator)

@ -133,11 +147,11 @@ func main() {
 	}

 	if opts.HtpasswdFile != "" {
-		log.Printf("using htpasswd file %s", opts.HtpasswdFile)
+		logger.Printf("using htpasswd file %s", opts.HtpasswdFile)
 		oauthproxy.HtpasswdFile, err = NewHtpasswdFromFile(opts.HtpasswdFile)
 		oauthproxy.DisplayHtpasswdForm = opts.DisplayHtpasswdForm
 		if err != nil {
-			log.Fatalf("FATAL: unable to open %s %s", opts.HtpasswdFile, err)
+			logger.Fatalf("FATAL: unable to open %s %s", opts.HtpasswdFile, err)
 		}
 	}

@ -145,9 +159,9 @@ func main() {

 	var handler http.Handler
 	if opts.GCPHealthChecks {
-		handler = gcpHealthcheck(LoggingHandler(os.Stdout, oauthproxy, opts.RequestLogging, opts.RequestLoggingFormat))
+		handler = gcpHealthcheck(LoggingHandler(oauthproxy))
 	} else {
-		handler = LoggingHandler(os.Stdout, oauthproxy, opts.RequestLogging, opts.RequestLoggingFormat)
+		handler = LoggingHandler(oauthproxy)
 	}
 	s := &Server{
 		Handler: handler,
--- a/oauthproxy.go
+++ b/oauthproxy.go
@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
-	"log"
 	"net"
 	"net/http"
 	"net/http/httputil"
@ -16,6 +15,7 @@ import (

 	"github.com/mbland/hmacauth"
 	"github.com/pusher/oauth2_proxy/cookie"
+	"github.com/pusher/oauth2_proxy/logger"
 	"github.com/pusher/oauth2_proxy/providers"
 	"github.com/yhat/wsutil"
 )
@ -185,7 +185,7 @@ func NewOAuthProxy(opts *Options, validator func(string) bool) *OAuthProxy {
 		path := u.Path
 		switch u.Scheme {
 		case httpScheme, httpsScheme:
-			log.Printf("mapping path %q => upstream %q", path, u)
+			logger.Printf("mapping path %q => upstream %q", path, u)
 			proxy := NewWebSocketOrRestReverseProxy(u, opts, auth)
 			serveMux.Handle(path, proxy)

@ -193,7 +193,7 @@ func NewOAuthProxy(opts *Options, validator func(string) bool) *OAuthProxy {
 			if u.Fragment != "" {
 				path = u.Fragment
 			}
-			log.Printf("mapping path %q => file system %q", path, u.Path)
+			logger.Printf("mapping path %q => file system %q", path, u.Path)
 			proxy := NewFileServer(path, u.Path)
 			serveMux.Handle(path, &UpstreamProxy{path, proxy, nil, nil})
 		default:
@ -201,7 +201,7 @@ func NewOAuthProxy(opts *Options, validator func(string) bool) *OAuthProxy {
 		}
 	}
 	for _, u := range opts.CompiledRegex {
-		log.Printf("compiled skip-auth-regex => %q", u)
+		logger.Printf("compiled skip-auth-regex => %q", u)
 	}

 	redirectURL := opts.redirectURL
@ -209,20 +209,20 @@ func NewOAuthProxy(opts *Options, validator func(string) bool) *OAuthProxy {
 		redirectURL.Path = fmt.Sprintf("%s/callback", opts.ProxyPrefix)
 	}

-	log.Printf("OAuthProxy configured for %s Client ID: %s", opts.provider.Data().ProviderName, opts.ClientID)
+	logger.Printf("OAuthProxy configured for %s Client ID: %s", opts.provider.Data().ProviderName, opts.ClientID)
 	refresh := "disabled"
 	if opts.CookieRefresh != time.Duration(0) {
 		refresh = fmt.Sprintf("after %s", opts.CookieRefresh)
 	}

-	log.Printf("Cookie settings: name:%s secure(https):%v httponly:%v expiry:%s domain:%s path:%s refresh:%s", opts.CookieName, opts.CookieSecure, opts.CookieHTTPOnly, opts.CookieExpire, opts.CookieDomain, opts.CookiePath, refresh)
+	logger.Printf("Cookie settings: name:%s secure(https):%v httponly:%v expiry:%s domain:%s path:%s refresh:%s", opts.CookieName, opts.CookieSecure, opts.CookieHTTPOnly, opts.CookieExpire, opts.CookieDomain, opts.CookiePath, refresh)

 	var cipher *cookie.Cipher
 	if opts.PassAccessToken || opts.SetAuthorization || opts.PassAuthorization || (opts.CookieRefresh != time.Duration(0)) {
 		var err error
 		cipher, err = cookie.NewCipher(secretBytes(opts.CookieSecret))
 		if err != nil {
-			log.Fatal("cookie-secret error: ", err)
+			logger.Fatal("cookie-secret error: ", err)
 		}
 	}

@ -425,7 +425,7 @@ func (p *OAuthProxy) makeCookie(req *http.Request, name string, value string, ex
 			domain = h
 		}
 		if !strings.HasSuffix(domain, p.CookieDomain) {
-			log.Printf("Warning: request host is %q but using configured cookie domain of %q", domain, p.CookieDomain)
+			logger.Printf("Warning: request host is %q but using configured cookie domain of %q", domain, p.CookieDomain)
 		}
 	}

@ -529,7 +529,6 @@ func (p *OAuthProxy) PingPage(rw http.ResponseWriter) {

 // ErrorPage writes an error response
 func (p *OAuthProxy) ErrorPage(rw http.ResponseWriter, code int, title string, message string) {
-	log.Printf("ErrorPage %d %s %s", code, title, message)
 	rw.WriteHeader(code)
 	t := struct {
 		Title       string
@ -588,9 +587,10 @@ func (p *OAuthProxy) ManualSignIn(rw http.ResponseWriter, req *http.Request) (st
 	}
 	// check auth
 	if p.HtpasswdFile.Validate(user, passwd) {
-		log.Printf("authenticated %q via HtpasswdFile", user)
+		logger.PrintAuthf(user, req, logger.AuthSuccess, "Authenticated via HtpasswdFile")
 		return user, true
 	}
+	logger.PrintAuthf(user, req, logger.AuthFailure, "Invalid authentication via HtpasswdFile")
 	return "", false
 }

@ -686,6 +686,7 @@ func (p *OAuthProxy) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
 func (p *OAuthProxy) SignIn(rw http.ResponseWriter, req *http.Request) {
 	redirect, err := p.GetRedirect(req)
 	if err != nil {
+		logger.Printf("Error obtaining redirect: %s", err.Error())
 		p.ErrorPage(rw, 500, "Internal Error", err.Error())
 		return
 	}
@ -714,12 +715,14 @@ func (p *OAuthProxy) SignOut(rw http.ResponseWriter, req *http.Request) {
 func (p *OAuthProxy) OAuthStart(rw http.ResponseWriter, req *http.Request) {
 	nonce, err := cookie.Nonce()
 	if err != nil {
+		logger.Printf("Error obtaining nonce: %s", err.Error())
 		p.ErrorPage(rw, 500, "Internal Error", err.Error())
 		return
 	}
 	p.SetCSRFCookie(rw, req, nonce)
 	redirect, err := p.GetRedirect(req)
 	if err != nil {
+		logger.Printf("Error obtaining redirect: %s", err.Error())
 		p.ErrorPage(rw, 500, "Internal Error", err.Error())
 		return
 	}
@ -735,24 +738,27 @@ func (p *OAuthProxy) OAuthCallback(rw http.ResponseWriter, req *http.Request) {
 	// finish the oauth cycle
 	err := req.ParseForm()
 	if err != nil {
+		logger.Printf("Error while parsing OAuth2 callback: %s" + err.Error())
 		p.ErrorPage(rw, 500, "Internal Error", err.Error())
 		return
 	}
 	errorString := req.Form.Get("error")
 	if errorString != "" {
+		logger.Printf("Error while parsing OAuth2 callback: %s ", errorString)
 		p.ErrorPage(rw, 403, "Permission Denied", errorString)
 		return
 	}

 	session, err := p.redeemCode(req.Host, req.Form.Get("code"))
 	if err != nil {
-		log.Printf("%s error redeeming code %s", remoteAddr, err)
+		logger.Printf("Error redeeming code during OAuth2 callback: %s ", errorString)
 		p.ErrorPage(rw, 500, "Internal Error", "Internal Error")
 		return
 	}

 	s := strings.SplitN(req.Form.Get("state"), ":", 2)
 	if len(s) != 2 {
+		logger.Printf("Error while parsing OAuth2 state: invalid length")
 		p.ErrorPage(rw, 500, "Internal Error", "Invalid State")
 		return
 	}
@ -760,12 +766,13 @@ func (p *OAuthProxy) OAuthCallback(rw http.ResponseWriter, req *http.Request) {
 	redirect := s[1]
 	c, err := req.Cookie(p.CSRFCookieName)
 	if err != nil {
+		logger.PrintAuthf(session.Email, req, logger.AuthFailure, "Invalid authentication via OAuth2: unable too obtain CSRF cookie")
 		p.ErrorPage(rw, 403, "Permission Denied", err.Error())
 		return
 	}
 	p.ClearCSRFCookie(rw, req)
 	if c.Value != nonce {
-		log.Printf("%s csrf token mismatch, potential attack", remoteAddr)
+		logger.PrintAuthf(session.Email, req, logger.AuthFailure, "Invalid authentication via OAuth2: csrf token mismatch, potential attack")
 		p.ErrorPage(rw, 403, "Permission Denied", "csrf failed")
 		return
 	}
@ -776,16 +783,16 @@ func (p *OAuthProxy) OAuthCallback(rw http.ResponseWriter, req *http.Request) {

 	// set cookie, or deny
 	if p.Validator(session.Email) && p.provider.ValidateGroup(session.Email) {
-		log.Printf("%s authentication complete %s", remoteAddr, session)
+		logger.PrintAuthf(session.Email, req, logger.AuthSuccess, "Authenticated via OAuth2: %s", session)
 		err := p.SaveSession(rw, req, session)
 		if err != nil {
-			log.Printf("%s %s", remoteAddr, err)
+			logger.Printf("%s %s", remoteAddr, err)
 			p.ErrorPage(rw, 500, "Internal Error", "Internal Error")
 			return
 		}
 		http.Redirect(rw, req, redirect, 302)
 	} else {
-		log.Printf("%s Permission Denied: %q is unauthorized", remoteAddr, session.Email)
+		logger.PrintAuthf(session.Email, req, logger.AuthSuccess, "Invalid authentication via OAuth2: unauthorized")
 		p.ErrorPage(rw, 403, "Permission Denied", "Invalid Account")
 	}
 }
@ -827,16 +834,16 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int

 	session, sessionAge, err := p.LoadCookiedSession(req)
 	if err != nil {
-		log.Printf("%s %s", remoteAddr, err)
+		logger.Printf("Error loading cookied session: %s", err)
 	}
 	if session != nil && sessionAge > p.CookieRefresh && p.CookieRefresh != time.Duration(0) {
-		log.Printf("%s refreshing %s old session cookie for %s (refresh after %s)", remoteAddr, sessionAge, session, p.CookieRefresh)
+		logger.Printf("Refreshing %s old session cookie for %s (refresh after %s)", sessionAge, session, p.CookieRefresh)
 		saveSession = true
 	}

 	var ok bool
 	if ok, err = p.provider.RefreshSessionIfNeeded(session); err != nil {
-		log.Printf("%s removing session. error refreshing access token %s %s", remoteAddr, err, session)
+		logger.Printf("%s removing session. error refreshing access token %s %s", remoteAddr, err, session)
 		clearSession = true
 		session = nil
 	} else if ok {
@ -845,7 +852,7 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int
 	}

 	if session != nil && session.IsExpired() {
-		log.Printf("%s removing session. token expired %s", remoteAddr, session)
+		logger.Printf("Removing session: token expired %s", session)
 		session = nil
 		saveSession = false
 		clearSession = true
@ -853,7 +860,7 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int

 	if saveSession && !revalidated && session != nil && session.AccessToken != "" {
 		if !p.provider.ValidateSessionState(session) {
-			log.Printf("%s removing session. error validating %s", remoteAddr, session)
+			logger.Printf("Removing session: error validating %s", session)
 			saveSession = false
 			session = nil
 			clearSession = true
@ -861,7 +868,7 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int
 	}

 	if session != nil && session.Email != "" && !p.Validator(session.Email) {
-		log.Printf("%s Permission Denied: removing session %s", remoteAddr, session)
+		logger.Printf(session.Email, req, logger.AuthFailure, "Invalid authentication via session: removing session %s", session)
 		session = nil
 		saveSession = false
 		clearSession = true
@ -870,7 +877,7 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int
 	if saveSession && session != nil {
 		err = p.SaveSession(rw, req, session)
 		if err != nil {
-			log.Printf("%s %s", remoteAddr, err)
+			logger.PrintAuthf(session.Email, req, logger.AuthError, "Save session error %s", err)
 			return http.StatusInternalServerError
 		}
 	}
@ -882,7 +889,7 @@ func (p *OAuthProxy) Authenticate(rw http.ResponseWriter, req *http.Request) int
 	if session == nil {
 		session, err = p.CheckBasicAuth(req)
 		if err != nil {
-			log.Printf("%s %s", remoteAddr, err)
+			logger.Printf("Error during basic auth validation: %s", err)
 		}
 	}

@ -958,10 +965,11 @@ func (p *OAuthProxy) CheckBasicAuth(req *http.Request) (*providers.SessionState,
 		return nil, fmt.Errorf("invalid format %s", b)
 	}
 	if p.HtpasswdFile.Validate(pair[0], pair[1]) {
-		log.Printf("authenticated %q via basic auth", pair[0])
+		logger.PrintAuthf(pair[0], req, logger.AuthSuccess, "Authenticated via basic auth and HTpasswd File")
 		return &providers.SessionState{User: pair[0]}, nil
 	}
-	return nil, fmt.Errorf("%s not in HtpasswdFile", pair[0])
+	logger.PrintAuthf(pair[0], req, logger.AuthFailure, "Invalid authentication via basic auth: not in Htpasswd File")
+	return nil, nil
 }

 // isAjax checks if a request is an ajax request
--- a/oauthproxy_test.go
+++ b/oauthproxy_test.go
@ -5,7 +5,6 @@ import (
 	"encoding/base64"
 	"io"
 	"io/ioutil"
-	"log"
 	"net"
 	"net/http"
 	"net/http/httptest"
@ -16,6 +15,7 @@ import (
 	"time"

 	"github.com/mbland/hmacauth"
+	"github.com/pusher/oauth2_proxy/logger"
 	"github.com/pusher/oauth2_proxy/providers"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@ -23,7 +23,7 @@ import (
 )

 func init() {
-	log.SetFlags(log.Ldate | log.Ltime | log.Lshortfile)
+	logger.SetFlags(logger.Lshortfile)

 }

@ -263,7 +263,7 @@ func (tp *TestProvider) ValidateSessionState(session *providers.SessionState) bo

 func TestBasicAuthPassword(t *testing.T) {
 	providerServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		log.Printf("%#v", r)
+		logger.Printf("%#v", r)
 		var payload string
 		switch r.URL.Path {
 		case "/oauth/token":
@ -355,7 +355,7 @@ func NewPassAccessTokenTest(opts PassAccessTokenTestOptions) *PassAccessTokenTes

 	t.providerServer = httptest.NewServer(
 		http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			log.Printf("%#v", r)
+			logger.Printf("%#v", r)
 			var payload string
 			switch r.URL.Path {
 			case "/oauth/token":
--- a/options.go
+++ b/options.go
@ -17,7 +17,9 @@ import (
 	oidc "github.com/coreos/go-oidc"
 	"github.com/dgrijalva/jwt-go"
 	"github.com/mbland/hmacauth"
+	"github.com/pusher/oauth2_proxy/logger"
 	"github.com/pusher/oauth2_proxy/providers"
+	"gopkg.in/natefinch/lumberjack.v2"
 )

 // Options holds Configuration Options that can be set by Command Line Flag,
@ -85,8 +87,19 @@ type Options struct {
 	Scope             string `flag:"scope" cfg:"scope" env:"OAUTH2_PROXY_SCOPE"`
 	ApprovalPrompt    string `flag:"approval-prompt" cfg:"approval_prompt" env:"OAUTH2_PROXY_APPROVAL_PROMPT"`

-	RequestLogging       bool   `flag:"request-logging" cfg:"request_logging" env:"OAUTH2_PROXY_REQUEST_LOGGING"`
-	RequestLoggingFormat string `flag:"request-logging-format" cfg:"request_logging_format" env:"OAUTH2_PROXY_REQUEST_LOGGING_FORMAT"`
+	// Configuration values for logging
+	LoggingFilename       string `flag:"logging-filename" cfg:"logging_filename" env:"OAUTH2_LOGGING_FILENAME"`
+	LoggingMaxSize        int    `flag:"logging-max-size" cfg:"logging_max_size" env:"OAUTH2_LOGGING_MAX_SIZE"`
+	LoggingMaxAge         int    `flag:"logging-max-age" cfg:"logging_max_age" env:"OAUTH2_LOGGING_MAX_AGE"`
+	LoggingMaxBackups     int    `flag:"logging-max-backups" cfg:"logging_max_backups" env:"OAUTH2_LOGGING_MAX_BACKUPS"`
+	LoggingLocalTime      bool   `flag:"logging-local-time" cfg:"logging_local_time" env:"OAUTH2_LOGGING_LOCAL_TIME"`
+	LoggingCompress       bool   `flag:"logging-compress" cfg:"logging_compress" env:"OAUTH2_LOGGING_COMPRESS"`
+	StandardLogging       bool   `flag:"standard-logging" cfg:"standard_logging" env:"OAUTH2_STANDARD_LOGGING"`
+	StandardLoggingFormat string `flag:"standard-logging-format" cfg:"standard_logging_format" env:"OAUTH2_STANDARD_LOGGING_FORMAT"`
+	RequestLogging        bool   `flag:"request-logging" cfg:"request_logging" env:"OAUTH2_REQUEST_LOGGING"`
+	RequestLoggingFormat  string `flag:"request-logging-format" cfg:"request_logging_format" env:"OAUTH2_REQUEST_LOGGING_FORMAT"`
+	AuthLogging           bool   `flag:"auth-logging" cfg:"auth_logging" env:"OAUTH2_LOGGING_AUTH_LOGGING"`
+	AuthLoggingFormat     string `flag:"auth-logging-format" cfg:"auth_logging_format" env:"OAUTH2_AUTH_LOGGING_FORMAT"`

 	SignatureKey    string `flag:"signature-key" cfg:"signature_key" env:"OAUTH2_PROXY_SIGNATURE_KEY"`
 	AcrValues       string `flag:"acr-values" cfg:"acr_values" env:"OAUTH2_PROXY_ACR_VALUES"`
@ -113,28 +126,38 @@ type SignatureData struct {
 // NewOptions constructs a new Options with defaulted values
 func NewOptions() *Options {
 	return &Options{
-		ProxyPrefix:          "/oauth2",
-		ProxyWebSockets:      true,
-		HTTPAddress:          "127.0.0.1:4180",
-		HTTPSAddress:         ":443",
-		DisplayHtpasswdForm:  true,
-		CookieName:           "_oauth2_proxy",
-		CookieSecure:         true,
-		CookieHTTPOnly:       true,
-		CookieExpire:         time.Duration(168) * time.Hour,
-		CookieRefresh:        time.Duration(0),
-		SetXAuthRequest:      false,
-		SkipAuthPreflight:    false,
-		PassBasicAuth:        true,
-		PassUserHeaders:      true,
-		PassAccessToken:      false,
-		PassHostHeader:       true,
-		SetAuthorization:     false,
-		PassAuthorization:    false,
-		ApprovalPrompt:       "force",
-		RequestLogging:       true,
-		SkipOIDCDiscovery:    false,
-		RequestLoggingFormat: defaultRequestLoggingFormat,
+		ProxyPrefix:           "/oauth2",
+		ProxyWebSockets:       true,
+		HTTPAddress:           "127.0.0.1:4180",
+		HTTPSAddress:          ":443",
+		DisplayHtpasswdForm:   true,
+		CookieName:            "_oauth2_proxy",
+		CookieSecure:          true,
+		CookieHTTPOnly:        true,
+		CookieExpire:          time.Duration(168) * time.Hour,
+		CookieRefresh:         time.Duration(0),
+		SetXAuthRequest:       false,
+		SkipAuthPreflight:     false,
+		PassBasicAuth:         true,
+		PassUserHeaders:       true,
+		PassAccessToken:       false,
+		PassHostHeader:        true,
+		SetAuthorization:      false,
+		PassAuthorization:     false,
+		ApprovalPrompt:        "force",
+		SkipOIDCDiscovery:     false,
+		LoggingFilename:       "",
+		LoggingMaxSize:        100,
+		LoggingMaxAge:         7,
+		LoggingMaxBackups:     0,
+		LoggingLocalTime:      true,
+		LoggingCompress:       false,
+		StandardLogging:       true,
+		StandardLoggingFormat: logger.DefaultStandardLoggingFormat,
+		RequestLogging:        true,
+		RequestLoggingFormat:  logger.DefaultRequestLoggingFormat,
+		AuthLogging:           true,
+		AuthLoggingFormat:     logger.DefaultAuthLoggingFormat,
 	}
 }

@ -285,6 +308,7 @@ func (o *Options) Validate() error {

 	msgs = parseSignatureKey(o, msgs)
 	msgs = validateCookieName(o, msgs)
+	msgs = setupLogger(o, msgs)

 	if len(msgs) != 0 {
 		return fmt.Errorf("Invalid configuration:\n  %s",
@ -414,3 +438,49 @@ func secretBytes(secret string) []byte {
 	}
 	return []byte(secret)
 }
+
+func setupLogger(o *Options, msgs []string) []string {
+	// Setup the log file
+	if len(o.LoggingFilename) > 0 {
+		// Validate that the file/dir can be written
+		file, err := os.OpenFile(o.LoggingFilename, os.O_WRONLY|os.O_CREATE, 0666)
+		if err != nil {
+			if os.IsPermission(err) {
+				return append(msgs, "unable to write to log file: "+o.LoggingFilename)
+			}
+		}
+		file.Close()
+
+		logger.Printf("Redirecting logging to file: %s", o.LoggingFilename)
+
+		logWriter := &lumberjack.Logger{
+			Filename:   o.LoggingFilename,
+			MaxSize:    o.LoggingMaxSize, // megabytes
+			MaxAge:     o.LoggingMaxAge,  // days
+			MaxBackups: o.LoggingMaxBackups,
+			LocalTime:  o.LoggingLocalTime,
+			Compress:   o.LoggingCompress,
+		}
+
+		logger.SetOutput(logWriter)
+	}
+
+	// Supply a sanity warning to the logger if all logging is disabled
+	if !o.StandardLogging && !o.AuthLogging && !o.RequestLogging {
+		logger.Print("Warning: Logging disabled. No further logs will be shown.")
+	}
+
+	// Pass configuration values to the standard logger
+	logger.SetStandardEnabled(o.StandardLogging)
+	logger.SetAuthEnabled(o.AuthLogging)
+	logger.SetReqEnabled(o.RequestLogging)
+	logger.SetStandardTemplate(o.StandardLoggingFormat)
+	logger.SetAuthTemplate(o.AuthLoggingFormat)
+	logger.SetReqTemplate(o.RequestLoggingFormat)
+
+	if !o.LoggingLocalTime {
+		logger.SetFlags(logger.Flags() | logger.LUTC)
+	}
+
+	return msgs
+}
--- a/providers/azure.go
+++ b/providers/azure.go
@ -3,12 +3,12 @@ package providers
 import (
 	"errors"
 	"fmt"
-	"log"
 	"net/http"
 	"net/url"

 	"github.com/bitly/go-simplejson"
 	"github.com/pusher/oauth2_proxy/api"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // AzureProvider represents an Azure based Identity Provider
@ -116,12 +116,12 @@ func (p *AzureProvider) GetEmailAddress(s *SessionState) (string, error) {
 	email, err = json.Get("userPrincipalName").String()

 	if err != nil {
-		log.Printf("failed making request %s", err)
+		logger.Printf("failed making request %s", err)
 		return "", err
 	}

 	if email == "" {
-		log.Printf("failed to get email address")
+		logger.Printf("failed to get email address")
 		return "", err
 	}

--- a/providers/github.go
+++ b/providers/github.go
@ -4,12 +4,13 @@ import (
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
-	"log"
 	"net/http"
 	"net/url"
 	"path"
 	"strconv"
 	"strings"
+
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // GitHubProvider represents an GitHub based Identity Provider
@ -116,13 +117,13 @@ func (p *GitHubProvider) hasOrg(accessToken string) (bool, error) {
 	var presentOrgs []string
 	for _, org := range orgs {
 		if p.Org == org.Login {
-			log.Printf("Found Github Organization: %q", org.Login)
+			logger.Printf("Found Github Organization: %q", org.Login)
 			return true, nil
 		}
 		presentOrgs = append(presentOrgs, org.Login)
 	}

-	log.Printf("Missing Organization:%q in %v", p.Org, presentOrgs)
+	logger.Printf("Missing Organization:%q in %v", p.Org, presentOrgs)
 	return false, nil
 }

@ -179,7 +180,7 @@ func (p *GitHubProvider) hasOrgAndTeam(accessToken string) (bool, error) {
 			ts := strings.Split(p.Team, ",")
 			for _, t := range ts {
 				if t == team.Slug {
-					log.Printf("Found Github Organization:%q Team:%q (Name:%q)", team.Org.Login, team.Slug, team.Name)
+					logger.Printf("Found Github Organization:%q Team:%q (Name:%q)", team.Org.Login, team.Slug, team.Name)
 					return true, nil
 				}
 			}
@ -187,13 +188,13 @@ func (p *GitHubProvider) hasOrgAndTeam(accessToken string) (bool, error) {
 		}
 	}
 	if hasOrg {
-		log.Printf("Missing Team:%q from Org:%q in teams: %v", p.Team, p.Org, presentTeams)
+		logger.Printf("Missing Team:%q from Org:%q in teams: %v", p.Team, p.Org, presentTeams)
 	} else {
 		var allOrgs []string
 		for org := range presentOrgs {
 			allOrgs = append(allOrgs, org)
 		}
-		log.Printf("Missing Organization:%q in %#v", p.Org, allOrgs)
+		logger.Printf("Missing Organization:%q in %#v", p.Org, allOrgs)
 	}
 	return false, nil
 }
@ -242,7 +243,7 @@ func (p *GitHubProvider) GetEmailAddress(s *SessionState) (string, error) {
 			resp.StatusCode, endpoint.String(), body)
 	}

-	log.Printf("got %d from %q %s", resp.StatusCode, endpoint.String(), body)
+	logger.Printf("got %d from %q %s", resp.StatusCode, endpoint.String(), body)

 	if err := json.Unmarshal(body, &emails); err != nil {
 		return "", fmt.Errorf("%s unmarshaling %s", err, body)
@ -292,7 +293,7 @@ func (p *GitHubProvider) GetUserName(s *SessionState) (string, error) {
 			resp.StatusCode, endpoint.String(), body)
 	}

-	log.Printf("got %d from %q %s", resp.StatusCode, endpoint.String(), body)
+	logger.Printf("got %d from %q %s", resp.StatusCode, endpoint.String(), body)

 	if err := json.Unmarshal(body, &user); err != nil {
 		return "", fmt.Errorf("%s unmarshaling %s", err, body)
--- a/providers/gitlab.go
+++ b/providers/gitlab.go
@ -1,11 +1,11 @@
 package providers

 import (
-	"log"
 	"net/http"
 	"net/url"

 	"github.com/pusher/oauth2_proxy/api"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // GitLabProvider represents an GitLab based Identity Provider
@ -49,12 +49,12 @@ func (p *GitLabProvider) GetEmailAddress(s *SessionState) (string, error) {
 	req, err := http.NewRequest("GET",
 		p.ValidateURL.String()+"?access_token="+s.AccessToken, nil)
 	if err != nil {
-		log.Printf("failed building request %s", err)
+		logger.Printf("failed building request %s", err)
 		return "", err
 	}
 	json, err := api.Request(req)
 	if err != nil {
-		log.Printf("failed making request %s", err)
+		logger.Printf("failed making request %s", err)
 		return "", err
 	}
 	return json.Get("email").String()
--- a/providers/google.go
+++ b/providers/google.go
@ -8,12 +8,12 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"log"
 	"net/http"
 	"net/url"
 	"strings"
 	"time"

+	"github.com/pusher/oauth2_proxy/logger"
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
 	admin "google.golang.org/api/admin/directory/v1"
@ -167,18 +167,18 @@ func (p *GoogleProvider) SetGroupRestriction(groups []string, adminEmail string,
 func getAdminService(adminEmail string, credentialsReader io.Reader) *admin.Service {
 	data, err := ioutil.ReadAll(credentialsReader)
 	if err != nil {
-		log.Fatal("can't read Google credentials file:", err)
+		logger.Fatal("can't read Google credentials file:", err)
 	}
 	conf, err := google.JWTConfigFromJSON(data, admin.AdminDirectoryUserReadonlyScope, admin.AdminDirectoryGroupReadonlyScope)
 	if err != nil {
-		log.Fatal("can't load Google credentials file:", err)
+		logger.Fatal("can't load Google credentials file:", err)
 	}
 	conf.Subject = adminEmail

 	client := conf.Client(oauth2.NoContext)
 	adminService, err := admin.New(client)
 	if err != nil {
-		log.Fatal(err)
+		logger.Fatal(err)
 	}
 	return adminService
 }
@ -186,7 +186,7 @@ func getAdminService(adminEmail string, credentialsReader io.Reader) *admin.Serv
 func userInGroup(service *admin.Service, groups []string, email string) bool {
 	user, err := fetchUser(service, email)
 	if err != nil {
-		log.Printf("error fetching user: %v", err)
+		logger.Printf("error fetching user: %v", err)
 		return false
 	}
 	id := user.Id
@ -196,9 +196,9 @@ func userInGroup(service *admin.Service, groups []string, email string) bool {
 		members, err := fetchGroupMembers(service, group)
 		if err != nil {
 			if err, ok := err.(*googleapi.Error); ok && err.Code == 404 {
-				log.Printf("error fetching members for group %s: group does not exist", group)
+				logger.Printf("error fetching members for group %s: group does not exist", group)
 			} else {
-				log.Printf("error fetching group members: %v", err)
+				logger.Printf("error fetching group members: %v", err)
 				return false
 			}
 		}
@ -274,7 +274,7 @@ func (p *GoogleProvider) RefreshSessionIfNeeded(s *SessionState) (bool, error) {
 	s.AccessToken = newToken
 	s.IDToken = newIDToken
 	s.ExpiresOn = time.Now().Add(duration).Truncate(time.Second)
-	log.Printf("refreshed access token %s (expired on %s)", s, origExpiration)
+	logger.Printf("refreshed access token %s (expired on %s)", s, origExpiration)
 	return true, nil
 }

--- a/providers/internal_util.go
+++ b/providers/internal_util.go
@ -2,11 +2,11 @@ package providers

 import (
 	"io/ioutil"
-	"log"
 	"net/http"
 	"net/url"

 	"github.com/pusher/oauth2_proxy/api"
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // stripToken is a helper function to obfuscate "access_token"
@ -24,14 +24,14 @@ func stripToken(endpoint string) string {
 func stripParam(param, endpoint string) string {
 	u, err := url.Parse(endpoint)
 	if err != nil {
-		log.Printf("error attempting to strip %s: %s", param, err)
+		logger.Printf("error attempting to strip %s: %s", param, err)
 		return endpoint
 	}

 	if u.RawQuery != "" {
 		values, err := url.ParseQuery(u.RawQuery)
 		if err != nil {
-			log.Printf("error attempting to strip %s: %s", param, err)
+			logger.Printf("error attempting to strip %s: %s", param, err)
 			return u.String()
 		}

@ -57,18 +57,18 @@ func validateToken(p Provider, accessToken string, header http.Header) bool {
 	}
 	resp, err := api.RequestUnparsedResponse(endpoint, header)
 	if err != nil {
-		log.Printf("GET %s", stripToken(endpoint))
-		log.Printf("token validation request failed: %s", err)
+		logger.Printf("GET %s", stripToken(endpoint))
+		logger.Printf("token validation request failed: %s", err)
 		return false
 	}

 	body, _ := ioutil.ReadAll(resp.Body)
 	resp.Body.Close()
-	log.Printf("%d GET %s %s", resp.StatusCode, stripToken(endpoint), body)
+	logger.Printf("%d GET %s %s", resp.StatusCode, stripToken(endpoint), body)

 	if resp.StatusCode == 200 {
 		return true
 	}
-	log.Printf("token validation request failed: status %d - %s", resp.StatusCode, body)
+	logger.Printf("token validation request failed: status %d - %s", resp.StatusCode, body)
 	return false
 }
--- a/templates.go
+++ b/templates.go
@ -2,18 +2,19 @@ package main

 import (
 	"html/template"
-	"log"
 	"path"
+
+	"github.com/pusher/oauth2_proxy/logger"
 )

 func loadTemplates(dir string) *template.Template {
 	if dir == "" {
 		return getTemplates()
 	}
-	log.Printf("using custom template directory %q", dir)
+	logger.Printf("using custom template directory %q", dir)
 	t, err := template.New("").ParseFiles(path.Join(dir, "sign_in.html"), path.Join(dir, "error.html"))
 	if err != nil {
-		log.Fatalf("failed parsing template %s", err)
+		logger.Fatalf("failed parsing template %s", err)
 	}
 	return t
 }
@ -151,7 +152,7 @@ func getTemplates() *template.Template {
 </html>
 {{end}}`)
 	if err != nil {
-		log.Fatalf("failed parsing template %s", err)
+		logger.Fatalf("failed parsing template %s", err)
 	}

 	t, err = t.Parse(`{{define "error.html"}}
@ -169,7 +170,7 @@ func getTemplates() *template.Template {
 </body>
 </html>{{end}}`)
 	if err != nil {
-		log.Fatalf("failed parsing template %s", err)
+		logger.Fatalf("failed parsing template %s", err)
 	}
 	return t
 }
--- a/validator.go
+++ b/validator.go
@ -3,11 +3,12 @@ package main
 import (
 	"encoding/csv"
 	"fmt"
-	"log"
 	"os"
 	"strings"
 	"sync/atomic"
 	"unsafe"
+
+	"github.com/pusher/oauth2_proxy/logger"
 )

 // UserMap holds information from the authenticated emails file
@ -22,7 +23,7 @@ func NewUserMap(usersFile string, done <-chan bool, onUpdate func()) *UserMap {
 	m := make(map[string]bool)
 	atomic.StorePointer(&um.m, unsafe.Pointer(&m))
 	if usersFile != "" {
-		log.Printf("using authenticated emails file %s", usersFile)
+		logger.Printf("using authenticated emails file %s", usersFile)
 		WatchForUpdates(usersFile, done, func() {
 			um.LoadAuthenticatedEmailsFile()
 			onUpdate()
@ -44,7 +45,7 @@ func (um *UserMap) IsValid(email string) (result bool) {
 func (um *UserMap) LoadAuthenticatedEmailsFile() {
 	r, err := os.Open(um.usersFile)
 	if err != nil {
-		log.Fatalf("failed opening authenticated-emails-file=%q, %s", um.usersFile, err)
+		logger.Fatalf("failed opening authenticated-emails-file=%q, %s", um.usersFile, err)
 	}
 	defer r.Close()
 	csvReader := csv.NewReader(r)
@ -53,7 +54,7 @@ func (um *UserMap) LoadAuthenticatedEmailsFile() {
 	csvReader.TrimLeadingSpace = true
 	records, err := csvReader.ReadAll()
 	if err != nil {
-		log.Printf("error reading authenticated-emails-file=%q, %s", um.usersFile, err)
+		logger.Printf("error reading authenticated-emails-file=%q, %s", um.usersFile, err)
 		return
 	}
 	updated := make(map[string]bool)
--- a/watcher.go
+++ b/watcher.go
@ -3,11 +3,11 @@
 package main

 import (
-	"log"
 	"os"
 	"path/filepath"
 	"time"

+	"github.com/pusher/oauth2_proxy/logger"
 	fsnotify "gopkg.in/fsnotify/fsnotify.v1"
 )

@ -24,7 +24,7 @@ func WaitForReplacement(filename string, op fsnotify.Op,
 	for {
 		if _, err := os.Stat(filename); err == nil {
 			if err := watcher.Add(filename); err == nil {
-				log.Printf("watching resumed for %s", filename)
+				logger.Printf("watching resumed for %s", filename)
 				return
 			}
 		}
@ -37,14 +37,14 @@ func WatchForUpdates(filename string, done <-chan bool, action func()) {
 	filename = filepath.Clean(filename)
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
-		log.Fatal("failed to create watcher for ", filename, ": ", err)
+		logger.Fatal("failed to create watcher for ", filename, ": ", err)
 	}
 	go func() {
 		defer watcher.Close()
 		for {
 			select {
 			case _ = <-done:
-				log.Printf("Shutting down watcher for: %s", filename)
+				logger.Printf("Shutting down watcher for: %s", filename)
 				return
 			case event := <-watcher.Events:
 				// On Arch Linux, it appears Chmod events precede Remove events,
@ -53,19 +53,19 @@ func WatchForUpdates(filename string, done <-chan bool, action func()) {
 				// UserMap.LoadAuthenticatedEmailsFile()) crashes when the file
 				// can't be opened.
 				if event.Op&(fsnotify.Remove|fsnotify.Rename|fsnotify.Chmod) != 0 {
-					log.Printf("watching interrupted on event: %s", event)
+					logger.Printf("watching interrupted on event: %s", event)
 					watcher.Remove(filename)
 					WaitForReplacement(filename, event.Op, watcher)
 				}
-				log.Printf("reloading after event: %s", event)
+				logger.Printf("reloading after event: %s", event)
 				action()
 			case err = <-watcher.Errors:
-				log.Printf("error watching %s: %s", filename, err)
+				logger.Printf("error watching %s: %s", filename, err)
 			}
 		}
 	}()
 	if err = watcher.Add(filename); err != nil {
-		log.Fatal("failed to add ", filename, " to watcher: ", err)
+		logger.Fatal("failed to add ", filename, " to watcher: ", err)
 	}
-	log.Printf("watching %s for updates", filename)
+	logger.Printf("watching %s for updates", filename)
 }
--- a/watcher_unsupported.go
+++ b/watcher_unsupported.go
@ -2,11 +2,9 @@

 package main

-import (
-	"log"
-)
+import "github.com/pusher/oauth2_proxy/logger"

 func WatchForUpdates(filename string, done <-chan bool, action func()) {
-	log.Printf("file watching not implemented on this platform")
+	logger.Printf("file watching not implemented on this platform")
 	go func() { <-done }()
 }