Support empty environment variables to simulate Apache behavior

Author: jung-kurt

README.md

@@ -163,6 +163,7 @@ looks like this:
 		exec script [args...]
 		env key1=val1 [key2=val2...]
 		pass_env key1 [key2...]
+		empty_env key1 [key2...]
 	}
 
 For example,
@@ -173,17 +174,24 @@ For example,
 		exec /usr/local/cgi-bin/phpwrap /usr/local/cgi-bin{match}
 		env DB=/usr/local/share/app/app.db SECRET=/usr/local/share/app/secret
 		pass_env HOME UID
+		empty_env CGI_LOCAL
 	}
 
 With the advanced syntax, the `exec` subdirective must appear exactly once. The
-`match` subdirective must appear at least once. The `env`, `pass_env`, and
-`except` subdirectives can appear any reasonable number of times.
+`match` subdirective must appear at least once. The `env`, `pass_env`,
+`empty_env`, and `except` subdirectives can appear any reasonable number of
+times.
 
 The `except` subdirective uses the same pattern matching logic that is used
 with the `match` subdirective. Any request that matches a `match` pattern is
 then checked with the patterns in `except`, if any. If any matches are made
 with the `except` pattern, the request is rejected.
 
+The empty_env subdirective is used to pass one or more empty environment
+variables. Some CGI scripts may expect the server to pass certain empty
+variables rather than leaving them unset. This subdirective allows you to deal
+with those situations.
+
 The values associated with environment variable keys are all subject to
 placeholder substitution, just as with the script name and arguments.
 

cgi.go

@@ -89,6 +89,9 @@ func setupCall(h handlerType, rule ruleType, lfStr, rtStr string,
 	for _, env := range rule.envs {
 		envAdd(env[0], env[1])
 	}
+	for _, env := range rule.emptyEnvs {
+		cgiHnd.Env = append(cgiHnd.Env, env+"=")
+	}
 	envAdd("PATH_INFO", rtStr)
 	envAdd("SCRIPT_FILENAME", cgiHnd.Path)
 	envAdd("SCRIPT_NAME", lfStr)

cgi_test.go

@@ -55,6 +55,7 @@ func TestServe(t *testing.T) {
   except /servertime/1934
   exec {.}/test/example --example
   env CGI_GLOBAL=12
+  empty_env CGI_LOCAL
 }`,
 	}
 
@@ -69,31 +70,56 @@ func TestServe(t *testing.T) {
 cgi /servertime {.}/test/example
 --- Request /servertime ---
 code [0], error [example error message]
-[---] [---] [---] [quixote] [] []
+PATH_INFO []
+CGI_GLOBAL []
+Arg 1 []
+QUERY_STRING []
+HTTP_TOKEN_CLAIM_USER [quixote]
+CGI_LOCAL is unset
 --- Request /servertime/1930/05/11?name=Edsger%20W.%20Dijkstra ---
 code [0], error [example error message]
-[/1930/05/11] [---] [---] [---] [name=Edsger%20W.%20Dijkstra] [quixote]
+PATH_INFO [/1930/05/11]
+CGI_GLOBAL []
+Arg 1 []
+QUERY_STRING [name=Edsger%20W.%20Dijkstra]
+HTTP_TOKEN_CLAIM_USER [quixote]
+CGI_LOCAL is unset
 --- Request /servertime/1934/02/15?name=Niklaus%20Wirth ---
 code [0], error [example error message]
-[/1934/02/15] [---] [---] [---] [name=Niklaus%20Wirth] [quixote]
+PATH_INFO [/1934/02/15]
+CGI_GLOBAL []
+Arg 1 []
+QUERY_STRING [name=Niklaus%20Wirth]
+HTTP_TOKEN_CLAIM_USER [quixote]
+CGI_LOCAL is unset
 --- Request /example.txt ---
 === Directive 1 ===
 cgi {
   match /servertime
   except /servertime/1934
   exec {.}/test/example --example
   env CGI_GLOBAL=12
+  empty_env CGI_LOCAL
 }
 --- Request /servertime ---
 code [0], error [example error message]
-[---] [12] [--example] [quixote] [] []
+PATH_INFO []
+CGI_GLOBAL [12]
+Arg 1 [--example]
+QUERY_STRING []
+HTTP_TOKEN_CLAIM_USER [quixote]
+CGI_LOCAL is set to []
 --- Request /servertime/1930/05/11?name=Edsger%20W.%20Dijkstra ---
 code [0], error [example error message]
-[/1930/05/11] [---] [12] [--example] [name=Edsger%20W.%20Dijkstra] [quixote]
+PATH_INFO [/1930/05/11]
+CGI_GLOBAL [12]
+Arg 1 [--example]
+QUERY_STRING [name=Edsger%20W.%20Dijkstra]
+HTTP_TOKEN_CLAIM_USER [quixote]
+CGI_LOCAL is set to []
 --- Request /servertime/1934/02/15?name=Niklaus%20Wirth ---
 --- Request /example.txt ---
 `
-
 	// Testing the ServeHTTP method requires OS-specific CGI scripts, because a
 	// system call is made to respond to the request.
 	if runtime.GOOS == "linux" || runtime.GOOS == "darwin" {

def.go

@@ -26,4 +26,6 @@ type ruleType struct {
 	envs [][2]string // [0..n]
 	// Environment keys to pass through for all apps
 	passEnvs []string // [0..n]
+	// Environment keys to send with empty values
+	emptyEnvs []string // [0..n]
 }

doc.go

@@ -160,6 +160,7 @@ looks like this:
 		exec script [args...]
 		env key1=val1 [key2=val2...]
 		pass_env key1 [key2...]
+		empty_env key1 [key2...]
 	}
 
 For example,
@@ -170,17 +171,24 @@ For example,
 		exec /usr/local/cgi-bin/phpwrap /usr/local/cgi-bin{match}
 		env DB=/usr/local/share/app/app.db SECRET=/usr/local/share/app/secret
 		pass_env HOME UID
+		empty_env CGI_LOCAL
 	}
 
 With the advanced syntax, the exec subdirective must appear exactly once. The
-match subdirective must appear at least once. The env, pass_env, and
-except subdirectives can appear any reasonable number of times.
+match subdirective must appear at least once. The env, pass_env,
+empty_env, and except subdirectives can appear any reasonable number of
+times.
 
 The except subdirective uses the same pattern matching logic that is used
 with the match subdirective. Any request that matches a match pattern is
 then checked with the patterns in except, if any. If any matches are made
 with the except pattern, the request is rejected.
 
+The empty_env subdirective is used to pass one or more empty environment
+variables. Some CGI scripts may expect the server to pass certain empty
+variables rather than leaving them unset. This subdirective allows you to deal
+with those situations.
+
 The values associated with environment variable keys are all subject to
 placeholder substitution, just as with the script name and arguments.
 

doc/cgi.md

@@ -166,6 +166,7 @@ looks like this:
 >   [exec][key] [script [args...]][subkey]
 >   [env][key] [key1=val1 [key2=val2...]][subkey]
 >   [pass_env][key] [key1 [key2...]][subkey]
+>   [empty_env][key] [key1 [key2...]][subkey]
 > }
 
 For example,
@@ -176,17 +177,24 @@ For example,
 		exec /usr/local/cgi-bin/phpwrap /usr/local/cgi-bin{match}
 		env DB=/usr/local/share/app/app.db SECRET=/usr/local/share/app/secret
 		pass_env HOME UID
+		empty_env CGI_LOCAL
 	}
 
 With the advanced syntax, the `exec` subdirective must appear exactly once. The
-`match` subdirective must appear at least once. The `env`, `pass_env`, and
-`except` subdirectives can appear any reasonable number of times.
+`match` subdirective must appear at least once. The `env`, `pass_env`,
+`empty_env`, and `except` subdirectives can appear any reasonable number of
+times.
 
 The `except` subdirective uses the same pattern matching logic that is used
 with the `match` subdirective. Any request that matches a `match` pattern is
 then checked with the patterns in `except`, if any. If any matches are made
 with the `except` pattern, the request is rejected.
 
+The empty_env subdirective is used to pass one or more empty environment
+variables. Some CGI scripts may expect the server to pass certain empty
+variables rather than leaving them unset. This subdirective allows you to deal
+with those situations.
+
 The values associated with environment variable keys are all subject to
 placeholder substitution, just as with the script name and arguments.
 

doc/doc.txt

@@ -195,6 +195,7 @@ looks like this:
 >   [exec][key] [script [args...]][subkey]
 >   [env][key] [key1=val1 [key2=val2...]][subkey]
 >   [pass_env][key] [key1 [key2...]][subkey]
+>   [empty_env][key] [key1 [key2...]][subkey]
 > }
 ~rg~
 	cgi {
@@ -203,6 +204,7 @@ looks like this:
 		exec script [args...]
 		env key1=val1 [key2=val2...]
 		pass_env key1 [key2...]
+		empty_env key1 [key2...]
 	}
 ~rgc~
 
@@ -214,17 +216,24 @@ For example,
 		exec /usr/local/cgi-bin/phpwrap /usr/local/cgi-bin{match}
 		env DB=/usr/local/share/app/app.db SECRET=/usr/local/share/app/secret
 		pass_env HOME UID
+		empty_env CGI_LOCAL
 	}
 
 With the advanced syntax, the `exec` subdirective must appear exactly once. The
-`match` subdirective must appear at least once. The `env`, `pass_env`, and
-`except` subdirectives can appear any reasonable number of times.
+`match` subdirective must appear at least once. The `env`, `pass_env`,
+`empty_env`, and `except` subdirectives can appear any reasonable number of
+times.
 
 The `except` subdirective uses the same pattern matching logic that is used
 with the `match` subdirective. Any request that matches a `match` pattern is
 then checked with the patterns in `except`, if any. If any matches are made
 with the `except` pattern, the request is rejected.
 
+The empty_env subdirective is used to pass one or more empty environment
+variables. Some CGI scripts may expect the server to pass certain empty
+variables rather than leaving them unset. This subdirective allows you to deal
+with those situations.
+
 The values associated with environment variable keys are all subject to
 placeholder substitution, just as with the script name and arguments.
 

setup.go

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017 Kurt Jung (Gmail: kurt.w.jung)
+ * Copyright (c) 2017-2018 Kurt Jung (Gmail: kurt.w.jung)
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -120,14 +120,16 @@ func parseBlock(c *caddy.Controller) (rule ruleType, err error) {
 				switch val {
 				case "match": // [1..n]
 					err = parseMatch(&rule, args)
-				case "except":
+				case "except": // [0..n]
 					err = parseExcept(&rule, args)
 				case "exec": // [1]
 					err = parseExec(&rule, args)
 				case "env": // [0..n]
 					err = parseEnv(&rule.envs, args)
 				case "pass_env": // [0..n]
 					rule.passEnvs = append(rule.passEnvs, args...)
+				case "empty_env": // [0..n]
+					rule.emptyEnvs = append(rule.emptyEnvs, args...)
 				case "}":
 					loop = false
 				}

setup_test.go

@@ -57,6 +57,7 @@ func Example_rule() {
   except utility.lua
   exec /usr/bin/lua /usr/local/cgi-bin/{match}
   pass_env LUA_PATH LUA_CPATH
+  empty_env REMOTE_USER CONTENT_TYPE
  }`,
 		`cgi {
   match *.py *.pyc
@@ -91,6 +92,8 @@ func Example_rule() {
 	//   Arg 0: /usr/local/cgi-bin/{match}
 	//   Pass env 0: LUA_PATH
 	//   Pass env 1: LUA_CPATH
+	//   Empty env 0: REMOTE_USER
+	//   Empty env 1: CONTENT_TYPE
 	// Rule 0
 	//   Match 0: *.py
 	//   Match 1: *.pyc

test/example

@@ -1,7 +1,15 @@
 #!/bin/bash
 
 printf "Content-type: text/plain\n\n"
-printf "[%s] [%s] [%s] [%s] [%s] [%s]\n" ${PATH_INFO----} ${CGI_LOCAL----} \
-  ${CGI_GLOBAL----} ${1----} ${QUERY_STRING----} ${HTTP_TOKEN_CLAIM_USER----}
+printf "PATH_INFO [%s]\n" ${PATH_INFO}
+printf "CGI_GLOBAL [%s]\n" ${CGI_GLOBAL}
+printf "Arg 1 [%s]\n" ${1}
+printf "QUERY_STRING [%s]\n" ${QUERY_STRING}
+printf "HTTP_TOKEN_CLAIM_USER [%s]\n" ${HTTP_TOKEN_CLAIM_USER}
+if [ -z ${CGI_LOCAL+x} ]; then 
+	printf "CGI_LOCAL is unset\n" 
+else
+	printf "CGI_LOCAL is set to [%s]\n" ${CGI_LOCAL}
+fi
 printf "example error message\n" > /dev/stderr
 exit 0