1 files changed, 46 insertions, 16 deletions

diff --git a/libgo/go/syscall/env_unix.go b/libgo/go/syscall/env_unix.go
index f64202ed11..b5ded9c763 100644
--- a/libgo/go/syscall/env_unix.go
+++ b/libgo/go/syscall/env_unix.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build darwin dragonfly freebsd linux netbsd openbsd
+// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris
 
 // Unix environment variables.
 
@@ -20,23 +20,33 @@ var (
 	// env maps from an environment variable to its first occurrence in envs.
 	env map[string]int
 
-	// envs is provided by the runtime. elements are expected to be
-	// of the form "key=value".
-	Envs []string
+	// envs is provided by the runtime. elements are expected to
+	// be of the form "key=value". An empty string means deleted
+	// (or a duplicate to be ignored).
+	envs []string = runtime_envs()
 )
 
-// setenv_c is provided by the runtime, but is a no-op if cgo isn't
-// loaded.
+func runtime_envs() []string // in package runtime
+
+// setenv_c and unsetenv_c are provided by the runtime but are no-ops
+// if cgo isn't loaded.
 func setenv_c(k, v string)
+func unsetenv_c(k string)
 
 func copyenv() {
 	env = make(map[string]int)
-	for i, s := range Envs {
+	for i, s := range envs {
 		for j := 0; j < len(s); j++ {
 			if s[j] == '=' {
 				key := s[:j]
 				if _, ok := env[key]; !ok {
-					env[key] = i
+					env[key] = i // first mention of key
+				} else {
+					// Clear duplicate keys. This permits Unsetenv to
+					// safely delete only the first item without
+					// worrying about unshadowing a later one,
+					// which might be a security problem.
+					envs[i] = ""
 				}
 				break
 			}
@@ -44,6 +54,20 @@ func copyenv() {
 	}
 }
 
+func Unsetenv(key string) error {
+	envOnce.Do(copyenv)
+
+	envLock.Lock()
+	defer envLock.Unlock()
+
+	if i, ok := env[key]; ok {
+		envs[i] = ""
+		delete(env, key)
+	}
+	unsetenv_c(key)
+	return nil
+}
+
 func Getenv(key string) (value string, found bool) {
 	envOnce.Do(copyenv)
 	if len(key) == 0 {
@@ -57,7 +81,7 @@ func Getenv(key string) (value string, found bool) {
 	if !ok {
 		return "", false
 	}
-	s := Envs[i]
+	s := envs[i]
 	for i := 0; i < len(s); i++ {
 		if s[i] == '=' {
 			return s[i+1:], true
@@ -88,10 +112,10 @@ func Setenv(key, value string) error {
 	i, ok := env[key]
 	kv := key + "=" + value
 	if ok {
-		Envs[i] = kv
+		envs[i] = kv
 	} else {
-		i = len(Envs)
-		Envs = append(Envs, kv)
+		i = len(envs)
+		envs = append(envs, kv)
 	}
 	env[key] = i
 	setenv_c(key, value)
@@ -104,16 +128,22 @@ func Clearenv() {
 	envLock.Lock()
 	defer envLock.Unlock()
 
+	for k := range env {
+		unsetenv_c(k)
+	}
 	env = make(map[string]int)
-	Envs = []string{}
-	// TODO(bradfitz): pass through to C
+	envs = []string{}
 }
 
 func Environ() []string {
 	envOnce.Do(copyenv)
 	envLock.RLock()
 	defer envLock.RUnlock()
-	a := make([]string, len(Envs))
-	copy(a, Envs)
+	a := make([]string, 0, len(envs))
+	for _, env := range envs {
+		if env != "" {
+			a = append(a, env)
+		}
+	}
 	return a
 }