selinux: implement missing selinux functions

checkPasswdAccess() is deprecated
http://linux.die.net/man/3/selinux_check_passwd_access

also, ensure context is initialized in run_shell()

Note: these stubs are just compatible with busybox source code
Should be enhanced, or implemented in libselinux...

Change-Id: I22ea2679191d5c0887b6ef8c77f09a032c226876

6 files changed, 60 insertions, 6 deletions

diff --git a/android/selinux/android_selinux.h b/android/selinux/android_selinux.h
index 3114a67..c39d87a 100644
--- a/android/selinux/android_selinux.h
+++ b/android/selinux/android_selinux.h
@@ -93,6 +93,16 @@ extern void matchpathcon_checkmatches(char *str);
  */
 extern int selinux_file_context_verify(const char *path, mode_t mode);
 
+/* Get the default security context for a user session for 'user'
+   spawned by 'fromcon' and set *newcon to refer to it.  The context
+   will be one of those authorized by the policy, but the selection
+   of a default is subject to user customizable preferences.
+   If 'fromcon' is NULL, defaults to current context.
+   Returns 0 on success or -1 otherwise.
+   Caller must free via freecon. */
+extern int get_default_context(const char* user, const char* fromcon,
+			char ** newcon);
+
 #define lgetfilecon_raw(path, context) \
 	lgetfilecon(path, context)
 
@@ -105,6 +115,9 @@ extern int selinux_file_context_verify(const char *path, mode_t mode);
 #define security_canonicalize_context_raw(context, newctx) \
 	security_canonicalize_context(context, newctx)
 
+#define getprevcon_raw(context) \
+	getprevcon(context)
+
 #define is_context_customizable(ctx) false
 
 #define selinux_log(type, ...) bb_error_msg(__VA_ARGS__)
diff --git a/android/selinux/stubs.c b/android/selinux/stubs.c
new file mode 100644
index 0000000..c3f442d
--- a/dev/null
+++ b/android/selinux/stubs.c
@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <selinux/selinux.h>
+
+/* create a new context with user name (may be unsafe) */
+int get_default_context(const char* user, const char* fromcon,
+	char ** newcon)
+{
+	char fmt[] = "u:r:%s:s0\0";
+	int len = strlen(user) + strlen(fmt);
+
+	*newcon = malloc(len);
+	if (!(*newcon))
+		return -1;
+	snprintf(*newcon, len, fmt, user);
+	return 0;
+}
+
+/* Compute a relabeling decision and set *newcon to refer to it.
+   Caller must free via freecon.
+   Stub not implemented in bionic, but declared in selinux.h */
+int security_compute_relabel(const char *scon, const char *tcon,
+	security_class_t tclass,
+	char ** newcon)
+{
+	if (tcon)
+		*newcon = strdup(tcon);
+	if (!(*newcon))
+		return -1;
+	return 0;
+}
+
+/* Check a permission in the passwd class.
+   Return 0 if granted or -1 otherwise. */
+int selinux_check_passwd_access(access_vector_t requested)
+{
+	return 0;
+}
\ No newline at end of file
diff --git a/busybox-full.sources b/busybox-full.sources
index dccbbca..773e1fe 100644
--- a/busybox-full.sources
+++ b/busybox-full.sources
@@ -67,7 +67,7 @@ procps/lsof.c procps/nmeter.c procps/pstree.c procps/pwdx.c procps/smemcap.c
 
 shell/ash.c shell/ash_ptr_hack.c shell/math.c shell/random.c shell/shell_common.c
 
-libbb/selinux_common.c android/selinux/matchpathcon.c
+libbb/selinux_common.c android/selinux/matchpathcon.c android/selinux/stubs.c
 selinux/chcon.c selinux/selinuxenabled.c
 selinux/getenforce.c selinux/sestatus.c selinux/setsebool.c
 selinux/getsebool.c selinux/runcon.c selinux/setenforce.c selinux/setfiles.c selinux/matchpathcon.c
diff --git a/busybox-minimal.sources b/busybox-minimal.sources
index 62641f0..5c9b8ec 100644
--- a/busybox-minimal.sources
+++ b/busybox-minimal.sources
@@ -25,7 +25,7 @@ procps/renice.c procps/sysctl.c procps/top.c procps/uptime.c procps/watch.c
 
 shell/ash.c shell/ash_ptr_hack.c shell/math.c shell/random.c shell/shell_common.c
 
-android/selinux/matchpathcon.c
+android/selinux/matchpathcon.c android/selinux/stubs.c
 libbb/selinux_common.c selinux/chcon.c selinux/selinuxenabled.c
 selinux/getenforce.c selinux/sestatus.c selinux/setsebool.c
 selinux/getsebool.c selinux/setenforce.c selinux/setfiles.c selinux/matchpathcon.c
diff --git a/libbb/run_shell.c b/libbb/run_shell.c
index 4d92c3c..9494f27 100644
--- a/libbb/run_shell.c
+++ b/libbb/run_shell.c
@@ -34,16 +34,18 @@
 #endif
 
 #if ENABLE_SELINUX
-static security_context_t current_sid;
+static security_context_t current_sid = NULL;
 
 void FAST_FUNC renew_current_security_context(void)
 {
-	freecon(current_sid);  /* Release old context  */
+	if (current_sid)
+		freecon(current_sid);  /* Release old context  */
 	getcon(&current_sid);  /* update */
 }
 void FAST_FUNC set_current_security_context(security_context_t sid)
 {
-	freecon(current_sid);  /* Release old context  */
+	if (current_sid)
+		freecon(current_sid);  /* Release old context  */
 	current_sid = sid;
 }
 
@@ -82,6 +84,7 @@ void FAST_FUNC run_shell(const char *shell, int loginshell, const char *command,
 	args[argno] = NULL;
 
 #if ENABLE_SELINUX
+	renew_current_security_context();
 	if (current_sid)
 		setexeccon(current_sid);
 	if (ENABLE_FEATURE_CLEAN_UP)
diff --git a/libbb/update_passwd.c b/libbb/update_passwd.c
index a30af6f..b2d0464 100644
--- a/libbb/update_passwd.c
+++ b/libbb/update_passwd.c
@@ -30,7 +30,7 @@ static void check_selinux_update_passwd(const char *username)
 	if (!seuser)
 		bb_error_msg_and_die("invalid context '%s'", context);
 	if (strcmp(seuser, username) != 0) {
-		if (checkPasswdAccess(PASSWD__PASSWD) != 0)
+		if (selinux_check_passwd_access(PASSWD__PASSWD) != 0)
 			bb_error_msg_and_die("SELinux: access denied");
 	}
 	if (ENABLE_FEATURE_CLEAN_UP)