Fixes to add "paranoid" option to popen. Checks some basic things.

Jeremy
(This used to be commit 3b8cbb10de322fd7a1063fb5b681790b10d24ab0)

5 files changed, 78 insertions, 5 deletions

diff --git a/source3/include/proto.h b/source3/include/proto.h
index d96d2f77c0..27d3de49b8 100644
--- a/source3/include/proto.h
+++ b/source3/include/proto.h
@@ -233,7 +233,7 @@ DIR *wsys_opendir(const smb_ucs2_t *wfname);
 smb_ucs2_t *wsys_getwd(smb_ucs2_t *s);
 int wsys_chown(const smb_ucs2_t *wfname, uid_t uid, gid_t gid);
 int wsys_chroot(const smb_ucs2_t *wfname);
-FILE *sys_popen(const char *command, const char *mode);
+FILE *sys_popen(const char *command, const char *mode, BOOL paranoid);
 int sys_pclose( FILE *fp);
 
 /*The following definitions come from  lib/talloc.c  */
diff --git a/source3/lib/system.c b/source3/lib/system.c
index 9ef0af494f..8ac07e26a5 100644
--- a/source3/lib/system.c
+++ b/source3/lib/system.c
@@ -963,7 +963,7 @@ typedef struct _popen_list
 
 static popen_list *popen_chain;
 
-FILE *sys_popen(const char *command, const char *mode)
+FILE *sys_popen(const char *command, const char *mode, BOOL paranoid)
 {
 	int parent_end, child_end;
 	int pipe_fds[2];
@@ -999,6 +999,61 @@ FILE *sys_popen(const char *command, const char *mode)
 	if(!(argl = extract_args(command)))
 		goto err_exit;
 
+	if(paranoid) {
+		/*
+		 * Do some basic paranioa checks. Do a stat on the parent
+		 * directory and ensure it's not world writable. Do a stat
+		 * on the file itself and ensure it's owned by root and not
+		 * world writable. Note this does *not* prevent symlink races,
+		 * but is a generic "don't let the admin screw themselves"
+		 * check.
+		 */
+
+		SMB_STRUCT_STAT st;
+		pstring dir_name;
+		char *ptr = strrchr(argl[0], '/');
+	
+		if(sys_stat(argl[0], &st) != 0)
+			goto err_exit;
+
+		if((st.st_uid != (uid_t)0) || (st.st_mode & S_IWOTH)) {
+			errno = EACCES;
+			goto err_exit;
+		}
+		
+		if(!ptr) {
+			/*
+			 * No '/' in name - use current directory.
+			 */
+			pstrcpy(dir_name, ".");
+		} else {
+
+			/*
+			 * Copy into a pstring and do the checks
+			 * again (in case we were length tuncated).
+			 */
+
+			pstrcpy(dir_name, argl[0]);
+			ptr = strrchr(dir_name, '/');
+			if(!ptr) {
+				errno = EINVAL;
+				goto err_exit;
+			}
+			if(strcmp(dir_name, "/") != 0)
+				*ptr = '\0';
+			if(!dir_name[0])
+				pstrcpy(dir_name, ".");
+		}
+
+		if(sys_stat(argl[0], &st) != 0)
+			goto err_exit;
+
+		if(!S_ISDIR(st.st_mode) || (st.st_mode & S_IWOTH)) {
+			errno = EACCES;
+			goto err_exit;
+		}
+	}
+
 	entry->child_pid = fork();
 
 	if (entry->child_pid == -1) {
diff --git a/source3/param/loadparm.c b/source3/param/loadparm.c
index 48dc6cf123..4f6178a569 100644
--- a/source3/param/loadparm.c
+++ b/source3/param/loadparm.c
@@ -2039,7 +2039,7 @@ static BOOL handle_source_env(char *pszParmValue,char **ptr)
 		DEBUG(4, ("handle_source_env: source env from pipe\n"));
 		p++;
 
-		if ((env = sys_popen(p, "r")) == NULL) {
+		if ((env = sys_popen(p, "r", True)) == NULL) {
 			DEBUG(0,("handle_source_env: Failed to popen %s. Error was %s\n", p, strerror(errno) ));
 			return(False);
 		}
@@ -2050,11 +2050,29 @@ static BOOL handle_source_env(char *pszParmValue,char **ptr)
 
 	} else {
 
+		SMB_STRUCT_STAT st;
+
 		DEBUG(4, ("handle_source_env: source env from file %s\n", fname));
 		if ((env = sys_fopen(fname, "r")) == NULL) {
 			DEBUG(0,("handle_source_env: Failed to open file %s, Error was %s\n", fname, strerror(errno) ));
 			return(False);
 		}
+
+		/*
+		 * Ensure this file is owned by root and not writable by world.
+		 */
+		if(fstat(fileno(env), &st) != 0) {
+			DEBUG(0,("handle_source_env: Failed to stat file %s, Error was %s\n", fname, strerror(errno) ));
+			fclose(env);
+			return False;
+		}
+
+		if((st.st_uid != (uid_t)0) || (st.st_mode & S_IWOTH)) {
+			DEBUG(0,("handle_source_env: unsafe to source env file %s. Not owned by root or world writable\n", fname ));
+			fclose(env);
+			return False;
+		}
+
 		result=source_env(env);
 		fclose(env);
 	}
diff --git a/source3/printing/print_svid.c b/source3/printing/print_svid.c
index 9891e158a2..21e8eeb643 100644
--- a/source3/printing/print_svid.c
+++ b/source3/printing/print_svid.c
@@ -49,7 +49,7 @@ static void populate_printers(void)
 {
 	FILE *fp;
 
-	if ((fp = sys_popen("/usr/bin/lpstat -v", "r")) != NULL) {
+	if ((fp = sys_popen("/usr/bin/lpstat -v", "r", False)) != NULL) {
 		char buf[BUFSIZ];
 
 		while (fgets(buf, sizeof (buf), fp) != NULL) {
diff --git a/source3/smbd/dfree.c b/source3/smbd/dfree.c
index 7866d60277..0a892bad05 100644
--- a/source3/smbd/dfree.c
+++ b/source3/smbd/dfree.c
@@ -217,7 +217,7 @@ static SMB_BIG_UINT disk_free(char *path, BOOL small_query,
 		slprintf (line, sizeof(pstring) - 1, "%s %s", dfree_command, path);
 		DEBUG (3, ("disk_free: Running command %s\n", line));
 
-		pp = sys_popen(line, "r");
+		pp = sys_popen(line, "r", False);
 		if (pp) {
 			fgets(line, sizeof(pstring), pp);
 			line[sizeof(pstring)-1] = '\0';