init: harden property service.
Don't create temporary files in a well-known location. Rather,
use mkstemp().
Don't read persistent property files from insecure files.
Change-Id: I81e2aca674a2a7ca54869f088737fb228d3af6d2
diff --git a/init/property_service.c b/init/property_service.c
index 5017375..c6c2e3f 100644
--- a/init/property_service.c
+++ b/init/property_service.c
@@ -123,7 +123,7 @@
/* dev is a tmpfs that we can use to carve a shared workspace
* out of, so let's do that...
*/
- fd = open("/dev/__properties__", O_RDWR | O_CREAT, 0600);
+ fd = open("/dev/__properties__", O_RDWR | O_CREAT | O_NOFOLLOW, 0600);
if (fd < 0)
return -1;
@@ -136,7 +136,7 @@
close(fd);
- fd = open("/dev/__properties__", O_RDONLY);
+ fd = open("/dev/__properties__", O_RDONLY | O_NOFOLLOW);
if (fd < 0)
return -1;
@@ -318,13 +318,12 @@
static void write_persistent_property(const char *name, const char *value)
{
- const char *tempPath = PERSISTENT_PROPERTY_DIR "/.temp";
+ char tempPath[PATH_MAX];
char path[PATH_MAX];
- int fd, length;
+ int fd;
- snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
-
- fd = open(tempPath, O_WRONLY|O_CREAT|O_TRUNC, 0600);
+ snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
+ fd = mkstemp(tempPath);
if (fd < 0) {
ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
return;
@@ -332,6 +331,7 @@
write(fd, value, strlen(value));
close(fd);
+ snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
if (rename(tempPath, path)) {
unlink(tempPath);
ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
@@ -343,8 +343,8 @@
prop_area *pa;
prop_info *pi;
- int namelen = strlen(name);
- int valuelen = strlen(value);
+ size_t namelen = strlen(name);
+ size_t valuelen = strlen(value);
if(namelen >= PROP_NAME_MAX) return -1;
if(valuelen >= PROP_VALUE_MAX) return -1;
@@ -423,13 +423,13 @@
/* Check socket options here */
if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
close(s);
- ERROR("Unable to recieve socket options\n");
+ ERROR("Unable to receive socket options\n");
return;
}
r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), 0));
if(r != sizeof(prop_msg)) {
- ERROR("sys_prop: mis-match msg size recieved: %d expected: %d errno: %d\n",
+ ERROR("sys_prop: mis-match msg size received: %d expected: %d errno: %d\n",
r, sizeof(prop_msg), errno);
close(s);
return;
@@ -528,10 +528,11 @@
static void load_persistent_properties()
{
DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
+ int dir_fd = dirfd(dir);
struct dirent* entry;
- char path[PATH_MAX];
char value[PROP_VALUE_MAX];
int fd, length;
+ struct stat sb;
if (dir) {
while ((entry = readdir(dir)) != NULL) {
@@ -542,20 +543,39 @@
continue;
#endif
/* open the file and read the property value */
- snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, entry->d_name);
- fd = open(path, O_RDONLY);
- if (fd >= 0) {
- length = read(fd, value, sizeof(value) - 1);
- if (length >= 0) {
- value[length] = 0;
- property_set(entry->d_name, value);
- } else {
- ERROR("Unable to read persistent property file %s errno: %d\n", path, errno);
- }
- close(fd);
- } else {
- ERROR("Unable to open persistent property file %s errno: %d\n", path, errno);
+ fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
+ if (fd < 0) {
+ ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
+ entry->d_name, errno);
+ continue;
}
+ if (fstat(fd, &sb) < 0) {
+ ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
+ close(fd);
+ continue;
+ }
+
+ // File must not be accessible to others, be owned by root/root, and
+ // not be a hard link to any other file.
+ if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
+ || (sb.st_uid != 0)
+ || (sb.st_gid != 0)
+ || (sb.st_nlink != 1)) {
+ ERROR("skipping insecure property file %s (uid=%lu gid=%lu nlink=%d mode=%o)\n",
+ entry->d_name, sb.st_uid, sb.st_gid, sb.st_nlink, sb.st_mode);
+ close(fd);
+ continue;
+ }
+
+ length = read(fd, value, sizeof(value) - 1);
+ if (length >= 0) {
+ value[length] = 0;
+ property_set(entry->d_name, value);
+ } else {
+ ERROR("Unable to read persistent property file %s errno: %d\n",
+ entry->d_name, errno);
+ }
+ close(fd);
}
closedir(dir);
} else {