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run-as: improve diagnostics on failure.

Browse source 
Bug: http://b/128523258
Test: manual
Change-Id: I4430a8d309c0e9b5315aaae3e7d223c05b7ea3e5
This commit is contained in:
Elliott Hughes 2019-03-13 11:15:06 -07:00
parent 6c5c085e41
commit 964932d7ce
1 changed files with 25 additions and 17 deletions
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42
run-as/run-as.cpp
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@ -70,32 +70,40 @@ static bool packagelist_parse_callback(pkg_info* this_package, void* userdata) {
return true; // Keep searching.
}
static bool check_directory(const char* path, uid_t uid) {
static void check_directory(const char* path, uid_t uid) {
struct stat st;
if (TEMP_FAILURE_RETRY(lstat(path, &st)) == -1) return false;
if (TEMP_FAILURE_RETRY(lstat(path, &st)) == -1) {
error(1, errno, "couldn't stat %s", path);
}
// /data/user/0 is a known safe symlink.
if (strcmp("/data/user/0", path) == 0) return true;
if (strcmp("/data/user/0", path) == 0) return;
// Must be a real directory, not a symlink.
if (!S_ISDIR(st.st_mode)) return false;
if (!S_ISDIR(st.st_mode)) {
error(1, 0, "%s not a directory: %o", path, st.st_mode);
}
// Must be owned by specific uid/gid.
if (st.st_uid != uid || st.st_gid != uid) return false;
if (st.st_uid != uid || st.st_gid != uid) {
error(1, 0, "%s has wrong owner: %d/%d, not %d", path, st.st_uid, st.st_gid, uid);
}
// Must not be readable or writable by others.
if ((st.st_mode & (S_IROTH|S_IWOTH)) != 0) return false;
return true;
if ((st.st_mode & (S_IROTH | S_IWOTH)) != 0) {
error(1, 0, "%s readable or writable by others: %o", path, st.st_mode);
}
}
// This function is used to check the data directory path for safety.
// We check that every sub-directory is owned by the 'system' user
// and exists and is not a symlink. We also check that the full directory
// path is properly owned by the user ID.
static bool check_data_path(const char* data_path, uid_t uid) {
static void check_data_path(const char* package_name, const char* data_path, uid_t uid) {
// The path should be absolute.
if (data_path[0] != '/') return false;
if (data_path[0] != '/') {
error(1, 0, "%s data path not absolute: %s", package_name, data_path);
}
// Look for all sub-paths, we do that by finding
// directory separators in the input path and
@ -110,26 +118,28 @@ static bool check_data_path(const char* data_path, uid_t uid) {
if (data_path[nn+1] == '\0') break;
/* found a separator, check that data_path is not too long. */
if (nn >= (int)(sizeof subpath)) return false;
if (nn >= (int)(sizeof subpath)) {
error(1, 0, "%s data path too long: %s", package_name, data_path);
}
/* reject any '..' subpath */
if (nn >= 3 &&
data_path[nn-3] == '/' &&
data_path[nn-2] == '.' &&
data_path[nn-1] == '.') {
return false;
error(1, 0, "%s contains '..': %s", package_name, data_path);
}
/* copy to 'subpath', then check ownership */
memcpy(subpath, data_path, nn);
subpath[nn] = '\0';
if (!check_directory(subpath, AID_SYSTEM)) return false;
check_directory(subpath, AID_SYSTEM);
}
// All sub-paths were checked, now verify that the full data
// directory is owned by the application uid.
return check_directory(data_path, uid);
check_directory(data_path, uid);
}
std::vector<gid_t> get_supplementary_gids(uid_t userAppId) {
@ -222,9 +232,7 @@ int main(int argc, char* argv[]) {
}
// Check that the data directory path is valid.
if (!check_data_path(info.data_dir, userAppId)) {
error(1, 0, "package has corrupt installation: %s", pkgname);
}
check_data_path(pkgname, info.data_dir, userAppId);
// Ensure that we change all real/effective/saved IDs at the
// same time to avoid nasty surprises.