libalpm: Do a sanity check before manipulating final DB URL

The change in commit 9d96bed9d6b57 causes download errors for the .db.sig file
in case the final URL for the .db file contains query strings or other
unexpected stuff. This commit isn't intended to be a total solution, but it
should eliminate the problem in the most obvious cases.

Signed-off-by: Allan McRae <allan@archlinux.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/libalpm/be_sync.c b/lib/libalpm/be_sync.c
index 45d47004..ea979e6d 100644
--- a/lib/libalpm/be_sync.c
+++ b/lib/libalpm/be_sync.c
@@ -241,9 +241,16 @@ int SYMEXPORT alpm_db_update(int force, alpm_db_t *db)
 			unlink(sigpath);
 			free(sigpath);
 
-			/* if we downloaded a DB, we want the .sig from the same server -
-			   this information is only available from the internal downloader */
-			if(handle->fetchcb == NULL) {
+
+			/* check if the final URL from internal downloader looks reasonable */
+			if(final_db_url != NULL) {
+				if(strlen(final_db_url) < 3 || strcmp(final_db_url + strlen(final_db_url) - 3, ".db") != 0) {
+					final_db_url = NULL;
+				}
+			}
+
+			/* if we downloaded a DB, we want the .sig from the same server */
+			if(final_db_url != NULL) {
 				/* print final_db_url into a buffer (leave space for .sig) */
 				len = strlen(final_db_url) + 5;
 			} else {
@@ -254,7 +261,7 @@ int SYMEXPORT alpm_db_update(int force, alpm_db_t *db)
 			/* TODO fix leak syncpath and umask unset */
 			MALLOC(payload.fileurl, len, RET_ERR(handle, ALPM_ERR_MEMORY, -1));
 
-			if(handle->fetchcb == NULL) {
+			if(final_db_url != NULL) {
 				snprintf(payload.fileurl, len, "%s.sig", final_db_url);
 			} else {
 				snprintf(payload.fileurl, len, "%s/%s.db.sig", server, db->treename);