[git commit] wget: check chunk length for overflowing off_t

Denys Vlasenko vda.linux at googlemail.com
Sun Apr 8 16:06:24 UTC 2018


commit: https://git.busybox.net/busybox/commit/?id=8e2174e9bd836e53c8b9c6e00d1bc6e2a718686e
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master

function                                             old     new   delta
retrieve_file_data                                   428     465     +37
wget_main                                           2386    2389      +3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 40/0)               Total: 40 bytes

Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 networking/wget.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/networking/wget.c b/networking/wget.c
index c9e576e69..2650b5384 100644
--- a/networking/wget.c
+++ b/networking/wget.c
@@ -801,7 +801,7 @@ static FILE* prepare_ftp_session(FILE **dfpp, struct host_info *target, len_and_
 	if (ftpcmd("SIZE ", target->path, sfp) == 213) {
 		G.content_len = BB_STRTOOFF(G.wget_buf + 4, NULL, 10);
 		if (G.content_len < 0 || errno) {
-			bb_error_msg_and_die("SIZE value is garbage");
+			bb_error_msg_and_die("bad SIZE value '%s'", G.wget_buf + 4);
 		}
 		G.got_clen = 1;
 	}
@@ -965,11 +965,19 @@ static void NOINLINE retrieve_file_data(FILE *dfp)
 		if (!G.chunked)
 			break;
 
-		fgets_trim_sanitize(dfp, NULL); /* Eat empty line */
+		/* Each chunk ends with "\r\n" - eat it */
+		fgets_trim_sanitize(dfp, NULL);
  get_clen:
+		/* chunk size format is "HEXNUM[;name[=val]]\r\n" */
 		fgets_trim_sanitize(dfp, NULL);
+		errno = 0;
 		G.content_len = STRTOOFF(G.wget_buf, NULL, 16);
-		/* FIXME: error check? */
+		/*
+		 * Had a bug with inputs like "ffffffff0001f400"
+		 * smashing the heap later. Ensure >= 0.
+		 */
+		if (G.content_len < 0 || errno)
+			bb_error_msg_and_die("bad chunk length '%s'", G.wget_buf);
 		if (G.content_len == 0)
 			break; /* all done! */
 		G.got_clen = 1;


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