From 5fff4353f66427b467eb29e5fdc1da4f2be028bb Mon Sep 17 00:00:00 2001 From: Josef Gajdusek Date: Mon, 14 Nov 2016 12:38:05 +0100 Subject: [PATCH] Fix heap overflow in the ultra.c decoder The Ultra type tile decoder does not use the _safe variant of the LZO decompress function, which allows a maliciuous server to overwrite parts of the heap by sending a larger-than-specified LZO data stream. --- libvncclient/ultra.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/libvncclient/ultra.c b/libvncclient/ultra.c index dac89b5..32a1b2b 100644 --- a/libvncclient/ultra.c +++ b/libvncclient/ultra.c @@ -86,14 +86,14 @@ HandleUltraBPP (rfbClient* client, int rx, int ry, int rw, int rh) /* uncompress the data */ uncompressedBytes = client->raw_buffer_size; - inflateResult = lzo1x_decompress( + inflateResult = lzo1x_decompress_safe( (lzo_byte *)client->ultra_buffer, toRead, (lzo_byte *)client->raw_buffer, (lzo_uintp) &uncompressedBytes, NULL); - + /* Note that uncompressedBytes will be 0 on output overrun */ if ((rw * rh * (BPP / 8)) != uncompressedBytes) - rfbClientLog("Ultra decompressed too little (%d < %d)", (rw * rh * (BPP / 8)), uncompressedBytes); + rfbClientLog("Ultra decompressed unexpected amount of data (%d != %d)\n", (rw * rh * (BPP / 8)), uncompressedBytes); /* Put the uncompressed contents of the update on the screen. */ if ( inflateResult == LZO_E_OK ) @@ -168,7 +168,7 @@ HandleUltraZipBPP (rfbClient* client, int rx, int ry, int rw, int rh) /* uncompress the data */ uncompressedBytes = client->raw_buffer_size; - inflateResult = lzo1x_decompress( + inflateResult = lzo1x_decompress_safe( (lzo_byte *)client->ultra_buffer, toRead, (lzo_byte *)client->raw_buffer, &uncompressedBytes, NULL); if ( inflateResult != LZO_E_OK )