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tftp: don't implicity trust the format of recevied packets

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The TFTP OACK code trusts that the incoming packet is formated as
ASCII text and can be processed by string functions. It also has a
loop limit overflow bug where if the packet length is less than 8, it
ends up looping over *all* of memory to find the 'blksize' string.

This patch solves the problem by forcing the packet to be null
terminated and using strstr() to search for the sub string.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Grant Likely
2007-08-29 18:26:24 -06:00
committed by Wolfgang Denk
parent d4a68f40a0
commit 8f1bc28408
1 changed files with 10 additions and 10 deletions
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20
net/tftp.c
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@@ -238,9 +238,9 @@ TftpSend (void)
static void
TftpHandler (uchar * pkt, unsigned dest, unsigned src, unsigned len)
{
char * blksize;
ushort proto;
ushort *s;
int i;
if (dest != TftpOurPort) {
#ifdef CONFIG_MCAST_TFTP
@@ -272,22 +272,22 @@ TftpHandler (uchar * pkt, unsigned dest, unsigned src, unsigned len)
case TFTP_OACK:
#ifdef ET_DEBUG
printf("Got OACK: %s %s\n", pkt, pkt+strlen(pkt)+1);
printf("Got OACK:\n");
print_buffer (0, pkt, 1, len, 16);
#endif
TftpState = STATE_OACK;
TftpServerPort = src;
/* Check for 'blksize' option */
for (i=0;i<len-8;i++) {
if (strcmp ((char*)pkt+i,"blksize") == 0) {
TftpBlkSize = (unsigned short)
simple_strtoul((char*)pkt+i+8,NULL,10);
pkt[len] = 0; /* NULL terminate so string ops work */
blksize = strstr((char*)pkt, "blksize");
if ((blksize) && (blksize + 8 < (char*)pkt + len)) {
TftpBlkSize = simple_strtoul(blksize + 8, NULL, 10);
#ifdef ET_DEBUG
printf ("Blocksize ack: %s, %d\n",
(char*)pkt+i+8,TftpBlkSize);
printf("Blocksize ack: %d\n", TftpBlkSize);
#endif
break;
}
}
#ifdef CONFIG_MCAST_TFTP
parse_multicast_oack((char *)pkt,len-1);
if ((Multicast) && (!MasterClient))