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dns: check length field in tcp response message

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The received length field in the message may be greater than the
size of the 'answer' buffer in which the message resides. Currently,
ABUF_SIZE is 768. And if we get a larger 'alens[i]', it will result
in an out-of-bounds reading in __dns_parse().

To fix this, limit the length to the size of the received buffer.
This commit is contained in:
Alexey Kodanev 2023-03-22 17:48:40 +03:00 • committed by Rich Felker
parent 1d5750b95c
commit 77327ed064
1 changed files with 1 additions and 0 deletions
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src/network/lookup_name.c
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@ -179,6 +179,7 @@ static int name_from_dns(struct address buf[static MAXADDRS], char canon[static
for (i=nq-1; i>=0; i--) {
ctx.rrtype = qtypes[i];
if (alens[i] > sizeof(abuf[i])) alens[i] = sizeof abuf[i];
__dns_parse(abuf[i], alens[i], dns_parse_callback, &ctx);
}