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Merge pull request #18587 from poettering/rr-count-workaround

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two fixes for handling misformed packets more gracefully.
This commit is contained in:
Yu Watanabe
2021-02-15 10:55:10 +09:00
committed by GitHub
parent d711322c13 894c7b7708
commit fcf99d0ec7
1 changed files with 21 additions and 1 deletions
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src/resolve/resolved-dns-packet.c
+21 -1
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@@ -2253,6 +2253,18 @@ static int dns_packet_extract_answer(DnsPacket *p, DnsAnswer **ret_answer) {
bool cache_flush = false;
size_t start;
if (p->rindex == p->size) {
/* If we reached the end of the packet already, but there are still more RRs
* declared, then that's a corrupt packet. Let's accept the packet anyway, since it's
* apparently a common bug in routers. Let's however suppress OPT support in this
* case, so that we force the rest of the logic into lowest DNS baseline support. Or
* to say this differently: if the DNS server doesn't even get the RR counts right,
* it's highly unlikely it gets EDNS right. */
log_debug("More resource records declared in packet than included, suppressing OPT.");
bad_opt = true;
break;
}
r = dns_packet_read_rr(p, &rr, &cache_flush, &start);
if (r < 0)
return r;
@@ -2352,8 +2364,10 @@ static int dns_packet_extract_answer(DnsPacket *p, DnsAnswer **ret_answer) {
previous = dns_resource_record_ref(rr);
}
if (bad_opt)
if (bad_opt) {
p->opt = dns_resource_record_unref(p->opt);
p->opt_start = p->opt_size = SIZE_MAX;
}
*ret_answer = TAKE_PTR(answer);
@@ -2380,6 +2394,12 @@ int dns_packet_extract(DnsPacket *p) {
if (r < 0)
return r;
if (p->rindex < p->size) {
log_debug("Trailing garbage in packet, suppressing OPT.");
p->opt = dns_resource_record_unref(p->opt);
p->opt_start = p->opt_size = SIZE_MAX;
}
p->question = TAKE_PTR(question);
p->answer = TAKE_PTR(answer);