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BUG/MEDIUM: DNS resolution response parsing broken

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In some cases, parsing of the DNS response is broken and the response is
considered as invalid, despite being valid.

The current patch fixes this issue. It's a temporary solution until I
rework the response parsing to store the response buffer into a real DNS
packet structure.
This commit is contained in:
Baptiste Assmann 2015-08-07 11:24:05 +02:00 committed by Willy Tarreau
parent 37bb372ea2
commit 2359ff1de2
1 changed files with 23 additions and 23 deletions
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26
src/dns.c
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@ -462,6 +462,7 @@ int dns_validate_dns_response(unsigned char *resp, unsigned char *bufend, char *
}
/* ptr now points to the name */
if ((*reader & 0xc0) != 0xc0) {
/* if cname is set, it means a CNAME recursion is in progress */
if (cname) {
/* check if the name can stand in response */
@ -470,6 +471,12 @@ int dns_validate_dns_response(unsigned char *resp, unsigned char *bufend, char *
/* compare cname and current name */
if (memcmp(ptr, cname, cnamelen) != 0)
return DNS_RESP_CNAME_ERROR;
cname = reader;
cnamelen = dns_str_to_dn_label_len((const char *)cname);
/* move forward cnamelen bytes + NULL byte */
reader += (cnamelen + 1);
}
/* compare server hostname to current name */
else if (dn_name) {
@ -479,23 +486,16 @@ int dns_validate_dns_response(unsigned char *resp, unsigned char *bufend, char *
if (memcmp(ptr, dn_name, dn_name_len) != 0)
return DNS_RESP_WRONG_NAME;
}
if ((*reader & 0xc0) == 0xc0) {
/* move forward 2 bytes for information pointer and address pointer */
reader += 2;
}
else {
if (cname) {
cname = reader;
cnamelen = dns_str_to_dn_label_len((const char *)cname);
/* move forward cnamelen bytes + NULL byte */
reader += (cnamelen + 1);
}
else {
reader += (len + 1);
}
}
else {
/* shortname in progress */
/* move forward 2 bytes for information pointer and address pointer */
reader += 2;
}
if (reader >= bufend)
return DNS_RESP_INVALID;