[Standard] Bound-check RR parsing in dns_get_mx() answer loop - #295
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[Standard] Bound-check RR parsing in dns_get_mx() answer loop#295iliaal wants to merge 1 commit into
iliaal wants to merge 1 commit into
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The dns_get_mx() answer loop parsed records with raw GETSHORT() after unvalidated dn_skipname() advances, so a reply whose last record name ends exactly at end of buffer made the type/class/ttl/rdlength and weight reads run up to ~12 bytes past the 64K querybuf stack union. Guard the fixed-size header fields the same way php_parserr() does with CHECKCP(10)/CHECKCP(2); rdata skips remain bounded by the cp < end loop condition and dn_skipname()'s own eom check. Sibling audit: every other GETSHORT()/dn_expand() walk lives inside php_parserr(), which is already CHECKCP-guarded on all paths.
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The dns_get_mx() answer loop parsed answer records with raw GETSHORT() reads after unvalidated dn_skipname() advances and no CHECKCP guards, so a crafted DNS reply whose last record name ends exactly at the end of the response buffer made the type/class/ttl/rdlength and weight reads run up to about 12 bytes past the end of the 64K querybuf stack union. This adds explicit bounds guards mirroring php_parserr()'s CHECKCP(10) and CHECKCP(2) checks before the fixed-size field reads; rdata skips stay bounded by the cp < end loop condition and dn_skipname()'s own eom check. Sibling audit found every other GETSHORT()/dn_expand() walk confined to php_parserr(), which is already guarded on all paths. No .phpt is shipped because a red test would need an LD_PRELOAD resolver mock serving a truncated hostile reply, which is not portable under run-tests.php; this is a code-inspection fix.