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Always nul-terminate the result passed to evdns_server_add_ptr_reply
In dnsserv_resolved(), we carefully made a nul-terminated copy of the answer in a PTR RESOLVED cell... then never used that nul-terminated copy. Ouch. Surprisingly this one isn't as huge a security problem as it could be. The only place where the input to dnsserv_resolved wasn't necessarily nul-terminated was when it was called indirectly from relay.c with the contents of a relay cell's payload. If the end of the payload was filled with junk, eventdns.c would take the strdup() of the name [This part is bad; we might crash there if the cell is in a bad part of the stack or the heap] and get a name of at least length 495[*]. eventdns.c then rejects any name of length over 255, so the bogus data would be neither transmitted nor altered. [*] If the name was less than 495 bytes long, the client wouldn't actually be reading off the end of the cell. Nonetheless this is a reasonably annoying bug. Better fix it. Found while looking at bug 2332, reported by doorss. Bugfix on 0.2.0.1-alpha.
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o Minor bugfixes
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- Fix a bug with handling misformed replies to reverse DNS lookup
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requests in DNSPort. Bugfix on Tor 0.2.0.1-alpha. Related to a bug
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reported by doorss.
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@ -275,7 +275,7 @@ dnsserv_resolved(edge_connection_t *conn,
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char *ans = tor_strndup(answer, answer_len);
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evdns_server_request_add_ptr_reply(req, NULL,
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name,
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(char*)answer, ttl);
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ans, ttl);
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tor_free(ans);
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} else if (answer_type == RESOLVED_TYPE_ERROR) {
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err = DNS_ERR_NOTEXIST;
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