Date: Wed, 26 Nov 2025 16:01:01 +0000 From: Gordon Tetlow <gordon@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: cd40a23fb249 - stable/14 - Mitigate YXDOMAIN and nodata non-referral answer poisoning. Message-ID: <6927243d.33e2b.2163aabb@gitrepo.freebsd.org>
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The branch stable/14 has been updated by gordon: URL: https://cgit.FreeBSD.org/src/commit/?id=cd40a23fb249bba461e38ca0c3d243a20a12eef4 commit cd40a23fb249bba461e38ca0c3d243a20a12eef4 Author: Gordon Tetlow <gordon@FreeBSD.org> AuthorDate: 2025-11-21 21:24:58 +0000 Commit: Gordon Tetlow <gordon@FreeBSD.org> CommitDate: 2025-11-26 16:00:45 +0000 Mitigate YXDOMAIN and nodata non-referral answer poisoning. Add a fix to apply scrubbing of unsolicited NS RRSets (and their respective address records) for YXDOMAIN and nodata non-referral answers. This prevents a malicious actor from exploiting a possible cache poison attack. Obtained from: NLnet Labs Security: FreeBSD-SA-25:10.unbound Security: CVE-2025-11411 (cherry picked from commit 2a3a6a1771148a709c2d9694c1d66c41ce8dee79) --- contrib/unbound/iterator/iter_scrub.c | 39 +++++++++++++++++++++++++++++++---- 1 file changed, 35 insertions(+), 4 deletions(-) diff --git a/contrib/unbound/iterator/iter_scrub.c b/contrib/unbound/iterator/iter_scrub.c index 553d3655f0e3..8507a3fb65ac 100644 --- a/contrib/unbound/iterator/iter_scrub.c +++ b/contrib/unbound/iterator/iter_scrub.c @@ -418,12 +418,13 @@ shorten_rrset(sldns_buffer* pkt, struct rrset_parse* rrset, int count) * @param qinfo: original query. * @param region: where to allocate synthesized CNAMEs. * @param env: module env with config options. + * @param zonename: name of server zone. * @return 0 on error. */ static int scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg, struct query_info* qinfo, struct regional* region, - struct module_env* env) + struct module_env* env, uint8_t* zonename) { uint8_t* sname = qinfo->qname; size_t snamelen = qinfo->qname_len; @@ -431,7 +432,8 @@ scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg, int cname_length = 0; /* number of CNAMEs, or DNAMEs */ if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR && - FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN) + FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NXDOMAIN && + FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_YXDOMAIN) return 1; /* For the ANSWER section, remove all "irrelevant" records and add @@ -470,6 +472,11 @@ scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg, &aliaslen, pkt)) { verbose(VERB_ALGO, "synthesized CNAME " "too long"); + if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_YXDOMAIN) { + prev = rrset; + rrset = rrset->rrset_all_next; + continue; + } return 0; } cname_length++; @@ -650,6 +657,29 @@ scrub_normalize(sldns_buffer* pkt, struct msg_parse* msg, "RRset:", pkt, msg, prev, &rrset); continue; } + /* Also delete promiscuous NS for other RCODEs */ + if(FLAGS_GET_RCODE(msg->flags) != LDNS_RCODE_NOERROR + && env->cfg->iter_scrub_promiscuous) { + remove_rrset("normalize: removing promiscuous " + "RRset:", pkt, msg, prev, &rrset); + continue; + } + /* Also delete promiscuous NS for NOERROR with nodata + * for authoritative answers, not for delegations. + * NOERROR with an_rrsets!=0 already handled. + * Also NOERROR and soa_in_auth already handled. + * NOERROR with an_rrsets==0, and not a referral. + * referral is (NS not the zonename, noSOA). + */ + if(FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR + && msg->an_rrsets == 0 + && !(dname_pkt_compare(pkt, rrset->dname, + zonename) != 0 && !soa_in_auth(msg)) + && env->cfg->iter_scrub_promiscuous) { + remove_rrset("normalize: removing promiscuous " + "RRset:", pkt, msg, prev, &rrset); + continue; + } if(nsset == NULL) { nsset = rrset; } else { @@ -1060,7 +1090,8 @@ scrub_message(sldns_buffer* pkt, struct msg_parse* msg, /* this is not required for basic operation but is a forgery * resistance (security) feature */ if((FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NOERROR || - FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN) && + FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_NXDOMAIN || + FLAGS_GET_RCODE(msg->flags) == LDNS_RCODE_YXDOMAIN) && msg->qdcount == 0) return 0; @@ -1074,7 +1105,7 @@ scrub_message(sldns_buffer* pkt, struct msg_parse* msg, } /* normalize the response, this cleans up the additional. */ - if(!scrub_normalize(pkt, msg, qinfo, region, env)) + if(!scrub_normalize(pkt, msg, qinfo, region, env, zonename)) return 0; /* delete all out-of-zone information */ if(!scrub_sanitize(pkt, msg, qinfo, zonename, env, ie, qstate))help
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