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unbound: Fix CVE-2025-5994

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A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been
discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is
also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND
configured to send ECS information along with queries to upstream name servers

CVE: CVE-2025-5994

Signed-off-by: Naman Jain <namanj1@kpit.com>
Signed-off-by: Anuj Mittal <anuj.mittal@oss.qualcomm.com>
This commit is contained in:
Naman Jain
2025-11-04 15:22:56 +05:30
committed by Anuj Mittal
parent ed7365bfad
commit 30dafc3958
2 changed files with 276 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
meta-networking/recipes-support/unbound/unbound/CVE-2025-5994.patch
+275
View File
@@ -0,0 +1,275 @@
Backport of:
From 5bf82f246481098a6473f296b21fc1229d276c0f Mon Sep 17 00:00:00 2001
From: "W.C.A. Wijngaards" <wouter@nlnetlabs.nl>
Date: Wed, 16 Jul 2025 10:02:01 +0200
Subject: [PATCH] - Fix RebirthDay Attack CVE-2025-5994, reported by Xiang Li
from AOSP Lab Nankai University.
CVE: CVE-2025-5994
Upstream-Status: Backport [https://github.com/NLnetLabs/unbound/commit/5bf82f246481098a6473f296b21fc1229d276c0f]
Signed-off-by: Naman Jain <namanj1@kpit.com>
---
edns-subnet/subnetmod.c | 152 ++++++++++++++++++++++++++++++++++++----
edns-subnet/subnetmod.h | 4 ++
2 files changed, 142 insertions(+), 14 deletions(-)
--- a/edns-subnet/subnetmod.c
+++ b/edns-subnet/subnetmod.c
@@ -51,6 +51,7 @@
#include "services/cache/dns.h"
#include "util/module.h"
#include "util/regional.h"
+#include "util/fptr_wlist.h"
#include "util/storage/slabhash.h"
#include "util/config_file.h"
#include "util/data/msgreply.h"
@@ -152,7 +153,8 @@ int ecs_whitelist_check(struct query_inf
/* Cache by default, might be disabled after parsing EDNS option
* received from nameserver. */
- if(!iter_stub_fwd_no_cache(qstate, &qstate->qinfo, NULL, NULL)) {
+ if(!iter_stub_fwd_no_cache(qstate, &qstate->qinfo, NULL, NULL)
+ && sq->ecs_client_in.subnet_validdata) {
qstate->no_cache_store = 0;
}
@@ -504,6 +506,69 @@ common_prefix(uint8_t *a, uint8_t *b, ui
return !memcmp(a, b, n) && ((net % 8) == 0 || a[n] == b[n]);
}
+/**
+ * Create sub request that looks up the query.
+ * @param qstate: query state
+ * @param sq: subnet qstate
+ * @return false on failure.
+ */
+static int
+generate_sub_request(struct module_qstate *qstate, struct subnet_qstate* sq)
+{
+ struct module_qstate* subq = NULL;
+ uint16_t qflags = 0; /* OPCODE QUERY, no flags */
+ int prime = 0;
+ int valrec = 0;
+ struct query_info qinf;
+ qinf.qname = qstate->qinfo.qname;
+ qinf.qname_len = qstate->qinfo.qname_len;
+ qinf.qtype = qstate->qinfo.qtype;
+ qinf.qclass = qstate->qinfo.qclass;
+ qinf.local_alias = NULL;
+
+ qflags |= BIT_RD;
+ if((qstate->query_flags & BIT_CD)!=0) {
+ qflags |= BIT_CD;
+ valrec = 1;
+ }
+
+ fptr_ok(fptr_whitelist_modenv_attach_sub(qstate->env->attach_sub));
+ if(!(*qstate->env->attach_sub)(qstate, &qinf, qflags, prime, valrec,
+ &subq)) {
+ return 0;
+ }
+ if(subq) {
+ /* It is possible to access the subquery module state. */
+ if(sq->ecs_client_in.subnet_source_mask == 0 &&
+ edns_opt_list_find(qstate->edns_opts_front_in,
+ qstate->env->cfg->client_subnet_opcode)) {
+ subq->no_cache_store = 1;
+ }
+ }
+ return 1;
+}
+
+/**
+ * Perform the query without subnet
+ * @param qstate: query state
+ * @param sq: subnet qstate
+ * @return module state
+ */
+static enum module_ext_state
+generate_lookup_without_subnet(struct module_qstate *qstate,
+ struct subnet_qstate* sq)
+{
+ verbose(VERB_ALGO, "subnetcache: make subquery to look up without subnet");
+ if(!generate_sub_request(qstate, sq)) {
+ verbose(VERB_ALGO, "Could not generate sub query");
+ qstate->return_rcode = LDNS_RCODE_FORMERR;
+ qstate->return_msg = NULL;
+ return module_finished;
+ }
+ sq->wait_subquery = 1;
+ return module_wait_subquery;
+}
+
static enum module_ext_state
eval_response(struct module_qstate *qstate, int id, struct subnet_qstate *sq)
{
@@ -539,14 +604,7 @@ eval_response(struct module_qstate *qsta
* is still useful to put it in the edns subnet cache for
* when a client explicitly asks for subnet specific answer. */
verbose(VERB_QUERY, "subnetcache: Authority indicates no support");
- if(!sq->started_no_cache_store) {
- lock_rw_wrlock(&sne->biglock);
- update_cache(qstate, id);
- lock_rw_unlock(&sne->biglock);
- }
- if (sq->subnet_downstream)
- cp_edns_bad_response(c_out, c_in);
- return module_finished;
+ return generate_lookup_without_subnet(qstate, sq);
}
/* Purposefully there was no sent subnet, and there is consequently
@@ -571,14 +629,14 @@ eval_response(struct module_qstate *qsta
!common_prefix(s_out->subnet_addr, s_in->subnet_addr,
s_out->subnet_source_mask))
{
- /* we can not accept, restart query without option */
+ /* we can not accept, perform query without option */
verbose(VERB_QUERY, "subnetcache: forged data");
s_out->subnet_validdata = 0;
(void)edns_opt_list_remove(&qstate->edns_opts_back_out,
qstate->env->cfg->client_subnet_opcode);
sq->subnet_sent = 0;
sq->subnet_sent_no_subnet = 0;
- return module_restart_next;
+ return generate_lookup_without_subnet(qstate, sq);
}
lock_rw_wrlock(&sne->biglock);
@@ -763,6 +821,9 @@ ecs_edns_back_parsed(struct module_qstat
} else if(sq->subnet_sent_no_subnet) {
/* The answer can be stored as scope 0, not in global cache. */
qstate->no_cache_store = 1;
+ } else if(sq->subnet_sent) {
+ /* Need another query to be able to store in global cache. */
+ qstate->no_cache_store = 1;
}
return 1;
@@ -780,6 +841,32 @@ subnetmod_operate(struct module_qstate *
strmodulevent(event));
log_query_info(VERB_QUERY, "subnetcache operate: query", &qstate->qinfo);
+ if(sq && sq->wait_subquery_done) {
+ /* The subquery lookup returned. */
+ if(sq->ecs_client_in.subnet_source_mask == 0 &&
+ edns_opt_list_find(qstate->edns_opts_front_in,
+ qstate->env->cfg->client_subnet_opcode)) {
+ if(!sq->started_no_cache_store &&
+ qstate->return_msg) {
+ lock_rw_wrlock(&sne->biglock);
+ update_cache(qstate, id);
+ lock_rw_unlock(&sne->biglock);
+ }
+ if (sq->subnet_downstream)
+ cp_edns_bad_response(&sq->ecs_client_out,
+ &sq->ecs_client_in);
+ /* It is a scope zero lookup, append edns subnet
+ * option to the querier. */
+ subnet_ecs_opt_list_append(&sq->ecs_client_out,
+ &qstate->edns_opts_front_out, qstate,
+ qstate->region);
+ }
+ sq->wait_subquery_done = 0;
+ qstate->ext_state[id] = module_finished;
+ qstate->no_cache_store = sq->started_no_cache_store;
+ qstate->no_cache_lookup = sq->started_no_cache_lookup;
+ return;
+ }
if((event == module_event_new || event == module_event_pass) &&
sq == NULL) {
struct edns_option* ecs_opt;
@@ -790,6 +877,8 @@ subnetmod_operate(struct module_qstate *
}
sq = (struct subnet_qstate*)qstate->minfo[id];
+ if(sq->wait_subquery)
+ return; /* Wait for that subquery to return */
if((ecs_opt = edns_opt_list_find(
qstate->edns_opts_front_in,
@@ -819,6 +908,14 @@ subnetmod_operate(struct module_qstate *
/* No clients are interested in result or we could not
* parse it, we don't do client subnet */
sq->ecs_server_out.subnet_validdata = 0;
+ if(edns_opt_list_find(qstate->edns_opts_front_in,
+ qstate->env->cfg->client_subnet_opcode)) {
+ /* aggregated this deaggregated state */
+ qstate->ext_state[id] =
+ generate_lookup_without_subnet(
+ qstate, sq);
+ return;
+ }
verbose(VERB_ALGO, "subnetcache: pass to next module");
qstate->ext_state[id] = module_wait_module;
return;
@@ -859,6 +956,14 @@ subnetmod_operate(struct module_qstate *
}
lock_rw_unlock(&sne->biglock);
}
+ if(sq->ecs_client_in.subnet_source_mask == 0 &&
+ edns_opt_list_find(qstate->edns_opts_front_in,
+ qstate->env->cfg->client_subnet_opcode)) {
+ /* client asked for resolution without edns subnet */
+ qstate->ext_state[id] = generate_lookup_without_subnet(
+ qstate, sq);
+ return;
+ }
sq->ecs_server_out.subnet_addr_fam =
sq->ecs_client_in.subnet_addr_fam;
@@ -895,6 +1000,8 @@ subnetmod_operate(struct module_qstate *
qstate->ext_state[id] = module_wait_module;
return;
}
+ if(sq && sq->wait_subquery)
+ return; /* Wait for that subquery to return */
/* Query handed back by next module, we have a 'final' answer */
if(sq && event == module_event_moddone) {
qstate->ext_state[id] = eval_response(qstate, id, sq);
@@ -943,10 +1050,27 @@ subnetmod_clear(struct module_qstate *AT
}
void
-subnetmod_inform_super(struct module_qstate *ATTR_UNUSED(qstate),
- int ATTR_UNUSED(id), struct module_qstate *ATTR_UNUSED(super))
+subnetmod_inform_super(struct module_qstate *qstate, int id,
+ struct module_qstate *super)
{
- /* Not used */
+ struct subnet_qstate* super_sq =
+ (struct subnet_qstate*)super->minfo[id];
+ log_query_info(VERB_ALGO, "subnetcache inform_super: query",
+ &super->qinfo);
+ super_sq->wait_subquery = 0;
+ super_sq->wait_subquery_done = 1;
+ if(qstate->return_rcode != LDNS_RCODE_NOERROR ||
+ !qstate->return_msg) {
+ super->return_msg = NULL;
+ super->return_rcode = LDNS_RCODE_SERVFAIL;
+ return;
+ }
+ super->return_rcode = LDNS_RCODE_NOERROR;
+ super->return_msg = dns_copy_msg(qstate->return_msg, super->region);
+ if(!super->return_msg) {
+ log_err("subnetcache: copy response, out of memory");
+ super->return_rcode = LDNS_RCODE_SERVFAIL;
+ }
}
size_t
--- a/edns-subnet/subnetmod.h
+++ b/edns-subnet/subnetmod.h
@@ -102,6 +102,10 @@ struct subnet_qstate {
int started_no_cache_store;
/** has the subnet module been started with no_cache_lookup? */
int started_no_cache_lookup;
+ /** Wait for subquery that has been started for nonsubnet lookup. */
+ int wait_subquery;
+ /** The subquery waited for is done. */
+ int wait_subquery_done;
};
void subnet_data_delete(void* d, void* ATTR_UNUSED(arg));
meta-networking/recipes-support/unbound/unbound_1.19.3.bb
+1
View File
@@ -16,6 +16,7 @@ SRC_URI = "git://github.com/NLnetLabs/unbound.git;protocol=https;nobranch=1 \
file://CVE-2024-43167.patch \
file://CVE-2024-43168_1.patch \
file://CVE-2024-43168_2.patch \
file://CVE-2025-5994.patch \
"
SRCREV = "48b6c60a24e9a5d6d369a7a37c9fe2a767f26abd"