From 64130ede5cd8f61edd35a1b488c874fa328a42b0 Mon Sep 17 00:00:00 2001 From: Tobias Brunner Date: Mon, 23 Mar 2026 18:02:19 +0100 Subject: [PATCH] constraints: Reject excluded directoryName (DN) name constraints There is an issue similar to the one fixed with the previous commit when using directoryName (DN) name constraints. Some RDNs have to be matched in a case-insensitive manner, which we e.g. do in `identification.c::rdn_equals`. By not doing it for name constraints, a malicious intermediate CA could evade an excluded name constraint just by modifying the case in such an RDN. While we could use the mentioned function in `dn_matches`, this doesn't properly fix the problem because the function is basically too strict. Especially in regards to RDNs of type UTF8String, which are only compared binary. To match these properly, we'd have to implement the string preparation described in RFC 5280, section 7.1 and the referenced RFCs. Until that's the case, we reject excluded name constraints of type directoryName as we are unable to enforce them. Fixes: a2b340764fac ("Implemented NameConstraint matching in constraints plugin") Fixes: CVE-2026-35331 --- .../plugins/constraints/constraints_validator.c | 10 +++++++++- src/libstrongswan/tests/suites/test_certnames.c | 12 ++++++------ 2 files changed, 15 insertions(+), 7 deletions(-) diff --git a/src/libstrongswan/plugins/constraints/constraints_validator.c b/src/libstrongswan/plugins/constraints/constraints_validator.c index cf12ca4e7..1f55d115b 100644 --- a/src/libstrongswan/plugins/constraints/constraints_validator.c +++ b/src/libstrongswan/plugins/constraints/constraints_validator.c @@ -401,9 +401,17 @@ static bool collect_constraints(x509_t *x509, bool permitted, hashtable_t **out) type = constraint->get_type(constraint); switch (type) { + case ID_DER_ASN1_DN: + if (!permitted) + { + DBG1(DBG_CFG, "excluded %N NameConstraint not supported", + id_type_names, type); + success = FALSE; + break; + } + /* fall-through */ case ID_FQDN: case ID_RFC822_ADDR: - case ID_DER_ASN1_DN: case ID_IPV4_ADDR_SUBNET: case ID_IPV6_ADDR_SUBNET: break; diff --git a/src/libstrongswan/tests/suites/test_certnames.c b/src/libstrongswan/tests/suites/test_certnames.c index 7773f8d47..14570eedf 100644 --- a/src/libstrongswan/tests/suites/test_certnames.c +++ b/src/libstrongswan/tests/suites/test_certnames.c @@ -253,11 +253,11 @@ static struct { char *subject; bool good; } excluded_dn[] = { - { "C=CH, O=another", "C=CH, O=strongSwan, CN=tester", TRUE }, - { "C=CH, O=another", "C=CH, O=anot", TRUE }, - { "C=CH, O=another", "C=CH, O=anot, CN=tester", TRUE }, + { "C=CH, O=another", "C=CH, O=strongSwan, CN=tester", FALSE }, + { "C=CH, O=another", "C=CH, O=anot", FALSE }, + { "C=CH, O=another", "C=CH, O=anot, CN=tester", FALSE }, { "C=CH, O=another", "C=CH, O=another, CN=tester", FALSE }, - { "C=CH, O=another", "C=CH, CN=tester, O=another", TRUE }, + { "C=CH, O=another", "C=CH, CN=tester, O=another", FALSE }, }; START_TEST(test_excluded_dn) @@ -427,9 +427,9 @@ static struct { char *subject; bool good; } excluded_dn_levels[] = { - { "C=CH, O=strongSwan", "C=CH", "C=DE", TRUE }, + { "C=CH, O=strongSwan", "C=CH", "C=DE", FALSE }, { "C=CH, O=strongSwan", "C=CH", "C=CH", FALSE }, - { "C=CH, O=strongSwan", "C=DE", "C=CH", TRUE }, + { "C=CH, O=strongSwan", "C=DE", "C=CH", FALSE }, { "C=CH, O=strongSwan", "C=DE", "C=DE", FALSE }, { "C=CH, O=strongSwan", "C=DE", "C=CH, O=strongSwan", FALSE }, { NULL, "C=CH", "C=CH, O=strongSwan", FALSE },