On Wed, Mar 03, 2021 at 05:36:12PM +0100, Theo Buehler wrote: > On Thu, Feb 25, 2021 at 09:34:30PM +0100, Tobias Heider wrote: > > Hi, > > > > while testing different x509 validator corner cases i found that a bunch of > > errors are currently not handled in libcrypto. > > > > In particular duplicate or undecodable extensions are ignored. > > The diff below sets EXFLAG_INVALID whenever X509_get_ext_d2i() returns > > an error (other than "not found") and later throws X509_V_ERR_UNSPECIFIED > > if EXFLAG_INVALID is set. > > Yes, we want this in some form. Apart from the X509_vfy bit this is a > subset of the changes in > > https://github.com/openssl/openssl/pull/10756 > > While I'd be happy to land this in a few smaller pieces, I think we want > most of those changes. In particular, I think we want to check for > EXFLAG_INVALID after all calls to x509v3_cache_extensions().
Below is an updated diff with checks for EXFLAG_INVALID after all calls to x509v3_cache_extensions(). I agree that we should also port the other changes but i'd rather do it in a follow-up diff. > > I don't currently understand why your x509_vfy change was not done (and > why they did not add a check to check_ca()). Also no idea, but they changed it again in: https://github.com/openssl/openssl/commit/33328581b83e8e9f573f08f0e2e0d6b32d095857 With this, x509v3_cache_extensions() returns (x->ex_flags & EXFLAG_INVALID) == 0 and x509_check_ca() gets a check for the return value. This change also seems like something we should consider for the future imho. Index: x509/x509_purp.c =================================================================== RCS file: /cvs/src/lib/libcrypto/x509/x509_purp.c,v retrieving revision 1.2 diff -u -p -r1.2 x509_purp.c --- x509/x509_purp.c 13 Sep 2020 15:06:17 -0000 1.2 +++ x509/x509_purp.c 13 Mar 2021 19:49:01 -0000 @@ -132,6 +132,8 @@ X509_check_purpose(X509 *x, int id, int CRYPTO_w_lock(CRYPTO_LOCK_X509); x509v3_cache_extensions(x); CRYPTO_w_unlock(CRYPTO_LOCK_X509); + if (x->ex_flags & EXFLAG_INVALID) + return X509_V_ERR_UNSPECIFIED; } if (id == -1) return 1; @@ -421,7 +423,12 @@ setup_crldp(X509 *x) { int i; - x->crldp = X509_get_ext_d2i(x, NID_crl_distribution_points, NULL, NULL); + x->crldp = X509_get_ext_d2i(x, NID_crl_distribution_points, &i, NULL); + if (x->crldp == NULL && i != -1) { + x->ex_flags |= EXFLAG_INVALID; + return; + } + for (i = 0; i < sk_DIST_POINT_num(x->crldp); i++) setup_dp(x, sk_DIST_POINT_value(x->crldp, i)); } @@ -449,7 +456,7 @@ x509v3_cache_extensions(X509 *x) x->ex_flags |= EXFLAG_V1; /* Handle basic constraints */ - if ((bs = X509_get_ext_d2i(x, NID_basic_constraints, NULL, NULL))) { + if ((bs = X509_get_ext_d2i(x, NID_basic_constraints, &i, NULL))) { if (bs->ca) x->ex_flags |= EXFLAG_CA; if (bs->pathlen) { @@ -463,10 +470,12 @@ x509v3_cache_extensions(X509 *x) x->ex_pathlen = -1; BASIC_CONSTRAINTS_free(bs); x->ex_flags |= EXFLAG_BCONS; + } else if (i != -1) { + x->ex_flags |= EXFLAG_INVALID; } /* Handle proxy certificates */ - if ((pci = X509_get_ext_d2i(x, NID_proxyCertInfo, NULL, NULL))) { + if ((pci = X509_get_ext_d2i(x, NID_proxyCertInfo, &i, NULL))) { if (x->ex_flags & EXFLAG_CA || X509_get_ext_by_NID(x, NID_subject_alt_name, -1) >= 0 || X509_get_ext_by_NID(x, NID_issuer_alt_name, -1) >= 0) { @@ -485,10 +494,12 @@ x509v3_cache_extensions(X509 *x) x->ex_pcpathlen = -1; PROXY_CERT_INFO_EXTENSION_free(pci); x->ex_flags |= EXFLAG_PROXY; + } else if (i != -1) { + x->ex_flags |= EXFLAG_INVALID; } /* Handle key usage */ - if ((usage = X509_get_ext_d2i(x, NID_key_usage, NULL, NULL))) { + if ((usage = X509_get_ext_d2i(x, NID_key_usage, &i, NULL))) { if (usage->length > 0) { x->ex_kusage = usage->data[0]; if (usage->length > 1) @@ -497,9 +508,12 @@ x509v3_cache_extensions(X509 *x) x->ex_kusage = 0; x->ex_flags |= EXFLAG_KUSAGE; ASN1_BIT_STRING_free(usage); + } else if (i != -1) { + x->ex_flags |= EXFLAG_INVALID; } + x->ex_xkusage = 0; - if ((extusage = X509_get_ext_d2i(x, NID_ext_key_usage, NULL, NULL))) { + if ((extusage = X509_get_ext_d2i(x, NID_ext_key_usage, &i, NULL))) { x->ex_flags |= EXFLAG_XKUSAGE; for (i = 0; i < sk_ASN1_OBJECT_num(extusage); i++) { switch (OBJ_obj2nid(sk_ASN1_OBJECT_value(extusage, i))) { @@ -538,19 +552,27 @@ x509v3_cache_extensions(X509 *x) } } sk_ASN1_OBJECT_pop_free(extusage, ASN1_OBJECT_free); + } else if (i != -1) { + x->ex_flags |= EXFLAG_INVALID; } - if ((ns = X509_get_ext_d2i(x, NID_netscape_cert_type, NULL, NULL))) { + if ((ns = X509_get_ext_d2i(x, NID_netscape_cert_type, &i, NULL))) { if (ns->length > 0) x->ex_nscert = ns->data[0]; else x->ex_nscert = 0; x->ex_flags |= EXFLAG_NSCERT; ASN1_BIT_STRING_free(ns); + } else if (i != -1) { + x->ex_flags |= EXFLAG_INVALID; } - x->skid = X509_get_ext_d2i(x, NID_subject_key_identifier, NULL, NULL); - x->akid = X509_get_ext_d2i(x, NID_authority_key_identifier, NULL, NULL); + x->skid = X509_get_ext_d2i(x, NID_subject_key_identifier, &i, NULL); + if (x->skid == NULL && i != -1) + x->ex_flags |= EXFLAG_INVALID; + x->akid = X509_get_ext_d2i(x, NID_authority_key_identifier, &i, NULL); + if (x->skid == NULL && i != -1) + x->ex_flags |= EXFLAG_INVALID; /* Does subject name match issuer? */ if (!X509_NAME_cmp(X509_get_subject_name(x), X509_get_issuer_name(x))) { @@ -561,7 +583,9 @@ x509v3_cache_extensions(X509 *x) x->ex_flags |= EXFLAG_SS; } - x->altname = X509_get_ext_d2i(x, NID_subject_alt_name, NULL, NULL); + x->altname = X509_get_ext_d2i(x, NID_subject_alt_name, &i, NULL); + if (x->altname == NULL && i != -1) + x->ex_flags |= EXFLAG_INVALID; x->nc = X509_get_ext_d2i(x, NID_name_constraints, &i, NULL); if (!x->nc && (i != -1)) x->ex_flags |= EXFLAG_INVALID; @@ -626,6 +650,8 @@ X509_check_ca(X509 *x) CRYPTO_w_lock(CRYPTO_LOCK_X509); x509v3_cache_extensions(x); CRYPTO_w_unlock(CRYPTO_LOCK_X509); + if (x->ex_flags & EXFLAG_INVALID) + return X509_V_ERR_UNSPECIFIED; } return check_ca(x); @@ -837,7 +863,11 @@ X509_check_issued(X509 *issuer, X509 *su X509_get_issuer_name(subject))) return X509_V_ERR_SUBJECT_ISSUER_MISMATCH; x509v3_cache_extensions(issuer); + if (issuer->ex_flags & EXFLAG_INVALID) + return X509_V_ERR_UNSPECIFIED; x509v3_cache_extensions(subject); + if (subject->ex_flags & EXFLAG_INVALID) + return X509_V_ERR_UNSPECIFIED; if (subject->akid) { int ret = X509_check_akid(issuer, subject->akid); Index: x509/x509_verify.c =================================================================== RCS file: /cvs/src/lib/libcrypto/x509/x509_verify.c,v retrieving revision 1.35 diff -u -p -r1.35 x509_verify.c --- x509/x509_verify.c 12 Mar 2021 15:53:38 -0000 1.35 +++ x509/x509_verify.c 13 Mar 2021 19:49:01 -0000 @@ -756,6 +756,10 @@ x509_verify_cert_extensions(struct x509_ CRYPTO_w_lock(CRYPTO_LOCK_X509); x509v3_cache_extensions(cert); CRYPTO_w_unlock(CRYPTO_LOCK_X509); + if (cert->ex_flags & EXFLAG_INVALID) { + ctx->error = X509_V_ERR_UNSPECIFIED; + return 0; + } } if (ctx->xsc != NULL)
