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-rw-r--r--crypto/x509/x509_lcl.h1
-rw-r--r--crypto/x509/x509_txt.c6
-rw-r--r--crypto/x509/x509_vfy.c160
-rw-r--r--crypto/x509/x509_vpm.c17
4 files changed, 158 insertions, 26 deletions
diff --git a/crypto/x509/x509_lcl.h b/crypto/x509/x509_lcl.h
index 0726201e8f..603c17737f 100644
--- a/crypto/x509/x509_lcl.h
+++ b/crypto/x509/x509_lcl.h
@@ -70,6 +70,7 @@ struct X509_VERIFY_PARAM_st {
int purpose; /* purpose to check untrusted certificates */
int trust; /* trust setting to check */
int depth; /* Verify depth */
+ int auth_level; /* Security level for chain verification */
STACK_OF(ASN1_OBJECT) *policies; /* Permissible policies */
/* Peer identity details */
STACK_OF(OPENSSL_STRING) *hosts; /* Set of acceptable names */
diff --git a/crypto/x509/x509_txt.c b/crypto/x509/x509_txt.c
index f7f27e97ef..8a9a7f0444 100644
--- a/crypto/x509/x509_txt.c
+++ b/crypto/x509/x509_txt.c
@@ -203,6 +203,12 @@ const char *X509_verify_cert_error_string(long n)
return ("IP address mismatch");
case X509_V_ERR_DANE_NO_MATCH:
return ("No matching DANE TLSA records");
+ case X509_V_ERR_EE_KEY_TOO_SMALL:
+ return ("EE certificate key too weak");
+ case X509_V_ERR_CA_KEY_TOO_SMALL:
+ return ("CA certificate key too weak");
+ case X509_V_ERR_CA_MD_TOO_WEAK:
+ return ("CA signature digest algorithm too weak");
default:
/* Printing an error number into a static buffer is not thread-safe */
diff --git a/crypto/x509/x509_vfy.c b/crypto/x509/x509_vfy.c
index 92f1c5c447..10fbeeff6d 100644
--- a/crypto/x509/x509_vfy.c
+++ b/crypto/x509/x509_vfy.c
@@ -126,6 +126,8 @@ static int check_cert(X509_STORE_CTX *ctx);
static int check_policy(X509_STORE_CTX *ctx);
static int get_issuer_sk(X509 **issuer, X509_STORE_CTX *ctx, X509 *x);
static int check_dane_issuer(X509_STORE_CTX *ctx, int depth);
+static int check_key_level(X509_STORE_CTX *ctx, X509 *cert);
+static int check_sig_level(X509_STORE_CTX *ctx, X509 *cert);
static int get_crl_score(X509_STORE_CTX *ctx, X509 **pissuer,
unsigned int *preasons, X509_CRL *crl, X509 *x);
@@ -221,6 +223,35 @@ static int verify_cb_crl(X509_STORE_CTX *ctx, int err)
return ctx->verify_cb(0, ctx);
}
+static int check_auth_level(X509_STORE_CTX *ctx)
+{
+ int i;
+ int num = sk_X509_num(ctx->chain);
+
+ if (ctx->param->auth_level <= 0)
+ return 1;
+
+ for (i = 0; i < num; ++i) {
+ X509 *cert = sk_X509_value(ctx->chain, i);
+
+ /*
+ * We've already checked the security of the leaf key, so here we only
+ * check the security of issuer keys.
+ */
+ if (i > 0 && !check_key_level(ctx, cert) &&
+ verify_cb_cert(ctx, cert, i, X509_V_ERR_CA_KEY_TOO_SMALL) == 0)
+ return 0;
+ /*
+ * We also check the signature algorithm security of all certificates
+ * except those of the trust anchor at index num-1.
+ */
+ if (i < num - 1 && !check_sig_level(ctx, cert) &&
+ verify_cb_cert(ctx, cert, i, X509_V_ERR_CA_MD_TOO_WEAK) == 0)
+ return 0;
+ }
+ return 1;
+}
+
static int verify_chain(X509_STORE_CTX *ctx)
{
int err;
@@ -232,6 +263,7 @@ static int verify_chain(X509_STORE_CTX *ctx)
*/
if ((ok = build_chain(ctx)) == 0 ||
(ok = check_chain_extensions(ctx)) == 0 ||
+ (ok = check_auth_level(ctx)) == 0 ||
(ok = check_name_constraints(ctx)) == 0 ||
(ok = check_id(ctx)) == 0 || 1)
X509_get_pubkey_parameters(NULL, ctx->chain);
@@ -294,6 +326,11 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
X509_up_ref(ctx->cert);
ctx->num_untrusted = 1;
+ /* If the peer's public key is too weak, we can stop early. */
+ if (!check_key_level(ctx, ctx->cert) &&
+ !verify_cb_cert(ctx, ctx->cert, 0, X509_V_ERR_EE_KEY_TOO_SMALL))
+ return 0;
+
/*
* If dane->trecs is an empty stack, we'll fail, since the user enabled
* DANE. If none of the TLSA records were usable, and it makes sense to
@@ -308,20 +345,19 @@ int X509_verify_cert(X509_STORE_CTX *ctx)
/*
* Given a STACK_OF(X509) find the issuer of cert (if any)
*/
-
static X509 *find_issuer(X509_STORE_CTX *ctx, STACK_OF(X509) *sk, X509 *x)
{
int i;
- X509 *issuer, *rv = NULL;;
+
for (i = 0; i < sk_X509_num(sk); i++) {
- issuer = sk_X509_value(sk, i);
- if (ctx->check_issued(ctx, x, issuer)) {
- rv = issuer;
- if (x509_check_cert_time(ctx, rv, -1))
- break;
- }
+ X509 *issuer = sk_X509_value(sk, i);
+
+ if (!ctx->check_issued(ctx, x, issuer))
+ continue;
+ if (x509_check_cert_time(ctx, issuer, -1))
+ return issuer;
}
- return rv;
+ return NULL;
}
/* Given a possible certificate and issuer check them */
@@ -2656,6 +2692,19 @@ static int dane_verify(X509_STORE_CTX *ctx)
return verify_chain(ctx);
}
+/* Get issuer, without duplicate suppression */
+static int get_issuer(X509 **issuer, X509_STORE_CTX *ctx, X509 *cert)
+{
+ STACK_OF(X509) *saved_chain = ctx->chain;
+ int ok;
+
+ ctx->chain = NULL;
+ ok = ctx->get_issuer(issuer, ctx, cert);
+ ctx->chain = saved_chain;
+
+ return ok;
+}
+
static int build_chain(X509_STORE_CTX *ctx)
{
struct dane_st *dane = (struct dane_st *)ctx->dane;
@@ -2735,12 +2784,19 @@ static int build_chain(X509_STORE_CTX *ctx)
/*
* Look in the trust store if enabled for first lookup, or we've run
- * out of untrusted issuers and search here is not disabled. When
- * we exceed the depth limit, we simulate absence of a match.
+ * out of untrusted issuers and search here is not disabled. When we
+ * reach the depth limit, we stop extending the chain, if by that point
+ * we've not found a trust-anchor, any trusted chain would be too long.
+ *
+ * The error reported to the application verify callback is at the
+ * maximal valid depth with the current certificate equal to the last
+ * not ultimately-trusted issuer. For example, with verify_depth = 0,
+ * the callback will report errors at depth=1 when the immediate issuer
+ * of the leaf certificate is not a trust anchor. No attempt will be
+ * made to locate an issuer for that certificate, since such a chain
+ * would be a-priori too long.
*/
if ((search & S_DOTRUSTED) != 0) {
- STACK_OF(X509) *hide = ctx->chain;
-
i = num = sk_X509_num(ctx->chain);
if ((search & S_DOALTERNATE) != 0) {
/*
@@ -2762,10 +2818,7 @@ static int build_chain(X509_STORE_CTX *ctx)
}
x = sk_X509_value(ctx->chain, i-1);
- /* Suppress duplicate suppression */
- ctx->chain = NULL;
- ok = (depth < num) ? 0 : ctx->get_issuer(&xtmp, ctx, x);
- ctx->chain = hide;
+ ok = (depth < num) ? 0 : get_issuer(&xtmp, ctx, x);
if (ok < 0) {
trust = X509_TRUST_REJECTED;
@@ -2892,12 +2945,12 @@ static int build_chain(X509_STORE_CTX *ctx)
num = sk_X509_num(ctx->chain);
OPENSSL_assert(num == ctx->num_untrusted);
x = sk_X509_value(ctx->chain, num-1);
- xtmp = (depth < num) ? NULL : find_issuer(ctx, sktmp, x);
/*
* Once we run out of untrusted issuers, we stop looking for more
* and start looking only in the trust store if enabled.
*/
+ xtmp = (ss || depth < num) ? NULL : find_issuer(ctx, sktmp, x);
if (xtmp == NULL) {
search &= ~S_DOUNTRUSTED;
if (may_trusted)
@@ -2905,23 +2958,21 @@ static int build_chain(X509_STORE_CTX *ctx)
continue;
}
- if (!sk_X509_push(ctx->chain, x = xtmp)) {
+ /* Drop this issuer from future consideration */
+ (void) sk_X509_delete_ptr(sktmp, xtmp);
+
+ if (!sk_X509_push(ctx->chain, xtmp)) {
X509err(X509_F_BUILD_CHAIN, ERR_R_MALLOC_FAILURE);
trust = X509_TRUST_REJECTED;
search = 0;
continue;
}
- X509_up_ref(x);
+
+ X509_up_ref(x = xtmp);
++ctx->num_untrusted;
ss = cert_self_signed(xtmp);
/*
- * Not strictly necessary, but saves cycles looking at the same
- * certificates over and over.
- */
- (void) sk_X509_delete_ptr(sktmp, x);
-
- /*
* Check for DANE-TA trust of the topmost untrusted certificate.
*/
switch (trust = check_dane_issuer(ctx, ctx->num_untrusted - 1)) {
@@ -2974,3 +3025,60 @@ static int build_chain(X509_STORE_CTX *ctx)
X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY);
}
}
+
+static const int minbits_table[] = { 80, 112, 128, 192, 256 };
+static const int NUM_AUTH_LEVELS = OSSL_NELEM(minbits_table);
+
+/*
+ * Check whether the public key of ``cert`` meets the security level of
+ * ``ctx``.
+ *
+ * Returns 1 on success, 0 otherwise.
+ */
+static int check_key_level(X509_STORE_CTX *ctx, X509 *cert)
+{
+ EVP_PKEY *pkey = X509_get0_pubkey(cert);
+ int level = ctx->param->auth_level;
+
+ /* Unsupported or malformed keys are not secure */
+ if (pkey == NULL)
+ return 0;
+
+ if (level <= 0)
+ return 1;
+ if (level > NUM_AUTH_LEVELS)
+ level = NUM_AUTH_LEVELS;
+
+ return EVP_PKEY_security_bits(pkey) >= minbits_table[level - 1];
+}
+
+/*
+ * Check whether the signature digest algorithm of ``cert`` meets the security
+ * level of ``ctx``. Should not be checked for trust anchors (whether
+ * self-signed or otherwise).
+ *
+ * Returns 1 on success, 0 otherwise.
+ */
+static int check_sig_level(X509_STORE_CTX *ctx, X509 *cert)
+{
+ int nid = X509_get_signature_nid(cert);
+ int mdnid = NID_undef;
+ int secbits = -1;
+ int level = ctx->param->auth_level;
+
+ if (level <= 0)
+ return 1;
+ if (level > NUM_AUTH_LEVELS)
+ level = NUM_AUTH_LEVELS;
+
+ /* Lookup signature algorithm digest */
+ if (nid && OBJ_find_sigid_algs(nid, &mdnid, NULL)) {
+ const EVP_MD *md;
+
+ /* Assume 4 bits of collision resistance for each hash octet */
+ if (mdnid != NID_undef && (md = EVP_get_digestbynid(mdnid)) != NULL)
+ secbits = EVP_MD_size(md) * 4;
+ }
+
+ return secbits >= minbits_table[level - 1];
+}
diff --git a/crypto/x509/x509_vpm.c b/crypto/x509/x509_vpm.c
index 41b0fde4a5..4a0bed021c 100644
--- a/crypto/x509/x509_vpm.c
+++ b/crypto/x509/x509_vpm.c
@@ -140,6 +140,7 @@ static void x509_verify_param_zero(X509_VERIFY_PARAM *param)
param->inh_flags = 0;
param->flags = 0;
param->depth = -1;
+ param->auth_level = -1; /* -1 means unset, 0 is explicit */
sk_ASN1_OBJECT_pop_free(param->policies, ASN1_OBJECT_free);
param->policies = NULL;
sk_OPENSSL_STRING_pop_free(param->hosts, str_free);
@@ -245,6 +246,7 @@ int X509_VERIFY_PARAM_inherit(X509_VERIFY_PARAM *dest,
x509_verify_param_copy(purpose, 0);
x509_verify_param_copy(trust, X509_TRUST_DEFAULT);
x509_verify_param_copy(depth, -1);
+ x509_verify_param_copy(auth_level, -1);
/* If overwrite or check time not set, copy across */
@@ -368,6 +370,11 @@ void X509_VERIFY_PARAM_set_depth(X509_VERIFY_PARAM *param, int depth)
param->depth = depth;
}
+void X509_VERIFY_PARAM_set_auth_level(X509_VERIFY_PARAM *param, int auth_level)
+{
+ param->auth_level = auth_level;
+}
+
void X509_VERIFY_PARAM_set_time(X509_VERIFY_PARAM *param, time_t t)
{
param->check_time = t;
@@ -493,6 +500,11 @@ int X509_VERIFY_PARAM_get_depth(const X509_VERIFY_PARAM *param)
return param->depth;
}
+int X509_VERIFY_PARAM_get_auth_level(const X509_VERIFY_PARAM *param)
+{
+ return param->auth_level;
+}
+
const char *X509_VERIFY_PARAM_get0_name(const X509_VERIFY_PARAM *param)
{
return param->name;
@@ -515,6 +527,7 @@ static const X509_VERIFY_PARAM default_table[] = {
0, /* purpose */
0, /* trust */
100, /* depth */
+ -1, /* auth_level */
NULL, /* policies */
vpm_empty_id},
{
@@ -525,6 +538,7 @@ static const X509_VERIFY_PARAM default_table[] = {
X509_PURPOSE_SMIME_SIGN, /* purpose */
X509_TRUST_EMAIL, /* trust */
-1, /* depth */
+ -1, /* auth_level */
NULL, /* policies */
vpm_empty_id},
{
@@ -535,6 +549,7 @@ static const X509_VERIFY_PARAM default_table[] = {
X509_PURPOSE_SMIME_SIGN, /* purpose */
X509_TRUST_EMAIL, /* trust */
-1, /* depth */
+ -1, /* auth_level */
NULL, /* policies */
vpm_empty_id},
{
@@ -545,6 +560,7 @@ static const X509_VERIFY_PARAM default_table[] = {
X509_PURPOSE_SSL_CLIENT, /* purpose */
X509_TRUST_SSL_CLIENT, /* trust */
-1, /* depth */
+ -1, /* auth_level */
NULL, /* policies */
vpm_empty_id},
{
@@ -555,6 +571,7 @@ static const X509_VERIFY_PARAM default_table[] = {
X509_PURPOSE_SSL_SERVER, /* purpose */
X509_TRUST_SSL_SERVER, /* trust */
-1, /* depth */
+ -1, /* auth_level */
NULL, /* policies */
vpm_empty_id}
};
generated by cgit v1.2.3 (git 2.25.1) at 2024-09-08 05:40:27 +0000