| From 959c59c7a0164117e7f8366466a32bb1f8d77ff1 Mon Sep 17 00:00:00 2001 |
| From: Pauli <pauli@openssl.org> |
| Date: Wed, 8 Mar 2023 15:28:20 +1100 |
| Subject: [PATCH] x509: excessive resource use verifying policy constraints |
| |
| A security vulnerability has been identified in all supported versions |
| of OpenSSL related to the verification of X.509 certificate chains |
| that include policy constraints. Attackers may be able to exploit this |
| vulnerability by creating a malicious certificate chain that triggers |
| exponential use of computational resources, leading to a denial-of-service |
| (DoS) attack on affected systems. |
| |
| Fixes CVE-2023-0464 |
| |
| Reviewed-by: Tomas Mraz <tomas@openssl.org> |
| Reviewed-by: Shane Lontis <shane.lontis@oracle.com> |
| (Merged from https://github.com/openssl/openssl/pull/20568) |
| --- |
| crypto/x509/pcy_local.h | 8 +++++++- |
| crypto/x509/pcy_node.c | 12 +++++++++--- |
| crypto/x509/pcy_tree.c | 36 ++++++++++++++++++++++++++---------- |
| 3 files changed, 42 insertions(+), 14 deletions(-) |
| |
| diff --git a/crypto/x509/pcy_local.h b/crypto/x509/pcy_local.h |
| index 18b53cc09e..cba107ca03 100644 |
| --- a/crypto/x509/pcy_local.h |
| +++ b/crypto/x509/pcy_local.h |
| @@ -111,6 +111,11 @@ struct X509_POLICY_LEVEL_st { |
| }; |
| |
| struct X509_POLICY_TREE_st { |
| + /* The number of nodes in the tree */ |
| + size_t node_count; |
| + /* The maximum number of nodes in the tree */ |
| + size_t node_maximum; |
| + |
| /* This is the tree 'level' data */ |
| X509_POLICY_LEVEL *levels; |
| int nlevel; |
| @@ -157,7 +162,8 @@ X509_POLICY_NODE *ossl_policy_tree_find_sk(STACK_OF(X509_POLICY_NODE) *sk, |
| X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level, |
| X509_POLICY_DATA *data, |
| X509_POLICY_NODE *parent, |
| - X509_POLICY_TREE *tree); |
| + X509_POLICY_TREE *tree, |
| + int extra_data); |
| void ossl_policy_node_free(X509_POLICY_NODE *node); |
| int ossl_policy_node_match(const X509_POLICY_LEVEL *lvl, |
| const X509_POLICY_NODE *node, const ASN1_OBJECT *oid); |
| diff --git a/crypto/x509/pcy_node.c b/crypto/x509/pcy_node.c |
| index 9d9a7ea179..450f95a655 100644 |
| --- a/crypto/x509/pcy_node.c |
| +++ b/crypto/x509/pcy_node.c |
| @@ -59,10 +59,15 @@ X509_POLICY_NODE *ossl_policy_level_find_node(const X509_POLICY_LEVEL *level, |
| X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level, |
| X509_POLICY_DATA *data, |
| X509_POLICY_NODE *parent, |
| - X509_POLICY_TREE *tree) |
| + X509_POLICY_TREE *tree, |
| + int extra_data) |
| { |
| X509_POLICY_NODE *node; |
| |
| + /* Verify that the tree isn't too large. This mitigates CVE-2023-0464 */ |
| + if (tree->node_maximum > 0 && tree->node_count >= tree->node_maximum) |
| + return NULL; |
| + |
| node = OPENSSL_zalloc(sizeof(*node)); |
| if (node == NULL) { |
| ERR_raise(ERR_LIB_X509V3, ERR_R_MALLOC_FAILURE); |
| @@ -70,7 +75,7 @@ X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level, |
| } |
| node->data = data; |
| node->parent = parent; |
| - if (level) { |
| + if (level != NULL) { |
| if (OBJ_obj2nid(data->valid_policy) == NID_any_policy) { |
| if (level->anyPolicy) |
| goto node_error; |
| @@ -90,7 +95,7 @@ X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level, |
| } |
| } |
| |
| - if (tree) { |
| + if (extra_data) { |
| if (tree->extra_data == NULL) |
| tree->extra_data = sk_X509_POLICY_DATA_new_null(); |
| if (tree->extra_data == NULL){ |
| @@ -103,6 +108,7 @@ X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level, |
| } |
| } |
| |
| + tree->node_count++; |
| if (parent) |
| parent->nchild++; |
| |
| diff --git a/crypto/x509/pcy_tree.c b/crypto/x509/pcy_tree.c |
| index fa45da5117..f953a05a41 100644 |
| --- a/crypto/x509/pcy_tree.c |
| +++ b/crypto/x509/pcy_tree.c |
| @@ -14,6 +14,17 @@ |
| |
| #include "pcy_local.h" |
| |
| +/* |
| + * If the maximum number of nodes in the policy tree isn't defined, set it to |
| + * a generous default of 1000 nodes. |
| + * |
| + * Defining this to be zero means unlimited policy tree growth which opens the |
| + * door on CVE-2023-0464. |
| + */ |
| +#ifndef OPENSSL_POLICY_TREE_NODES_MAX |
| +# define OPENSSL_POLICY_TREE_NODES_MAX 1000 |
| +#endif |
| + |
| static void expected_print(BIO *channel, |
| X509_POLICY_LEVEL *lev, X509_POLICY_NODE *node, |
| int indent) |
| @@ -163,6 +174,9 @@ static int tree_init(X509_POLICY_TREE **ptree, STACK_OF(X509) *certs, |
| return X509_PCY_TREE_INTERNAL; |
| } |
| |
| + /* Limit the growth of the tree to mitigate CVE-2023-0464 */ |
| + tree->node_maximum = OPENSSL_POLICY_TREE_NODES_MAX; |
| + |
| /* |
| * http://tools.ietf.org/html/rfc5280#section-6.1.2, figure 3. |
| * |
| @@ -180,7 +194,7 @@ static int tree_init(X509_POLICY_TREE **ptree, STACK_OF(X509) *certs, |
| if ((data = ossl_policy_data_new(NULL, |
| OBJ_nid2obj(NID_any_policy), 0)) == NULL) |
| goto bad_tree; |
| - if (ossl_policy_level_add_node(level, data, NULL, tree) == NULL) { |
| + if (ossl_policy_level_add_node(level, data, NULL, tree, 1) == NULL) { |
| ossl_policy_data_free(data); |
| goto bad_tree; |
| } |
| @@ -239,7 +253,8 @@ static int tree_init(X509_POLICY_TREE **ptree, STACK_OF(X509) *certs, |
| * Return value: 1 on success, 0 otherwise |
| */ |
| static int tree_link_matching_nodes(X509_POLICY_LEVEL *curr, |
| - X509_POLICY_DATA *data) |
| + X509_POLICY_DATA *data, |
| + X509_POLICY_TREE *tree) |
| { |
| X509_POLICY_LEVEL *last = curr - 1; |
| int i, matched = 0; |
| @@ -249,13 +264,13 @@ static int tree_link_matching_nodes(X509_POLICY_LEVEL *curr, |
| X509_POLICY_NODE *node = sk_X509_POLICY_NODE_value(last->nodes, i); |
| |
| if (ossl_policy_node_match(last, node, data->valid_policy)) { |
| - if (ossl_policy_level_add_node(curr, data, node, NULL) == NULL) |
| + if (ossl_policy_level_add_node(curr, data, node, tree, 0) == NULL) |
| return 0; |
| matched = 1; |
| } |
| } |
| if (!matched && last->anyPolicy) { |
| - if (ossl_policy_level_add_node(curr, data, last->anyPolicy, NULL) == NULL) |
| + if (ossl_policy_level_add_node(curr, data, last->anyPolicy, tree, 0) == NULL) |
| return 0; |
| } |
| return 1; |
| @@ -268,7 +283,8 @@ static int tree_link_matching_nodes(X509_POLICY_LEVEL *curr, |
| * Return value: 1 on success, 0 otherwise. |
| */ |
| static int tree_link_nodes(X509_POLICY_LEVEL *curr, |
| - const X509_POLICY_CACHE *cache) |
| + const X509_POLICY_CACHE *cache, |
| + X509_POLICY_TREE *tree) |
| { |
| int i; |
| |
| @@ -276,7 +292,7 @@ static int tree_link_nodes(X509_POLICY_LEVEL *curr, |
| X509_POLICY_DATA *data = sk_X509_POLICY_DATA_value(cache->data, i); |
| |
| /* Look for matching nodes in previous level */ |
| - if (!tree_link_matching_nodes(curr, data)) |
| + if (!tree_link_matching_nodes(curr, data, tree)) |
| return 0; |
| } |
| return 1; |
| @@ -307,7 +323,7 @@ static int tree_add_unmatched(X509_POLICY_LEVEL *curr, |
| /* Curr may not have anyPolicy */ |
| data->qualifier_set = cache->anyPolicy->qualifier_set; |
| data->flags |= POLICY_DATA_FLAG_SHARED_QUALIFIERS; |
| - if (ossl_policy_level_add_node(curr, data, node, tree) == NULL) { |
| + if (ossl_policy_level_add_node(curr, data, node, tree, 1) == NULL) { |
| ossl_policy_data_free(data); |
| return 0; |
| } |
| @@ -370,7 +386,7 @@ static int tree_link_any(X509_POLICY_LEVEL *curr, |
| /* Finally add link to anyPolicy */ |
| if (last->anyPolicy && |
| ossl_policy_level_add_node(curr, cache->anyPolicy, |
| - last->anyPolicy, NULL) == NULL) |
| + last->anyPolicy, tree, 0) == NULL) |
| return 0; |
| return 1; |
| } |
| @@ -553,7 +569,7 @@ static int tree_calculate_user_set(X509_POLICY_TREE *tree, |
| extra->flags = POLICY_DATA_FLAG_SHARED_QUALIFIERS |
| | POLICY_DATA_FLAG_EXTRA_NODE; |
| node = ossl_policy_level_add_node(NULL, extra, anyPolicy->parent, |
| - tree); |
| + tree, 1); |
| } |
| if (!tree->user_policies) { |
| tree->user_policies = sk_X509_POLICY_NODE_new_null(); |
| @@ -580,7 +596,7 @@ static int tree_evaluate(X509_POLICY_TREE *tree) |
| |
| for (i = 1; i < tree->nlevel; i++, curr++) { |
| cache = ossl_policy_cache_set(curr->cert); |
| - if (!tree_link_nodes(curr, cache)) |
| + if (!tree_link_nodes(curr, cache, tree)) |
| return X509_PCY_TREE_INTERNAL; |
| |
| if (!(curr->flags & X509_V_FLAG_INHIBIT_ANY) |
| -- |
| 2.40.0.348.gf938b09366-goog |
| |