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+From 959c59c7a0164117e7f8366466a32bb1f8d77ff1 Mon Sep 17 00:00:00 2001
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+From: Pauli <[email protected]>
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+Date: Wed, 8 Mar 2023 15:28:20 +1100
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+Subject: [PATCH] x509: excessive resource use verifying policy constraints
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+
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+A security vulnerability has been identified in all supported versions
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+of OpenSSL related to the verification of X.509 certificate chains
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+that include policy constraints. Attackers may be able to exploit this
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+vulnerability by creating a malicious certificate chain that triggers
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+exponential use of computational resources, leading to a denial-of-service
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+(DoS) attack on affected systems.
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+
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+Fixes CVE-2023-0464
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+
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+Reviewed-by: Tomas Mraz <[email protected]>
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+Reviewed-by: Shane Lontis <[email protected]>
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+(Merged from https://github.com/openssl/openssl/pull/20568)
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+
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+--- a/crypto/x509/pcy_local.h
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++++ b/crypto/x509/pcy_local.h
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+@@ -111,6 +111,11 @@ struct X509_POLICY_LEVEL_st {
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+ };
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+
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+ struct X509_POLICY_TREE_st {
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++ /* The number of nodes in the tree */
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++ size_t node_count;
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++ /* The maximum number of nodes in the tree */
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++ size_t node_maximum;
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++
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+ /* This is the tree 'level' data */
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+ X509_POLICY_LEVEL *levels;
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+ int nlevel;
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+@@ -157,7 +162,8 @@ X509_POLICY_NODE *ossl_policy_tree_find_
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+ X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level,
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+ X509_POLICY_DATA *data,
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+ X509_POLICY_NODE *parent,
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+- X509_POLICY_TREE *tree);
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++ X509_POLICY_TREE *tree,
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++ int extra_data);
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+ void ossl_policy_node_free(X509_POLICY_NODE *node);
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+ int ossl_policy_node_match(const X509_POLICY_LEVEL *lvl,
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+ const X509_POLICY_NODE *node, const ASN1_OBJECT *oid);
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+--- a/crypto/x509/pcy_node.c
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++++ b/crypto/x509/pcy_node.c
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+@@ -59,10 +59,15 @@ X509_POLICY_NODE *ossl_policy_level_find
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+ X509_POLICY_NODE *ossl_policy_level_add_node(X509_POLICY_LEVEL *level,
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+ X509_POLICY_DATA *data,
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+ X509_POLICY_NODE *parent,
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+- X509_POLICY_TREE *tree)
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++ X509_POLICY_TREE *tree,
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++ int extra_data)
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+ {
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+ X509_POLICY_NODE *node;
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+
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++ /* Verify that the tree isn't too large. This mitigates CVE-2023-0464 */
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++ if (tree->node_maximum > 0 && tree->node_count >= tree->node_maximum)
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++ return NULL;
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++
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+ node = OPENSSL_zalloc(sizeof(*node));
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+ if (node == NULL) {
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+ ERR_raise(ERR_LIB_X509V3, ERR_R_MALLOC_FAILURE);
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+@@ -70,7 +75,7 @@ X509_POLICY_NODE *ossl_policy_level_add_
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+ }
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+ node->data = data;
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+ node->parent = parent;
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+- if (level) {
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++ if (level != NULL) {
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+ if (OBJ_obj2nid(data->valid_policy) == NID_any_policy) {
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+ if (level->anyPolicy)
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+ goto node_error;
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+@@ -90,7 +95,7 @@ X509_POLICY_NODE *ossl_policy_level_add_
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+ }
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+ }
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+
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+- if (tree) {
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++ if (extra_data) {
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+ if (tree->extra_data == NULL)
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+ tree->extra_data = sk_X509_POLICY_DATA_new_null();
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+ if (tree->extra_data == NULL){
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+@@ -103,6 +108,7 @@ X509_POLICY_NODE *ossl_policy_level_add_
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+ }
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+ }
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+
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++ tree->node_count++;
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+ if (parent)
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+ parent->nchild++;
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+
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+--- a/crypto/x509/pcy_tree.c
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++++ b/crypto/x509/pcy_tree.c
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+@@ -14,6 +14,17 @@
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+
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+ #include "pcy_local.h"
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+
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++/*
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++ * If the maximum number of nodes in the policy tree isn't defined, set it to
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++ * a generous default of 1000 nodes.
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++ *
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++ * Defining this to be zero means unlimited policy tree growth which opens the
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++ * door on CVE-2023-0464.
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++ */
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++#ifndef OPENSSL_POLICY_TREE_NODES_MAX
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++# define OPENSSL_POLICY_TREE_NODES_MAX 1000
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++#endif
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++
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+ static void expected_print(BIO *channel,
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+ X509_POLICY_LEVEL *lev, X509_POLICY_NODE *node,
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+ int indent)
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+@@ -163,6 +174,9 @@ static int tree_init(X509_POLICY_TREE **
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+ return X509_PCY_TREE_INTERNAL;
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+ }
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+
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++ /* Limit the growth of the tree to mitigate CVE-2023-0464 */
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++ tree->node_maximum = OPENSSL_POLICY_TREE_NODES_MAX;
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++
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+ /*
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+ * http://tools.ietf.org/html/rfc5280#section-6.1.2, figure 3.
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+ *
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+@@ -180,7 +194,7 @@ static int tree_init(X509_POLICY_TREE **
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+ if ((data = ossl_policy_data_new(NULL,
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+ OBJ_nid2obj(NID_any_policy), 0)) == NULL)
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+ goto bad_tree;
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+- if (ossl_policy_level_add_node(level, data, NULL, tree) == NULL) {
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++ if (ossl_policy_level_add_node(level, data, NULL, tree, 1) == NULL) {
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+ ossl_policy_data_free(data);
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+ goto bad_tree;
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+ }
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+@@ -239,7 +253,8 @@ static int tree_init(X509_POLICY_TREE **
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+ * Return value: 1 on success, 0 otherwise
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+ */
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+ static int tree_link_matching_nodes(X509_POLICY_LEVEL *curr,
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+- X509_POLICY_DATA *data)
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++ X509_POLICY_DATA *data,
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++ X509_POLICY_TREE *tree)
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+ {
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+ X509_POLICY_LEVEL *last = curr - 1;
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+ int i, matched = 0;
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+@@ -249,13 +264,13 @@ static int tree_link_matching_nodes(X509
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+ X509_POLICY_NODE *node = sk_X509_POLICY_NODE_value(last->nodes, i);
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+
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+ if (ossl_policy_node_match(last, node, data->valid_policy)) {
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+- if (ossl_policy_level_add_node(curr, data, node, NULL) == NULL)
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++ if (ossl_policy_level_add_node(curr, data, node, tree, 0) == NULL)
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+ return 0;
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+ matched = 1;
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+ }
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+ }
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+ if (!matched && last->anyPolicy) {
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+- if (ossl_policy_level_add_node(curr, data, last->anyPolicy, NULL) == NULL)
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++ if (ossl_policy_level_add_node(curr, data, last->anyPolicy, tree, 0) == NULL)
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+ return 0;
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+ }
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+ return 1;
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+@@ -268,7 +283,8 @@ static int tree_link_matching_nodes(X509
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+ * Return value: 1 on success, 0 otherwise.
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+ */
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+ static int tree_link_nodes(X509_POLICY_LEVEL *curr,
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+- const X509_POLICY_CACHE *cache)
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++ const X509_POLICY_CACHE *cache,
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++ X509_POLICY_TREE *tree)
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+ {
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+ int i;
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+
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+@@ -276,7 +292,7 @@ static int tree_link_nodes(X509_POLICY_L
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+ X509_POLICY_DATA *data = sk_X509_POLICY_DATA_value(cache->data, i);
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+
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+ /* Look for matching nodes in previous level */
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+- if (!tree_link_matching_nodes(curr, data))
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++ if (!tree_link_matching_nodes(curr, data, tree))
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+ return 0;
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+ }
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+ return 1;
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+@@ -307,7 +323,7 @@ static int tree_add_unmatched(X509_POLIC
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+ /* Curr may not have anyPolicy */
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+ data->qualifier_set = cache->anyPolicy->qualifier_set;
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+ data->flags |= POLICY_DATA_FLAG_SHARED_QUALIFIERS;
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+- if (ossl_policy_level_add_node(curr, data, node, tree) == NULL) {
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++ if (ossl_policy_level_add_node(curr, data, node, tree, 1) == NULL) {
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+ ossl_policy_data_free(data);
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+ return 0;
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+ }
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+@@ -370,7 +386,7 @@ static int tree_link_any(X509_POLICY_LEV
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+ /* Finally add link to anyPolicy */
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+ if (last->anyPolicy &&
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+ ossl_policy_level_add_node(curr, cache->anyPolicy,
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+- last->anyPolicy, NULL) == NULL)
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++ last->anyPolicy, tree, 0) == NULL)
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+ return 0;
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+ return 1;
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+ }
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+@@ -553,7 +569,7 @@ static int tree_calculate_user_set(X509_
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+ extra->flags = POLICY_DATA_FLAG_SHARED_QUALIFIERS
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+ | POLICY_DATA_FLAG_EXTRA_NODE;
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+ node = ossl_policy_level_add_node(NULL, extra, anyPolicy->parent,
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+- tree);
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++ tree, 1);
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+ }
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+ if (!tree->user_policies) {
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+ tree->user_policies = sk_X509_POLICY_NODE_new_null();
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+@@ -580,7 +596,7 @@ static int tree_evaluate(X509_POLICY_TRE
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+
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+ for (i = 1; i < tree->nlevel; i++, curr++) {
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+ cache = ossl_policy_cache_set(curr->cert);
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+- if (!tree_link_nodes(curr, cache))
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++ if (!tree_link_nodes(curr, cache, tree))
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+ return X509_PCY_TREE_INTERNAL;
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+
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+ if (!(curr->flags & X509_V_FLAG_INHIBIT_ANY)
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