Fix DH_check() excessive time with over sized modulus

The DH_check() function checks numerous aspects of the key or parameters that have been supplied. Some of those checks use the supplied modulus value even if it is excessively large. There is already a maximum DH modulus size (10,000 bits) over which OpenSSL will not generate or derive keys. DH_check() will however still perform various tests for validity on such a large modulus. We introduce a new maximum (32,768) over which DH_check() will just fail. An application that calls DH_check() and supplies a key or parameters obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function DH_check() is itself called by a number of other OpenSSL functions. An application calling any of those other functions may similarly be affected. The other functions affected by this are DH_check_ex() and EVP_PKEY_param_check(). CVE-2023-3446 Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com> Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de> Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from #21452)
openssl · Jul 19, 2023 · 8780a89 · 8780a89
1 parent fe824ce
commit 8780a89
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Showing 5 changed files with 15 additions and 3 deletions.
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
@@ -101,6 +101,12 @@ int DH_check(const DH *dh, int *ret)
     BN_CTX *ctx = NULL;
     BIGNUM *t1 = NULL, *t2 = NULL;
 
+    /* Don't do any checks at all with an excessively large modulus */
+    if (BN_num_bits(dh->p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
+        DHerr(DH_F_DH_CHECK, DH_R_MODULUS_TOO_LARGE);
+        return 0;
+    }
+
     if (!DH_check_params(dh, ret))
         return 0;
 

diff --git a/crypto/dh/dh_err.c b/crypto/dh/dh_err.c
@@ -1,6 +1,6 @@
 /*
  * Generated by util/mkerr.pl DO NOT EDIT
- * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -18,6 +18,7 @@ static const ERR_STRING_DATA DH_str_functs[] = {
     {ERR_PACK(ERR_LIB_DH, DH_F_DHPARAMS_PRINT_FP, 0), "DHparams_print_fp"},
     {ERR_PACK(ERR_LIB_DH, DH_F_DH_BUILTIN_GENPARAMS, 0),
      "dh_builtin_genparams"},
+    {ERR_PACK(ERR_LIB_DH, DH_F_DH_CHECK, 0), "DH_check"},
     {ERR_PACK(ERR_LIB_DH, DH_F_DH_CHECK_EX, 0), "DH_check_ex"},
     {ERR_PACK(ERR_LIB_DH, DH_F_DH_CHECK_PARAMS_EX, 0), "DH_check_params_ex"},
     {ERR_PACK(ERR_LIB_DH, DH_F_DH_CHECK_PUB_KEY_EX, 0), "DH_check_pub_key_ex"},

diff --git a/crypto/err/openssl.txt b/crypto/err/openssl.txt
@@ -1,4 +1,4 @@
-# Copyright 1999-2021 The OpenSSL Project Authors. All Rights Reserved.
+# Copyright 1999-2023 The OpenSSL Project Authors. All Rights Reserved.
 #
 # Licensed under the OpenSSL license (the "License").  You may not use
 # this file except in compliance with the License.  You can obtain a copy
@@ -401,6 +401,7 @@ CT_F_SCT_SET_VERSION:104:SCT_set_version
 DH_F_COMPUTE_KEY:102:compute_key
 DH_F_DHPARAMS_PRINT_FP:101:DHparams_print_fp
 DH_F_DH_BUILTIN_GENPARAMS:106:dh_builtin_genparams
+DH_F_DH_CHECK:126:DH_check
 DH_F_DH_CHECK_EX:121:DH_check_ex
 DH_F_DH_CHECK_PARAMS_EX:122:DH_check_params_ex
 DH_F_DH_CHECK_PUB_KEY_EX:123:DH_check_pub_key_ex

diff --git a/include/openssl/dh.h b/include/openssl/dh.h
@@ -29,6 +29,9 @@ extern "C" {
 # ifndef OPENSSL_DH_MAX_MODULUS_BITS
 #  define OPENSSL_DH_MAX_MODULUS_BITS    10000
 # endif
+# ifndef OPENSSL_DH_CHECK_MAX_MODULUS_BITS
+#  define OPENSSL_DH_CHECK_MAX_MODULUS_BITS  32768
+# endif
 
 # define OPENSSL_DH_FIPS_MIN_MODULUS_BITS 1024
 

diff --git a/include/openssl/dherr.h b/include/openssl/dherr.h
@@ -1,6 +1,6 @@
 /*
  * Generated by util/mkerr.pl DO NOT EDIT
- * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -30,6 +30,7 @@ int ERR_load_DH_strings(void);
 #  define DH_F_COMPUTE_KEY                                 102
 #  define DH_F_DHPARAMS_PRINT_FP                           101
 #  define DH_F_DH_BUILTIN_GENPARAMS                        106
+#  define DH_F_DH_CHECK                                    126
 #  define DH_F_DH_CHECK_EX                                 121
 #  define DH_F_DH_CHECK_PARAMS_EX                          122
 #  define DH_F_DH_CHECK_PUB_KEY_EX                         123