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155 lines
5.9 KiB
155 lines
5.9 KiB
From 0814467cc1b6a2839877277d3efa69cdd4582dd7 Mon Sep 17 00:00:00 2001
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From: Richard Levitte <levitte@openssl.org>
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Date: Fri, 20 Oct 2023 09:18:19 +0200
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Subject: [PATCH] Make DH_check_pub_key() and DH_generate_key() safer yet
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We already check for an excessively large P in DH_generate_key(), but not in
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DH_check_pub_key(), and none of them check for an excessively large Q.
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This change adds all the missing excessive size checks of P and Q.
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It's to be noted that behaviours surrounding excessively sized P and Q
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differ. DH_check() raises an error on the excessively sized P, but only
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sets a flag for the excessively sized Q. This behaviour is mimicked in
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DH_check_pub_key().
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Reviewed-by: Tomas Mraz <tomas@openssl.org>
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Reviewed-by: Matt Caswell <matt@openssl.org>
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Reviewed-by: Hugo Landau <hlandau@openssl.org>
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(Merged from https://github.com/openssl/openssl/pull/22518)
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(cherry picked from commit ddeb4b6c6d527e54ce9a99cba785c0f7776e54b6)
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Backported-by: Clemens Lang <cllang@redhat.com>
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---
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crypto/dh/dh_check.c | 17 +++++++++++++++++
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crypto/dh/dh_err.c | 1 +
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crypto/dh/dh_key.c | 10 ++++++++++
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crypto/err/openssl.txt | 1 +
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include/openssl/dh.h | 6 ++++--
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include/openssl/dherr.h | 1 +
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6 files changed, 34 insertions(+), 2 deletions(-)
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diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
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index ae1b03bc92..424a3bb4cd 100644
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--- a/crypto/dh/dh_check.c
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+++ b/crypto/dh/dh_check.c
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@@ -198,10 +198,27 @@ int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
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BN_CTX *ctx = NULL;
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*ret = 0;
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+
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ctx = BN_CTX_new();
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if (ctx == NULL)
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goto err;
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BN_CTX_start(ctx);
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+
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+ /* Don't do any checks at all with an excessively large modulus */
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+ if (BN_num_bits(dh->p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
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+ DHerr(DH_F_DH_CHECK, DH_R_MODULUS_TOO_LARGE);
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+ *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;
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+ goto err;
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+ }
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+ if (dh->q != NULL && BN_ucmp(dh->p, dh->q) < 0) {
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+ *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;
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+ /* This may look strange here, but returning 1 after setting ret is
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+ * correct. See also the behavior of the pub_key^q == 1 mod p check
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+ * further down, which behaves in the same way. */
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+ ok = 1;
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+ goto err;
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+ }
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+
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tmp = BN_CTX_get(ctx);
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if (tmp == NULL || !BN_set_word(tmp, 1))
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goto err;
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diff --git a/crypto/dh/dh_err.c b/crypto/dh/dh_err.c
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index 92800d3fcc..b3b1e7a706 100644
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--- a/crypto/dh/dh_err.c
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+++ b/crypto/dh/dh_err.c
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@@ -87,6 +87,7 @@ static const ERR_STRING_DATA DH_str_reasons[] = {
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{ERR_PACK(ERR_LIB_DH, 0, DH_R_PARAMETER_ENCODING_ERROR),
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"parameter encoding error"},
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{ERR_PACK(ERR_LIB_DH, 0, DH_R_PEER_KEY_ERROR), "peer key error"},
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+ {ERR_PACK(ERR_LIB_DH, 0, DH_R_Q_TOO_LARGE), "q too large"},
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{ERR_PACK(ERR_LIB_DH, 0, DH_R_SHARED_INFO_ERROR), "shared info error"},
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{ERR_PACK(ERR_LIB_DH, 0, DH_R_UNABLE_TO_CHECK_GENERATOR),
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"unable to check generator"},
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diff --git a/crypto/dh/dh_key.c b/crypto/dh/dh_key.c
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index 117f2fa883..9f5e6f6d4c 100644
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--- a/crypto/dh/dh_key.c
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+++ b/crypto/dh/dh_key.c
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@@ -140,6 +140,11 @@ static int generate_key(DH *dh)
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return 0;
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}
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+ if (dh->q != NULL && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) {
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+ DHerr(DH_F_GENERATE_KEY, DH_R_Q_TOO_LARGE);
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+ return 0;
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+ }
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+
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ctx = BN_CTX_new();
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if (ctx == NULL)
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goto err;
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@@ -250,6 +255,12 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
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goto err;
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}
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+
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+ if (dh->q != NULL && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) {
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+ DHerr(DH_F_COMPUTE_KEY, DH_R_Q_TOO_LARGE);
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+ goto err;
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+ }
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+
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#ifdef OPENSSL_FIPS
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if (FIPS_mode()
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&& (BN_num_bits(dh->p) < OPENSSL_DH_FIPS_MIN_MODULUS_BITS)) {
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diff --git a/crypto/err/openssl.txt b/crypto/err/openssl.txt
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index c0a3cd720b..5e0ff47516 100644
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--- a/crypto/err/openssl.txt
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+++ b/crypto/err/openssl.txt
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@@ -2151,6 +2151,7 @@DH_R_NO_PARAMETERS_SET:107:no parameters set
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DH_R_NO_PRIVATE_VALUE:100:no private value
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DH_R_PARAMETER_ENCODING_ERROR:105:parameter encoding error
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DH_R_PEER_KEY_ERROR:111:peer key error
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+DH_R_Q_TOO_LARGE:130:q too large
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DH_R_SHARED_INFO_ERROR:113:shared info error
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DH_R_UNABLE_TO_CHECK_GENERATOR:121:unable to check generator
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DSA_R_BAD_Q_VALUE:102:bad q value
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diff --git a/include/openssl/dh.h b/include/openssl/dh.h
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index 6c6ff3636a..b7df43b44f 100644
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--- a/include/openssl/dh.h
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+++ b/include/openssl/dh.h
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@@ -72,14 +72,16 @@ DECLARE_ASN1_ITEM(DHparams)
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/* #define DH_GENERATOR_3 3 */
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# define DH_GENERATOR_5 5
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-/* DH_check error codes */
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+/* DH_check error codes, some of them shared with DH_check_pub_key */
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# define DH_CHECK_P_NOT_PRIME 0x01
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# define DH_CHECK_P_NOT_SAFE_PRIME 0x02
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# define DH_UNABLE_TO_CHECK_GENERATOR 0x04
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# define DH_NOT_SUITABLE_GENERATOR 0x08
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# define DH_CHECK_Q_NOT_PRIME 0x10
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-# define DH_CHECK_INVALID_Q_VALUE 0x20
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+# define DH_CHECK_INVALID_Q_VALUE 0x20 /* +DH_check_pub_key */
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# define DH_CHECK_INVALID_J_VALUE 0x40
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+/* DH_MODULUS_TOO_SMALL is 0x80 upstream */
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+# define DH_MODULUS_TOO_LARGE 0x100 /* +DH_check_pub_key */
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/* DH_check_pub_key error codes */
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# define DH_CHECK_PUBKEY_TOO_SMALL 0x01
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diff --git a/include/openssl/dherr.h b/include/openssl/dherr.h
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index 528c819856..d66c35aa8e 100644
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--- a/include/openssl/dherr.h
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+++ b/include/openssl/dherr.h
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@@ -87,6 +87,7 @@ int ERR_load_DH_strings(void);
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# define DH_R_NON_FIPS_METHOD 202
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# define DH_R_PARAMETER_ENCODING_ERROR 105
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# define DH_R_PEER_KEY_ERROR 111
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+# define DH_R_Q_TOO_LARGE 130
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# define DH_R_SHARED_INFO_ERROR 113
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# define DH_R_UNABLE_TO_CHECK_GENERATOR 121
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--
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2.41.0
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