From db925ae2e65d0d925adef429afc37f75bd1c2017 Mon Sep 17 00:00:00 2001 From: Richard Levitte Date: Fri, 20 Oct 2023 09:18:19 +0200 Subject: [PATCH] Make DH_check_pub_key() and DH_generate_key() safer yet We already check for an excessively large P in DH_generate_key(), but not in DH_check_pub_key(), and none of them check for an excessively large Q. This change adds all the missing excessive size checks of P and Q. It's to be noted that behaviours surrounding excessively sized P and Q differ. DH_check() raises an error on the excessively sized P, but only sets a flag for the excessively sized Q. This behaviour is mimicked in DH_check_pub_key(). Reviewed-by: Tomas Mraz Reviewed-by: Matt Caswell Reviewed-by: Hugo Landau (Merged from https://github.com/openssl/openssl/pull/22518) (cherry picked from commit ddeb4b6c6d527e54ce9a99cba785c0f7776e54b6) --- crypto/dh/dh_check.c | 12 ++++++++++++ crypto/dh/dh_err.c | 3 ++- crypto/dh/dh_key.c | 12 ++++++++++++ crypto/err/openssl.txt | 1 + include/crypto/dherr.h | 2 +- include/openssl/dh.h | 6 +++--- include/openssl/dherr.h | 3 ++- 7 files changed, 33 insertions(+), 6 deletions(-) Index: openssl-1.1.1w/crypto/dh/dh_err.c =================================================================== --- openssl-1.1.1w.orig/crypto/dh/dh_err.c +++ openssl-1.1.1w/crypto/dh/dh_err.c @@ -21,6 +21,7 @@ static const ERR_STRING_DATA DH_str_func {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, 0), "DH_check_pub_key"}, {ERR_PACK(ERR_LIB_DH, DH_F_DH_CHECK_PUB_KEY_EX, 0), "DH_check_pub_key_ex"}, {ERR_PACK(ERR_LIB_DH, DH_F_DH_CMS_DECRYPT, 0), "dh_cms_decrypt"}, {ERR_PACK(ERR_LIB_DH, DH_F_DH_CMS_SET_PEERKEY, 0), "dh_cms_set_peerkey"}, @@ -87,6 +88,7 @@ static const ERR_STRING_DATA DH_str_reas {ERR_PACK(ERR_LIB_DH, 0, DH_R_PARAMETER_ENCODING_ERROR), "parameter encoding error"}, {ERR_PACK(ERR_LIB_DH, 0, DH_R_PEER_KEY_ERROR), "peer key error"}, + {ERR_PACK(ERR_LIB_DH, 0, DH_R_Q_TOO_LARGE), "q too large"}, {ERR_PACK(ERR_LIB_DH, 0, DH_R_SHARED_INFO_ERROR), "shared info error"}, {ERR_PACK(ERR_LIB_DH, 0, DH_R_UNABLE_TO_CHECK_GENERATOR), "unable to check generator"}, Index: openssl-1.1.1w/crypto/err/openssl.txt =================================================================== --- openssl-1.1.1w.orig/crypto/err/openssl.txt +++ openssl-1.1.1w/crypto/err/openssl.txt @@ -404,6 +404,7 @@ DH_F_DH_BUILTIN_GENPARAMS:106:dh_builtin 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:128:DH_check_pub_key DH_F_DH_CHECK_PUB_KEY_EX:123:DH_check_pub_key_ex DH_F_DH_CMS_DECRYPT:114:dh_cms_decrypt DH_F_DH_CMS_SET_PEERKEY:115:dh_cms_set_peerkey @@ -2226,6 +2227,7 @@ DH_R_NO_PARAMETERS_SET:107:no parameters DH_R_NO_PRIVATE_VALUE:100:no private value DH_R_PARAMETER_ENCODING_ERROR:105:parameter encoding error DH_R_PEER_KEY_ERROR:111:peer key error +DH_R_Q_TOO_LARGE:130:q too large DH_R_SHARED_INFO_ERROR:113:shared info error DH_R_UNABLE_TO_CHECK_GENERATOR:121:unable to check generator DSA_R_BAD_Q_VALUE:102:bad q value Index: openssl-1.1.1w/include/openssl/dherr.h =================================================================== --- openssl-1.1.1w.orig/include/openssl/dherr.h +++ openssl-1.1.1w/include/openssl/dherr.h @@ -31,6 +31,7 @@ int ERR_load_DH_strings(void); # 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 128 # define DH_F_DH_CHECK_PUB_KEY_EX 123 # define DH_F_DH_CMS_DECRYPT 114 # define DH_F_DH_CMS_SET_PEERKEY 115 @@ -84,6 +85,7 @@ int ERR_load_DH_strings(void); # define DH_R_NO_PRIVATE_VALUE 100 # define DH_R_PARAMETER_ENCODING_ERROR 105 # define DH_R_PEER_KEY_ERROR 111 +# define DH_R_Q_TOO_LARGE 130 # define DH_R_SHARED_INFO_ERROR 113 # define DH_R_UNABLE_TO_CHECK_GENERATOR 121 Index: openssl-1.1.1w/crypto/dh/dh_check.c =================================================================== --- openssl-1.1.1w.orig/crypto/dh/dh_check.c +++ openssl-1.1.1w/crypto/dh/dh_check.c @@ -260,6 +260,18 @@ static int dh_check_pub_key_int(const DH */ int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) { + /* 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_PUB_KEY, DH_R_MODULUS_TOO_LARGE); + *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID; + return 0; + } + + if (dh->q != NULL && BN_ucmp(dh->p, dh->q) < 0) { + *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID; + return 1; + } + return dh_check_pub_key_int(dh, dh->q, pub_key, ret); } Index: openssl-1.1.1w/crypto/dh/dh_key.c =================================================================== --- openssl-1.1.1w.orig/crypto/dh/dh_key.c +++ openssl-1.1.1w/crypto/dh/dh_key.c @@ -51,6 +51,12 @@ int DH_compute_key(unsigned char *key, c int ret = 0, i; volatile size_t npad = 0, mask = 1; + if (dh->q != NULL + && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) { + DHerr(DH_F_DH_COMPUTE_KEY, DH_R_Q_TOO_LARGE); + return 0; + } + /* compute the key; ret is constant unless compute_key is external */ if ((ret = dh->meth->compute_key(key, pub_key, dh)) <= 0) return ret; @@ -147,6 +153,12 @@ static int generate_key(DH *dh) return 0; } + if (dh->q != NULL + && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) { + DHerr(DH_F_GENERATE_KEY, DH_R_Q_TOO_LARGE); + return 0; + } + ctx = BN_CTX_new(); if (ctx == NULL) goto err; Index: openssl-1.1.1w/doc/man3/DH_generate_parameters.pod =================================================================== --- openssl-1.1.1w.orig/doc/man3/DH_generate_parameters.pod +++ openssl-1.1.1w/doc/man3/DH_generate_parameters.pod @@ -73,6 +73,10 @@ The generator B is not suitable. Note that the lack of this bit doesn't guarantee that B is suitable, unless B

is known to be a strong prime. +=item DH_MODULUS_TOO_LARGE + +The modulus is too large. + =back DH_check() confirms that the Diffie-Hellman parameters B are valid. The Index: openssl-1.1.1w/include/openssl/dh.h =================================================================== --- openssl-1.1.1w.orig/include/openssl/dh.h +++ openssl-1.1.1w/include/openssl/dh.h @@ -78,8 +78,9 @@ DECLARE_ASN1_ITEM(DHparams) # define DH_UNABLE_TO_CHECK_GENERATOR 0x04 # define DH_NOT_SUITABLE_GENERATOR 0x08 # define DH_CHECK_Q_NOT_PRIME 0x10 -# define DH_CHECK_INVALID_Q_VALUE 0x20 +# define DH_CHECK_INVALID_Q_VALUE 0x20 /* +DH_check_pub_key */ # define DH_CHECK_INVALID_J_VALUE 0x40 +# define DH_MODULUS_TOO_LARGE 0x100 /* +DH_check_pub_key */ /* DH_check_pub_key error codes */ # define DH_CHECK_PUBKEY_TOO_SMALL 0x01