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| 1 | +Backport of: |
| 2 | + |
| 3 | +From db925ae2e65d0d925adef429afc37f75bd1c2017 Mon Sep 17 00:00:00 2001 |
| 4 | +From: Richard Levitte < [email protected]> |
| 5 | +Date: Fri, 20 Oct 2023 09:18:19 +0200 |
| 6 | +Subject: [PATCH] Make DH_check_pub_key() and DH_generate_key() safer yet |
| 7 | + |
| 8 | +We already check for an excessively large P in DH_generate_key(), but not in |
| 9 | +DH_check_pub_key(), and none of them check for an excessively large Q. |
| 10 | + |
| 11 | +This change adds all the missing excessive size checks of P and Q. |
| 12 | + |
| 13 | +It's to be noted that behaviours surrounding excessively sized P and Q |
| 14 | +differ. DH_check() raises an error on the excessively sized P, but only |
| 15 | +sets a flag for the excessively sized Q. This behaviour is mimicked in |
| 16 | +DH_check_pub_key(). |
| 17 | + |
| 18 | +Reviewed-by: Tomas Mraz < [email protected]> |
| 19 | +Reviewed-by: Matt Caswell < [email protected]> |
| 20 | +Reviewed-by: Hugo Landau < [email protected]> |
| 21 | +(Merged from https://github.com/openssl/openssl/pull/22518) |
| 22 | + |
| 23 | +(cherry picked from commit ddeb4b6c6d527e54ce9a99cba785c0f7776e54b6) |
| 24 | +--- |
| 25 | + crypto/dh/dh_check.c | 12 ++++++++++++ |
| 26 | + crypto/dh/dh_err.c | 3 ++- |
| 27 | + crypto/dh/dh_key.c | 12 ++++++++++++ |
| 28 | + crypto/err/openssl.txt | 1 + |
| 29 | + include/crypto/dherr.h | 2 +- |
| 30 | + include/openssl/dh.h | 6 +++--- |
| 31 | + include/openssl/dherr.h | 3 ++- |
| 32 | + 7 files changed, 33 insertions(+), 6 deletions(-) |
| 33 | + |
| 34 | +--- a/crypto/dh/dh_check.c |
| 35 | ++++ b/crypto/dh/dh_check.c |
| 36 | +@@ -201,6 +201,19 @@ int DH_check_pub_key(const DH *dh, const |
| 37 | + if (ctx == NULL) |
| 38 | + goto err; |
| 39 | + BN_CTX_start(ctx); |
| 40 | ++ |
| 41 | ++ /* Don't do any checks at all with an excessively large modulus */ |
| 42 | ++ if (BN_num_bits(dh->p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) { |
| 43 | ++ DHerr(DH_F_DH_CHECK, DH_R_MODULUS_TOO_LARGE); |
| 44 | ++ *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID; |
| 45 | ++ goto err; |
| 46 | ++ } |
| 47 | ++ |
| 48 | ++ if (dh->q != NULL && BN_ucmp(dh->p, dh->q) < 0) { |
| 49 | ++ *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID; |
| 50 | ++ goto out; |
| 51 | ++ } |
| 52 | ++ |
| 53 | + tmp = BN_CTX_get(ctx); |
| 54 | + if (tmp == NULL || !BN_set_word(tmp, 1)) |
| 55 | + goto err; |
| 56 | +@@ -219,6 +232,7 @@ int DH_check_pub_key(const DH *dh, const |
| 57 | + *ret |= DH_CHECK_PUBKEY_INVALID; |
| 58 | + } |
| 59 | + |
| 60 | ++ out: |
| 61 | + ok = 1; |
| 62 | + err: |
| 63 | + BN_CTX_end(ctx); |
| 64 | +--- a/crypto/dh/dh_err.c |
| 65 | ++++ b/crypto/dh/dh_err.c |
| 66 | +@@ -82,6 +82,7 @@ static const ERR_STRING_DATA DH_str_reas |
| 67 | + {ERR_PACK(ERR_LIB_DH, 0, DH_R_PARAMETER_ENCODING_ERROR), |
| 68 | + "parameter encoding error"}, |
| 69 | + {ERR_PACK(ERR_LIB_DH, 0, DH_R_PEER_KEY_ERROR), "peer key error"}, |
| 70 | ++ {ERR_PACK(ERR_LIB_DH, 0, DH_R_Q_TOO_LARGE), "q too large"}, |
| 71 | + {ERR_PACK(ERR_LIB_DH, 0, DH_R_SHARED_INFO_ERROR), "shared info error"}, |
| 72 | + {ERR_PACK(ERR_LIB_DH, 0, DH_R_UNABLE_TO_CHECK_GENERATOR), |
| 73 | + "unable to check generator"}, |
| 74 | +--- a/crypto/dh/dh_key.c |
| 75 | ++++ b/crypto/dh/dh_key.c |
| 76 | +@@ -87,6 +87,12 @@ static int generate_key(DH *dh) |
| 77 | + return 0; |
| 78 | + } |
| 79 | + |
| 80 | ++ if (dh->q != NULL |
| 81 | ++ && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) { |
| 82 | ++ DHerr(DH_F_GENERATE_KEY, DH_R_Q_TOO_LARGE); |
| 83 | ++ return 0; |
| 84 | ++ } |
| 85 | ++ |
| 86 | + ctx = BN_CTX_new(); |
| 87 | + if (ctx == NULL) |
| 88 | + goto err; |
| 89 | +@@ -180,6 +186,12 @@ static int compute_key(unsigned char *ke |
| 90 | + goto err; |
| 91 | + } |
| 92 | + |
| 93 | ++ if (dh->q != NULL |
| 94 | ++ && BN_num_bits(dh->q) > OPENSSL_DH_MAX_MODULUS_BITS) { |
| 95 | ++ DHerr(DH_F_COMPUTE_KEY, DH_R_Q_TOO_LARGE); |
| 96 | ++ goto err; |
| 97 | ++ } |
| 98 | ++ |
| 99 | + ctx = BN_CTX_new(); |
| 100 | + if (ctx == NULL) |
| 101 | + goto err; |
| 102 | +--- a/crypto/err/openssl.txt |
| 103 | ++++ b/crypto/err/openssl.txt |
| 104 | +@@ -2110,6 +2110,7 @@ DH_R_NO_PARAMETERS_SET:107:no parameters |
| 105 | + DH_R_NO_PRIVATE_VALUE:100:no private value |
| 106 | + DH_R_PARAMETER_ENCODING_ERROR:105:parameter encoding error |
| 107 | + DH_R_PEER_KEY_ERROR:111:peer key error |
| 108 | ++DH_R_Q_TOO_LARGE:130:q too large |
| 109 | + DH_R_SHARED_INFO_ERROR:113:shared info error |
| 110 | + DH_R_UNABLE_TO_CHECK_GENERATOR:121:unable to check generator |
| 111 | + DSA_R_BAD_Q_VALUE:102:bad q value |
| 112 | +--- a/include/openssl/dh.h |
| 113 | ++++ b/include/openssl/dh.h |
| 114 | +@@ -71,14 +71,16 @@ DECLARE_ASN1_ITEM(DHparams) |
| 115 | + /* #define DH_GENERATOR_3 3 */ |
| 116 | + # define DH_GENERATOR_5 5 |
| 117 | + |
| 118 | +-/* DH_check error codes */ |
| 119 | ++/* DH_check error codes, some of them shared with DH_check_pub_key */ |
| 120 | + # define DH_CHECK_P_NOT_PRIME 0x01 |
| 121 | + # define DH_CHECK_P_NOT_SAFE_PRIME 0x02 |
| 122 | + # define DH_UNABLE_TO_CHECK_GENERATOR 0x04 |
| 123 | + # define DH_NOT_SUITABLE_GENERATOR 0x08 |
| 124 | + # define DH_CHECK_Q_NOT_PRIME 0x10 |
| 125 | +-# define DH_CHECK_INVALID_Q_VALUE 0x20 |
| 126 | ++# define DH_CHECK_INVALID_Q_VALUE 0x20 /* +DH_check_pub_key */ |
| 127 | + # define DH_CHECK_INVALID_J_VALUE 0x40 |
| 128 | ++# define DH_MODULUS_TOO_SMALL 0x80 |
| 129 | ++# define DH_MODULUS_TOO_LARGE 0x100 /* +DH_check_pub_key */ |
| 130 | + |
| 131 | + /* DH_check_pub_key error codes */ |
| 132 | + # define DH_CHECK_PUBKEY_TOO_SMALL 0x01 |
| 133 | +--- a/include/openssl/dherr.h |
| 134 | ++++ b/include/openssl/dherr.h |
| 135 | +@@ -82,6 +82,7 @@ int ERR_load_DH_strings(void); |
| 136 | + # define DH_R_NO_PRIVATE_VALUE 100 |
| 137 | + # define DH_R_PARAMETER_ENCODING_ERROR 105 |
| 138 | + # define DH_R_PEER_KEY_ERROR 111 |
| 139 | ++# define DH_R_Q_TOO_LARGE 130 |
| 140 | + # define DH_R_SHARED_INFO_ERROR 113 |
| 141 | + # define DH_R_UNABLE_TO_CHECK_GENERATOR 121 |
| 142 | + |
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