Stop supporting the long-retired X9.31 standard

This isolates the three API functions from the library so they can be
easily removed and any attempt to use RSA_X931_PADDING mode will now
result in an error.

ok jsing

2 files changed, 57 insertions, 113 deletions

diff --git a/src/lib/libcrypto/rsa/rsa_eay.c b/src/lib/libcrypto/rsa/rsa_eay.c
index b307a8bd88..e65319bda1 100644
--- a/src/lib/libcrypto/rsa/rsa_eay.c
+++ b/src/lib/libcrypto/rsa/rsa_eay.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: rsa_eay.c,v 1.58 2023/04/05 11:31:38 tb Exp $ */
+/* $OpenBSD: rsa_eay.c,v 1.59 2023/04/15 18:48:52 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -382,14 +382,11 @@ RSA_eay_private_encrypt(int flen, const unsigned char *from, unsigned char *to,
         case RSA_PKCS1_PADDING:
                 i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
                 break;
-        case RSA_X931_PADDING:
-                i = RSA_padding_add_X931(buf, num, from, flen);
-                break;
         case RSA_NO_PADDING:
                 i = RSA_padding_add_none(buf, num, from, flen);
                 break;
         default:
-                RSAerror(RSA_R_UNKNOWN_PADDING_TYPE);
+                RSAerror(RSA_R_ILLEGAL_OR_UNSUPPORTED_PADDING_MODE);
                 goto err;
         }
         if (i <= 0)
@@ -449,14 +446,11 @@ RSA_eay_private_encrypt(int flen, const unsigned char *from, unsigned char *to,
                         goto err;
 
         if (padding == RSA_X931_PADDING) {
-                if (!BN_sub(f, rsa->n, ret))
-                        goto err;
-                if (BN_cmp(ret, f) > 0)
-                        res = f;
-                else
-                        res = ret;
-        } else
-                res = ret;
+                RSAerror(RSA_R_ILLEGAL_OR_UNSUPPORTED_PADDING_MODE);
+                goto err;
+        }
+
+        res = ret;
 
         /* put in leading 0 bytes if the number is less than the
          * length of the modulus */
@@ -667,9 +661,10 @@ RSA_eay_public_decrypt(int flen, const unsigned char *from, unsigned char *to,
             rsa->_method_mod_n))
                 goto err;
 
-        if (padding == RSA_X931_PADDING && (ret->d[0] & 0xf) != 12)
-                if (!BN_sub(ret, rsa->n, ret))
-                        goto err;
+        if (padding == RSA_X931_PADDING) {
+                RSAerror(RSA_R_ILLEGAL_OR_UNSUPPORTED_PADDING_MODE);
+                goto err;
+        }
 
         p = buf;
         i = BN_bn2bin(ret, p);
@@ -678,9 +673,6 @@ RSA_eay_public_decrypt(int flen, const unsigned char *from, unsigned char *to,
         case RSA_PKCS1_PADDING:
                 r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
                 break;
-        case RSA_X931_PADDING:
-                r = RSA_padding_check_X931(to, num, buf, i, num);
-                break;
         case RSA_NO_PADDING:
                 r = RSA_padding_check_none(to, num, buf, i, num);
                 break;
diff --git a/src/lib/libcrypto/rsa/rsa_pmeth.c b/src/lib/libcrypto/rsa/rsa_pmeth.c
index 3747f1dd28..688c0d64db 100644
--- a/src/lib/libcrypto/rsa/rsa_pmeth.c
+++ b/src/lib/libcrypto/rsa/rsa_pmeth.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: rsa_pmeth.c,v 1.35 2023/03/06 08:31:34 tb Exp $ */
+/* $OpenBSD: rsa_pmeth.c,v 1.36 2023/04/15 18:48:52 tb Exp $ */
 /* Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
  * project 2006.
  */
@@ -187,7 +187,7 @@ static int
 pkey_rsa_sign(EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
     const unsigned char *tbs, size_t tbslen)
 {
-        int ret;
+        int ret = -1;
         RSA_PKEY_CTX *rctx = ctx->data;
         RSA *rsa = ctx->pkey->pkey.rsa;
 
@@ -197,21 +197,11 @@ pkey_rsa_sign(EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                         return -1;
                 }
 
-                if (rctx->pad_mode == RSA_X931_PADDING) {
-                        if ((size_t)EVP_PKEY_size(ctx->pkey) < tbslen + 1) {
-                                RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);
-                                return -1;
-                        }
-                        if (!setup_tbuf(rctx, ctx)) {
-                                RSAerror(ERR_R_MALLOC_FAILURE);
-                                return -1;
-                        }
-                        memcpy(rctx->tbuf, tbs, tbslen);
-                        rctx->tbuf[tbslen] =
-                            RSA_X931_hash_id(EVP_MD_type(rctx->md));
-                        ret = RSA_private_encrypt(tbslen + 1, rctx->tbuf, sig,
-                            rsa, RSA_X931_PADDING);
-                } else if (rctx->pad_mode == RSA_PKCS1_PADDING) {
+                if (rctx->pad_mode != RSA_PKCS1_PADDING &&
+                    rctx->pad_mode != RSA_PKCS1_PSS_PADDING)
+                        return -1;
+
+                if (rctx->pad_mode == RSA_PKCS1_PADDING) {
                         unsigned int sltmp;
 
                         ret = RSA_sign(EVP_MD_type(rctx->md), tbs, tbslen, sig,
@@ -227,8 +217,6 @@ pkey_rsa_sign(EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
                                 return -1;
                         ret = RSA_private_encrypt(RSA_size(rsa), rctx->tbuf,
                             sig, rsa, RSA_NO_PADDING);
-                } else {
-                        return -1;
                 }
         } else {
                 ret = RSA_private_encrypt(tbslen, tbs, sig, ctx->pkey->pkey.rsa,
@@ -248,36 +236,16 @@ pkey_rsa_verifyrecover(EVP_PKEY_CTX *ctx, unsigned char *rout, size_t *routlen,
         RSA_PKEY_CTX *rctx = ctx->data;
 
         if (rctx->md) {
-                if (rctx->pad_mode == RSA_X931_PADDING) {
-                        if (!setup_tbuf(rctx, ctx))
-                                return -1;
-                        ret = RSA_public_decrypt(siglen, sig, rctx->tbuf,
-                            ctx->pkey->pkey.rsa, RSA_X931_PADDING);
-                        if (ret < 1)
-                                return 0;
-                        ret--;
-                        if (rctx->tbuf[ret] !=
-                            RSA_X931_hash_id(EVP_MD_type(rctx->md))) {
-                                RSAerror(RSA_R_ALGORITHM_MISMATCH);
-                                return 0;
-                        }
-                        if (ret != EVP_MD_size(rctx->md)) {
-                                RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
-                                return 0;
-                        }
-                        if (rout)
-                                memcpy(rout, rctx->tbuf, ret);
-                } else if (rctx->pad_mode == RSA_PKCS1_PADDING) {
-                        size_t sltmp;
+                size_t sltmp;
 
-                        ret = int_rsa_verify(EVP_MD_type(rctx->md), NULL, 0,
-                            rout, &sltmp, sig, siglen, ctx->pkey->pkey.rsa);
-                        if (ret <= 0)
-                                return 0;
-                        ret = sltmp;
-                } else {
+                if (rctx->pad_mode != RSA_PKCS1_PADDING)
                         return -1;
-                }
+
+                ret = int_rsa_verify(EVP_MD_type(rctx->md), NULL, 0,
+                    rout, &sltmp, sig, siglen, ctx->pkey->pkey.rsa);
+                if (ret <= 0)
+                        return 0;
+                ret = sltmp;
         } else {
                 ret = RSA_public_decrypt(siglen, sig, rout, ctx->pkey->pkey.rsa,
                     rctx->pad_mode);
@@ -295,6 +263,7 @@ pkey_rsa_verify(EVP_PKEY_CTX *ctx, const unsigned char *sig, size_t siglen,
         RSA_PKEY_CTX *rctx = ctx->data;
         RSA *rsa = ctx->pkey->pkey.rsa;
         size_t rslen;
+        int ret;
 
         if (rctx->md) {
                 if (rctx->pad_mode == RSA_PKCS1_PADDING)
@@ -304,32 +273,24 @@ pkey_rsa_verify(EVP_PKEY_CTX *ctx, const unsigned char *sig, size_t siglen,
                         RSAerror(RSA_R_INVALID_DIGEST_LENGTH);
                         return -1;
                 }
-                if (rctx->pad_mode == RSA_X931_PADDING) {
-                        if (pkey_rsa_verifyrecover(ctx, NULL, &rslen, sig,
-                            siglen) <= 0)
-                                return 0;
-                } else if (rctx->pad_mode == RSA_PKCS1_PSS_PADDING) {
-                        int ret;
 
-                        if (!setup_tbuf(rctx, ctx))
-                                return -1;
-                        ret = RSA_public_decrypt(siglen, sig, rctx->tbuf,
-                            rsa, RSA_NO_PADDING);
-                        if (ret <= 0)
-                                return 0;
-                        ret = RSA_verify_PKCS1_PSS_mgf1(rsa, tbs, rctx->md,
-                            rctx->mgf1md, rctx->tbuf, rctx->saltlen);
-                        if (ret <= 0)
-                                return 0;
-                        return 1;
-                } else {
+                if (rctx->pad_mode != RSA_PKCS1_PSS_PADDING)
                         return -1;
-                }
-        } else {
-                int ret;
 
                 if (!setup_tbuf(rctx, ctx))
                         return -1;
+                ret = RSA_public_decrypt(siglen, sig, rctx->tbuf,
+                    rsa, RSA_NO_PADDING);
+                if (ret <= 0)
+                        return 0;
+                ret = RSA_verify_PKCS1_PSS_mgf1(rsa, tbs, rctx->md,
+                    rctx->mgf1md, rctx->tbuf, rctx->saltlen);
+                if (ret <= 0)
+                        return 0;
+                return 1;
+        } else {
+                if (!setup_tbuf(rctx, ctx))
+                        return -1;
 
                 if ((ret = RSA_public_decrypt(siglen, sig, rctx->tbuf, rsa,
                     rctx->pad_mode)) <= 0)
@@ -404,34 +365,27 @@ check_padding_md(const EVP_MD *md, int padding)
         if (md == NULL)
                 return 1;
 
-        if (padding == RSA_NO_PADDING) {
-                RSAerror(RSA_R_INVALID_PADDING_MODE);
+        if (padding == RSA_NO_PADDING || padding == RSA_X931_PADDING) {
+                RSAerror(RSA_R_ILLEGAL_OR_UNSUPPORTED_PADDING_MODE);
                 return 0;
         }
 
-        if (padding == RSA_X931_PADDING) {
-                if (RSA_X931_hash_id(EVP_MD_type(md)) == -1) {
-                        RSAerror(RSA_R_INVALID_X931_DIGEST);
-                        return 0;
-                }
-        } else {
-                /* List of all supported RSA digests. */
-                switch(EVP_MD_type(md)) {
-                case NID_sha1:
-                case NID_sha224:
-                case NID_sha256:
-                case NID_sha384:
-                case NID_sha512:
-                case NID_md5:
-                case NID_md5_sha1:
-                case NID_md4:
-                case NID_ripemd160:
-                        return 1;
+        /* List of all supported RSA digests. */
+        switch(EVP_MD_type(md)) {
+        case NID_sha1:
+        case NID_sha224:
+        case NID_sha256:
+        case NID_sha384:
+        case NID_sha512:
+        case NID_md5:
+        case NID_md5_sha1:
+        case NID_md4:
+        case NID_ripemd160:
+                return 1;
 
-                default:
-                        RSAerror(RSA_R_INVALID_DIGEST);
-                        return 0;
-                }
+        default:
+                RSAerror(RSA_R_INVALID_DIGEST);
+                return 0;
         }
 
         return 1;
@@ -637,8 +591,6 @@ pkey_rsa_ctrl_str(EVP_PKEY_CTX *ctx, const char *type, const char *value)
                         pm = RSA_PKCS1_OAEP_PADDING;
                 else if (!strcmp(value, "oaep"))
                         pm = RSA_PKCS1_OAEP_PADDING;
-                else if (!strcmp(value, "x931"))
-                        pm = RSA_X931_PADDING;
                 else if (!strcmp(value, "pss"))
                         pm = RSA_PKCS1_PSS_PADDING;
                 else {