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/lib/libcrypto/rsa/rsa_eay.c b/lib/libcrypto/rsa/rsa_eay.c
index b307a8bd88e..e65319bda1c 100644
--- a/lib/libcrypto/rsa/rsa_eay.c
+++ b/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/lib/libcrypto/rsa/rsa_pmeth.c b/lib/libcrypto/rsa/rsa_pmeth.c
index 3747f1dd288..688c0d64dbc 100644
--- a/lib/libcrypto/rsa/rsa_pmeth.c
+++ b/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 {