/* $OpenBSD: rsa_sign.c,v 1.38 2025/05/10 05:54:38 tb Exp $ */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */ #include <stdio.h> #include <string.h> #include <openssl/bn.h> #include <openssl/objects.h> #include <openssl/rsa.h> #include <openssl/x509.h> #include "asn1_local.h" #include "err_local.h" #include "rsa_local.h" #include "x509_local.h" /* Size of an SSL signature: MD5+SHA1 */ #define SSL_SIG_LENGTH 36 static int encode_pkcs1(unsigned char **, int *, int , const unsigned char *, unsigned int); /* * encode_pkcs1 encodes a DigestInfo prefix of hash `type' and digest `m', as * described in EMSA-PKCS-v1_5-ENCODE, RFC 8017 section 9. step 2. This * encodes the DigestInfo (T and tLen) but does not add the padding. * * On success, it returns one and sets `*out' to a newly allocated buffer * containing the result and `*out_len' to its length. Freeing `*out' is * the caller's responsibility. Failure is indicated by zero. */ static int encode_pkcs1(unsigned char **out, int *out_len, int type, const unsigned char *m, unsigned int m_len) { X509_SIG sig; X509_ALGOR algor; ASN1_TYPE parameter; ASN1_OCTET_STRING digest; uint8_t *der = NULL; int len; sig.algor = &algor; if ((sig.algor->algorithm = OBJ_nid2obj(type)) == NULL) { RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); return 0; } if (sig.algor->algorithm->length == 0) { RSAerror( RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD); return 0; } parameter.type = V_ASN1_NULL; parameter.value.ptr = NULL; sig.algor->parameter = ¶meter; sig.digest = &digest; sig.digest->data = (unsigned char *)m; /* TMP UGLY CAST */ sig.digest->length = m_len; if ((len = i2d_X509_SIG(&sig, &der)) < 0) return 0; *out = der; *out_len = len; return 1; } int RSA_sign(int type, const unsigned char *m, unsigned int m_len, unsigned char *sigret, unsigned int *siglen, RSA *rsa) { const unsigned char *encoded = NULL; unsigned char *tmps = NULL; int encrypt_len, encoded_len = 0, ret = 0; if (rsa->meth->rsa_sign != NULL) return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa); /* Compute the encoded digest. */ if (type == NID_md5_sha1) { /* * NID_md5_sha1 corresponds to the MD5/SHA1 combination in * TLS 1.1 and earlier. It has no DigestInfo wrapper but * otherwise is RSASSA-PKCS-v1.5. */ if (m_len != SSL_SIG_LENGTH) { RSAerror(RSA_R_INVALID_DIGEST_LENGTH); return 0; } encoded_len = SSL_SIG_LENGTH; encoded = m; } else { if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len)) goto err; encoded = tmps; } if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) { RSAerror(RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY); goto err; } if ((encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, rsa, RSA_PKCS1_PADDING)) <= 0) goto err; *siglen = encrypt_len; ret = 1; err: freezero(tmps, (size_t)encoded_len); return (ret); } LCRYPTO_ALIAS(RSA_sign); /* * int_rsa_verify verifies an RSA signature in `sigbuf' using `rsa'. It may be * called in two modes. If `rm' is NULL, it verifies the signature for the * digest `m'. Otherwise, it recovers the digest from the signature, writing the * digest to `rm' and the length to `*prm_len'. `type' is the NID of the digest * algorithm to use. It returns one on successful verification and zero * otherwise. */ int int_rsa_verify(int type, const unsigned char *m, unsigned int m_len, unsigned char *rm, size_t *prm_len, const unsigned char *sigbuf, size_t siglen, RSA *rsa) { unsigned char *decrypt_buf, *encoded = NULL; int decrypt_len, encoded_len = 0, ret = 0; if (siglen != (size_t)RSA_size(rsa)) { RSAerror(RSA_R_WRONG_SIGNATURE_LENGTH); return 0; } /* Recover the encoded digest. */ if ((decrypt_buf = malloc(siglen)) == NULL) { RSAerror(ERR_R_MALLOC_FAILURE); goto err; } if ((decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, rsa, RSA_PKCS1_PADDING)) <= 0) goto err; if (type == NID_md5_sha1) { /* * NID_md5_sha1 corresponds to the MD5/SHA1 combination in * TLS 1.1 and earlier. It has no DigestInfo wrapper but * otherwise is RSASSA-PKCS1-v1_5. */ if (decrypt_len != SSL_SIG_LENGTH) { RSAerror(RSA_R_INVALID_DIGEST_LENGTH); goto err; } if (rm != NULL) { memcpy(rm, decrypt_buf, SSL_SIG_LENGTH); *prm_len = SSL_SIG_LENGTH; } else { if (m_len != SSL_SIG_LENGTH) { RSAerror(RSA_R_INVALID_MESSAGE_LENGTH); goto err; } if (timingsafe_bcmp(decrypt_buf, m, SSL_SIG_LENGTH) != 0) { RSAerror(RSA_R_BAD_SIGNATURE); goto err; } } } else { /* * If recovering the digest, extract a digest-sized output from * the end of `decrypt_buf' for `encode_pkcs1', then compare the * decryption output as in a standard verification. */ if (rm != NULL) { const EVP_MD *md; if ((md = EVP_get_digestbynid(type)) == NULL) { RSAerror(RSA_R_UNKNOWN_ALGORITHM_TYPE); goto err; } if ((m_len = EVP_MD_size(md)) > (size_t)decrypt_len) { RSAerror(RSA_R_INVALID_DIGEST_LENGTH); goto err; } m = decrypt_buf + decrypt_len - m_len; } /* Construct the encoded digest and ensure it matches */ if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len)) goto err; if (encoded_len != decrypt_len || timingsafe_bcmp(encoded, decrypt_buf, encoded_len) != 0) { RSAerror(RSA_R_BAD_SIGNATURE); goto err; } /* Output the recovered digest. */ if (rm != NULL) { memcpy(rm, m, m_len); *prm_len = m_len; } } ret = 1; err: freezero(encoded, (size_t)encoded_len); freezero(decrypt_buf, siglen); return ret; } int RSA_verify(int dtype, const unsigned char *m, unsigned int m_len, const unsigned char *sigbuf, unsigned int siglen, RSA *rsa) { if (rsa->meth->rsa_verify != NULL) return rsa->meth->rsa_verify(dtype, m, m_len, sigbuf, siglen, rsa); return int_rsa_verify(dtype, m, m_len, NULL, NULL, sigbuf, siglen, rsa); } LCRYPTO_ALIAS(RSA_verify);
