/*

 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the OpenSSL license (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <stdio.h>

#include "internal/cryptlib.h"

#include <openssl/bn.h>

#include <openssl/rsa.h>

#include <openssl/objects.h>

#include <openssl/x509.h>

#include "internal/x509_int.h"

#include "rsa_locl.h"

/* Size of an SSL signature: MD5+SHA1 */

#define SSL_SIG_LENGTH  36

/*

 * encode_pkcs1 encodes a DigestInfo prefix of hash |type| and digest |m|, as

 * described in EMSA-PKCS1-v1_5-ENCODE, RFC 3447 section 9.2 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. The caller must free

 * |*out| with |OPENSSL_free|. Otherwise, it returns 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;

    sig.algor->algorithm = OBJ_nid2obj(type);

    if (sig.algor->algorithm == NULL) {

        RSAerr(RSA_F_ENCODE_PKCS1, RSA_R_UNKNOWN_ALGORITHM_TYPE);

        return 0;

    }

    if (OBJ_length(sig.algor->algorithm) == 0) {

        RSAerr(RSA_F_ENCODE_PKCS1,

               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 = &parameter;

    sig.digest = &digest;

    sig.digest->data = (unsigned char *)m;

    sig.digest->length = m_len;

    len = i2d_X509_SIG(&sig, &der);

    if (len < 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)

{

    int encrypt_len, encoded_len = 0, ret = 0;

    unsigned char *tmps = NULL;

    const unsigned char *encoded = NULL;

    if (rsa->meth->rsa_sign) {

        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-PKCS1-v1_5.

         */

        if (m_len != SSL_SIG_LENGTH) {

            RSAerr(RSA_F_RSA_SIGN, RSA_R_INVALID_MESSAGE_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) {

        RSAerr(RSA_F_RSA_SIGN, RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);

        goto err;

    }

    encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, rsa,

                                      RSA_PKCS1_PADDING);

    if (encrypt_len <= 0)

        goto err;

    *siglen = encrypt_len;

    ret = 1;

err:

    OPENSSL_clear_free(tmps, (size_t)encoded_len);

    return ret;

}

/*

 * 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 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)

{

    int decrypt_len, ret = 0, encoded_len = 0;

    unsigned char *decrypt_buf = NULL, *encoded = NULL;

    if (siglen != (size_t)RSA_size(rsa)) {

        RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_WRONG_SIGNATURE_LENGTH);

        return 0;

    }

    /* Recover the encoded digest. */

    decrypt_buf = OPENSSL_malloc(siglen);

    if (decrypt_buf == NULL) {

        RSAerr(RSA_F_INT_RSA_VERIFY, ERR_R_MALLOC_FAILURE);

        goto err;

    }

    decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, rsa,

                                     RSA_PKCS1_PADDING);

    if (decrypt_len <= 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) {

            RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);

            goto err;

        }

        if (rm != NULL) {

            memcpy(rm, decrypt_buf, SSL_SIG_LENGTH);

            *prm_len = SSL_SIG_LENGTH;

        } else {

            if (m_len != SSL_SIG_LENGTH) {

                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);

                goto err;

            }

            if (memcmp(decrypt_buf, m, SSL_SIG_LENGTH) != 0) {

                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);

                goto err;

            }

        }

    } else if (type == NID_mdc2 && decrypt_len == 2 + 16

               && decrypt_buf[0] == 0x04 && decrypt_buf[1] == 0x10) {

        /*

         * Oddball MDC2 case: signature can be OCTET STRING. check for correct

         * tag and length octets.

         */

        if (rm != NULL) {

            memcpy(rm, decrypt_buf + 2, 16);

            *prm_len = 16;

        } else {

            if (m_len != 16) {

                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);

                goto err;

            }

            if (memcmp(m, decrypt_buf + 2, 16) != 0) {

                RSAerr(RSA_F_INT_RSA_VERIFY, 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 = EVP_get_digestbynid(type);

            if (md == NULL) {

                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_UNKNOWN_ALGORITHM_TYPE);

                goto err;

            }

            m_len = EVP_MD_size(md);

            if (m_len > (size_t)decrypt_len) {

                RSAerr(RSA_F_INT_RSA_VERIFY, 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

            || memcmp(encoded, decrypt_buf, encoded_len) != 0) {

            RSAerr(RSA_F_INT_RSA_VERIFY, 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:

    OPENSSL_clear_free(encoded, (size_t)encoded_len);

    OPENSSL_clear_free(decrypt_buf, siglen);

    return ret;

}

int RSA_verify(int type, const unsigned char *m, unsigned int m_len,

               const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)

{

    if (rsa->meth->rsa_verify) {

        return rsa->meth->rsa_verify(type, m, m_len, sigbuf, siglen, rsa);

    }

    return int_rsa_verify(type, m, m_len, NULL, NULL, sigbuf, siglen, rsa);

}