1/*
2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <stdio.h>
11#include "internal/cryptlib.h"
12#include <openssl/bn.h>
13#include <openssl/rsa.h>
14#include <openssl/objects.h>
15#include <openssl/x509.h>
16#include "crypto/x509.h"
17#include "rsa_local.h"
18
19/* Size of an SSL signature: MD5+SHA1 */
20#define SSL_SIG_LENGTH  36
21
22/*
23 * encode_pkcs1 encodes a DigestInfo prefix of hash |type| and digest |m|, as
24 * described in EMSA-PKCS1-v1_5-ENCODE, RFC 3447 section 9.2 step 2. This
25 * encodes the DigestInfo (T and tLen) but does not add the padding.
26 *
27 * On success, it returns one and sets |*out| to a newly allocated buffer
28 * containing the result and |*out_len| to its length. The caller must free
29 * |*out| with |OPENSSL_free|. Otherwise, it returns zero.
30 */
31static int encode_pkcs1(unsigned char **out, int *out_len, int type,
32                        const unsigned char *m, unsigned int m_len)
33{
34    X509_SIG sig;
35    X509_ALGOR algor;
36    ASN1_TYPE parameter;
37    ASN1_OCTET_STRING digest;
38    uint8_t *der = NULL;
39    int len;
40
41    sig.algor = &algor;
42    sig.algor->algorithm = OBJ_nid2obj(type);
43    if (sig.algor->algorithm == NULL) {
44        RSAerr(RSA_F_ENCODE_PKCS1, RSA_R_UNKNOWN_ALGORITHM_TYPE);
45        return 0;
46    }
47    if (OBJ_length(sig.algor->algorithm) == 0) {
48        RSAerr(RSA_F_ENCODE_PKCS1,
49               RSA_R_THE_ASN1_OBJECT_IDENTIFIER_IS_NOT_KNOWN_FOR_THIS_MD);
50        return 0;
51    }
52    parameter.type = V_ASN1_NULL;
53    parameter.value.ptr = NULL;
54    sig.algor->parameter = &parameter;
55
56    sig.digest = &digest;
57    sig.digest->data = (unsigned char *)m;
58    sig.digest->length = m_len;
59
60    len = i2d_X509_SIG(&sig, &der);
61    if (len < 0)
62        return 0;
63
64    *out = der;
65    *out_len = len;
66    return 1;
67}
68
69int RSA_sign(int type, const unsigned char *m, unsigned int m_len,
70             unsigned char *sigret, unsigned int *siglen, RSA *rsa)
71{
72    int encrypt_len, encoded_len = 0, ret = 0;
73    unsigned char *tmps = NULL;
74    const unsigned char *encoded = NULL;
75
76    if (rsa->meth->rsa_sign) {
77        return rsa->meth->rsa_sign(type, m, m_len, sigret, siglen, rsa);
78    }
79
80    /* Compute the encoded digest. */
81    if (type == NID_md5_sha1) {
82        /*
83         * NID_md5_sha1 corresponds to the MD5/SHA1 combination in TLS 1.1 and
84         * earlier. It has no DigestInfo wrapper but otherwise is
85         * RSASSA-PKCS1-v1_5.
86         */
87        if (m_len != SSL_SIG_LENGTH) {
88            RSAerr(RSA_F_RSA_SIGN, RSA_R_INVALID_MESSAGE_LENGTH);
89            return 0;
90        }
91        encoded_len = SSL_SIG_LENGTH;
92        encoded = m;
93    } else {
94        if (!encode_pkcs1(&tmps, &encoded_len, type, m, m_len))
95            goto err;
96        encoded = tmps;
97    }
98
99    if (encoded_len > RSA_size(rsa) - RSA_PKCS1_PADDING_SIZE) {
100        RSAerr(RSA_F_RSA_SIGN, RSA_R_DIGEST_TOO_BIG_FOR_RSA_KEY);
101        goto err;
102    }
103    encrypt_len = RSA_private_encrypt(encoded_len, encoded, sigret, rsa,
104                                      RSA_PKCS1_PADDING);
105    if (encrypt_len <= 0)
106        goto err;
107
108    *siglen = encrypt_len;
109    ret = 1;
110
111err:
112    OPENSSL_clear_free(tmps, (size_t)encoded_len);
113    return ret;
114}
115
116/*
117 * int_rsa_verify verifies an RSA signature in |sigbuf| using |rsa|. It may be
118 * called in two modes. If |rm| is NULL, it verifies the signature for digest
119 * |m|. Otherwise, it recovers the digest from the signature, writing the digest
120 * to |rm| and the length to |*prm_len|. |type| is the NID of the digest
121 * algorithm to use. It returns one on successful verification and zero
122 * otherwise.
123 */
124int int_rsa_verify(int type, const unsigned char *m, unsigned int m_len,
125                   unsigned char *rm, size_t *prm_len,
126                   const unsigned char *sigbuf, size_t siglen, RSA *rsa)
127{
128    int decrypt_len, ret = 0, encoded_len = 0;
129    unsigned char *decrypt_buf = NULL, *encoded = NULL;
130
131    if (siglen != (size_t)RSA_size(rsa)) {
132        RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_WRONG_SIGNATURE_LENGTH);
133        return 0;
134    }
135
136    /* Recover the encoded digest. */
137    decrypt_buf = OPENSSL_malloc(siglen);
138    if (decrypt_buf == NULL) {
139        RSAerr(RSA_F_INT_RSA_VERIFY, ERR_R_MALLOC_FAILURE);
140        goto err;
141    }
142
143    decrypt_len = RSA_public_decrypt((int)siglen, sigbuf, decrypt_buf, rsa,
144                                     RSA_PKCS1_PADDING);
145    if (decrypt_len <= 0)
146        goto err;
147
148    if (type == NID_md5_sha1) {
149        /*
150         * NID_md5_sha1 corresponds to the MD5/SHA1 combination in TLS 1.1 and
151         * earlier. It has no DigestInfo wrapper but otherwise is
152         * RSASSA-PKCS1-v1_5.
153         */
154        if (decrypt_len != SSL_SIG_LENGTH) {
155            RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
156            goto err;
157        }
158
159        if (rm != NULL) {
160            memcpy(rm, decrypt_buf, SSL_SIG_LENGTH);
161            *prm_len = SSL_SIG_LENGTH;
162        } else {
163            if (m_len != SSL_SIG_LENGTH) {
164                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);
165                goto err;
166            }
167
168            if (memcmp(decrypt_buf, m, SSL_SIG_LENGTH) != 0) {
169                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
170                goto err;
171            }
172        }
173    } else if (type == NID_mdc2 && decrypt_len == 2 + 16
174               && decrypt_buf[0] == 0x04 && decrypt_buf[1] == 0x10) {
175        /*
176         * Oddball MDC2 case: signature can be OCTET STRING. check for correct
177         * tag and length octets.
178         */
179        if (rm != NULL) {
180            memcpy(rm, decrypt_buf + 2, 16);
181            *prm_len = 16;
182        } else {
183            if (m_len != 16) {
184                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_MESSAGE_LENGTH);
185                goto err;
186            }
187
188            if (memcmp(m, decrypt_buf + 2, 16) != 0) {
189                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
190                goto err;
191            }
192        }
193    } else {
194        /*
195         * If recovering the digest, extract a digest-sized output from the end
196         * of |decrypt_buf| for |encode_pkcs1|, then compare the decryption
197         * output as in a standard verification.
198         */
199        if (rm != NULL) {
200            const EVP_MD *md = EVP_get_digestbynid(type);
201            if (md == NULL) {
202                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_UNKNOWN_ALGORITHM_TYPE);
203                goto err;
204            }
205
206            m_len = EVP_MD_size(md);
207            if (m_len > (size_t)decrypt_len) {
208                RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_INVALID_DIGEST_LENGTH);
209                goto err;
210            }
211            m = decrypt_buf + decrypt_len - m_len;
212        }
213
214        /* Construct the encoded digest and ensure it matches. */
215        if (!encode_pkcs1(&encoded, &encoded_len, type, m, m_len))
216            goto err;
217
218        if (encoded_len != decrypt_len
219            || memcmp(encoded, decrypt_buf, encoded_len) != 0) {
220            RSAerr(RSA_F_INT_RSA_VERIFY, RSA_R_BAD_SIGNATURE);
221            goto err;
222        }
223
224        /* Output the recovered digest. */
225        if (rm != NULL) {
226            memcpy(rm, m, m_len);
227            *prm_len = m_len;
228        }
229    }
230
231    ret = 1;
232
233err:
234    OPENSSL_clear_free(encoded, (size_t)encoded_len);
235    OPENSSL_clear_free(decrypt_buf, siglen);
236    return ret;
237}
238
239int RSA_verify(int type, const unsigned char *m, unsigned int m_len,
240               const unsigned char *sigbuf, unsigned int siglen, RSA *rsa)
241{
242
243    if (rsa->meth->rsa_verify) {
244        return rsa->meth->rsa_verify(type, m, m_len, sigbuf, siglen, rsa);
245    }
246
247    return int_rsa_verify(type, m, m_len, NULL, NULL, sigbuf, siglen, rsa);
248}
249