aboutsummaryrefslogtreecommitdiff
path: root/src/packet_crypt.c
blob: 2fd8e0fe6ab607d48d2eed618c3e94a9941bda39 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
/*
 * crypt.c - blowfish-cbc code
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003 by Aris Adamantiadis
 *
 * The SSH Library is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * The SSH Library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#include "config.h"
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#ifndef _WIN32
#include <netinet/in.h>
#include <arpa/inet.h>
#endif

#ifdef OPENSSL_CRYPTO
#include <openssl/evp.h>
#include <openssl/hmac.h>
#endif

#include "libssh/priv.h"
#include "libssh/session.h"
#include "libssh/wrapper.h"
#include "libssh/crypto.h"
#include "libssh/buffer.h"

/** @internal
 * @brief decrypt the packet length from a raw encrypted packet, and store the first decrypted
 * blocksize.
 * @returns native byte-ordered decrypted length of the upcoming packet
 */
uint32_t ssh_packet_decrypt_len(ssh_session session,
                                uint8_t *destination,
                                uint8_t *source)
{
    struct ssh_crypto_struct *crypto = NULL;
    uint32_t decrypted;
    int rc;

    crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_IN);
    if (crypto != NULL) {
        if (crypto->in_cipher->aead_decrypt_length != NULL) {
            crypto->in_cipher->aead_decrypt_length(
                    crypto->in_cipher, source, destination,
                    crypto->in_cipher->lenfield_blocksize,
                    session->recv_seq);
        } else {
            rc = ssh_packet_decrypt(
                    session,
                    destination,
                    source,
                    0,
                    crypto->in_cipher->blocksize);
            if (rc < 0) {
                return 0;
            }
        }
    } else {
        memcpy(destination, source, 8);
    }
    memcpy(&decrypted,destination,sizeof(decrypted));

    return ntohl(decrypted);
}

/** @internal
 * @brief decrypts the content of an SSH packet.
 * @param[source] source packet, including the encrypted length field
 * @param[start] index in the packet that was not decrypted yet.
 * @param[encrypted_size] size of the encrypted data to be decrypted after start.
 */
int ssh_packet_decrypt(ssh_session session,
                       uint8_t *destination,
                       uint8_t *source,
                       size_t start,
                       size_t encrypted_size)
{
    struct ssh_crypto_struct *crypto = NULL;
    struct ssh_cipher_struct *cipher = NULL;

    if (encrypted_size <= 0) {
        return SSH_ERROR;
    }

    crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_IN);
    cipher = crypto->in_cipher;

    if (encrypted_size % cipher->blocksize != 0) {
        ssh_set_error(session,
                      SSH_FATAL,
                      "Cryptographic functions must be used on multiple of "
                      "blocksize (received %" PRIdS ")",
                      encrypted_size);
        return SSH_ERROR;
    }

    if (cipher->aead_decrypt != NULL) {
        return cipher->aead_decrypt(cipher,
                                    source,
                                    destination,
                                    encrypted_size,
                                    session->recv_seq);
    } else {
        cipher->decrypt(cipher, source + start, destination, encrypted_size);
    }

    return 0;
}

unsigned char *ssh_packet_encrypt(ssh_session session, void *data, uint32_t len)
{
  struct ssh_crypto_struct *crypto = NULL;
  struct ssh_cipher_struct *cipher = NULL;
  HMACCTX ctx = NULL;
  char *out = NULL;
  unsigned int finallen, blocksize;
  uint32_t seq, lenfield_blocksize;
  enum ssh_hmac_e type;

  assert(len);

  crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_OUT);
  if (crypto == NULL) {
      return NULL; /* nothing to do here */
  }

  blocksize = crypto->out_cipher->blocksize;
  lenfield_blocksize = crypto->out_cipher->lenfield_blocksize;
  if ((len - lenfield_blocksize) % blocksize != 0) {
      ssh_set_error(session, SSH_FATAL, "Cryptographic functions must be set"
                    " on at least one blocksize (received %d)", len);
      return NULL;
  }
  out = calloc(1, len);
  if (out == NULL) {
    return NULL;
  }

  type = crypto->out_hmac;
  seq = ntohl(session->send_seq);
  cipher = crypto->out_cipher;

  if (cipher->aead_encrypt != NULL) {
      cipher->aead_encrypt(cipher, data, out, len,
            crypto->hmacbuf, session->send_seq);
  } else {
      ctx = hmac_init(crypto->encryptMAC, hmac_digest_len(type), type);
      if (ctx == NULL) {
        SAFE_FREE(out);
        return NULL;
      }
      hmac_update(ctx,(unsigned char *)&seq,sizeof(uint32_t));
      hmac_update(ctx,data,len);
      hmac_final(ctx, crypto->hmacbuf, &finallen);

#ifdef DEBUG_CRYPTO
      ssh_print_hexa("mac: ",data,hmac_digest_len(type));
      if (finallen != hmac_digest_len(type)) {
        printf("Final len is %d\n",finallen);
      }
      ssh_print_hexa("Packet hmac", crypto->hmacbuf, hmac_digest_len(type));
#endif
      cipher->encrypt(cipher, data, out, len);
  }
  memcpy(data, out, len);
  explicit_bzero(out, len);
  SAFE_FREE(out);

  return crypto->hmacbuf;
}

static int secure_memcmp(const void *s1, const void *s2, size_t n)
{
    int rc = 0;
    const unsigned char *p1 = s1;
    const unsigned char *p2 = s2;
    for (; n > 0; --n) {
        rc |= *p1++ ^ *p2++;
    }
    return (rc != 0);
}

/**
 * @internal
 *
 * @brief Verify the hmac of a packet
 *
 * @param  session      The session to use.
 * @param  data         The pointer to the data to verify the hmac from.
 * @param  len          The length of the given data.
 * @param  mac          The mac to compare with the hmac.
 *
 * @return              0 if hmac and mac are equal, < 0 if not or an error
 *                      occurred.
 */
int ssh_packet_hmac_verify(ssh_session session,
                           const void *data,
                           size_t len,
                           uint8_t *mac,
                           enum ssh_hmac_e type)
{
  struct ssh_crypto_struct *crypto = NULL;
  unsigned char hmacbuf[DIGEST_MAX_LEN] = {0};
  HMACCTX ctx;
  unsigned int hmaclen;
  uint32_t seq;

  /* AEAD types have no mac checking */
  if (type == SSH_HMAC_AEAD_POLY1305 ||
      type == SSH_HMAC_AEAD_GCM) {
      return SSH_OK;
  }

  crypto = ssh_packet_get_current_crypto(session, SSH_DIRECTION_IN);
  ctx = hmac_init(crypto->decryptMAC, hmac_digest_len(type), type);
  if (ctx == NULL) {
    return -1;
  }

  seq = htonl(session->recv_seq);

  hmac_update(ctx, (unsigned char *) &seq, sizeof(uint32_t));
  hmac_update(ctx, data, len);
  hmac_final(ctx, hmacbuf, &hmaclen);

#ifdef DEBUG_CRYPTO
  ssh_print_hexa("received mac",mac,hmaclen);
  ssh_print_hexa("Computed mac",hmacbuf,hmaclen);
  ssh_print_hexa("seq",(unsigned char *)&seq,sizeof(uint32_t));
#endif
  if (secure_memcmp(mac, hmacbuf, hmaclen) == 0) {
    return 0;
  }

  return -1;
}