aboutsummaryrefslogtreecommitdiff
path: root/src/knownhosts.c
blob: cf353ef5f25090f8d15039f1138e7e714eceaf1c (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
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
/*
 * known_hosts: Host and public key verification.
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2009 by Aris Adamantiadis
 * Copyright (c) 2009-2017 by Andreas Schneider <asn@cryptomilk.org>
 *
 * 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 <ctype.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#include "libssh/priv.h"
#include "libssh/session.h"
#include "libssh/options.h"
#include "libssh/misc.h"
#include "libssh/pki.h"

static int hash_hostname(const char *name,
                         unsigned char *salt,
                         unsigned int salt_size,
                         unsigned char **hash,
                         unsigned int *hash_size)
{
    HMACCTX mac_ctx;

    mac_ctx = hmac_init(salt, salt_size, SSH_HMAC_SHA1);
    if (mac_ctx == NULL) {
        return SSH_ERROR;
    }

    hmac_update(mac_ctx, name, strlen(name));
    hmac_final(mac_ctx, *hash, hash_size);

    return SSH_OK;
}

static int match_hashed_hostname(const char *host, const char *hashed_host)
{
    char *hashed;
    char *b64_hash;
    ssh_buffer salt = NULL;
    ssh_buffer hash = NULL;
    unsigned char hashed_buf[256] = {0};
    unsigned char *hashed_buf_ptr = hashed_buf;
    unsigned int hashed_buf_size = sizeof(hashed_buf);
    int cmp;
    int rc;
    int match = 0;

    cmp = strncmp(hashed_host, "|1|", 3);
    if (cmp != 0) {
        return 0;
    }

    hashed = strdup(hashed_host + 3);
    if (hashed == NULL) {
        return 0;
    }

    b64_hash = strchr(hashed, '|');
    if (b64_hash == NULL) {
        goto error;
    }
    *b64_hash = '\0';
    b64_hash++;

    salt = base64_to_bin(hashed);
    if (salt == NULL) {
        goto error;
    }

    hash = base64_to_bin(b64_hash);
    if (hash == NULL) {
        goto error;
    }

    rc = hash_hostname(host,
                       ssh_buffer_get(salt),
                       ssh_buffer_get_len(salt),
                       &hashed_buf_ptr,
                       &hashed_buf_size);
    if (rc != SSH_OK) {
        goto error;
    }

    if (hashed_buf_size != ssh_buffer_get_len(hash)) {
        goto error;
    }

    cmp = memcmp(hashed_buf, ssh_buffer_get(hash), hashed_buf_size);
    if (cmp == 0) {
        match = 1;
    }

error:
    free(hashed);
    ssh_buffer_free(salt);
    ssh_buffer_free(hash);

    return match;
}

/**
 * @brief Free an allocated ssh_knownhosts_entry.
 *
 * Use SSH_KNOWNHOSTS_ENTRY_FREE() to set the pointer to NULL.
 *
 * @param[in]  entry     The entry to free.
 */
void ssh_knownhosts_entry_free(struct ssh_knownhosts_entry *entry)
{
    if (entry == NULL) {
        return;
    }

    SAFE_FREE(entry->hostname);
    SAFE_FREE(entry->unparsed);
    ssh_key_free(entry->publickey);
    SAFE_FREE(entry->comment);
    SAFE_FREE(entry);
}

static int known_hosts_read_line(FILE *fp,
                                 char *buf,
                                 size_t buf_size,
                                 size_t *buf_len,
                                 size_t *lineno)
{
    while (fgets(buf, buf_size, fp) != NULL) {
        size_t len;
        if (buf[0] == '\0') {
            continue;
        }

        *lineno += 1;
        len = strlen(buf);
        if (buf_len != NULL) {
            *buf_len = len;
        }
        if (buf[len - 1] == '\n' || feof(fp)) {
            return 0;
        } else {
            errno = E2BIG;
            return -1;
        }
    }

    return -1;
}

static int ssh_known_hosts_read_entries(const char *match,
                                        const char *filename,
                                        struct ssh_list **entries)
{
    struct ssh_list *entry_list;
    char line[8192];
    size_t lineno = 0;
    size_t len = 0;
    FILE *fp;
    int rc;

    fp = fopen(filename, "r");
    if (fp == NULL) {
        return SSH_ERROR;
    }

    entry_list = ssh_list_new();
    if (entry_list == NULL) {
        return SSH_ERROR;
    }

    for (rc = known_hosts_read_line(fp, line, sizeof(line), &len, &lineno);
         rc == 0;
         rc = known_hosts_read_line(fp, line, sizeof(line), &len, &lineno)) {
        struct ssh_knownhosts_entry *entry = NULL;
        char *p;

        if (line[len] != '\n') {
            len = strcspn(line, "\n");
        }
        line[len] = '\0';

        /* Skip leading spaces */
        for (p = line; isspace((int)p[0]); p++);

        /* Skip comments and empty lines */
        if (p[0] == '\0' || p[0] == '#') {
            continue;
        }

        rc = ssh_known_hosts_parse_line(match,
                                        line,
                                        &entry);
        if (rc == SSH_AGAIN) {
            continue;
        } else if (rc != SSH_OK) {
            goto error;
        }
        ssh_list_append(entry_list, entry);
    }

    *entries = entry_list;

    return SSH_OK;
error:
    ssh_list_free(entry_list);
    return SSH_ERROR;
}

/**
 * @brief Parse a line from a known_hosts entry into a structure
 *
 * This parses an known_hosts entry into a structure with the key in a libssh
 * consumeable form. You can use the PKI key function to further work with it.
 *
 * @param[in]  hostname     The hostname to match the line to
 *
 * @param[in]  line         The line to compare and parse if we have a hostname
 *                          match.
 *
 * @param[in]  entry        A pointer to store the the allocated known_hosts
 *                          entry structure. The user needs to free the memory
 *                          using SSH_KNOWNHOSTS_ENTRY_FREE().
 *
 * @return SSH_OK on success, SSH_ERROR otherwise.
 */
int ssh_known_hosts_parse_line(const char *hostname,
                               const char *line,
                               struct ssh_knownhosts_entry **entry)
{
    struct ssh_knownhosts_entry *e = NULL;
    char *known_host = NULL;
    char *p;
    enum ssh_keytypes_e key_type;
    int match = 0;
    int rc = SSH_OK;

    known_host = strdup(line);
    if (known_host == NULL) {
        return SSH_ERROR;
    }

    /* match pattern for hostname or hashed hostname */
    p = strtok(known_host, " ");
    if (p == NULL ) {
        free(known_host);
        return SSH_ERROR;
    }

    e = calloc(1, sizeof(struct ssh_knownhosts_entry));
    if (e == NULL) {
        free(known_host);
        return SSH_ERROR;
    }

    if (hostname != NULL) {
        char *match_pattern = NULL;
        char *q;

        /* Hashed */
        if (p[0] == '|') {
            match = match_hashed_hostname(hostname, p);
        }

        for (q = strtok(p, ",");
             q != NULL;
             q = strtok(NULL, ",")) {
            int cmp;

            cmp = match_hostname(hostname, q, strlen(q));
            if (cmp == 1) {
                match = 1;
                break;
            }
        }
        SAFE_FREE(match_pattern);

        if (match == 0) {
            rc = SSH_AGAIN;
            goto out;
        }

        e->hostname = strdup(hostname);
        if (e->hostname == NULL) {
            rc = SSH_ERROR;
            goto out;
        }
    }

    /* Restart parsing */
    SAFE_FREE(known_host);
    known_host = strdup(line);
    if (known_host == NULL) {
        return SSH_ERROR;
    }

    p = strtok(known_host, " ");
    if (p == NULL ) {
        free(known_host);
        return SSH_ERROR;
    }

    e->unparsed = strdup(p);
    if (e->unparsed == NULL) {
        rc = SSH_ERROR;
        goto out;
    }

    /* pubkey type */
    p = strtok(NULL, " ");
    if (p == NULL) {
        rc = SSH_ERROR;
        goto out;
    }

    key_type = ssh_key_type_from_name(p);
    if (key_type == SSH_KEYTYPE_UNKNOWN) {
        SSH_LOG(SSH_LOG_WARN, "key type '%s' unknown!", p);
        rc = SSH_ERROR;
        goto out;
    }

    /* public key */
    p = strtok(NULL, " ");
    if (p == NULL) {
        rc = SSH_ERROR;
        goto out;
    }

    rc = ssh_pki_import_pubkey_base64(p,
                                      key_type,
                                      &e->publickey);
    if (rc != SSH_OK) {
        SSH_LOG(SSH_LOG_WARN,
                "Failed to parse %s key for entry: %s!",
                ssh_key_type_to_char(key_type),
                e->unparsed);
        goto out;
    }

    /* comment */
    p = strtok(NULL, " ");
    if (p != NULL) {
        p = strstr(line, p);
        e->comment = strdup(p);
        if (e->comment == NULL) {
            rc = SSH_ERROR;
            goto out;
        }
    }

    *entry = e;
    SAFE_FREE(known_host);

    return SSH_OK;
out:
    SAFE_FREE(known_host);
    ssh_knownhosts_entry_free(e);
    return rc;
}