summaryrefslogtreecommitdiffstats
path: root/src/sss_client/nss_mc_common.c
blob: d910e17ba62f8e21a970cb0948a406bfa17be34f (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
/*
 * System Security Services Daemon. NSS client interface
 *
 * Copyright (C) Simo Sorce 2011
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* NSS interfaces to mmap cache */

#include "config.h"

#include <stdio.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>
#include "nss_mc.h"

/* FIXME: hook up to library destructor to avoid leaks */
/* FIXME: temporarily open passwd file on our own, later we will probably
 * use socket passing from the main process */
/* FIXME: handle name upper/lower casing ? Maybe a flag passed down by
 * sssd or a flag in sss_mc_header ? per domain ? */

errno_t sss_nss_check_header(struct sss_cli_mc_ctx *ctx)
{
    struct sss_mc_header h;
    int count;

    /* retry barrier protected reading max 5 times then give up */
    for (count = 5; count > 0; count--) {
        memcpy(&h, ctx->mmap_base, sizeof(struct sss_mc_header));
        if (MC_VALID_BARRIER(h.b1) && h.b1 == h.b2) {
            /* record is consistent so we can proceed */
            break;
        }
    }
    if (count == 0) {
        /* couldn't successfully read header we have to give up */
        return EIO;
    }

    if (h.major_vno != SSS_MC_MAJOR_VNO ||
        h.minor_vno != SSS_MC_MINOR_VNO ||
        h.status == SSS_MC_HEADER_RECYCLED) {
        return EINVAL;
    }

    /* first time we check the header, let's fill our own struct */
    if (ctx->data_table == NULL) {
        ctx->seed = h.seed;
        ctx->data_table = MC_PTR_ADD(ctx->mmap_base, h.data_table);
        ctx->hash_table = MC_PTR_ADD(ctx->mmap_base, h.hash_table);
        ctx->dt_size = h.dt_size;
        ctx->ht_size = h.ht_size;
    } else {
        if (ctx->seed != h.seed ||
            ctx->data_table != MC_PTR_ADD(ctx->mmap_base, h.data_table) ||
            ctx->hash_table != MC_PTR_ADD(ctx->mmap_base, h.hash_table) ||
            ctx->dt_size != h.dt_size ||
            ctx->ht_size != h.ht_size) {
            return EINVAL;
        }
    }

    return 0;
}

errno_t sss_nss_mc_get_ctx(const char *name, struct sss_cli_mc_ctx *ctx)
{
    struct stat fdstat;
    char *file = NULL;
    char *envval;
    int ret;

    envval = getenv("_SSS_MC_SPECIAL");
    if (envval && strcmp(envval, "NO") == 0) {
        return EPERM;
    }

    if (ctx->initialized) {
        ret = sss_nss_check_header(ctx);
        goto done;
    }

    ret = asprintf(&file, "%s/%s", SSS_NSS_MCACHE_DIR, name);
    if (ret == -1) {
        ret = ENOMEM;
        goto done;
    }

    ctx->fd = open(file, O_RDONLY|O_CLOEXEC);
    if (ctx->fd == -1) {
        ret = EIO;
        goto done;
    }

    ret = fstat(ctx->fd, &fdstat);
    if (ret == -1) {
        ret = EIO;
        goto done;
    }

    if (fdstat.st_size < MC_HEADER_SIZE) {
        ret = ENOMEM;
        goto done;
    }
    ctx->mmap_size = fdstat.st_size;

    ctx->mmap_base = mmap(NULL, ctx->mmap_size,
                          PROT_READ, MAP_SHARED, ctx->fd, 0);
    if (ctx->mmap_base == MAP_FAILED) {
        ret = ENOMEM;
        goto done;
    }

    ret = sss_nss_check_header(ctx);
    if (ret != 0) {
        goto done;
    }

    ctx->initialized = true;

    ret = 0;

done:
    if (ret) {
        if ((ctx->mmap_base != NULL) && (ctx->mmap_size != 0)) {
            munmap(ctx->mmap_base, ctx->mmap_size);
        }
        if (ctx->fd != -1) {
            close(ctx->fd);
        }
        memset(ctx, 0, sizeof(struct sss_cli_mc_ctx));
    }
    free(file);
    return ret;
}

uint32_t sss_nss_mc_hash(struct sss_cli_mc_ctx *ctx,
                         const char *key, size_t len)
{
    return murmurhash3(key, len, ctx->seed) % MC_HT_ELEMS(ctx->ht_size);
}

errno_t sss_nss_mc_get_record(struct sss_cli_mc_ctx *ctx,
                              uint32_t slot, struct sss_mc_rec **_rec)
{
    struct sss_mc_rec *rec;
    void *rec_buf = NULL;
    size_t buf_size = 0;
    size_t rec_len;
    uint32_t b1;
    uint32_t b2;
    int count;
    int ret;

    /* try max 5 times */
    for (count = 5; count > 0; count--) {
        rec = MC_SLOT_TO_PTR(ctx->data_table, slot, struct sss_mc_rec);

        /* fetch record length */
        b1 = rec->b1;
        __sync_synchronize();
        rec_len = rec->len;
        __sync_synchronize();
        b2 = rec->b1;
        if (!MC_VALID_BARRIER(b1) || b1 != b2) {
            /* record is inconsistent, retry */
            continue;
        }

        if (rec_len > buf_size) {
            free(rec_buf);
            rec_buf = malloc(rec_len);
            if (!rec_buf) {
                ret = ENOMEM;
                goto done;
            }
            buf_size = rec_len;
        }
        /* we cannot access data directly, we must copy data and then
         * access the copy */
        memcpy(rec_buf, rec, rec_len);
        rec = (struct sss_mc_rec *)rec_buf;

        /* we must check data is consistent again after the copy */
        if (MC_VALID_BARRIER(rec->b1) &&
            rec->b1 == rec->b2 &&
            rec->len == rec_len) {
            /* record is consistent, use it */
            break;
        }
    }
    if (count == 0) {
        /* couldn't successfully read header we have to give up */
        ret = EIO;
        goto done;
    }

    *_rec = rec;
    ret = 0;

done:
    if (ret) {
        free(rec_buf);
        *_rec = NULL;
    }
    return ret;
}

/*
 * returns strings froma a buffer.
 *
 * Call first time with *cookie set to null, then call again
 * with the returned cookie.
 * On the last string the cookie will be reset to null and
 * all strings will have been returned.
 * In case the last string is not zero terminated EINVAL is returned.
 */
errno_t sss_nss_str_ptr_from_buffer(char **str, void **cookie,
                                    char *buf, size_t len)
{
    char *max = buf + len;
    char *ret;
    char *p;

    if (*cookie == NULL) {
        p = buf;
    } else {
        p = *((char **)cookie);
    }

    ret = p;

    while (p < max) {
        if (*p == '\0') {
            break;
        }
        p++;
    }
    if (p >= max) {
        return EINVAL;
    }
    p++;
    if (p == max) {
        *cookie = NULL;
    } else {
        *cookie = p;
    }

    *str = ret;
    return 0;
}