src/basic/khash.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2016 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <linux/if_alg.h>
  21 #include <stdbool.h>
  22 #include <sys/socket.h>
  23
  24 #include "alloc-util.h"
  25 #include "fd-util.h"
  26 #include "hexdecoct.h"
  27 #include "khash.h"
  28 #include "macro.h"
  29 #include "missing.h"
  30 #include "string-util.h"
  31 #include "util.h"
  32
  33 /* On current kernels the maximum digest (according to "grep digestsize /proc/crypto | sort -u") is actually 32, but
  34  * let's add some extra room, the few wasted bytes don't really matter... */
  35 #define LONGEST_DIGEST 128
  36
  37 struct khash {
  38         int fd;
  39         char *algorithm;
  40         uint8_t digest[LONGEST_DIGEST+1];
  41         size_t digest_size;
  42         bool digest_valid;
  43 };
  44
  45 int khash_new_with_key(khash **ret, const char *algorithm, const void *key, size_t key_size) {
  46         union {
  47                 struct sockaddr sa;
  48                 struct sockaddr_alg alg;
  49         } sa = {
  50                 .alg.salg_family = AF_ALG,
  51                 .alg.salg_type = "hash",
  52         };
  53
  54         _cleanup_(khash_unrefp) khash *h = NULL;
  55         _cleanup_close_ int fd = -1;
  56         ssize_t n;
  57
  58         assert(ret);
  59         assert(key || key_size == 0);
  60
  61         /* Filter out an empty algorithm early, as we do not support an algorithm by that name. */
  62         if (isempty(algorithm))
  63                 return -EINVAL;
  64
  65         /* Overly long hash algorithm names we definitely do not support */
  66         if (strlen(algorithm) >= sizeof(sa.alg.salg_name))
  67                 return -EOPNOTSUPP;
  68
  69         fd = socket(AF_ALG, SOCK_SEQPACKET|SOCK_CLOEXEC, 0);
  70         if (fd < 0)
  71                 return -errno;
  72
  73         strcpy((char*) sa.alg.salg_name, algorithm);
  74         if (bind(fd, &sa.sa, sizeof(sa)) < 0) {
  75                 if (errno == ENOENT)
  76                         return -EOPNOTSUPP;
  77                 return -errno;
  78         }
  79
  80         if (key) {
  81                 if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, key, key_size) < 0)
  82                         return -errno;
  83         }
  84
  85         h = new0(khash, 1);
  86         if (!h)
  87                 return -ENOMEM;
  88
  89         h->fd = accept4(fd, NULL, 0, SOCK_CLOEXEC);
  90         if (h->fd < 0)
  91                 return -errno;
  92
  93         h->algorithm = strdup(algorithm);
  94         if (!h->algorithm)
  95                 return -ENOMEM;
  96
  97         /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
  98         (void) send(h->fd, NULL, 0, 0);
  99
 100         /* Figure out the digest size */
 101         n = recv(h->fd, h->digest, sizeof(h->digest), 0);
 102         if (n < 0)
 103                 return -errno;
 104         if (n >= LONGEST_DIGEST) /* longer than what we expected? If so, we don't support this */
 105                 return -EOPNOTSUPP;
 106
 107         h->digest_size = (size_t) n;
 108         h->digest_valid = true;
 109
 110         /* Temporary fix for rc kernel bug: https://bugzilla.redhat.com/show_bug.cgi?id=1395896 */
 111         (void) send(h->fd, NULL, 0, 0);
 112
 113         *ret = h;
 114         h = NULL;
 115
 116         return 0;
 117 }
 118
 119 int khash_new(khash **ret, const char *algorithm) {
 120         return khash_new_with_key(ret, algorithm, NULL, 0);
 121 }
 122
 123 khash* khash_unref(khash *h) {
 124         if (!h)
 125                 return NULL;
 126
 127         safe_close(h->fd);
 128         free(h->algorithm);
 129         free(h);
 130
 131         return NULL;
 132 }
 133
 134 int khash_dup(khash *h, khash **ret) {
 135         _cleanup_(khash_unrefp) khash *copy = NULL;
 136
 137         assert(h);
 138         assert(ret);
 139
 140         copy = newdup(khash, h, 1);
 141         if (!copy)
 142                 return -ENOMEM;
 143
 144         copy->fd = -1;
 145         copy->algorithm = strdup(h->algorithm);
 146         if (!copy->algorithm)
 147                 return -ENOMEM;
 148
 149         copy->fd = accept4(h->fd, NULL, 0, SOCK_CLOEXEC);
 150         if (copy->fd < 0)
 151                 return -errno;
 152
 153         *ret = copy;
 154         copy = NULL;
 155
 156         return 0;
 157 }
 158
 159 const char *khash_get_algorithm(khash *h) {
 160         assert(h);
 161
 162         return h->algorithm;
 163 }
 164
 165 size_t khash_get_size(khash *h) {
 166         assert(h);
 167
 168         return h->digest_size;
 169 }
 170
 171 int khash_reset(khash *h) {
 172         ssize_t n;
 173
 174         assert(h);
 175
 176         n = send(h->fd, NULL, 0, 0);
 177         if (n < 0)
 178                 return -errno;
 179
 180         h->digest_valid = false;
 181
 182         return 0;
 183 }
 184
 185 int khash_put(khash *h, const void *buffer, size_t size) {
 186         ssize_t n;
 187
 188         assert(h);
 189         assert(buffer || size == 0);
 190
 191         if (size <= 0)
 192                 return 0;
 193
 194         n = send(h->fd, buffer, size, MSG_MORE);
 195         if (n < 0)
 196                 return -errno;
 197
 198         h->digest_valid = false;
 199
 200         return 0;
 201 }
 202
 203 int khash_put_iovec(khash *h, const struct iovec *iovec, size_t n) {
 204         struct msghdr mh = {
 205                 mh.msg_iov = (struct iovec*) iovec,
 206                 mh.msg_iovlen = n,
 207         };
 208         ssize_t k;
 209
 210         assert(h);
 211         assert(iovec || n == 0);
 212
 213         if (n <= 0)
 214                 return 0;
 215
 216         k = sendmsg(h->fd, &mh, MSG_MORE);
 217         if (k < 0)
 218                 return -errno;
 219
 220         h->digest_valid = false;
 221
 222         return 0;
 223 }
 224
 225 static int retrieve_digest(khash *h) {
 226         ssize_t n;
 227
 228         assert(h);
 229
 230         if (h->digest_valid)
 231                 return 0;
 232
 233         n = recv(h->fd, h->digest, h->digest_size, 0);
 234         if (n < 0)
 235                 return n;
 236         if ((size_t) n != h->digest_size) /* digest size changed? */
 237                 return -EIO;
 238
 239         h->digest_valid = true;
 240
 241         return 0;
 242 }
 243
 244 int khash_digest_data(khash *h, const void **ret) {
 245         int r;
 246
 247         assert(h);
 248         assert(ret);
 249
 250         r = retrieve_digest(h);
 251         if (r < 0)
 252                 return r;
 253
 254         *ret = h->digest;
 255         return 0;
 256 }
 257
 258 int khash_digest_string(khash *h, char **ret) {
 259         int r;
 260         char *p;
 261
 262         assert(h);
 263         assert(ret);
 264
 265         r = retrieve_digest(h);
 266         if (r < 0)
 267                 return r;
 268
 269         p = hexmem(h->digest, h->digest_size);
 270         if (!p)
 271                 return -ENOMEM;
 272
 273         *ret = p;
 274         return 0;
 275 }