diff options
Diffstat (limited to 'lib/random.c')
| -rw-r--r-- | lib/random.c | 245 |
1 files changed, 245 insertions, 0 deletions
diff --git a/lib/random.c b/lib/random.c new file mode 100644 index 0000000..ee5df63 --- /dev/null +++ b/lib/random.c @@ -0,0 +1,245 @@ +/* + * cryptsetup kernel RNG access functions + * + * Copyright (C) 2010-2021 Red Hat, Inc. All rights reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include <stdlib.h> +#include <string.h> +#include <errno.h> +#include <assert.h> +#include <sys/select.h> + +#include "libcryptsetup.h" +#include "internal.h" + +static int random_initialised = 0; + +#define URANDOM_DEVICE "/dev/urandom" +static int urandom_fd = -1; + +#define RANDOM_DEVICE "/dev/random" +static int random_fd = -1; + +/* Read random chunk - gathered data usually appears with this granularity */ +#define RANDOM_DEVICE_CHUNK 8 + +/* Timeout to print warning if no random data (entropy) */ +#define RANDOM_DEVICE_TIMEOUT 5 + +/* URANDOM_DEVICE access */ +static int _get_urandom(struct crypt_device *ctx __attribute__((unused)), + char *buf, size_t len) +{ + int r; + size_t old_len = len; + char *old_buf = buf; + + assert(urandom_fd != -1); + + while(len) { + r = read(urandom_fd, buf, len); + if (r == -1 && errno != EINTR) + return -EINVAL; + if (r > 0) { + len -= r; + buf += r; + } + } + + assert(len == 0); + assert((size_t)(buf - old_buf) == old_len); + + return 0; +} + +static void _get_random_progress(struct crypt_device *ctx, int warn, + size_t expected_len, size_t read_len) +{ + if (warn) + log_std(ctx, + _("System is out of entropy while generating volume key.\n" + "Please move mouse or type some text in another window " + "to gather some random events.\n")); + + log_std(ctx, _("Generating key (%d%% done).\n"), + (int)((expected_len - read_len) * 100 / expected_len)); +} + +/* RANDOM_DEVICE access */ +static int _get_random(struct crypt_device *ctx, char *buf, size_t len) +{ + int r, warn_once = 1; + size_t n, old_len = len; + char *old_buf = buf; + fd_set fds; + struct timeval tv; + + assert(random_fd != -1); + + while (len) { + FD_ZERO(&fds); + FD_SET(random_fd, &fds); + + tv.tv_sec = RANDOM_DEVICE_TIMEOUT; + tv.tv_usec = 0; + + r = select(random_fd + 1, &fds, NULL, NULL, &tv); + if(r == -1) + return -EINVAL; + + if(!r) { + _get_random_progress(ctx, warn_once, old_len, len); + warn_once = 0; + continue; + } + + do { + n = RANDOM_DEVICE_CHUNK; + if (len < RANDOM_DEVICE_CHUNK) + n = len; + + r = read(random_fd, buf, n); + + if (r == -1 && errno == EINTR) { + r = 0; + continue; + } + + /* bogus read? */ + if(r > (int)n) + return -EINVAL; + + /* random device is opened with O_NONBLOCK, EAGAIN is expected */ + if (r == -1 && (errno != EAGAIN && errno != EWOULDBLOCK)) + return -EINVAL; + + if (r > 0) { + len -= r; + buf += r; + } + } while (len && r > 0); + } + + assert(len == 0); + assert((size_t)(buf - old_buf) == old_len); + + if (!warn_once) + _get_random_progress(ctx, 0, old_len, len); + + return 0; +} +/* Initialisation of both RNG file descriptors is mandatory */ +int crypt_random_init(struct crypt_device *ctx) +{ + if (random_initialised) + return 0; + + /* Used for CRYPT_RND_NORMAL */ + if(urandom_fd == -1) + urandom_fd = open(URANDOM_DEVICE, O_RDONLY | O_CLOEXEC); + if(urandom_fd == -1) + goto fail; + + /* Used for CRYPT_RND_KEY */ + if(random_fd == -1) + random_fd = open(RANDOM_DEVICE, O_RDONLY | O_NONBLOCK | O_CLOEXEC); + if(random_fd == -1) + goto fail; + + if (crypt_fips_mode()) + log_verbose(ctx, _("Running in FIPS mode.")); + + random_initialised = 1; + return 0; +fail: + crypt_random_exit(); + log_err(ctx, _("Fatal error during RNG initialisation.")); + return -ENOSYS; +} + +int crypt_random_get(struct crypt_device *ctx, char *buf, size_t len, int quality) +{ + int status, rng_type; + + switch(quality) { + case CRYPT_RND_NORMAL: + status = _get_urandom(ctx, buf, len); + break; + case CRYPT_RND_SALT: + if (crypt_fips_mode()) + status = crypt_backend_rng(buf, len, quality, 1); + else + status = _get_urandom(ctx, buf, len); + break; + case CRYPT_RND_KEY: + if (crypt_fips_mode()) { + status = crypt_backend_rng(buf, len, quality, 1); + break; + } + rng_type = ctx ? crypt_get_rng_type(ctx) : + crypt_random_default_key_rng(); + switch (rng_type) { + case CRYPT_RNG_URANDOM: + status = _get_urandom(ctx, buf, len); + break; + case CRYPT_RNG_RANDOM: + status = _get_random(ctx, buf, len); + break; + default: + abort(); + } + break; + default: + log_err(ctx, _("Unknown RNG quality requested.")); + return -EINVAL; + } + + if (status) + log_err(ctx, _("Error reading from RNG.")); + + return status; +} + +void crypt_random_exit(void) +{ + random_initialised = 0; + + if(random_fd != -1) { + (void)close(random_fd); + random_fd = -1; + } + + if(urandom_fd != -1) { + (void)close(urandom_fd); + urandom_fd = -1; + } +} + +int crypt_random_default_key_rng(void) +{ + /* coverity[pointless_string_compare] */ + if (!strcmp(DEFAULT_RNG, RANDOM_DEVICE)) + return CRYPT_RNG_RANDOM; + + /* coverity[pointless_string_compare] */ + if (!strcmp(DEFAULT_RNG, URANDOM_DEVICE)) + return CRYPT_RNG_URANDOM; + + /* RNG misconfiguration is fatal */ + abort(); +} |