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Diffstat (limited to 'libmisc/salt.c')
| -rw-r--r-- | libmisc/salt.c | 566 |
1 files changed, 566 insertions, 0 deletions
diff --git a/libmisc/salt.c b/libmisc/salt.c new file mode 100644 index 0000000..e5f633a --- /dev/null +++ b/libmisc/salt.c @@ -0,0 +1,566 @@ +/* + * SPDX-FileCopyrightText: Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl> + * SPDX-FileCopyrightText: J.T. Conklin <jtc@netbsd.org> + * + * SPDX-License-Identifier: Unlicense + */ + +/* + * salt.c - generate a random salt string for crypt() + * + * Written by Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl>, + * it is in the public domain. + * + * l64a was Written by J.T. Conklin <jtc@netbsd.org>. Public domain. + */ + +#include <config.h> + +#ident "$Id$" + +#include <assert.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#if HAVE_SYS_RANDOM_H +#include <sys/random.h> +#endif +#include "prototypes.h" +#include "defines.h" +#include "getdef.h" +#include "shadowlog.h" + +#if (defined CRYPT_GENSALT_IMPLEMENTS_AUTO_ENTROPY && \ + CRYPT_GENSALT_IMPLEMENTS_AUTO_ENTROPY) +#define USE_XCRYPT_GENSALT 1 +#else +#define USE_XCRYPT_GENSALT 0 +#endif + +/* Add the salt prefix. */ +#define MAGNUM(array,ch) (array)[0]=(array)[2]='$',(array)[1]=(ch),(array)[3]='\0' + +#ifdef USE_BCRYPT +/* Use $2b$ as prefix for compatibility with OpenBSD's bcrypt. */ +#define BCRYPTMAGNUM(array) (array)[0]=(array)[3]='$',(array)[1]='2',(array)[2]='b',(array)[4]='\0' +#define BCRYPT_SALT_SIZE 22 +/* Default number of rounds if not explicitly specified. */ +#define B_ROUNDS_DEFAULT 13 +/* Minimum number of rounds. */ +#define B_ROUNDS_MIN 4 +/* Maximum number of rounds. */ +#define B_ROUNDS_MAX 31 +#endif /* USE_BCRYPT */ + +#ifdef USE_SHA_CRYPT +/* Fixed salt len for sha{256,512}crypt. */ +#define SHA_CRYPT_SALT_SIZE 16 +/* Default number of rounds if not explicitly specified. */ +#define SHA_ROUNDS_DEFAULT 5000 +/* Minimum number of rounds. */ +#define SHA_ROUNDS_MIN 1000 +/* Maximum number of rounds. */ +#define SHA_ROUNDS_MAX 999999999 +#endif + +#ifdef USE_YESCRYPT +/* + * Default number of base64 characters used for the salt. + * 24 characters gives a 144 bits (18 bytes) salt. Unlike the more + * traditional 128 bits (16 bytes) salt, this 144 bits salt is always + * represented by the same number of base64 characters without padding + * issue, even with a non-standard base64 encoding scheme. + */ +#define YESCRYPT_SALT_SIZE 24 +/* Default cost if not explicitly specified. */ +#define Y_COST_DEFAULT 5 +/* Minimum cost. */ +#define Y_COST_MIN 1 +/* Maximum cost. */ +#define Y_COST_MAX 11 +#endif + +/* Fixed salt len for md5crypt. */ +#define MD5_CRYPT_SALT_SIZE 8 + +/* Generate salt of size salt_size. */ +#define MAX_SALT_SIZE 44 +#define MIN_SALT_SIZE 8 + +/* Maximum size of the generated salt string. */ +#define GENSALT_SETTING_SIZE 100 + +/* local function prototypes */ +static long read_random_bytes (void); +#if !USE_XCRYPT_GENSALT +static /*@observer@*/const char *gensalt (size_t salt_size); +#endif /* !USE_XCRYPT_GENSALT */ +#if defined(USE_SHA_CRYPT) || defined(USE_BCRYPT) +static long shadow_random (long min, long max); +#endif /* USE_SHA_CRYPT || USE_BCRYPT */ +#ifdef USE_SHA_CRYPT +static /*@observer@*/unsigned long SHA_get_salt_rounds (/*@null@*/const int *prefered_rounds); +static /*@observer@*/void SHA_salt_rounds_to_buf (char *buf, unsigned long rounds); +#endif /* USE_SHA_CRYPT */ +#ifdef USE_BCRYPT +static /*@observer@*/unsigned long BCRYPT_get_salt_rounds (/*@null@*/const int *prefered_rounds); +static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, unsigned long rounds); +#endif /* USE_BCRYPT */ +#ifdef USE_YESCRYPT +static /*@observer@*/unsigned long YESCRYPT_get_salt_cost (/*@null@*/const int *prefered_cost); +static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, unsigned long cost); +#endif /* USE_YESCRYPT */ + +#if !USE_XCRYPT_GENSALT && !defined(HAVE_L64A) +static /*@observer@*/char *l64a (long value) +{ + static char buf[8]; + char *s = buf; + int digit; + int i; + + if (value < 0) { + errno = EINVAL; + return(NULL); + } + + for (i = 0; value != 0 && i < 6; i++) { + digit = value & 0x3f; + + if (digit < 2) { + *s = digit + '.'; + } else if (digit < 12) { + *s = digit + '0' - 2; + } else if (digit < 38) { + *s = digit + 'A' - 12; + } else { + *s = digit + 'a' - 38; + } + + value >>= 6; + s++; + } + + *s = '\0'; + + return buf; +} +#endif /* !USE_XCRYPT_GENSALT && !defined(HAVE_L64A) */ + +/* Read sizeof (long) random bytes from /dev/urandom. */ +static long read_random_bytes (void) +{ + long randval = 0; + +#ifdef HAVE_ARC4RANDOM_BUF + /* arc4random_buf, if it exists, can never fail. */ + arc4random_buf (&randval, sizeof (randval)); + goto end; +#endif + +#ifdef HAVE_GETENTROPY + /* getentropy may exist but lack kernel support. */ + if (getentropy (&randval, sizeof (randval)) == 0) { + goto end; + } +#endif + +#ifdef HAVE_GETRANDOM + /* Likewise getrandom. */ + if ((size_t) getrandom (&randval, sizeof (randval), 0) == sizeof (randval)) { + goto end; + } +#endif + + /* Use /dev/urandom as a last resort. */ + FILE *f = fopen ("/dev/urandom", "r"); + if (NULL == f) { + goto fail; + } + + if (fread (&randval, sizeof (randval), 1, f) != 1) { + fclose(f); + goto fail; + } + + fclose(f); + goto end; + +fail: + fprintf (log_get_logfd(), + _("Unable to obtain random bytes.\n")); + exit (1); + +end: + return randval; +} + +#if defined(USE_SHA_CRYPT) || defined(USE_BCRYPT) +/* + * Return a random number between min and max (both included). + * + * It favors slightly the higher numbers. + */ +static long shadow_random (long min, long max) +{ + double drand; + long ret; + + drand = (double) (read_random_bytes () & RAND_MAX) / (double) RAND_MAX; + drand *= (double) (max - min + 1); + /* On systems were this is not random() range is lower, we favor + * higher numbers of salt. */ + ret = (long) (max + 1 - drand); + /* And we catch limits, and use the highest number */ + if ((ret < min) || (ret > max)) { + ret = max; + } + return ret; +} +#endif /* USE_SHA_CRYPT || USE_BCRYPT */ + +#ifdef USE_SHA_CRYPT +/* Return the the rounds number for the SHA crypt methods. */ +static /*@observer@*/unsigned long SHA_get_salt_rounds (/*@null@*/const int *prefered_rounds) +{ + unsigned long rounds; + + if (NULL == prefered_rounds) { + long min_rounds = getdef_long ("SHA_CRYPT_MIN_ROUNDS", -1); + long max_rounds = getdef_long ("SHA_CRYPT_MAX_ROUNDS", -1); + + if ((-1 == min_rounds) && (-1 == max_rounds)) { + rounds = SHA_ROUNDS_DEFAULT; + } + else { + if (-1 == min_rounds) { + min_rounds = max_rounds; + } + + if (-1 == max_rounds) { + max_rounds = min_rounds; + } + + if (min_rounds > max_rounds) { + max_rounds = min_rounds; + } + + rounds = (unsigned long) shadow_random (min_rounds, max_rounds); + } + } else if (0 == *prefered_rounds) { + rounds = SHA_ROUNDS_DEFAULT; + } else { + rounds = (unsigned long) *prefered_rounds; + } + + /* Sanity checks. The libc should also check this, but this + * protects against a rounds_prefix overflow. */ + if (rounds < SHA_ROUNDS_MIN) { + rounds = SHA_ROUNDS_MIN; + } + + if (rounds > SHA_ROUNDS_MAX) { + rounds = SHA_ROUNDS_MAX; + } + + return rounds; +} + +/* + * Fill a salt prefix specifying the rounds number for the SHA crypt methods + * to a buffer. + */ +static /*@observer@*/void SHA_salt_rounds_to_buf (char *buf, unsigned long rounds) +{ + const size_t buf_begin = strlen (buf); + + /* Nothing to do here if SHA_ROUNDS_DEFAULT is used. */ + if (rounds == SHA_ROUNDS_DEFAULT) { + return; + } + + /* + * Check if the result buffer is long enough. + * We are going to write a maximum of 17 bytes, + * plus one byte for the terminator. + * rounds=XXXXXXXXX$ + * 00000000011111111 + * 12345678901234567 + */ + assert (GENSALT_SETTING_SIZE > buf_begin + 17); + + (void) snprintf (buf + buf_begin, 18, "rounds=%lu$", rounds); +} +#endif /* USE_SHA_CRYPT */ + +#ifdef USE_BCRYPT +/* Return the the rounds number for the BCRYPT method. */ +static /*@observer@*/unsigned long BCRYPT_get_salt_rounds (/*@null@*/const int *prefered_rounds) +{ + unsigned long rounds; + + if (NULL == prefered_rounds) { + long min_rounds = getdef_long ("BCRYPT_MIN_ROUNDS", -1); + long max_rounds = getdef_long ("BCRYPT_MAX_ROUNDS", -1); + + if ((-1 == min_rounds) && (-1 == max_rounds)) { + rounds = B_ROUNDS_DEFAULT; + } else { + if (-1 == min_rounds) { + min_rounds = max_rounds; + } + + if (-1 == max_rounds) { + max_rounds = min_rounds; + } + + if (min_rounds > max_rounds) { + max_rounds = min_rounds; + } + + rounds = (unsigned long) shadow_random (min_rounds, max_rounds); + } + } else if (0 == *prefered_rounds) { + rounds = B_ROUNDS_DEFAULT; + } else { + rounds = (unsigned long) *prefered_rounds; + } + + /* Sanity checks. */ + if (rounds < B_ROUNDS_MIN) { + rounds = B_ROUNDS_MIN; + } + +#if USE_XCRYPT_GENSALT + if (rounds > B_ROUNDS_MAX) { + rounds = B_ROUNDS_MAX; + } +#else /* USE_XCRYPT_GENSALT */ + /* + * Use 19 as an upper bound for now, + * because musl doesn't allow rounds >= 20. + * If musl ever supports > 20 rounds, + * rounds should be set to B_ROUNDS_MAX. + */ + if (rounds > 19) { + rounds = 19; + } +#endif /* USE_XCRYPT_GENSALT */ + + return rounds; +} + +/* + * Fill a salt prefix specifying the rounds number for the BCRYPT method + * to a buffer. + */ +static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, unsigned long rounds) +{ + const size_t buf_begin = strlen (buf); + + /* + * Check if the result buffer is long enough. + * We are going to write three bytes, + * plus one byte for the terminator. + * XX$ + * 000 + * 123 + */ + assert (GENSALT_SETTING_SIZE > buf_begin + 3); + + (void) snprintf (buf + buf_begin, 4, "%2.2lu$", rounds); +} +#endif /* USE_BCRYPT */ + +#ifdef USE_YESCRYPT +/* Return the the cost number for the YESCRYPT method. */ +static /*@observer@*/unsigned long YESCRYPT_get_salt_cost (/*@null@*/const int *prefered_cost) +{ + unsigned long cost; + + if (NULL == prefered_cost) { + cost = getdef_num ("YESCRYPT_COST_FACTOR", Y_COST_DEFAULT); + } else if (0 == *prefered_cost) { + cost = Y_COST_DEFAULT; + } else { + cost = (unsigned long) *prefered_cost; + } + + /* Sanity checks. */ + if (cost < Y_COST_MIN) { + cost = Y_COST_MIN; + } + + if (cost > Y_COST_MAX) { + cost = Y_COST_MAX; + } + + return cost; +} + +/* + * Fill a salt prefix specifying the cost for the YESCRYPT method + * to a buffer. + */ +static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, unsigned long cost) +{ + const size_t buf_begin = strlen (buf); + + /* + * Check if the result buffer is long enough. + * We are going to write four bytes, + * plus one byte for the terminator. + * jXX$ + * 0000 + * 1234 + */ + assert (GENSALT_SETTING_SIZE > buf_begin + 4); + + buf[buf_begin + 0] = 'j'; + if (cost < 3) { + buf[buf_begin + 1] = 0x36 + cost; + } else if (cost < 6) { + buf[buf_begin + 1] = 0x34 + cost; + } else { + buf[buf_begin + 1] = 0x3b + cost; + } + buf[buf_begin + 2] = cost >= 3 ? 'T' : '5'; + buf[buf_begin + 3] = '$'; + buf[buf_begin + 4] = '\0'; +} +#endif /* USE_YESCRYPT */ + +#if !USE_XCRYPT_GENSALT +static /*@observer@*/const char *gensalt (size_t salt_size) +{ + static char salt[MAX_SALT_SIZE + 6]; + + memset (salt, '\0', MAX_SALT_SIZE + 6); + + assert (salt_size >= MIN_SALT_SIZE && + salt_size <= MAX_SALT_SIZE); + strcat (salt, l64a (read_random_bytes ())); + do { + strcat (salt, l64a (read_random_bytes ())); + } while (strlen (salt) < salt_size); + + salt[salt_size] = '\0'; + + return salt; +} +#endif /* !USE_XCRYPT_GENSALT */ + +/* + * Generate 8 base64 ASCII characters of random salt. If MD5_CRYPT_ENAB + * in /etc/login.defs is "yes", the salt string will be prefixed by "$1$" + * (magic) and pw_encrypt() will execute the MD5-based FreeBSD-compatible + * version of crypt() instead of the standard one. + * Other methods can be set with ENCRYPT_METHOD + * + * The method can be forced with the meth parameter. + * If NULL, the method will be defined according to the ENCRYPT_METHOD + * variable, and if not set according to the MD5_CRYPT_ENAB variable, + * which can both be set inside the login.defs file. + * + * If meth is specified, an additional parameter can be provided. + * * For the SHA256 and SHA512 method, this specifies the number of rounds + * (if not NULL). + * * For the YESCRYPT method, this specifies the cost factor (if not NULL). + */ +/*@observer@*/const char *crypt_make_salt (/*@null@*//*@observer@*/const char *meth, /*@null@*/void *arg) +{ + static char result[GENSALT_SETTING_SIZE]; + size_t salt_len = MAX_SALT_SIZE; + const char *method; + unsigned long rounds = 0; + + memset (result, '\0', GENSALT_SETTING_SIZE); + + if (NULL != meth) + method = meth; + else { + method = getdef_str ("ENCRYPT_METHOD"); + if (NULL == method) { + method = getdef_bool ("MD5_CRYPT_ENAB") ? "MD5" : "DES"; + } + } + + if (0 == strcmp (method, "MD5")) { + MAGNUM(result, '1'); + salt_len = MD5_CRYPT_SALT_SIZE; + rounds = 0; +#ifdef USE_BCRYPT + } else if (0 == strcmp (method, "BCRYPT")) { + BCRYPTMAGNUM(result); + salt_len = BCRYPT_SALT_SIZE; + rounds = BCRYPT_get_salt_rounds ((int *) arg); + BCRYPT_salt_rounds_to_buf (result, rounds); +#endif /* USE_BCRYPT */ +#ifdef USE_YESCRYPT + } else if (0 == strcmp (method, "YESCRYPT")) { + MAGNUM(result, 'y'); + salt_len = YESCRYPT_SALT_SIZE; + rounds = YESCRYPT_get_salt_cost ((int *) arg); + YESCRYPT_salt_cost_to_buf (result, rounds); +#endif /* USE_YESCRYPT */ +#ifdef USE_SHA_CRYPT + } else if (0 == strcmp (method, "SHA256")) { + MAGNUM(result, '5'); + salt_len = SHA_CRYPT_SALT_SIZE; + rounds = SHA_get_salt_rounds ((int *) arg); + SHA_salt_rounds_to_buf (result, rounds); + } else if (0 == strcmp (method, "SHA512")) { + MAGNUM(result, '6'); + salt_len = SHA_CRYPT_SALT_SIZE; + rounds = SHA_get_salt_rounds ((int *) arg); + SHA_salt_rounds_to_buf (result, rounds); +#endif /* USE_SHA_CRYPT */ + } else if (0 != strcmp (method, "DES")) { + fprintf (log_get_logfd(), + _("Invalid ENCRYPT_METHOD value: '%s'.\n" + "Defaulting to DES.\n"), + method); + salt_len = MAX_SALT_SIZE; + rounds = 0; + memset (result, '\0', GENSALT_SETTING_SIZE); + } + +#if USE_XCRYPT_GENSALT + /* + * Prepare DES setting for crypt_gensalt(), if result + * has not been filled with anything previously. + */ + if ('\0' == result[0]) { + /* Avoid -Wunused-but-set-variable. */ + salt_len = GENSALT_SETTING_SIZE - 1; + rounds = 0; + memset (result, '.', salt_len); + result[salt_len] = '\0'; + } + + char *retval = crypt_gensalt (result, rounds, NULL, 0); + + /* Should not happen, but... */ + if (NULL == retval) { + fprintf (log_get_logfd(), + _("Unable to generate a salt from setting " + "\"%s\", check your settings in " + "ENCRYPT_METHOD and the corresponding " + "configuration for your selected hash " + "method.\n"), result); + + exit (1); + } + + return retval; +#else /* USE_XCRYPT_GENSALT */ + /* Check if the result buffer is long enough. */ + assert (GENSALT_SETTING_SIZE > strlen (result) + salt_len); + + /* Concatenate a pseudo random salt. */ + strncat (result, gensalt (salt_len), + GENSALT_SETTING_SIZE - strlen (result) - 1); + + return result; +#endif /* USE_XCRYPT_GENSALT */ +} |