From ea04eb301d08c0c58f1120f87d4ec184d3983ce5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Bj=C3=B6rn=20Esser?= Date: Tue, 15 Jun 2021 14:23:42 +0200 Subject: [PATCH] libmisc/salt.c: Use crypt_gensalt(), if available in libcrypt. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Most Linux distributions, including Fedora and RHEL 8, are shipping with libxcrypt >= 4.0. Since that version of libxcrypt the provided family of crypt_gensalt() functions are able to use automatic entropy drawn from secure system ressources, like arc4random(), getentropy() or getrandom(). Anyways, the settings generated by crypt_gensalt() are always guaranteed to works with the crypt() function. Using crypt_gensalt() is also needed to make proper use of newer hashing methods, like yescrypt, provided by libxcrypt. Signed-off-by: Björn Esser --- libmisc/salt.c | 132 +++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 105 insertions(+), 27 deletions(-) diff --git a/libmisc/salt.c b/libmisc/salt.c index 13408a53..9fd34332 100644 --- a/libmisc/salt.c +++ b/libmisc/salt.c @@ -22,6 +22,13 @@ #include "defines.h" #include "getdef.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' @@ -77,21 +84,26 @@ /* 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@*/void SHA_salt_rounds_to_buf (char *buf, /*@null@*/int *prefered_rounds); +static /*@observer@*/const unsigned long SHA_get_salt_rounds (/*@null@*/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@*/void BCRYPT_salt_rounds_to_buf (char *buf, /*@null@*/int *prefered_rounds); +static /*@observer@*/const unsigned long BCRYPT_get_salt_rounds (/*@null@*/int *prefered_rounds); +static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, unsigned long rounds); #endif /* USE_BCRYPT */ #ifdef USE_YESCRYPT -static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, /*@null@*/int *prefered_cost); +static /*@observer@*/const unsigned long YESCRYPT_get_salt_cost (/*@null@*/int *prefered_cost); +static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, unsigned long cost); #endif /* USE_YESCRYPT */ -#ifndef HAVE_L64A +#if !USE_XCRYPT_GENSALT && !defined(HAVE_L64A) static /*@observer@*/char *l64a (long value) { static char buf[8]; @@ -125,7 +137,7 @@ static /*@observer@*/char *l64a (long value) return buf; } -#endif /* !HAVE_L64A */ +#endif /* !USE_XCRYPT_GENSALT && !defined(HAVE_L64A) */ /* Read sizeof (long) random bytes from /dev/urandom. */ static long read_random_bytes (void) @@ -199,14 +211,10 @@ static long shadow_random (long min, long max) #endif /* USE_SHA_CRYPT || USE_BCRYPT */ #ifdef USE_SHA_CRYPT -/* - * 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, /*@null@*/int *prefered_rounds) +/* Return the the rounds number for the SHA crypt methods. */ +static /*@observer@*/const unsigned long SHA_get_salt_rounds (/*@null@*/int *prefered_rounds) { unsigned long rounds; - const size_t buf_begin = strlen (buf); if (NULL == prefered_rounds) { long min_rounds = getdef_long ("SHA_CRYPT_MIN_ROUNDS", -1); @@ -245,6 +253,17 @@ static /*@observer@*/void SHA_salt_rounds_to_buf (char *buf, /*@null@*/int *pref 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; @@ -265,14 +284,10 @@ static /*@observer@*/void SHA_salt_rounds_to_buf (char *buf, /*@null@*/int *pref #endif /* USE_SHA_CRYPT */ #ifdef USE_BCRYPT -/* - * 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, /*@null@*/int *prefered_rounds) +/* Return the the rounds number for the BCRYPT method. */ +static /*@observer@*/const unsigned long BCRYPT_get_salt_rounds (/*@null@*/int *prefered_rounds) { unsigned long rounds; - const size_t buf_begin = strlen (buf); if (NULL == prefered_rounds) { long min_rounds = getdef_long ("BCRYPT_MIN_ROUNDS", -1); @@ -306,6 +321,11 @@ static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, /*@null@*/int *p 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. @@ -314,6 +334,18 @@ static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, /*@null@*/int *p /* rounds = B_ROUNDS_MAX; */ 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. @@ -330,14 +362,10 @@ static /*@observer@*/void BCRYPT_salt_rounds_to_buf (char *buf, /*@null@*/int *p #endif /* USE_BCRYPT */ #ifdef USE_YESCRYPT -/* - * Fill a salt prefix specifying the cost for the YESCRYPT method - * to a buffer. - */ -static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, /*@null@*/int *prefered_cost) +/* Return the the cost number for the YESCRYPT method. */ +static /*@observer@*/const unsigned long YESCRYPT_get_salt_cost (/*@null@*/int *prefered_cost) { unsigned long cost; - const size_t buf_begin = strlen (buf); if (NULL == prefered_cost) { cost = getdef_num ("YESCRYPT_COST_FACTOR", Y_COST_DEFAULT); @@ -356,6 +384,17 @@ static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, /*@null@*/int *p 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, @@ -380,6 +419,7 @@ static /*@observer@*/void YESCRYPT_salt_cost_to_buf (char *buf, /*@null@*/int *p } #endif /* USE_YESCRYPT */ +#if !USE_XCRYPT_GENSALT static /*@observer@*/const char *gensalt (size_t salt_size) { static char salt[MAX_SALT_SIZE + 6]; @@ -397,6 +437,7 @@ static /*@observer@*/const char *gensalt (size_t salt_size) return salt; } +#endif /* !USE_XCRYPT_GENSALT */ /* * Generate 8 base64 ASCII characters of random salt. If MD5_CRYPT_ENAB @@ -420,6 +461,7 @@ static /*@observer@*/const char *gensalt (size_t salt_size) 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); @@ -435,27 +477,32 @@ static /*@observer@*/const char *gensalt (size_t salt_size) 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; - BCRYPT_salt_rounds_to_buf (result, (int *) arg); + 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; - YESCRYPT_salt_cost_to_buf (result, (int *) arg); + 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; - SHA_salt_rounds_to_buf (result, (int *) arg); + 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; - SHA_salt_rounds_to_buf (result, (int *) arg); + 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 (shadow_logfd, @@ -463,9 +510,39 @@ static /*@observer@*/const char *gensalt (size_t salt_size) "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 (shadow_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); @@ -474,4 +551,5 @@ static /*@observer@*/const char *gensalt (size_t salt_size) GENSALT_SETTING_SIZE - strlen (result) - 1); return result; +#endif /* USE_XCRYPT_GENSALT */ }