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Diffstat (limited to 'src/shared/libcrypt-util.c')
| -rw-r--r-- | src/shared/libcrypt-util.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/src/shared/libcrypt-util.c b/src/shared/libcrypt-util.c new file mode 100644 index 0000000..5b31541 --- /dev/null +++ b/src/shared/libcrypt-util.c @@ -0,0 +1,212 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#if HAVE_CRYPT_H +/* libxcrypt is a replacement for glibc's libcrypt, and libcrypt might be + * removed from glibc at some point. As part of the removal, defines for + * crypt(3) are dropped from unistd.h, and we must include crypt.h instead. + * + * Newer versions of glibc (v2.0+) already ship crypt.h with a definition + * of crypt(3) as well, so we simply include it if it is present. MariaDB, + * MySQL, PostgreSQL, Perl and some other wide-spread packages do it the + * same way since ages without any problems. + */ +# include <crypt.h> +#else +# include <unistd.h> +#endif + +#include <errno.h> +#include <stdlib.h> + +#include "alloc-util.h" +#include "errno-util.h" +#include "libcrypt-util.h" +#include "log.h" +#include "macro.h" +#include "memory-util.h" +#include "missing_stdlib.h" +#include "random-util.h" +#include "string-util.h" +#include "strv.h" + +int make_salt(char **ret) { + +#if HAVE_CRYPT_GENSALT_RA + const char *e; + char *salt; + + /* If we have crypt_gensalt_ra() we default to the "preferred method" (i.e. usually yescrypt). + * crypt_gensalt_ra() is usually provided by libxcrypt. */ + + e = secure_getenv("SYSTEMD_CRYPT_PREFIX"); + if (!e) +#if HAVE_CRYPT_PREFERRED_METHOD + e = crypt_preferred_method(); +#else + e = "$6$"; +#endif + + log_debug("Generating salt for hash prefix: %s", e); + + salt = crypt_gensalt_ra(e, 0, NULL, 0); + if (!salt) + return -errno; + + *ret = salt; + return 0; +#else + /* If crypt_gensalt_ra() is not available, we use SHA512 and generate the salt on our own. */ + + static const char table[] = + "abcdefghijklmnopqrstuvwxyz" + "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789" + "./"; + + uint8_t raw[16]; + char *salt, *j; + size_t i; + int r; + + /* This is a bit like crypt_gensalt_ra(), but doesn't require libcrypt, and doesn't do anything but + * SHA512, i.e. is legacy-free and minimizes our deps. */ + + assert_cc(sizeof(table) == 64U + 1U); + + log_debug("Generating fallback salt for hash prefix: $6$"); + + /* Insist on the best randomness by setting RANDOM_BLOCK, this is about keeping passwords secret after all. */ + r = genuine_random_bytes(raw, sizeof(raw), RANDOM_BLOCK); + if (r < 0) + return r; + + salt = new(char, 3+sizeof(raw)+1+1); + if (!salt) + return -ENOMEM; + + /* We only bother with SHA512 hashed passwords, the rest is legacy, and we don't do legacy. */ + j = stpcpy(salt, "$6$"); + for (i = 0; i < sizeof(raw); i++) + j[i] = table[raw[i] & 63]; + j[i++] = '$'; + j[i] = 0; + + *ret = salt; + return 0; +#endif +} + +#if HAVE_CRYPT_RA +# define CRYPT_RA_NAME "crypt_ra" +#else +# define CRYPT_RA_NAME "crypt_r" + +/* Provide a poor man's fallback that uses a fixed size buffer. */ + +static char* systemd_crypt_ra(const char *phrase, const char *setting, void **data, int *size) { + assert(data); + assert(size); + + /* We allocate the buffer because crypt(3) says: struct crypt_data may be quite large (32kB in this + * implementation of libcrypt; over 128kB in some other implementations). This is large enough that + * it may be unwise to allocate it on the stack. */ + + if (!*data) { + *data = new0(struct crypt_data, 1); + if (!*data) { + errno = -ENOMEM; + return NULL; + } + + *size = (int) (sizeof(struct crypt_data)); + } + + char *t = crypt_r(phrase, setting, *data); + if (!t) + return NULL; + + /* crypt_r may return a pointer to an invalid hashed password on error. Our callers expect NULL on + * error, so let's just return that. */ + if (t[0] == '*') + return NULL; + + return t; +} + +#define crypt_ra systemd_crypt_ra + +#endif + +int hash_password_full(const char *password, void **cd_data, int *cd_size, char **ret) { + _cleanup_free_ char *salt = NULL; + _cleanup_(erase_and_freep) void *_cd_data = NULL; + char *p; + int r, _cd_size = 0; + + assert(!!cd_data == !!cd_size); + + r = make_salt(&salt); + if (r < 0) + return log_debug_errno(r, "Failed to generate salt: %m"); + + errno = 0; + p = crypt_ra(password, salt, cd_data ?: &_cd_data, cd_size ?: &_cd_size); + if (!p) + return log_debug_errno(errno_or_else(SYNTHETIC_ERRNO(EINVAL)), + CRYPT_RA_NAME "() failed: %m"); + + p = strdup(p); + if (!p) + return -ENOMEM; + + *ret = p; + return 0; +} + +bool looks_like_hashed_password(const char *s) { + /* Returns false if the specified string is certainly not a hashed UNIX password. crypt(5) lists + * various hashing methods. We only reject (return false) strings which are documented to have + * different meanings. + * + * In particular, we allow locked passwords, i.e. strings starting with "!", including just "!", + * i.e. the locked empty password. See also fc58c0c7bf7e4f525b916e3e5be0de2307fef04e. + */ + if (!s) + return false; + + s += strspn(s, "!"); /* Skip (possibly duplicated) locking prefix */ + + return !STR_IN_SET(s, "x", "*"); +} + +int test_password_one(const char *hashed_password, const char *password) { + _cleanup_(erase_and_freep) void *cd_data = NULL; + int cd_size = 0; + const char *k; + + errno = 0; + k = crypt_ra(password, hashed_password, &cd_data, &cd_size); + if (!k) { + if (errno == ENOMEM) + return -ENOMEM; + /* Unknown or unavailable hashing method or string too short */ + return 0; + } + + return streq(k, hashed_password); +} + +int test_password_many(char **hashed_password, const char *password) { + char **hpw; + int r; + + STRV_FOREACH(hpw, hashed_password) { + r = test_password_one(*hpw, password); + if (r < 0) + return r; + if (r > 0) + return true; + } + + return false; +} |