Add a helper function that does make_salt+crypt_r

[thirdparty/systemd.git] / src / shared / libcrypt-util.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#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 "missing_stdlib.h"
#include "random-util.h"
#include "string-util.h"
#include "strv.h"

int make_salt(char **ret) {

#ifdef XCRYPT_VERSION_MAJOR
        const char *e;
        char *salt;

        /* If we have libxcrypt we default to the "preferred method" (i.e. usually yescrypt), and generate it
         * with crypt_gensalt_ra(). */

        e = secure_getenv("SYSTEMD_CRYPT_PREFIX");
        if (!e)
                e = crypt_preferred_method();

        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 libxcrypt is not used, we use SHA512 and generate the salt on our own since crypt_gensalt_ra()
         * is not available. */

        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);

        /* 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
}

int hash_password(const char *password, char **ret) {
        _cleanup_free_ char *salt = NULL;
        char *p;
        struct crypt_data cd = {};
        int r;

        r = make_salt(&salt);
        if (r < 0)
                return log_debug_errno(r, "Failed to generate salt: %m");

        errno = 0;
        p = crypt_r(password, salt, &cd);
        if (!p)
                return log_debug_errno(errno_or_else(SYNTHETIC_ERRNO(EINVAL)),
                                       "crypt_r() 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", "*");
}