Merge pull request #17082 from poettering/nspawn-ctty-tweaks

nspawn controlling tty tweaks

TODO

@@ -20,11 +20,23 @@ Janitorial Clean-ups:
 
 Features:
 
-* nss-systemd: also synthesize shadow records for users/groups
+* add wrapper for mount() that uses O_PATH on the destination and than mounts
+  to /proc/self/fd/xxx so that we basically have a mount() with O_NOFOLLOW like
+  behaviour. (in case of bind mounts do it on both source and target)
 
-* nspawn: move "incoming mount" directory to /run/host, move "inaccessible"
-  nodes to /run/host, move notify socket (for sd_notify() between payload and
-  container manager)
+* add root=tmpfs that mounts a tmpfs to /sysroot (to be used in combination
+  with usr=…, for a similar effect as systemd.volatile=yes but without the
+  "hide-out" effect). Also, add root=gpt-auto-late support or so, that is like
+  root=gpt-auto but initially mounts a tmpfs to /sysroot, and then revisits
+  later after systemd-repart ran. Usecase: let's ship images with only /usr
+  partition, then on first boot create the root partition. In this case we want
+  to read the repart data from /usr before the root partition exists. Add
+  usr=gpt-auto that automatically finds a /usr partition.
+
+* homed: keep an fd to the homedir open at all times, to keep the fs pinned
+  (autofs and such) while user is loged in.
+
+* nss-systemd: also synthesize shadow records for users/groups
 
 * make use of new glibc 2.32 APIs sigabbrev_np() and strerrorname_np().
 
@@ -65,9 +77,6 @@ Features:
   often for one, let's turn it off entirely for a while. Use that for the
   /proc/self/mountinfo logic.
 
-* move our systemd-user PAM snippet to /usr/, which PAM appears to support
-  these days
-
 * nspawn: support time namespaces
 
 * systemd-firstboot: make sure to always use chase_symlinks() before

man/systemd-nspawn.xml

@@ -1370,15 +1370,18 @@
 
         <listitem><para>Configures how to set up standard input, output and error output for the container
         payload, as well as the <filename>/dev/console</filename> device for the container. Takes one of
-        <option>interactive</option>, <option>read-only</option>, <option>passive</option>, or
-        <option>pipe</option>. If <option>interactive</option>, a pseudo-TTY is allocated and made available
-        as <filename>/dev/console</filename> in the container. It is then bi-directionally connected to the
-        standard input and output passed to <command>systemd-nspawn</command>. <option>read-only</option> is
-        similar but only the output of the container is propagated and no input from the caller is read. If
-        <option>passive</option>, a pseudo TTY is allocated, but it is not connected anywhere. Finally, in
-        <option>pipe</option> mode no pseudo TTY is allocated, but the standard input, output and error
-        output file descriptors passed to <command>systemd-nspawn</command> are passed on — as they are — to
-        the container payload, see the following paragraph. Defaults to <option>interactive</option> if
+        <option>interactive</option>, <option>read-only</option>, <option>passive</option>,
+        <option>pipe</option> or <option>autopipe</option>. If <option>interactive</option>, a pseudo-TTY is
+        allocated and made available as <filename>/dev/console</filename> in the container. It is then
+        bi-directionally connected to the standard input and output passed to
+        <command>systemd-nspawn</command>. <option>read-only</option> is similar but only the output of the
+        container is propagated and no input from the caller is read. If <option>passive</option>, a pseudo
+        TTY is allocated, but it is not connected anywhere. In <option>pipe</option> mode no pseudo TTY is
+        allocated, but the standard input, output and error output file descriptors passed to
+        <command>systemd-nspawn</command> are passed on — as they are — to the container payload, see the
+        following paragraph. Finally, <option>autopipe</option> mode operates like
+        <option>interactive</option> when <command>systemd-nspawn</command> is invoked on a terminal, and
+        like <option>pipe</option> otherwise. Defaults to <option>interactive</option> if
         <command>systemd-nspawn</command> is invoked from a terminal, and <option>read-only</option>
         otherwise.</para>
 

meson.build

@@ -882,6 +882,17 @@ libm = cc.find_library('m')
 libdl = cc.find_library('dl')
 libcrypt = cc.find_library('crypt')
 
+crypt_header = conf.get('HAVE_CRYPT_H') == 1 ? \
+               '''#include <crypt.h>''' : '''#include <unistd.h>'''
+foreach ident : [
+        ['crypt_ra',          crypt_header],
+        ['crypt_gensalt_ra',  crypt_header]]
+
+        have = cc.has_function(ident[0], prefix : ident[1], args : '-D_GNU_SOURCE',
+                               dependencies : libcrypt)
+        conf.set10('HAVE_' + ident[0].to_upper(), have)
+endforeach
+
 libcap = dependency('libcap', required : false)
 if not libcap.found()
         # Compat with Ubuntu 14.04 which ships libcap w/o .pc file

src/firstboot/firstboot.c

@@ -802,7 +802,7 @@ static int write_root_shadow(const char *shadow_path, const char *hashed_passwor
 
 static int process_root_args(void) {
         _cleanup_close_ int lock = -1;
-        struct crypt_data cd = {};
+        _cleanup_(erase_and_freep) char *_hashed_password = NULL;
         const char *password, *hashed_password;
         const char *etc_passwd, *etc_shadow;
         int r;
@@ -866,20 +866,13 @@ static int process_root_args(void) {
                 password = "x";
                 hashed_password = arg_root_password;
         } else if (arg_root_password) {
-                _cleanup_free_ char *salt = NULL;
-                /* hashed_password points inside cd after crypt_r returns so cd has function scope. */
+                r = hash_password(arg_root_password, &_hashed_password);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to hash password: %m");
 
                 password = "x";
+                hashed_password = _hashed_password;
 
-                r = make_salt(&salt);
-                if (r < 0)
-                        return log_error_errno(r, "Failed to get salt: %m");
-
-                errno = 0;
-                hashed_password = crypt_r(arg_root_password, salt, &cd);
-                if (!hashed_password)
-                        return log_error_errno(errno == 0 ? SYNTHETIC_ERRNO(EINVAL) : errno,
-                                        "Failed to encrypt password: %m");
         } else if (arg_delete_root_password)
                 password = hashed_password = "";
         else

src/home/home-util.c

@@ -1,7 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
 #include "dns-domain.h"
-#include "errno-util.h"
 #include "home-util.h"
 #include "libcrypt-util.h"
 #include "memory-util.h"
@@ -134,35 +133,3 @@ int bus_message_append_secret(sd_bus_message *m, UserRecord *secret) {
 
         return sd_bus_message_append(m, "s", formatted);
 }
-
-int test_password_one(const char *hashed_password, const char *password) {
-        struct crypt_data cc = {};
-        const char *k;
-        bool b;
-
-        errno = 0;
-        k = crypt_r(password, hashed_password, &cc);
-        if (!k) {
-                explicit_bzero_safe(&cc, sizeof(cc));
-                return errno_or_else(EINVAL);
-        }
-
-        b = streq(k, hashed_password);
-        explicit_bzero_safe(&cc, sizeof(cc));
-        return b;
-}
-
-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;
-}

src/home/home-util.h

@@ -21,6 +21,3 @@ int bus_message_append_secret(sd_bus_message *m, UserRecord *secret);
 /* Many of our operations might be slow due to crypto, fsck, recursive chown() and so on. For these
  * operations permit a *very* long timeout */
 #define HOME_SLOW_BUS_CALL_TIMEOUT_USEC (2*USEC_PER_MINUTE)
-
-int test_password_one(const char *hashed_password, const char *password);
-int test_password_many(char **hashed_password, const char *password);

src/home/homectl-fido2.c

@@ -70,31 +70,23 @@ static int add_fido2_salt(
                 size_t secret_size) {
 
         _cleanup_(json_variant_unrefp) JsonVariant *l = NULL, *w = NULL, *e = NULL;
-        _cleanup_(erase_and_freep) char *base64_encoded = NULL;
-        _cleanup_free_ char *unix_salt = NULL;
-        struct crypt_data cd = {};
-        char *k;
+        _cleanup_(erase_and_freep) char *base64_encoded = NULL, *hashed = NULL;
         int r;
 
-        r = make_salt(&unix_salt);
-        if (r < 0)
-                return log_error_errno(r, "Failed to generate salt: %m");
-
         /* Before using UNIX hashing on the supplied key we base64 encode it, since crypt_r() and friends
          * expect a NUL terminated string, and we use a binary key */
         r = base64mem(secret, secret_size, &base64_encoded);
         if (r < 0)
                 return log_error_errno(r, "Failed to base64 encode secret key: %m");
 
-        errno = 0;
-        k = crypt_r(base64_encoded, unix_salt, &cd);
-        if (!k)
+        r = hash_password(base64_encoded, &hashed);
+        if (r < 0)
                 return log_error_errno(errno_or_else(EINVAL), "Failed to UNIX hash secret key: %m");
 
         r = json_build(&e, JSON_BUILD_OBJECT(
                                        JSON_BUILD_PAIR("credential", JSON_BUILD_BASE64(cid, cid_size)),
                                        JSON_BUILD_PAIR("salt", JSON_BUILD_BASE64(fido2_salt, fido2_salt_size)),
-                                       JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_STRING(k))));
+                                       JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_STRING(hashed))));
         if (r < 0)
                 return log_error_errno(r, "Failed to build FIDO2 salt JSON key object: %m");
 

src/home/homectl-pkcs11.c

@@ -134,10 +134,7 @@ static int add_pkcs11_encrypted_key(
                 const void *decrypted_key, size_t decrypted_key_size) {
 
         _cleanup_(json_variant_unrefp) JsonVariant *l = NULL, *w = NULL, *e = NULL;
-        _cleanup_(erase_and_freep) char *base64_encoded = NULL;
-        _cleanup_free_ char *salt = NULL;
-        struct crypt_data cd = {};
-        char *k;
+        _cleanup_(erase_and_freep) char *base64_encoded = NULL, *hashed = NULL;
         int r;
 
         assert(v);
@@ -147,25 +144,20 @@ static int add_pkcs11_encrypted_key(
         assert(decrypted_key);
         assert(decrypted_key_size > 0);
 
-        r = make_salt(&salt);
-        if (r < 0)
-                return log_error_errno(r, "Failed to generate salt: %m");
-
         /* Before using UNIX hashing on the supplied key we base64 encode it, since crypt_r() and friends
          * expect a NUL terminated string, and we use a binary key */
         r = base64mem(decrypted_key, decrypted_key_size, &base64_encoded);
         if (r < 0)
                 return log_error_errno(r, "Failed to base64 encode secret key: %m");
 
-        errno = 0;
-        k = crypt_r(base64_encoded, salt, &cd);
-        if (!k)
+        r = hash_password(base64_encoded, &hashed);
+        if (r < 0)
                 return log_error_errno(errno_or_else(EINVAL), "Failed to UNIX hash secret key: %m");
 
         r = json_build(&e, JSON_BUILD_OBJECT(
                                        JSON_BUILD_PAIR("uri", JSON_BUILD_STRING(uri)),
                                        JSON_BUILD_PAIR("data", JSON_BUILD_BASE64(encrypted_key, encrypted_key_size)),
-                                       JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_STRING(k))));
+                                       JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_STRING(hashed))));
         if (r < 0)
                 return log_error_errno(r, "Failed to build encrypted JSON key object: %m");
 

src/home/homectl-recovery-key.c

@@ -183,9 +183,7 @@ static int print_qr_code(const char *secret) {
 }
 
 int identity_add_recovery_key(JsonVariant **v) {
-        _cleanup_(erase_and_freep) char *unix_salt = NULL, *password = NULL;
-        struct crypt_data cd = {};
-        char *k;
+        _cleanup_(erase_and_freep) char *password = NULL, *hashed = NULL;
         int r;
 
         assert(v);
@@ -196,17 +194,12 @@ int identity_add_recovery_key(JsonVariant **v) {
                 return r;
 
         /* Let's UNIX hash it */
-        r = make_salt(&unix_salt);
+        r = hash_password(password, &hashed);
         if (r < 0)
-                return log_error_errno(r, "Failed to generate salt: %m");
-
-        errno = 0;
-        k = crypt_r(password, unix_salt, &cd);
-        if (!k)
                 return log_error_errno(errno_or_else(EINVAL), "Failed to UNIX hash secret key: %m");
 
         /* Let's now add the "privileged" version of the recovery key */
-        r = add_privileged(v, k);
+        r = add_privileged(v, hashed);
         if (r < 0)
                 return r;
 

src/home/homework.c

@@ -17,6 +17,7 @@
 #include "homework-mount.h"
 #include "homework-pkcs11.h"
 #include "homework.h"
+#include "libcrypt-util.h"
 #include "main-func.h"
 #include "memory-util.h"
 #include "missing_magic.h"

src/home/user-record-pwquality.c

@@ -3,6 +3,7 @@
 #include "bus-common-errors.h"
 #include "errno-util.h"
 #include "home-util.h"
+#include "libcrypt-util.h"
 #include "pwquality-util.h"
 #include "strv.h"
 #include "user-record-pwquality.h"

src/home/user-record-util.c

@@ -806,20 +806,13 @@ int user_record_make_hashed_password(UserRecord *h, char **secret, bool extend)
         }
 
         STRV_FOREACH(i, secret) {
-                _cleanup_free_ char *salt = NULL;
-                struct crypt_data cd = {};
-                char *k;
+                _cleanup_(erase_and_freep) char *hashed = NULL;
 
-                r = make_salt(&salt);
+                r = hash_password(*i, &hashed);
                 if (r < 0)
                         return r;
 
-                errno = 0;
-                k = crypt_r(*i, salt, &cd);
-                if (!k)
-                        return errno_or_else(EINVAL);
-
-                r = strv_extend(&np, k);
+                r = strv_consume(&np, TAKE_PTR(hashed));
                 if (r < 0)
                         return r;
         }

src/nspawn/nspawn-stub-pid1.c

@@ -53,12 +53,6 @@ int stub_pid1(sd_id128_t uuid) {
         assert_se(sigfillset(&fullmask) >= 0);
         assert_se(sigprocmask(SIG_BLOCK, &fullmask, &oldmask) >= 0);
 
-        /* Surrender the terminal this stub may control so that child processes can have a controlling terminal
-         * without resorting to setsid hacks. */
-        r = ioctl(STDIN_FILENO, TIOCNOTTY);
-        if (r < 0 && errno != ENOTTY)
-                return log_error_errno(errno, "Failed to surrender controlling terminal: %m");
-
         pid = fork();
         if (pid < 0)
                 return log_error_errno(errno, "Failed to fork child pid: %m");
@@ -66,7 +60,10 @@ int stub_pid1(sd_id128_t uuid) {
         if (pid == 0) {
                 /* Return in the child */
                 assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) >= 0);
-                setsid();
+
+                if (setsid() < 0)
+                        return log_error_errno(errno, "Failed to become session leader in payload process: %m");
+
                 return 0;
         }
 
@@ -76,6 +73,12 @@ int stub_pid1(sd_id128_t uuid) {
         (void) close_all_fds(NULL, 0);
         log_open();
 
+        if (ioctl(STDIN_FILENO, TIOCNOTTY) < 0) {
+                if (errno != ENOTTY)
+                        log_warning_errno(errno, "Unexpected error from TIOCNOTTY ioctl in init stub process, ignoring: %m");
+        } else
+                log_warning("Expected TIOCNOTTY to fail, but it succeeded in init stub process, ignoring.");
+
         /* Flush out /proc/self/environ, so that we don't leak the environment from the host into the container. Also,
          * set $container= and $container_uuid= so that clients in the container that query it from /proc/1/environ
          * find them set. */

src/nspawn/nspawn.c

@@ -11,10 +11,12 @@
 #endif
 #include <stdlib.h>
 #include <sys/file.h>
+#include <sys/ioctl.h>
 #include <sys/personality.h>
 #include <sys/prctl.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <termios.h>
 #include <unistd.h>
 
 #include "sd-bus.h"
@@ -254,10 +256,11 @@ STATIC_DESTRUCTOR_REGISTER(arg_sysctl, strv_freep);
 
 static int handle_arg_console(const char *arg) {
         if (streq(arg, "help")) {
-                puts("interactive\n"
-                     "read-only\n"
+                puts("autopipe\n"
+                     "interactive\n"
                      "passive\n"
-                     "pipe");
+                     "pipe\n"
+                     "read-only");
                 return 0;
         }
 
@@ -267,9 +270,20 @@ static int handle_arg_console(const char *arg) {
                 arg_console_mode = CONSOLE_READ_ONLY;
         else if (streq(arg, "passive"))
                 arg_console_mode = CONSOLE_PASSIVE;
-        else if (streq(arg, "pipe"))
+        else if (streq(arg, "pipe")) {
+                if (isatty(STDIN_FILENO) > 0 && isatty(STDOUT_FILENO) > 0)
+                        log_full(arg_quiet ? LOG_DEBUG : LOG_NOTICE,
+                                 "Console mode 'pipe' selected, but standard input/output are connected to an interactive TTY. "
+                                 "Most likely you want to use 'interactive' console mode for proper interactivity and shell job control. "
+                                 "Proceeding anyway.");
+
                 arg_console_mode = CONSOLE_PIPE;
+        } else if (streq(arg, "autopipe")) {
+                if (isatty(STDIN_FILENO) > 0 && isatty(STDOUT_FILENO) > 0)
+                        arg_console_mode = CONSOLE_INTERACTIVE;
                 else
+                        arg_console_mode = CONSOLE_PIPE;
+        } else
                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Unknown console mode: %s", optarg);
 
         arg_settings_mask |= SETTING_CONSOLE_MODE;
@@ -2269,10 +2283,12 @@ static int setup_pts(const char *dest) {
 }
 
 static int setup_stdio_as_dev_console(void) {
-        int terminal;
+        _cleanup_close_ int terminal = -1;
         int r;
 
-        terminal = open_terminal("/dev/console", O_RDWR);
+        /* We open the TTY in O_NOCTTY mode, so that we do not become controller yet. We'll do that later
+         * explicitly, if we are configured to. */
+        terminal = open_terminal("/dev/console", O_RDWR|O_NOCTTY);
         if (terminal < 0)
                 return log_error_errno(terminal, "Failed to open console: %m");
 
@@ -2284,6 +2300,7 @@ static int setup_stdio_as_dev_console(void) {
 
         /* invalidates 'terminal' on success and failure */
         r = rearrange_stdio(terminal, terminal, terminal);
+        TAKE_FD(terminal);
         if (r < 0)
                 return log_error_errno(r, "Failed to move console to stdin/stdout/stderr: %m");
 
@@ -3366,8 +3383,7 @@ static int inner_child(
          * wait until the parent is ready with the
          * setup, too... */
         if (!barrier_place_and_sync(barrier)) /* #5 */
-                return log_error_errno(SYNTHETIC_ERRNO(ESRCH),
-                                       "Parent died too early");
+                return log_error_errno(SYNTHETIC_ERRNO(ESRCH), "Parent died too early");
 
         if (arg_chdir)
                 if (chdir(arg_chdir) < 0)
@@ -3379,6 +3395,13 @@ static int inner_child(
                         return r;
         }
 
+        if (arg_console_mode != CONSOLE_PIPE) {
+                /* So far our pty wasn't controlled by any process. Finally, it's time to change that, if we
+                 * are configured for that. Acquire it as controlling tty. */
+                if (ioctl(STDIN_FILENO, TIOCSCTTY) < 0)
+                        return log_error_errno(errno, "Failed to acquire controlling TTY: %m");
+        }
+
         log_debug("Inner child completed, invoking payload.");
 
         /* Now, explicitly close the log, so that we then can close all remaining fds. Closing the log explicitly first

src/shared/libcrypt-util.c

@@ -1,12 +1,29 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
+#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"
@@ -14,12 +31,12 @@
 
 int make_salt(char **ret) {
 
-#ifdef XCRYPT_VERSION_MAJOR
+#if HAVE_CRYPT_GENSALT_RA
         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(). */
+        /* 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)
@@ -34,8 +51,7 @@ int make_salt(char **ret) {
         *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. */
+        /* If crypt_gensalt_ra() is not available, we use SHA512 and generate the salt on our own. */
 
         static const char table[] =
                 "abcdefghijklmnopqrstuvwxyz"
@@ -53,6 +69,8 @@ int make_salt(char **ret) {
 
         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)
@@ -74,6 +92,73 @@ int make_salt(char **ret) {
 #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
@@ -89,3 +174,35 @@ bool looks_like_hashed_password(const char *s) {
 
         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;
+}

src/shared/libcrypt-util.h

@@ -1,22 +1,13 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 #pragma once
 
-#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>
-#endif
-
 #include <stdbool.h>
-#include <stdlib.h>
 
 int make_salt(char **ret);
-
+int hash_password_full(const char *password, void **cd_data, int *cd_size, char **ret);
+static inline int hash_password(const char *password, char **ret) {
+        return hash_password_full(password, NULL, NULL, ret);
+}
 bool looks_like_hashed_password(const char *s);
+int test_password_one(const char *hashed_password, const char *password);
+int test_password_many(char **hashed_password, const char *password);

src/test/meson.build

@@ -301,6 +301,10 @@ tests += [
          [],
          []],
 
+        [['src/test/test-libcrypt-util.c'],
+         [],
+         []],
+
         [['src/test/test-offline-passwd.c',
           'src/shared/offline-passwd.c',
           'src/shared/offline-passwd.h'],

src/test/test-libcrypt-util.c

@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#if HAVE_CRYPT_H
+#  include <crypt.h>
+#else
+#  include <unistd.h>
+#endif
+
+#include "strv.h"
+#include "tests.h"
+#include "libcrypt-util.h"
+
+static int test_hash_password(void) {
+        log_info("/* %s */", __func__);
+
+        /* As a warmup exercise, check if we can hash passwords. */
+
+        bool have_sane_hash = false;
+        const char *hash;
+
+        FOREACH_STRING(hash,
+                       "ew3bU1.hoKk4o",
+                       "$1$gc5rWpTB$wK1aul1PyBn9AX1z93stk1",
+                       "$2b$12$BlqcGkB/7BFvNMXKGxDea.5/8D6FTny.cbNcHW/tqcrcyo6ZJd8u2",
+                       "$5$lGhDrcrao9zb5oIK$05KlOVG3ocknx/ThreqXE/gk.XzFFBMTksc4t2CPDUD",
+                       "$6$c7wB/3GiRk0VHf7e$zXJ7hN0aLZapE.iO4mn/oHu6.prsXTUG/5k1AxpgR85ELolyAcaIGRgzfwJs3isTChMDBjnthZyaMCfCNxo9I.",
+                       "$y$j9T$$9cKOWsAm4m97WiYk61lPPibZpy3oaGPIbsL4koRe/XD") {
+                int b;
+
+                b = test_password_one(hash, "ppp");
+                log_info("%s: %s", hash, yes_no(b));
+#if defined(XCRYPT_VERSION_MAJOR)
+                /* xcrypt is supposed to always implement all methods. */
+                assert_se(b);
+#endif
+
+                if (b && IN_SET(hash[1], '6', 'y'))
+                        have_sane_hash = true;
+        }
+
+        return have_sane_hash;
+}
+
+static void test_hash_password_full(void) {
+        log_info("/* %s */", __func__);
+
+        _cleanup_free_ void *cd_data = NULL;
+        const char *i;
+        int cd_size = 0;
+
+        log_info("sizeof(struct crypt_data): %zu bytes", sizeof(struct crypt_data));
+
+        for (unsigned c = 0; c < 2; c++)
+                FOREACH_STRING(i, "abc123", "h⸿sło") {
+                        _cleanup_free_ char *hashed;
+
+                        if (c == 0)
+                                assert_se(hash_password_full(i, &cd_data, &cd_size, &hashed) == 0);
+                        else
+                                assert_se(hash_password_full(i, NULL, NULL, &hashed) == 0);
+                        log_debug("\"%s\" → \"%s\"", i, hashed);
+                        log_info("crypt_r[a] buffer size: %i bytes", cd_size);
+
+                        assert_se(test_password_one(hashed, i) == true);
+                        assert_se(test_password_one(i, hashed) <= 0); /* We get an error for non-utf8 */
+                        assert_se(test_password_one(hashed, "foobar") == false);
+                        assert_se(test_password_many(STRV_MAKE(hashed), i) == true);
+                        assert_se(test_password_many(STRV_MAKE(hashed), "foobar") == false);
+                        assert_se(test_password_many(STRV_MAKE(hashed, hashed, hashed), "foobar") == false);
+                        assert_se(test_password_many(STRV_MAKE("$y$j9T$dlCXwkX0GC5L6B8Gf.4PN/$VCyEH",
+                                                               hashed,
+                                                               "$y$j9T$SAayASazWZIQeJd9AS02m/$"),
+                                                     i) == true);
+                        assert_se(test_password_many(STRV_MAKE("$W$j9T$dlCXwkX0GC5L6B8Gf.4PN/$VCyEH", /* no such method exists... */
+                                                               hashed,
+                                                               "$y$j9T$SAayASazWZIQeJd9AS02m/$"),
+                                                     i) == true);
+                        assert_se(test_password_many(STRV_MAKE("$y$j9T$dlCXwkX0GC5L6B8Gf.4PN/$VCyEH",
+                                                               hashed,
+                                                               "$y$j9T$SAayASazWZIQeJd9AS02m/$"),
+                                                     "") == false);
+                        assert_se(test_password_many(STRV_MAKE("$W$j9T$dlCXwkX0GC5L6B8Gf.4PN/$VCyEH", /* no such method exists... */
+                                                               hashed,
+                                                               "$y$j9T$SAayASazWZIQeJd9AS02m/$"),
+                                                     "") == false);
+                }
+}
+
+int main(int argc, char *argv[]) {
+        test_setup_logging(LOG_DEBUG);
+
+#if defined(__powerpc__) && !defined(XCRYPT_VERSION_MAJOR)
+        return log_tests_skipped("crypt_r() causes a buffer overflow on ppc64el, see https://github.com/systemd/systemd/pull/16981#issuecomment-691203787");
+#endif
+
+        if (!test_hash_password())
+                return log_tests_skipped("crypt doesn't support yescrypt or sha512crypt");
+
+        test_hash_password_full();
+
+        return 0;
+}