ask-password: add support for caching passwords in the kernel keyring

This adds support for caching harddisk passwords in the kernel keyring
if it is available, thus supporting caching without Plymouth being
around.

This is also useful for hooking up "gdm-auto-login" with the collected
boot-time harddisk password, in order to support gnome keyring
passphrase unlocking via the HDD password, if it is the same.

Any passwords added to the kernel keyring this way have a timeout of
2.5min at which time they are purged from the kernel.

1 files changed, 194 insertions, 47 deletions

diff --git a/src/shared/ask-password-api.c b/src/shared/ask-password-api.c
index 314f983b20..f8cf11b297 100644
--- a/src/shared/ask-password-api.c
+++ b/src/shared/ask-password-api.c
@@ -33,6 +33,7 @@
 #include <unistd.h>
 
 #include "formats-util.h"
+#include "missing.h"
 #include "mkdir.h"
 #include "random-util.h"
 #include "signal-util.h"
@@ -42,6 +43,133 @@
 #include "util.h"
 #include "ask-password-api.h"
 
+#define KEYRING_TIMEOUT_USEC ((5 * USEC_PER_MINUTE) / 2)
+
+static int lookup_key(const char *keyname, key_serial_t *ret) {
+        key_serial_t serial;
+
+        assert(keyname);
+        assert(ret);
+
+        serial = request_key("user", keyname, NULL, 0);
+        if (serial == -1)
+                return -errno;
+
+        *ret = serial;
+        return 0;
+}
+
+static int retrieve_key(key_serial_t serial, char ***ret) {
+        _cleanup_free_ char *p = NULL;
+        long m = 100, n;
+        char **l;
+
+        assert(ret);
+
+        for (;;) {
+                p = new(char, m);
+                if (!p)
+                        return -ENOMEM;
+
+                n = keyctl(KEYCTL_READ, (unsigned long) serial, (unsigned long) p, (unsigned long) m, 0);
+                if (n < 0)
+                        return -errno;
+
+                if (n < m)
+                        break;
+
+                free(p);
+                m *= 2;
+        }
+
+        l = strv_parse_nulstr(p, n);
+        if (!l)
+                return -ENOMEM;
+
+        *ret = l;
+        return 0;
+}
+
+static int add_to_keyring(const char *keyname, AskPasswordFlags flags, char **passwords) {
+        _cleanup_strv_free_ char **l = NULL;
+        _cleanup_free_ char *p = NULL;
+        key_serial_t serial;
+        size_t n;
+        int r;
+
+        assert(keyname);
+        assert(passwords);
+
+        if (!(flags & ASK_PASSWORD_PUSH_CACHE))
+                return 0;
+
+        r = lookup_key(keyname, &serial);
+        if (r >= 0) {
+                r = retrieve_key(serial, &l);
+                if (r < 0)
+                        return r;
+        } else if (r != -ENOKEY)
+                return r;
+
+        r = strv_extend_strv(&l, passwords, true);
+        if (r <= 0)
+                return r;
+
+        r = strv_make_nulstr(l, &p, &n);
+        if (r < 0)
+                return r;
+
+        /* Truncate trailing NUL */
+        assert(n > 0);
+        assert(p[n-1] == 0);
+
+        serial = add_key("user", keyname, p, n-1, KEY_SPEC_USER_KEYRING);
+        if (serial == -1)
+                return -errno;
+
+        if (keyctl(KEYCTL_SET_TIMEOUT,
+                   (unsigned long) serial,
+                   (unsigned long) DIV_ROUND_UP(KEYRING_TIMEOUT_USEC, USEC_PER_SEC), 0, 0) < 0)
+                log_debug_errno(errno, "Failed to adjust timeout: %m");
+
+        log_debug("Added key to keyring as %" PRIi32 ".", serial);
+
+        return 1;
+}
+
+static int add_to_keyring_and_log(const char *keyname, AskPasswordFlags flags, char **passwords) {
+        int r;
+
+        assert(keyname);
+        assert(passwords);
+
+        r = add_to_keyring(keyname, flags, passwords);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to add password to keyring: %m");
+
+        return 0;
+}
+
+int ask_password_keyring(const char *keyname, AskPasswordFlags flags, char ***ret) {
+
+        key_serial_t serial;
+        int r;
+
+        assert(keyname);
+        assert(ret);
+
+        if (!(flags & ASK_PASSWORD_ACCEPT_CACHED))
+                return -EUNATCH;
+
+        r = lookup_key(keyname, &serial);
+        if (r == -ENOSYS) /* when retrieving the distinction doesn't matter */
+                return -ENOKEY;
+        if (r < 0)
+                return r;
+
+        return retrieve_key(serial, ret);
+}
+
 static void backspace_chars(int ttyfd, size_t p) {
 
         if (ttyfd < 0)
@@ -56,10 +184,11 @@ static void backspace_chars(int ttyfd, size_t p) {
 
 int ask_password_tty(
                 const char *message,
+                const char *keyname,
                 usec_t until,
-                bool echo,
+                AskPasswordFlags flags,
                 const char *flag_file,
-                char **_passphrase) {
+                char **ret) {
 
         struct termios old_termios, new_termios;
         char passphrase[LINE_MAX], *x;
@@ -68,15 +197,19 @@ int ask_password_tty(
         _cleanup_close_ int ttyfd = -1, notify = -1;
         struct pollfd pollfd[2];
         bool reset_tty = false;
-        bool silent_mode = false;
         bool dirty = false;
         enum {
                 POLL_TTY,
                 POLL_INOTIFY
         };
 
-        assert(message);
-        assert(_passphrase);
+        assert(ret);
+
+        if (flags & ASK_PASSWORD_NO_TTY)
+                return -EUNATCH;
+
+        if (!message)
+                message = "Password:";
 
         if (flag_file) {
                 notify = inotify_init1(IN_CLOEXEC|IN_NONBLOCK);
@@ -147,7 +280,7 @@ int ask_password_tty(
                                 goto finish;
                         }
 
-                k = poll(pollfd, notify > 0 ? 2 : 1, sleep_for);
+                k = poll(pollfd, notify >= 0 ? 2 : 1, sleep_for);
                 if (k < 0) {
                         if (errno == EINTR)
                                 continue;
@@ -159,7 +292,7 @@ int ask_password_tty(
                         goto finish;
                 }
 
-                if (notify > 0 && pollfd[POLL_INOTIFY].revents != 0)
+                if (notify >= 0 && pollfd[POLL_INOTIFY].revents != 0)
                         flush_fd(notify);
 
                 if (pollfd[POLL_TTY].revents == 0)
@@ -180,7 +313,7 @@ int ask_password_tty(
                         break;
                 else if (c == 21) { /* C-u */
 
-                        if (!silent_mode)
+                        if (!(flags & ASK_PASSWORD_SILENT))
                                 backspace_chars(ttyfd, p);
                         p = 0;
 
@@ -188,28 +321,28 @@ int ask_password_tty(
 
                         if (p > 0) {
 
-                                if (!silent_mode)
+                                if (!(flags & ASK_PASSWORD_SILENT))
                                         backspace_chars(ttyfd, 1);
 
                                 p--;
-                        } else if (!dirty && !silent_mode) {
+                        } else if (!dirty && !(flags & ASK_PASSWORD_SILENT)) {
 
-                                silent_mode = true;
+                                flags |= ASK_PASSWORD_SILENT;
 
                                 /* There are two ways to enter silent
                                  * mode. Either by pressing backspace
-                                 * as first key (and only as first key),
-                                 * or ... */
+                                 * as first key (and only as first
+                                 * key), or ... */
                                 if (ttyfd >= 0)
                                         loop_write(ttyfd, "(no echo) ", 10, false);
 
                         } else if (ttyfd >= 0)
                                 loop_write(ttyfd, "\a", 1, false);
 
-                } else if (c == '\t' && !silent_mode) {
+                } else if (c == '\t' && !(flags & ASK_PASSWORD_SILENT)) {
 
                         backspace_chars(ttyfd, p);
-                        silent_mode = true;
+                        flags |= ASK_PASSWORD_SILENT;
 
                         /* ... or by pressing TAB at any time. */
 
@@ -223,8 +356,8 @@ int ask_password_tty(
 
                         passphrase[p++] = c;
 
-                        if (!silent_mode && ttyfd >= 0)
-                                loop_write(ttyfd, echo ? &c : "*", 1, false);
+                        if (!(flags & ASK_PASSWORD_SILENT) && ttyfd >= 0)
+                                loop_write(ttyfd, (flags & ASK_PASSWORD_ECHO) ? &c : "*", 1, false);
 
                         dirty = true;
                 }
@@ -236,7 +369,10 @@ int ask_password_tty(
                 goto finish;
         }
 
-        *_passphrase = x;
+        if (keyname)
+                (void) add_to_keyring_and_log(keyname, flags, STRV_MAKE(x));
+
+        *ret = x;
         r = 0;
 
 finish:
@@ -289,10 +425,10 @@ int ask_password_agent(
                 const char *message,
                 const char *icon,
                 const char *id,
+                const char *keyname,
                 usec_t until,
-                bool echo,
-                bool accept_cached,
-                char ***_passphrases) {
+                AskPasswordFlags flags,
+                char ***ret) {
 
         enum {
                 FD_SOCKET,
@@ -300,17 +436,20 @@ int ask_password_agent(
                 _FD_MAX
         };
 
+        _cleanup_close_ int socket_fd = -1, signal_fd = -1, fd = -1;
         char temp[] = "/run/systemd/ask-password/tmp.XXXXXX";
         char final[sizeof(temp)] = "";
-        _cleanup_fclose_ FILE *f = NULL;
         _cleanup_free_ char *socket_name = NULL;
-        _cleanup_close_ int socket_fd = -1, signal_fd = -1, fd = -1;
-        sigset_t mask, oldmask;
+        _cleanup_strv_free_ char **l = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
         struct pollfd pollfd[_FD_MAX];
+        sigset_t mask, oldmask;
         int r;
 
-        assert(_passphrases);
+        assert(ret);
 
+        if (flags & ASK_PASSWORD_NO_AGENT)
+                return -EUNATCH;
 
         assert_se(sigemptyset(&mask) >= 0);
         assert_se(sigset_add_many(&mask, SIGINT, SIGTERM, -1) >= 0);
@@ -355,8 +494,8 @@ int ask_password_agent(
                 "NotAfter="USEC_FMT"\n",
                 getpid(),
                 socket_name,
-                accept_cached ? 1 : 0,
-                echo ? 1 : 0,
+                (flags & ASK_PASSWORD_ACCEPT_CACHED) ? 1 : 0,
+                (flags & ASK_PASSWORD_ECHO) ? 1 : 0,
                 until);
 
         if (message)
@@ -476,38 +615,38 @@ int ask_password_agent(
                 }
 
                 if (passphrase[0] == '+') {
-                        char **l;
-
+                        /* An empty message refers to the empty password */
                         if (n == 1)
                                 l = strv_new("", NULL);
                         else
                                 l = strv_parse_nulstr(passphrase+1, n-1);
-                                /* An empty message refers to the empty password */
-
                         if (!l) {
                                 r = -ENOMEM;
                                 goto finish;
                         }
 
                         if (strv_length(l) <= 0) {
-                                strv_free(l);
+                                l = strv_free(l);
                                 log_debug("Invalid packet");
                                 continue;
                         }
 
-                        *_passphrases = l;
+                        break;
+                }
 
-                } else if (passphrase[0] == '-') {
+                if (passphrase[0] == '-') {
                         r = -ECANCELED;
                         goto finish;
-                } else {
-                        log_debug("Invalid packet");
-                        continue;
                 }
 
-                break;
+                log_debug("Invalid packet");
         }
 
+        if (keyname)
+                (void) add_to_keyring_and_log(keyname, flags, l);
+
+        *ret = l;
+        l = NULL;
         r = 0;
 
 finish:
@@ -520,7 +659,6 @@ finish:
                 (void) unlink(final);
 
         assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) == 0);
-
         return r;
 }
 
@@ -528,19 +666,25 @@ int ask_password_auto(
                 const char *message,
                 const char *icon,
                 const char *id,
+                const char *keyname,
                 usec_t until,
-                bool accept_cached,
-                char ***_passphrases) {
+                AskPasswordFlags flags,
+                char ***ret) {
 
         int r;
 
-        assert(message);
-        assert(_passphrases);
+        assert(ret);
 
-        if (isatty(STDIN_FILENO)) {
+        if ((flags & ASK_PASSWORD_ACCEPT_CACHED) && keyname) {
+                r = ask_password_keyring(keyname, flags, ret);
+                if (r != -ENOKEY)
+                        return r;
+        }
+
+        if (!(flags & ASK_PASSWORD_NO_TTY) && isatty(STDIN_FILENO)) {
                 char *s = NULL, **l = NULL;
 
-                r = ask_password_tty(message, until, false, NULL, &s);
+                r = ask_password_tty(message, keyname, until, flags, NULL, &s);
                 if (r < 0)
                         return r;
 
@@ -548,9 +692,12 @@ int ask_password_auto(
                 if (r < 0)
                         return -ENOMEM;
 
-                *_passphrases = l;
+                *ret = l;
                 return 0;
         }
 
-        return ask_password_agent(message, icon, id, until, false, accept_cached, _passphrases);
+        if (!(flags & ASK_PASSWORD_NO_AGENT))
+                return ask_password_agent(message, icon, id, keyname, until, flags, ret);
+
+        return -EUNATCH;
 }