homectl: teach homectl to generate recovery keys

4 files changed, 330 insertions, 23 deletions

diff --git a/src/home/homectl-recovery-key.c b/src/home/homectl-recovery-key.c
new file mode 100644
index 0000000000..9d7f345f1e
--- /dev/null
+++ b/src/home/homectl-recovery-key.c
@@ -0,0 +1,253 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#if HAVE_QRENCODE
+#include <qrencode.h>
+#include "qrcode-util.h"
+#endif
+
+#include "dlfcn-util.h"
+#include "errno-util.h"
+#include "homectl-recovery-key.h"
+#include "libcrypt-util.h"
+#include "locale-util.h"
+#include "memory-util.h"
+#include "modhex.h"
+#include "random-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+
+static int make_recovery_key(char **ret) {
+        _cleanup_(erase_and_freep) char *formatted = NULL;
+        _cleanup_(erase_and_freep) uint8_t *key = NULL;
+        int r;
+
+        assert(ret);
+
+        key = new(uint8_t, MODHEX_RAW_LENGTH);
+        if (!key)
+                return log_oom();
+
+        r = genuine_random_bytes(key, MODHEX_RAW_LENGTH, RANDOM_BLOCK);
+        if (r < 0)
+                return log_error_errno(r, "Failed to gather entropy for recovery key: %m");
+
+        /* Let's now format it as 64 modhex chars, and after each 8 chars insert a dash */
+        formatted = new(char, MODHEX_FORMATTED_LENGTH);
+        if (!formatted)
+                return log_oom();
+
+        for (size_t i = 0, j = 0; i < MODHEX_RAW_LENGTH; i++) {
+                formatted[j++] = modhex_alphabet[key[i] >> 4];
+                formatted[j++] = modhex_alphabet[key[i] & 0xF];
+
+                if (i % 4 == 3)
+                        formatted[j++] = '-';
+        }
+
+        formatted[MODHEX_FORMATTED_LENGTH-1] = 0;
+
+        *ret = TAKE_PTR(formatted);
+        return 0;
+}
+
+static int add_privileged(JsonVariant **v, const char *hashed) {
+        _cleanup_(json_variant_unrefp) JsonVariant *e = NULL, *w = NULL, *l = NULL;
+        int r;
+
+        assert(v);
+        assert(hashed);
+
+        r = json_build(&e, JSON_BUILD_OBJECT(
+                                       JSON_BUILD_PAIR("type", JSON_BUILD_STRING("modhex64")),
+                                       JSON_BUILD_PAIR("hashedPassword", JSON_BUILD_STRING(hashed))));
+        if (r < 0)
+                return log_error_errno(r, "Failed to build recover key JSON object: %m");
+
+        json_variant_sensitive(e);
+
+        w = json_variant_ref(json_variant_by_key(*v, "privileged"));
+        l = json_variant_ref(json_variant_by_key(w, "recoveryKey"));
+
+        r = json_variant_append_array(&l, e);
+        if (r < 0)
+                return log_error_errno(r, "Failed append recovery key: %m");
+
+        r = json_variant_set_field(&w, "recoveryKey", l);
+        if (r < 0)
+                return log_error_errno(r, "Failed to set recovery key array: %m");
+
+        r = json_variant_set_field(v, "privileged", w);
+        if (r < 0)
+                return log_error_errno(r, "Failed to update privileged field: %m");
+
+        return 0;
+}
+
+static int add_public(JsonVariant **v) {
+        _cleanup_strv_free_ char **types = NULL;
+        int r;
+
+        assert(v);
+
+        r = json_variant_strv(json_variant_by_key(*v, "recoveryKeyType"), &types);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse recovery key type list: %m");
+
+        r = strv_extend(&types, "modhex64");
+        if (r < 0)
+                return log_oom();
+
+        r = json_variant_set_field_strv(v, "recoveryKeyType", types);
+        if (r < 0)
+                return log_error_errno(r, "Failed to update recovery key types: %m");
+
+        return 0;
+}
+
+static int add_secret(JsonVariant **v, const char *password) {
+        _cleanup_(json_variant_unrefp) JsonVariant *w = NULL, *l = NULL;
+        _cleanup_(strv_free_erasep) char **passwords = NULL;
+        int r;
+
+        assert(v);
+        assert(password);
+
+        w = json_variant_ref(json_variant_by_key(*v, "secret"));
+        l = json_variant_ref(json_variant_by_key(w, "password"));
+
+        r = json_variant_strv(l, &passwords);
+        if (r < 0)
+                return log_error_errno(r, "Failed to convert password array: %m");
+
+        r = strv_extend(&passwords, password);
+        if (r < 0)
+                return log_oom();
+
+        r = json_variant_new_array_strv(&l, passwords);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate new password array JSON: %m");
+
+        json_variant_sensitive(l);
+
+        r = json_variant_set_field(&w, "password", l);
+        if (r < 0)
+                return log_error_errno(r, "Failed to update password field: %m");
+
+        r = json_variant_set_field(v, "secret", w);
+        if (r < 0)
+                return log_error_errno(r, "Failed to update secret object: %m");
+
+        return 0;
+}
+
+static int print_qr_code(const char *secret) {
+#if HAVE_QRENCODE
+        QRcode* (*sym_QRcode_encodeString)(const char *string, int version, QRecLevel level, QRencodeMode hint, int casesensitive);
+        void (*sym_QRcode_free)(QRcode *qrcode);
+        _cleanup_(dlclosep) void *dl = NULL;
+        QRcode* qr;
+        int r;
+
+        /* If this is not an UTF-8 system or ANSI colors aren't supported/disabled don't print any QR
+         * codes */
+        if (!is_locale_utf8() || !colors_enabled())
+                return -EOPNOTSUPP;
+
+        dl = dlopen("libqrencode.so.4", RTLD_LAZY);
+        if (!dl)
+                return log_debug_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                       "QRCODE support is not installed: %s", dlerror());
+
+        r = dlsym_many_and_warn(
+                        dl,
+                        LOG_DEBUG,
+                        &sym_QRcode_encodeString, "QRcode_encodeString",
+                        &sym_QRcode_free, "QRcode_free",
+                        NULL);
+        if (r < 0)
+                return r;
+
+        qr = sym_QRcode_encodeString(secret, 0, QR_ECLEVEL_L, QR_MODE_8, 0);
+        if (!qr)
+                return -ENOMEM;
+
+        fprintf(stderr, "\nYou may optionally scan the recovery key off screen:\n\n");
+
+        write_qrcode(stderr, qr);
+
+        fputc('\n', stderr);
+
+        sym_QRcode_free(qr);
+#endif
+        return 0;
+}
+
+int identity_add_recovery_key(JsonVariant **v) {
+        _cleanup_(erase_and_freep) char *unix_salt = NULL, *password = NULL;
+        struct crypt_data cd = {};
+        char *k;
+        int r;
+
+        assert(v);
+
+        /* First, let's generate a secret key  */
+        r = make_recovery_key(&password);
+        if (r < 0)
+                return r;
+
+        /* Let's UNIX hash it */
+        r = make_salt(&unix_salt);
+        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);
+        if (r < 0)
+                return r;
+
+        /* Let's then add the public information about the recovery key */
+        r = add_public(v);
+        if (r < 0)
+                return r;
+
+        /* Finally, let's add the new key to the secret part, too */
+        r = add_secret(v, password);
+        if (r < 0)
+                return r;
+
+        /* We output the key itself with a trailing newline to stdout and the decoration around it to stderr
+         * instead. */
+
+        fflush(stdout);
+        fprintf(stderr,
+                "A secret recovery key has been generated for this account:\n\n"
+                "    %s%s%s",
+                emoji_enabled() ? special_glyph(SPECIAL_GLYPH_LOCK_AND_KEY) : "",
+                emoji_enabled() ? " " : "",
+                ansi_highlight());
+        fflush(stderr);
+
+        fputs(password, stdout);
+        fflush(stdout);
+
+        fputs(ansi_normal(), stderr);
+        fflush(stderr);
+
+        fputc('\n', stdout);
+        fflush(stdout);
+
+        fputs("\nPlease save this secret recovery key at a secure location. It may be used to\n"
+              "regain access to the account if the other configured access credentials have\n"
+              "been lost or forgotten. The recovery key may be entered in place of a password\n"
+              "whenever authentication is requested.\n", stderr);
+        fflush(stderr);
+
+        print_qr_code(password);
+
+        return 0;
+}
diff --git a/src/home/homectl-recovery-key.h b/src/home/homectl-recovery-key.h
new file mode 100644
index 0000000000..489d35fa5b
--- /dev/null
+++ b/src/home/homectl-recovery-key.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include "json.h"
+
+int identity_add_recovery_key(JsonVariant **v);
diff --git a/src/home/homectl.c b/src/home/homectl.c
index 9e80a1d60f..b83fa837ad 100644
--- a/src/home/homectl.c
+++ b/src/home/homectl.c
@@ -17,6 +17,7 @@
 #include "home-util.h"
 #include "homectl-fido2.h"
 #include "homectl-pkcs11.h"
+#include "homectl-recovery-key.h"
 #include "locale-util.h"
 #include "main-func.h"
 #include "memory-util.h"
@@ -53,6 +54,7 @@ static uint64_t arg_disk_size = UINT64_MAX;
 static uint64_t arg_disk_size_relative = UINT64_MAX;
 static char **arg_pkcs11_token_uri = NULL;
 static char **arg_fido2_device = NULL;
+static bool arg_recovery_key = false;
 static bool arg_json = false;
 static JsonFormatFlags arg_json_format_flags = 0;
 static bool arg_and_resize = false;
@@ -938,6 +940,12 @@ static int acquire_new_home_record(UserRecord **ret) {
                         return r;
         }
 
+        if (arg_recovery_key) {
+                r = identity_add_recovery_key(&v);
+                if (r < 0)
+                        return r;
+        }
+
         r = update_last_change(&v, true, false);
         if (r < 0)
                 return r;
@@ -960,7 +968,8 @@ static int acquire_new_home_record(UserRecord **ret) {
 static int acquire_new_password(
                 const char *user_name,
                 UserRecord *hr,
-                bool suggest) {
+                bool suggest,
+                char **ret) {
 
         unsigned i = 5;
         char *e;
@@ -971,9 +980,17 @@ static int acquire_new_password(
 
         e = getenv("NEWPASSWORD");
         if (e) {
+                _cleanup_(erase_and_freep) char *copy = NULL;
+
                 /* As above, this is not for use, just for testing */
 
-                r = user_record_set_password(hr, STRV_MAKE(e), /* prepend = */ false);
+                if (ret) {
+                        copy = strdup(e);
+                        if (!copy)
+                                return log_oom();
+                }
+
+                r = user_record_set_password(hr, STRV_MAKE(e), /* prepend = */ true);
                 if (r < 0)
                         return log_error_errno(r, "Failed to store password: %m");
 
@@ -982,6 +999,9 @@ static int acquire_new_password(
                 if (unsetenv("NEWPASSWORD") < 0)
                         return log_error_errno(errno, "Failed to unset $NEWPASSWORD: %m");
 
+                if (ret)
+                        *ret = TAKE_PTR(copy);
+
                 return 0;
         }
 
@@ -1011,10 +1031,21 @@ static int acquire_new_password(
                         return log_error_errno(r, "Failed to acquire password: %m");
 
                 if (strv_equal(first, second)) {
-                        r = user_record_set_password(hr, first, /* prepend = */ false);
+                        _cleanup_(erase_and_freep) char *copy = NULL;
+
+                        if (ret) {
+                                copy = strdup(first[0]);
+                                if (!copy)
+                                        return log_oom();
+                        }
+
+                        r = user_record_set_password(hr, first, /* prepend = */ true);
                         if (r < 0)
                                 return log_error_errno(r, "Failed to store password: %m");
 
+                        if (ret)
+                                *ret = TAKE_PTR(copy);
+
                         return 0;
                 }
 
@@ -1025,7 +1056,6 @@ static int acquire_new_password(
 static int create_home(int argc, char *argv[], void *userdata) {
         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
         _cleanup_(user_record_unrefp) UserRecord *hr = NULL;
-        _cleanup_strv_free_ char **original_hashed_passwords = NULL;
         int r;
 
         r = acquire_bus(&bus);
@@ -1067,27 +1097,24 @@ static int create_home(int argc, char *argv[], void *userdata) {
         if (r < 0)
                 return r;
 
-        /* Remember the original hashed passwords before we add our own, so that we can return to them later,
-         * should the entered password turn out not to be acceptable. */
-        original_hashed_passwords = strv_copy(hr->hashed_password);
-        if (!original_hashed_passwords)
-                return log_oom();
-
-        /* If the JSON record carries no plain text password, then let's query it manually. */
-        if (!hr->password) {
+        /* If the JSON record carries no plain text password (besides the recovery key), then let's query it
+         * manually. */
+        if (strv_length(hr->password) <= arg_recovery_key) {
 
                 if (strv_isempty(hr->hashed_password)) {
+                        _cleanup_(erase_and_freep) char *new_password = NULL;
+
                         /* No regular (i.e. non-PKCS#11) hashed passwords set in the record, let's fix that. */
-                        r = acquire_new_password(hr->user_name, hr, /* suggest = */ true);
+                        r = acquire_new_password(hr->user_name, hr, /* suggest = */ true, &new_password);
                         if (r < 0)
                                 return r;
 
-                        r = user_record_make_hashed_password(hr, hr->password, /* extend = */ true);
+                        r = user_record_make_hashed_password(hr, STRV_MAKE(new_password), /* extend = */ false);
                         if (r < 0)
                                 return log_error_errno(r, "Failed to hash password: %m");
                 } else {
                         /* There's a hash password set in the record, acquire the unhashed version of it. */
-                        r = acquire_existing_password(hr->user_name, hr, false);
+                        r = acquire_existing_password(hr->user_name, hr, /* emphasize_current= */ false);
                         if (r < 0)
                                 return r;
                 }
@@ -1125,18 +1152,16 @@ static int create_home(int argc, char *argv[], void *userdata) {
                 r = sd_bus_call(bus, m, HOME_SLOW_BUS_CALL_TIMEOUT_USEC, &error, NULL);
                 if (r < 0) {
                         if (sd_bus_error_has_name(&error, BUS_ERROR_LOW_PASSWORD_QUALITY)) {
+                                _cleanup_(erase_and_freep) char *new_password = NULL;
+
                                 log_error_errno(r, "%s", bus_error_message(&error, r));
                                 log_info("(Use --enforce-password-policy=no to turn off password quality checks for this account.)");
 
-                                r = user_record_set_hashed_password(hr, original_hashed_passwords);
+                                r = acquire_new_password(hr->user_name, hr, /* suggest = */ false, &new_password);
                                 if (r < 0)
                                         return r;
 
-                                r = acquire_new_password(hr->user_name, hr, /* suggest = */ false);
-                                if (r < 0)
-                                        return r;
-
-                                r = user_record_make_hashed_password(hr, hr->password, /* extend = */ true);
+                                r = user_record_make_hashed_password(hr, STRV_MAKE(new_password), /* extend = */ false);
                                 if (r < 0)
                                         return log_error_errno(r, "Failed to hash passwords: %m");
                         } else {
@@ -1489,7 +1514,7 @@ static int passwd_home(int argc, char *argv[], void *userdata) {
         if (!new_secret)
                 return log_oom();
 
-        r = acquire_new_password(username, new_secret, /* suggest = */ true);
+        r = acquire_new_password(username, new_secret, /* suggest = */ true, NULL);
         if (r < 0)
                 return r;
 
@@ -1519,7 +1544,7 @@ static int passwd_home(int argc, char *argv[], void *userdata) {
 
                                 log_error_errno(r, "%s", bus_error_message(&error, r));
 
-                                r = acquire_new_password(username, new_secret, /* suggest = */ false);
+                                r = acquire_new_password(username, new_secret, /* suggest = */ false, NULL);
 
                         } else if (sd_bus_error_has_name(&error, BUS_ERROR_BAD_PASSWORD_AND_NO_TOKEN))
 
@@ -1914,6 +1939,7 @@ static int help(int argc, char *argv[], void *userdata) {
                "                              private key and matching X.509 certificate\n"
                "     --fido2-device=PATH      Path to FIDO2 hidraw device with hmac-secret\n"
                "                              extension\n"
+               "     --recovery-key=BOOL      Add a recovery key\n"
                "\n%4$sAccount Management User Record Properties:%5$s\n"
                "     --locked=BOOL            Set locked account state\n"
                "     --not-before=TIMESTAMP   Do not allow logins before\n"
@@ -2061,6 +2087,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_AUTO_LOGIN,
                 ARG_PKCS11_TOKEN_URI,
                 ARG_FIDO2_DEVICE,
+                ARG_RECOVERY_KEY,
                 ARG_AND_RESIZE,
                 ARG_AND_CHANGE_PASSWORD,
         };
@@ -2139,6 +2166,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "export-format",               required_argument, NULL, ARG_EXPORT_FORMAT               },
                 { "pkcs11-token-uri",            required_argument, NULL, ARG_PKCS11_TOKEN_URI            },
                 { "fido2-device",                required_argument, NULL, ARG_FIDO2_DEVICE                },
+                { "recovery-key",                required_argument, NULL, ARG_RECOVERY_KEY                },
                 { "and-resize",                  required_argument, NULL, ARG_AND_RESIZE                  },
                 { "and-change-password",         required_argument, NULL, ARG_AND_CHANGE_PASSWORD         },
                 {}
@@ -3169,6 +3197,24 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
                 }
 
+                case ARG_RECOVERY_KEY: {
+                        const char *p;
+
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --recovery-key= argument: %s", optarg);
+
+                        arg_recovery_key = r;
+
+                        FOREACH_STRING(p, "recoveryKey", "recoveryKeyType") {
+                                r = drop_from_identity(p);
+                                if (r < 0)
+                                        return r;
+                        }
+
+                        break;
+                }
+
                 case 'j':
                         arg_json = true;
                         arg_json_format_flags = JSON_FORMAT_PRETTY_AUTO|JSON_FORMAT_COLOR_AUTO;
diff --git a/src/home/meson.build b/src/home/meson.build
index 37e59f3a63..69bacacf80 100644
--- a/src/home/meson.build
+++ b/src/home/meson.build
@@ -77,6 +77,8 @@ homectl_sources = files('''
         homectl-fido2.h
         homectl-pkcs11.c
         homectl-pkcs11.h
+        homectl-recovery-key.c
+        homectl-recovery-key.h
         homectl.c
         modhex.c
         modhex.h