cryptsetup: add fido2 support

1 files changed, 190 insertions, 0 deletions

diff --git a/src/cryptsetup/cryptsetup-fido2.c b/src/cryptsetup/cryptsetup-fido2.c
new file mode 100644
index 0000000000..5edda0cf9d
--- /dev/null
+++ b/src/cryptsetup/cryptsetup-fido2.c
@@ -0,0 +1,190 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "ask-password-api.h"
+#include "cryptsetup-fido2.h"
+#include "fileio.h"
+#include "hexdecoct.h"
+#include "json.h"
+#include "libfido2-util.h"
+#include "parse-util.h"
+#include "random-util.h"
+#include "strv.h"
+
+int acquire_fido2_key(
+                const char *volume_name,
+                const char *friendly_name,
+                const char *device,
+                const char *rp_id,
+                const void *cid,
+                size_t cid_size,
+                const char *key_file,
+                size_t key_file_size,
+                uint64_t key_file_offset,
+                const void *key_data,
+                size_t key_data_size,
+                usec_t until,
+                void **ret_decrypted_key,
+                size_t *ret_decrypted_key_size) {
+
+        AskPasswordFlags flags = ASK_PASSWORD_PUSH_CACHE | ASK_PASSWORD_ACCEPT_CACHED;
+        _cleanup_strv_free_erase_ char **pins = NULL;
+        _cleanup_free_ void *loaded_salt = NULL;
+        const char *salt;
+        size_t salt_size;
+        char *e;
+        int r;
+
+        assert(cid);
+        assert(key_file || key_data);
+
+        if (key_data) {
+                salt = key_data;
+                salt_size = key_data_size;
+        } else {
+                _cleanup_free_ char *bindname = NULL;
+
+                /* If we read the salt via AF_UNIX, make this client recognizable */
+                if (asprintf(&bindname, "@%" PRIx64"/cryptsetup-fido2/%s", random_u64(), volume_name) < 0)
+                        return log_oom();
+
+                r = read_full_file_full(
+                                AT_FDCWD, key_file,
+                                key_file_offset == 0 ? UINT64_MAX : key_file_offset,
+                                key_file_size == 0 ? SIZE_MAX : key_file_size,
+                                READ_FULL_FILE_CONNECT_SOCKET,
+                                bindname,
+                                (char**) &loaded_salt, &salt_size);
+                if (r < 0)
+                        return r;
+
+                salt = loaded_salt;
+        }
+
+        e = getenv("PIN");
+        if (e) {
+                pins = strv_new(e);
+                if (!pins)
+                        return log_oom();
+
+                string_erase(e);
+                if (unsetenv("PIN") < 0)
+                        return log_error_errno(errno, "Failed to unset $PIN: %m");
+        }
+
+        for (;;) {
+                r = fido2_use_hmac_hash(
+                                device,
+                                rp_id ?: "io.systemd.cryptsetup",
+                                salt, salt_size,
+                                cid, cid_size,
+                                pins,
+                                /* up= */ true,
+                                ret_decrypted_key,
+                                ret_decrypted_key_size);
+                if (!IN_SET(r,
+                            -ENOANO,   /* needs pin */
+                            -ENOLCK))  /* pin incorrect */
+                        return r;
+
+                pins = strv_free_erase(pins);
+
+                r = ask_password_auto("Please enter security token PIN:", "drive-harddisk", NULL, "fido2-pin", until, flags, &pins);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to ask for user pasword: %m");
+
+                flags &= ~ASK_PASSWORD_ACCEPT_CACHED;
+        }
+}
+
+int find_fido2_auto_data(
+                struct crypt_device *cd,
+                char **ret_rp_id,
+                void **ret_salt,
+                size_t *ret_salt_size,
+                void **ret_cid,
+                size_t *ret_cid_size,
+                int *ret_keyslot) {
+
+        _cleanup_free_ void *cid = NULL, *salt = NULL;
+        size_t cid_size = 0, salt_size = 0;
+        _cleanup_free_ char *rp = NULL;
+        int r, keyslot = -1;
+
+        assert(cd);
+        assert(ret_salt);
+        assert(ret_salt_size);
+        assert(ret_cid);
+        assert(ret_cid_size);
+        assert(ret_keyslot);
+
+        /* Loads FIDO2 metadata from LUKS2 JSON token headers. */
+
+        for (int token = 0; token < LUKS2_TOKENS_MAX; token ++) {
+                _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+                JsonVariant *w;
+
+                r = cryptsetup_get_token_as_json(cd, token, "systemd-fido2", &v);
+                if (IN_SET(r, -ENOENT, -EINVAL, -EMEDIUMTYPE))
+                        continue;
+                if (r < 0)
+                        return log_error_errno(r, "Failed to read JSON token data off disk: %m");
+
+                if (cid)
+                        return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ),
+                                               "Multiple FIDO2 tokens enrolled, cannot automatically determine token.");
+
+                w = json_variant_by_key(v, "fido2-credential");
+                if (!w || !json_variant_is_string(w))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "FIDO2 token data lacks 'fido2-credential' field.");
+
+                r = unbase64mem(json_variant_string(w), (size_t) -1, &cid, &cid_size);
+                if (r < 0)
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "Invalid base64 data in 'fido2-credential' field.");
+
+                w = json_variant_by_key(v, "fido2-salt");
+                if (!w || !json_variant_is_string(w))
+                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "FIDO2 token data lacks 'fido2-salt' field.");
+
+                assert(!salt);
+                assert(salt_size == 0);
+                r = unbase64mem(json_variant_string(w), (size_t) -1, &salt, &salt_size);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to decode base64 encoded salt.");
+
+                assert(keyslot < 0);
+                keyslot = cryptsetup_get_keyslot_from_token(v);
+                if (keyslot < 0)
+                        return log_error_errno(keyslot, "Failed to extract keyslot index from FIDO2 JSON data: %m");
+
+                w = json_variant_by_key(v, "fido2-rp");
+                if (w) {
+                        /* The "rp" field is optional. */
+
+                        if (!json_variant_is_string(w))
+                                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                                       "FIDO2 token data's 'fido2-rp' field is not a string.");
+
+                        assert(!rp);
+                        rp = strdup(json_variant_string(w));
+                        if (!rp)
+                                return log_oom();
+                }
+        }
+
+        if (!cid)
+                return log_error_errno(SYNTHETIC_ERRNO(ENXIO),
+                                       "No valid FIDO2 token data found.");
+
+        log_info("Automatically discovered security FIDO2 token unlocks volume.");
+
+        *ret_rp_id = TAKE_PTR(rp);
+        *ret_cid = TAKE_PTR(cid);
+        *ret_cid_size = cid_size;
+        *ret_salt = TAKE_PTR(salt);
+        *ret_salt_size = salt_size;
+        *ret_keyslot = keyslot;
+        return 0;
+}