diff options
Diffstat (limited to '')
| -rw-r--r-- | src/shared/cryptsetup-fido2.c | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/src/shared/cryptsetup-fido2.c b/src/shared/cryptsetup-fido2.c new file mode 100644 index 0000000..285b82a --- /dev/null +++ b/src/shared/cryptsetup-fido2.c @@ -0,0 +1,276 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "ask-password-api.h" +#include "cryptsetup-fido2.h" +#include "env-util.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, + bool headless, + Fido2EnrollFlags required, + void **ret_decrypted_key, + size_t *ret_decrypted_key_size, + AskPasswordFlags ask_password_flags) { + + _cleanup_(erase_and_freep) char *envpw = NULL; + _cleanup_strv_free_erase_ char **pins = NULL; + _cleanup_free_ void *loaded_salt = NULL; + bool device_exists = false; + const char *salt; + size_t salt_size; + int r; + + if ((required & (FIDO2ENROLL_PIN | FIDO2ENROLL_UP | FIDO2ENROLL_UV)) && headless) + return log_error_errno(SYNTHETIC_ERRNO(ENOPKG), + "Local verification is required to unlock this volume, but the 'headless' parameter was set."); + + ask_password_flags |= ASK_PASSWORD_PUSH_CACHE | ASK_PASSWORD_ACCEPT_CACHED; + + 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; + } + + r = getenv_steal_erase("PIN", &envpw); + if (r < 0) + return log_error_errno(r, "Failed to acquire password from environment: %m"); + if (r > 0) { + pins = strv_new(envpw); + if (!pins) + return log_oom(); + } + + for (;;) { + if (!device_exists) { + /* Before we inquire for the PIN we'll need, if we never talked to the device, check + * if the device actually is plugged in. Otherwise we'll ask for the PIN already when + * the device is not plugged in, which is confusing. */ + + r = fido2_have_device(device); + if (r < 0) + return r; + if (r == 0) /* no device found, return EAGAIN so that caller will wait/watch udev */ + return -EAGAIN; + + device_exists = true; /* now we know for sure, a device exists, no need to ask again */ + } + + /* Always make an attempt before asking for PIN. + * fido2_use_hmac_hash() will perform a pre-flight check for whether the credential for + * can be found on one of the connected devices. This way, we can avoid prompting the user + * for a PIN when we are sure that no device can be used. */ + r = fido2_use_hmac_hash( + device, + rp_id ?: "io.systemd.cryptsetup", + salt, salt_size, + cid, cid_size, + pins, + required, + ret_decrypted_key, + ret_decrypted_key_size); + if (!IN_SET(r, + -ENOANO, /* needs pin */ + -ENOLCK)) /* pin incorrect */ + return r; + + device_exists = true; /* that a PIN is needed/wasn't correct means that we managed to + * talk to a device */ + + if (headless) + return log_error_errno(SYNTHETIC_ERRNO(ENOPKG), "PIN querying disabled via 'headless' option. Use the '$PIN' environment variable."); + + pins = strv_free_erase(pins); + r = ask_password_auto("Please enter security token PIN:", "drive-harddisk", NULL, "fido2-pin", "cryptsetup.fido2-pin", until, ask_password_flags, &pins); + if (r < 0) + return log_error_errno(r, "Failed to ask for user password: %m"); + + ask_password_flags &= ~ASK_PASSWORD_ACCEPT_CACHED; + } +} + +int acquire_fido2_key_auto( + struct crypt_device *cd, + const char *name, + const char *friendly_name, + const char *fido2_device, + usec_t until, + bool headless, + void **ret_decrypted_key, + size_t *ret_decrypted_key_size, + AskPasswordFlags ask_password_flags) { + + _cleanup_free_ void *cid = NULL; + size_t cid_size = 0; + int r, ret = -ENOENT; + Fido2EnrollFlags required = 0; + + assert(cd); + assert(name); + assert(ret_decrypted_key); + assert(ret_decrypted_key_size); + + /* Loads FIDO2 metadata from LUKS2 JSON token headers. */ + + for (int token = 0; token < sym_crypt_token_max(CRYPT_LUKS2); token ++) { + _cleanup_(json_variant_unrefp) JsonVariant *v = NULL; + JsonVariant *w; + _cleanup_free_ void *salt = NULL; + _cleanup_free_ char *rp = NULL; + size_t salt_size = 0; + int ks; + + 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"); + + ks = cryptsetup_get_keyslot_from_token(v); + if (ks < 0) { + /* Handle parsing errors of the keyslots field gracefully, since it's not 'owned' by + * us, but by the LUKS2 spec */ + log_warning_errno(ks, "Failed to extract keyslot index from FIDO2 JSON data token %i, skipping: %m", token); + continue; + } + + 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_MAX, &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_MAX, &salt, &salt_size); + if (r < 0) + return log_error_errno(r, "Failed to decode base64 encoded salt."); + + 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(); + } + + w = json_variant_by_key(v, "fido2-clientPin-required"); + if (w) { + /* The "fido2-clientPin-required" field is optional. */ + + if (!json_variant_is_boolean(w)) + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), + "FIDO2 token data's 'fido2-clientPin-required' field is not a boolean."); + + SET_FLAG(required, FIDO2ENROLL_PIN, json_variant_boolean(w)); + } else + required |= FIDO2ENROLL_PIN_IF_NEEDED; /* compat with 248, where the field was unset */ + + w = json_variant_by_key(v, "fido2-up-required"); + if (w) { + /* The "fido2-up-required" field is optional. */ + + if (!json_variant_is_boolean(w)) + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), + "FIDO2 token data's 'fido2-up-required' field is not a boolean."); + + SET_FLAG(required, FIDO2ENROLL_UP, json_variant_boolean(w)); + } else + required |= FIDO2ENROLL_UP_IF_NEEDED; /* compat with 248 */ + + w = json_variant_by_key(v, "fido2-uv-required"); + if (w) { + /* The "fido2-uv-required" field is optional. */ + + if (!json_variant_is_boolean(w)) + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), + "FIDO2 token data's 'fido2-uv-required' field is not a boolean."); + + SET_FLAG(required, FIDO2ENROLL_UV, json_variant_boolean(w)); + } else + required |= FIDO2ENROLL_UV_OMIT; /* compat with 248 */ + + ret = acquire_fido2_key( + name, + friendly_name, + fido2_device, + rp, + cid, cid_size, + /* key_file= */ NULL, /* salt is read from LUKS header instead of key_file */ + /* key_file_size= */ 0, + /* key_file_offset= */ 0, + salt, salt_size, + until, + headless, + required, + ret_decrypted_key, ret_decrypted_key_size, + ask_password_flags); + if (ret == 0) + break; + } + + if (!cid) + return log_error_errno(SYNTHETIC_ERRNO(ENXIO), + "No valid FIDO2 token data found."); + + if (ret == -EAGAIN) /* fido2 device does not exist, or UV is blocked; caller will prompt for retry */ + return log_debug_errno(ret, "FIDO2 token does not exist, or UV is blocked."); + if (ret < 0) + return log_error_errno(ret, "Failed to unlock LUKS volume with FIDO2 token: %m"); + + log_info("Unlocked volume via automatically discovered security FIDO2 token."); + return ret; +} |