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Systemd/src/home/homectl-fido2.c

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/* SPDX-License-Identifier: LGPL-2.1+ */
#if HAVE_LIBFIDO2
#include <fido.h>
#endif
#include "ask-password-api.h"
#include "errno-util.h"
#include "format-table.h"
#include "hexdecoct.h"
#include "homectl-fido2.h"
#include "homectl-pkcs11.h"
#include "libcrypt-util.h"
#include "locale-util.h"
#include "memory-util.h"
#include "random-util.h"
#include "strv.h"
#if HAVE_LIBFIDO2
static int add_fido2_credential_id(
JsonVariant **v,
const void *cid,
size_t cid_size) {
_cleanup_(json_variant_unrefp) JsonVariant *w = NULL;
_cleanup_strv_free_ char **l = NULL;
_cleanup_free_ char *escaped = NULL;
int r;
assert(v);
assert(cid);
r = base64mem(cid, cid_size, &escaped);
if (r < 0)
return log_error_errno(r, "Failed to base64 encode FIDO2 credential ID: %m");
w = json_variant_ref(json_variant_by_key(*v, "fido2HmacCredential"));
if (w) {
r = json_variant_strv(w, &l);
if (r < 0)
return log_error_errno(r, "Failed to parse FIDO2 credential ID list: %m");
if (strv_contains(l, escaped))
return 0;
}
r = strv_extend(&l, escaped);
if (r < 0)
return log_oom();
w = json_variant_unref(w);
r = json_variant_new_array_strv(&w, l);
if (r < 0)
return log_error_errno(r, "Failed to create FIDO2 credential ID JSON: %m");
r = json_variant_set_field(v, "fido2HmacCredential", w);
if (r < 0)
return log_error_errno(r, "Failed to update FIDO2 credential ID: %m");
return 0;
}
static int add_fido2_salt(
JsonVariant **v,
const void *cid,
size_t cid_size,
const void *fido2_salt,
size_t fido2_salt_size,
const void *secret,
size_t secret_size) {
_cleanup_(json_variant_unrefp) JsonVariant *l = NULL, *w = NULL, *e = NULL;
_cleanup_(erase_and_freep) char *base64_encoded = NULL, *hashed = NULL;
int r;
/* 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");
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(hashed))));
if (r < 0)
return log_error_errno(r, "Failed to build FIDO2 salt JSON key object: %m");
w = json_variant_ref(json_variant_by_key(*v, "privileged"));
l = json_variant_ref(json_variant_by_key(w, "fido2HmacSalt"));
r = json_variant_append_array(&l, e);
if (r < 0)
return log_error_errno(r, "Failed append FIDO2 salt: %m");
r = json_variant_set_field(&w, "fido2HmacSalt", l);
if (r < 0)
return log_error_errno(r, "Failed to set FDO2 salt: %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;
}
#endif
#define FIDO2_SALT_SIZE 32
int identity_add_fido2_parameters(
JsonVariant **v,
const char *device) {
#if HAVE_LIBFIDO2
_cleanup_(fido_cbor_info_free) fido_cbor_info_t *di = NULL;
_cleanup_(fido_assert_free) fido_assert_t *a = NULL;
_cleanup_(erase_and_freep) char *used_pin = NULL;
_cleanup_(fido_cred_free) fido_cred_t *c = NULL;
_cleanup_(fido_dev_free) fido_dev_t *d = NULL;
_cleanup_(erase_and_freep) void *salt = NULL;
JsonVariant *un, *realm, *rn;
bool found_extension = false;
const void *cid, *secret;
const char *fido_un;
size_t n, cid_size, secret_size;
char **e;
int r;
/* Construction is like this: we generate a salt of 32 bytes. We then ask the FIDO2 device to
* HMAC-SHA256 it for us with its internal key. The result is the key used by LUKS and account
* authentication. LUKS and UNIX password auth all do their own salting before hashing, so that FIDO2
* device never sees the volume key.
*
* S = HMAC-SHA256(I, D)
*
* with: S → LUKS/account authentication key (never stored)
* I → internal key on FIDO2 device (stored in the FIDO2 device)
* D → salt we generate here (stored in the privileged part of the JSON record)
*
*/
assert(v);
assert(device);
salt = malloc(FIDO2_SALT_SIZE);
if (!salt)
return log_oom();
r = genuine_random_bytes(salt, FIDO2_SALT_SIZE, RANDOM_BLOCK);
if (r < 0)
return log_error_errno(r, "Failed to generate salt: %m");
d = fido_dev_new();
if (!d)
return log_oom();
r = fido_dev_open(d, device);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to open FIDO2 device %s: %s", device, fido_strerr(r));
if (!fido_dev_is_fido2(d))
return log_error_errno(SYNTHETIC_ERRNO(ENODEV),
"Specified device %s is not a FIDO2 device.", device);
di = fido_cbor_info_new();
if (!di)
return log_oom();
r = fido_dev_get_cbor_info(d, di);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to get CBOR device info for %s: %s", device, fido_strerr(r));
e = fido_cbor_info_extensions_ptr(di);
n = fido_cbor_info_extensions_len(di);
for (size_t i = 0; i < n; i++)
if (streq(e[i], "hmac-secret")) {
found_extension = true;
break;
}
if (!found_extension)
return log_error_errno(SYNTHETIC_ERRNO(ENODEV),
"Specified device %s is a FIDO2 device, but does not support the required HMAC-SECRET extension.", device);
c = fido_cred_new();
if (!c)
return log_oom();
r = fido_cred_set_extensions(c, FIDO_EXT_HMAC_SECRET);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to enable HMAC-SECRET extension on FIDO2 credential: %s", fido_strerr(r));
r = fido_cred_set_rp(c, "io.systemd.home", "Home Directory");
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 credential relying party ID/name: %s", fido_strerr(r));
r = fido_cred_set_type(c, COSE_ES256);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 credential type to ES256: %s", fido_strerr(r));
un = json_variant_by_key(*v, "userName");
if (!un)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"userName field of user record is missing");
if (!json_variant_is_string(un))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"userName field of user record is not a string");
realm = json_variant_by_key(*v, "realm");
if (realm) {
if (!json_variant_is_string(realm))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"realm field of user record is not a string");
fido_un = strjoina(json_variant_string(un), json_variant_string(realm));
} else
fido_un = json_variant_string(un);
rn = json_variant_by_key(*v, "realName");
if (rn && !json_variant_is_string(rn))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
"realName field of user record is not a string");
r = fido_cred_set_user(c,
(const unsigned char*) fido_un, strlen(fido_un), /* We pass the user ID and name as the same */
fido_un,
rn ? json_variant_string(rn) : NULL,
NULL /* icon URL */);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 credential user data: %s", fido_strerr(r));
r = fido_cred_set_clientdata_hash(c, (const unsigned char[32]) {}, 32);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 client data hash: %s", fido_strerr(r));
r = fido_cred_set_rk(c, FIDO_OPT_FALSE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to turn off FIDO2 resident key option of credential: %s", fido_strerr(r));
r = fido_cred_set_uv(c, FIDO_OPT_FALSE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to turn off FIDO2 user verification option of credential: %s", fido_strerr(r));
log_info("Initializing FIDO2 credential on security token.");
log_notice("%s%s(Hint: This might require verification of user presence on security token.)",
emoji_enabled() ? special_glyph(SPECIAL_GLYPH_TOUCH) : "",
emoji_enabled() ? " " : "");
r = fido_dev_make_cred(d, c, NULL);
if (r == FIDO_ERR_PIN_REQUIRED) {
_cleanup_free_ char *text = NULL;
if (asprintf(&text, "Please enter security token PIN:") < 0)
return log_oom();
for (;;) {
_cleanup_(strv_free_erasep) char **pin = NULL;
char **i;
r = ask_password_auto(text, "user-home", NULL, "fido2-pin", USEC_INFINITY, 0, &pin);
if (r < 0)
return log_error_errno(r, "Failed to acquire user PIN: %m");
r = FIDO_ERR_PIN_INVALID;
STRV_FOREACH(i, pin) {
if (isempty(*i)) {
log_info("PIN may not be empty.");
continue;
}
r = fido_dev_make_cred(d, c, *i);
if (r == FIDO_OK) {
used_pin = strdup(*i);
if (!used_pin)
return log_oom();
break;
}
if (r != FIDO_ERR_PIN_INVALID)
break;
}
if (r != FIDO_ERR_PIN_INVALID)
break;
log_notice("PIN incorrect, please try again.");
}
}
if (r == FIDO_ERR_PIN_AUTH_BLOCKED)
return log_notice_errno(SYNTHETIC_ERRNO(EPERM),
"Token PIN is currently blocked, please remove and reinsert token.");
if (r == FIDO_ERR_ACTION_TIMEOUT)
return log_error_errno(SYNTHETIC_ERRNO(ENOSTR),
"Token action timeout. (User didn't interact with token quickly enough.)");
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to generate FIDO2 credential: %s", fido_strerr(r));
cid = fido_cred_id_ptr(c);
if (!cid)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to get FIDO2 credential ID.");
cid_size = fido_cred_id_len(c);
a = fido_assert_new();
if (!a)
return log_oom();
r = fido_assert_set_extensions(a, FIDO_EXT_HMAC_SECRET);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to enable HMAC-SECRET extension on FIDO2 assertion: %s", fido_strerr(r));
r = fido_assert_set_hmac_salt(a, salt, FIDO2_SALT_SIZE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set salt on FIDO2 assertion: %s", fido_strerr(r));
r = fido_assert_set_rp(a, "io.systemd.home");
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion ID: %s", fido_strerr(r));
r = fido_assert_set_clientdata_hash(a, (const unsigned char[32]) {}, 32);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion client data hash: %s", fido_strerr(r));
r = fido_assert_allow_cred(a, cid, cid_size);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to add FIDO2 assertion credential ID: %s", fido_strerr(r));
r = fido_assert_set_up(a, FIDO_OPT_FALSE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to turn off FIDO2 assertion user presence: %s", fido_strerr(r));
log_info("Generating secret key on FIDO2 security token.");
r = fido_dev_get_assert(d, a, used_pin);
if (r == FIDO_ERR_UP_REQUIRED) {
r = fido_assert_set_up(a, FIDO_OPT_TRUE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to turn on FIDO2 assertion user presence: %s", fido_strerr(r));
log_notice("%s%sIn order to allow secret key generation, please verify presence on security token.",
emoji_enabled() ? special_glyph(SPECIAL_GLYPH_TOUCH) : "",
emoji_enabled() ? " " : "");
r = fido_dev_get_assert(d, a, used_pin);
}
if (r == FIDO_ERR_ACTION_TIMEOUT)
return log_error_errno(SYNTHETIC_ERRNO(ENOSTR),
"Token action timeout. (User didn't interact with token quickly enough.)");
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to ask token for assertion: %s", fido_strerr(r));
secret = fido_assert_hmac_secret_ptr(a, 0);
if (!secret)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to retrieve HMAC secret.");
secret_size = fido_assert_hmac_secret_len(a, 0);
r = add_fido2_credential_id(v, cid, cid_size);
if (r < 0)
return r;
r = add_fido2_salt(v,
cid,
cid_size,
salt,
FIDO2_SALT_SIZE,
secret,
secret_size);
if (r < 0)
return r;
/* If we acquired the PIN also include it in the secret section of the record, so that systemd-homed
* can use it if it needs to, given that it likely needs to decrypt the key again to pass to LUKS or
* fscrypt. */
r = identity_add_token_pin(v, used_pin);
if (r < 0)
return r;
return 0;
#else
return log_error_errno(EOPNOTSUPP, "FIDO2 tokens not supported on this build.");
#endif
}
int list_fido2_devices(void) {
#if HAVE_LIBFIDO2
_cleanup_(table_unrefp) Table *t = NULL;
size_t allocated = 64, found = 0;
fido_dev_info_t *di = NULL;
int r;
di = fido_dev_info_new(allocated);
if (!di)
return log_oom();
r = fido_dev_info_manifest(di, allocated, &found);
if (r == FIDO_ERR_INTERNAL || (r == FIDO_OK && found == 0)) {
/* The library returns FIDO_ERR_INTERNAL when no devices are found. I wish it wouldn't. */
log_info("No FIDO2 devices found.");
r = 0;
goto finish;
}
if (r != FIDO_OK) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to enumerate FIDO2 devices: %s", fido_strerr(r));
goto finish;
}
t = table_new("path", "manufacturer", "product");
if (!t) {
r = log_oom();
goto finish;
}
for (size_t i = 0; i < found; i++) {
const fido_dev_info_t *entry;
entry = fido_dev_info_ptr(di, i);
if (!entry) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to get device information for FIDO device %zu.", i);
goto finish;
}
r = table_add_many(
t,
TABLE_PATH, fido_dev_info_path(entry),
TABLE_STRING, fido_dev_info_manufacturer_string(entry),
TABLE_STRING, fido_dev_info_product_string(entry));
if (r < 0) {
table_log_add_error(r);
goto finish;
}
}
r = table_print(t, stdout);
if (r < 0) {
log_error_errno(r, "Failed to show device table: %m");
goto finish;
}
r = 0;
finish:
fido_dev_info_free(&di, allocated);
return r;
#else
return log_error_errno(EOPNOTSUPP, "FIDO2 tokens not supported on this build.");
#endif
}
int find_fido2_auto(char **ret) {
#if HAVE_LIBFIDO2
_cleanup_free_ char *copy = NULL;
size_t di_size = 64, found = 0;
const fido_dev_info_t *entry;
fido_dev_info_t *di = NULL;
const char *path;
int r;
di = fido_dev_info_new(di_size);
if (!di)
return log_oom();
r = fido_dev_info_manifest(di, di_size, &found);
if (r == FIDO_ERR_INTERNAL || (r == FIDO_OK && found == 0)) {
/* The library returns FIDO_ERR_INTERNAL when no devices are found. I wish it wouldn't. */
r = log_error_errno(SYNTHETIC_ERRNO(ENODEV), "No FIDO2 devices found.");
goto finish;
}
if (r != FIDO_OK) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to enumerate FIDO2 devices: %s", fido_strerr(r));
goto finish;
}
if (found > 1) {
r = log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ), "More than one FIDO2 device found.");
goto finish;
}
entry = fido_dev_info_ptr(di, 0);
if (!entry) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to get device information for FIDO device 0.");
goto finish;
}
path = fido_dev_info_path(entry);
if (!path) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to query FIDO device path.");
goto finish;
}
copy = strdup(path);
if (!copy) {
r = log_oom();
goto finish;
}
*ret = TAKE_PTR(copy);
r = 0;
finish:
fido_dev_info_free(&di, di_size);
return r;
#else
return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
"FIDO2 tokens not supported on this build.");
#endif
}
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