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Systemd/src/home/homectl-fido2.c
Lennart Poettering 2af3966af3 homectl: add acquired fido2 PIN to user record 
If we successfully acquired the PIN for the fido2 key, let's add it to
our user record, so that we can pass it to homed, which will need it
too.
2020-07-01 11:20:26 +02:00

540 lines
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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;
_cleanup_free_ char *unix_salt = NULL;
struct crypt_data cd = {};
char *k;
int r;
r = make_salt(&unix_salt);
if (r < 0)
return log_error_errno(r, "Failed to generate salt: %m");
/* 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");
errno = 0;
k = crypt_r(base64_encoded, unix_salt, &cd);
if (!k)
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(k))));
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(EOPNOTSUPP, "FIDO2 tokens not supported on this build.");
#endif
}
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