homed: split out HMAC-HASH fido2 decode code into src/shared/

That way we can use it later on in systemd-cryptsetup to unlock devices
with FIDO2 tokens.
This commit is contained in:
Lennart Poettering 2020-11-26 13:30:24 +01:00
parent 17599e129b
commit ebcb3f38d2
3 changed files with 264 additions and 179 deletions

View File

@ -5,138 +5,34 @@
#include "hexdecoct.h"
#include "homework-fido2.h"
#include "libfido2-util.h"
#include "strv.h"
#include "memory-util.h"
static int fido2_use_specific_token(
const char *path,
int fido2_use_token(
UserRecord *h,
UserRecord *secret,
const Fido2HmacSalt *salt,
char **ret) {
_cleanup_(fido_cbor_info_free_wrapper) fido_cbor_info_t *di = NULL;
_cleanup_(fido_assert_free_wrapper) fido_assert_t *a = NULL;
_cleanup_(fido_dev_free_wrapper) fido_dev_t *d = NULL;
bool found_extension = false;
size_t n, hmac_size;
const void *hmac;
char **e;
_cleanup_(erase_and_freep) void *hmac = NULL;
size_t hmac_size;
int r;
d = sym_fido_dev_new();
if (!d)
return log_oom();
assert(h);
assert(secret);
assert(salt);
assert(ret);
r = sym_fido_dev_open(d, path);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to open FIDO2 device %s: %s", path, sym_fido_strerr(r));
if (!sym_fido_dev_is_fido2(d))
return log_error_errno(SYNTHETIC_ERRNO(ENODEV),
"Specified device %s is not a FIDO2 device.", path);
di = sym_fido_cbor_info_new();
if (!di)
return log_oom();
r = sym_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", path, sym_fido_strerr(r));
e = sym_fido_cbor_info_extensions_ptr(di);
n = sym_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.", path);
a = sym_fido_assert_new();
if (!a)
return log_oom();
r = sym_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", sym_fido_strerr(r));
r = sym_fido_assert_set_hmac_salt(a, salt->salt, salt->salt_size);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set salt on FIDO2 assertion: %s", sym_fido_strerr(r));
r = sym_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", sym_fido_strerr(r));
r = sym_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", sym_fido_strerr(r));
r = sym_fido_assert_allow_cred(a, salt->credential.id, salt->credential.size);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to add FIDO2 assertion credential ID: %s", sym_fido_strerr(r));
r = sym_fido_assert_set_up(a, h->fido2_user_presence_permitted <= 0 ? FIDO_OPT_FALSE : FIDO_OPT_TRUE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion user presence: %s", sym_fido_strerr(r));
log_info("Asking FIDO2 token for authentication.");
r = sym_fido_dev_get_assert(d, a, NULL); /* try without pin first */
if (r == FIDO_ERR_PIN_REQUIRED) {
char **i;
/* OK, we needed a pin, try with all pins in turn */
STRV_FOREACH(i, secret->token_pin) {
r = sym_fido_dev_get_assert(d, a, *i);
if (r != FIDO_ERR_PIN_INVALID)
break;
}
}
switch (r) {
case FIDO_OK:
break;
case FIDO_ERR_NO_CREDENTIALS:
return log_error_errno(SYNTHETIC_ERRNO(EBADSLT),
"Wrong security token; needed credentials not present on token.");
case FIDO_ERR_PIN_REQUIRED:
return log_error_errno(SYNTHETIC_ERRNO(ENOANO),
"Security token requires PIN.");
case FIDO_ERR_PIN_AUTH_BLOCKED:
return log_error_errno(SYNTHETIC_ERRNO(EOWNERDEAD),
"PIN of security token is blocked, please remove/reinsert token.");
case FIDO_ERR_PIN_INVALID:
return log_error_errno(SYNTHETIC_ERRNO(ENOLCK),
"PIN of security token incorrect.");
case FIDO_ERR_UP_REQUIRED:
return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE),
"User presence required.");
case FIDO_ERR_ACTION_TIMEOUT:
return log_error_errno(SYNTHETIC_ERRNO(ENOSTR),
"Token action timeout. (User didn't interact with token quickly enough.)");
default:
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to ask token for assertion: %s", sym_fido_strerr(r));
}
hmac = sym_fido_assert_hmac_secret_ptr(a, 0);
if (!hmac)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to retrieve HMAC secret.");
hmac_size = sym_fido_assert_hmac_secret_len(a, 0);
r = fido2_use_hmac_hash(
NULL,
"io.systemd.home",
salt->salt, salt->salt_size,
salt->credential.id, salt->credential.size,
secret->token_pin,
h->fido2_user_presence_permitted > 0,
&hmac,
&hmac_size);
if (r < 0)
return r;
r = base64mem(hmac, hmac_size, ret);
if (r < 0)
@ -144,59 +40,3 @@ static int fido2_use_specific_token(
return 0;
}
int fido2_use_token(UserRecord *h, UserRecord *secret, const Fido2HmacSalt *salt, char **ret) {
size_t allocated = 64, found = 0;
fido_dev_info_t *di = NULL;
int r;
r = dlopen_libfido2();
if (r < 0)
return log_error_errno(r, "FIDO2 support is not installed.");
di = sym_fido_dev_info_new(allocated);
if (!di)
return log_oom();
r = sym_fido_dev_info_manifest(di, allocated, &found);
if (r == FIDO_ERR_INTERNAL) {
/* The library returns FIDO_ERR_INTERNAL when no devices are found. I wish it wouldn't. */
r = log_debug_errno(SYNTHETIC_ERRNO(EAGAIN), "Got FIDO_ERR_INTERNAL, assuming no devices.");
goto finish;
}
if (r != FIDO_OK) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to enumerate FIDO2 devices: %s", sym_fido_strerr(r));
goto finish;
}
for (size_t i = 0; i < found; i++) {
const fido_dev_info_t *entry;
const char *path;
entry = sym_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;
}
path = sym_fido_dev_info_path(entry);
if (!path) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to query FIDO device path.");
goto finish;
}
r = fido2_use_specific_token(path, h, secret, salt, ret);
if (!IN_SET(r,
-EBADSLT, /* device doesn't understand our credential hash */
-ENODEV /* device is not a FIDO2 device with HMAC-SECRET */))
goto finish;
}
r = -EAGAIN;
finish:
sym_fido_dev_info_free(&di, allocated);
return r;
}

View File

@ -121,6 +121,239 @@ int dlopen_libfido2(void) {
return 1;
}
static int fido2_use_hmac_hash_specific_token(
const char *path,
const char *rp_id,
const void *salt,
size_t salt_size,
const void *cid,
size_t cid_size,
char **pins,
bool up, /* user presence permitted */
void **ret_hmac,
size_t *ret_hmac_size) {
_cleanup_(fido_cbor_info_free_wrapper) fido_cbor_info_t *di = NULL;
_cleanup_(fido_assert_free_wrapper) fido_assert_t *a = NULL;
_cleanup_(fido_dev_free_wrapper) fido_dev_t *d = NULL;
_cleanup_(erase_and_freep) void *hmac_copy = NULL;
bool found_extension = false;
size_t n, hmac_size;
const void *hmac;
char **e;
int r;
assert(path);
assert(rp_id);
assert(salt);
assert(cid);
assert(ret_hmac);
assert(ret_hmac_size);
d = sym_fido_dev_new();
if (!d)
return log_oom();
r = sym_fido_dev_open(d, path);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to open FIDO2 device %s: %s", path, sym_fido_strerr(r));
if (!sym_fido_dev_is_fido2(d))
return log_error_errno(SYNTHETIC_ERRNO(ENODEV),
"Specified device %s is not a FIDO2 device.", path);
di = sym_fido_cbor_info_new();
if (!di)
return log_oom();
r = sym_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", path, sym_fido_strerr(r));
e = sym_fido_cbor_info_extensions_ptr(di);
n = sym_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.", path);
a = sym_fido_assert_new();
if (!a)
return log_oom();
r = sym_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", sym_fido_strerr(r));
r = sym_fido_assert_set_hmac_salt(a, salt, salt_size);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set salt on FIDO2 assertion: %s", sym_fido_strerr(r));
r = sym_fido_assert_set_rp(a, rp_id);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion ID: %s", sym_fido_strerr(r));
r = sym_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", sym_fido_strerr(r));
r = sym_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", sym_fido_strerr(r));
r = sym_fido_assert_set_up(a, FIDO_OPT_FALSE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion user presence: %s", sym_fido_strerr(r));
log_info("Asking FIDO2 token for authentication.");
r = sym_fido_dev_get_assert(d, a, NULL); /* try without pin and without up first */
if (r == FIDO_ERR_UP_REQUIRED && up) {
r = sym_fido_assert_set_up(a, FIDO_OPT_TRUE);
if (r != FIDO_OK)
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to set FIDO2 assertion user presence: %s", sym_fido_strerr(r));
log_info("Security token requires user presence.");
r = sym_fido_dev_get_assert(d, a, NULL); /* try without pin but with up now */
}
if (r == FIDO_ERR_PIN_REQUIRED) {
char **i;
/* OK, we needed a pin, try with all pins in turn */
STRV_FOREACH(i, pins) {
r = sym_fido_dev_get_assert(d, a, *i);
if (r != FIDO_ERR_PIN_INVALID)
break;
}
}
switch (r) {
case FIDO_OK:
break;
case FIDO_ERR_NO_CREDENTIALS:
return log_error_errno(SYNTHETIC_ERRNO(EBADSLT),
"Wrong security token; needed credentials not present on token.");
case FIDO_ERR_PIN_REQUIRED:
return log_error_errno(SYNTHETIC_ERRNO(ENOANO),
"Security token requires PIN.");
case FIDO_ERR_PIN_AUTH_BLOCKED:
return log_error_errno(SYNTHETIC_ERRNO(EOWNERDEAD),
"PIN of security token is blocked, please remove/reinsert token.");
case FIDO_ERR_PIN_INVALID:
return log_error_errno(SYNTHETIC_ERRNO(ENOLCK),
"PIN of security token incorrect.");
case FIDO_ERR_UP_REQUIRED:
return log_error_errno(SYNTHETIC_ERRNO(EMEDIUMTYPE),
"User presence required.");
case FIDO_ERR_ACTION_TIMEOUT:
return log_error_errno(SYNTHETIC_ERRNO(ENOSTR),
"Token action timeout. (User didn't interact with token quickly enough.)");
default:
return log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to ask token for assertion: %s", sym_fido_strerr(r));
}
hmac = sym_fido_assert_hmac_secret_ptr(a, 0);
if (!hmac)
return log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to retrieve HMAC secret.");
hmac_size = sym_fido_assert_hmac_secret_len(a, 0);
hmac_copy = memdup(hmac, hmac_size);
if (!hmac_copy)
return log_oom();
*ret_hmac = TAKE_PTR(hmac_copy);
*ret_hmac_size = hmac_size;
return 0;
}
int fido2_use_hmac_hash(
const char *device,
const char *rp_id,
const void *salt,
size_t salt_size,
const void *cid,
size_t cid_size,
char **pins,
bool up, /* user presence permitted */
void **ret_hmac,
size_t *ret_hmac_size) {
size_t allocated = 64, found = 0;
fido_dev_info_t *di = NULL;
int r;
r = dlopen_libfido2();
if (r < 0)
return log_error_errno(r, "FIDO2 support is not installed.");
if (device)
return fido2_use_hmac_hash_specific_token(device, rp_id, salt, salt_size, cid, cid_size, pins, up, ret_hmac, ret_hmac_size);
di = sym_fido_dev_info_new(allocated);
if (!di)
return log_oom();
r = sym_fido_dev_info_manifest(di, allocated, &found);
if (r == FIDO_ERR_INTERNAL) {
/* The library returns FIDO_ERR_INTERNAL when no devices are found. I wish it wouldn't. */
r = log_debug_errno(SYNTHETIC_ERRNO(EAGAIN), "Got FIDO_ERR_INTERNAL, assuming no devices.");
goto finish;
}
if (r != FIDO_OK) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO), "Failed to enumerate FIDO2 devices: %s", sym_fido_strerr(r));
goto finish;
}
for (size_t i = 0; i < found; i++) {
const fido_dev_info_t *entry;
const char *path;
entry = sym_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;
}
path = sym_fido_dev_info_path(entry);
if (!path) {
r = log_error_errno(SYNTHETIC_ERRNO(EIO),
"Failed to query FIDO device path.");
goto finish;
}
r = fido2_use_hmac_hash_specific_token(path, rp_id, salt, salt_size, cid, cid_size, pins, up, ret_hmac, ret_hmac_size);
if (!IN_SET(r,
-EBADSLT, /* device doesn't understand our credential hash */
-ENODEV /* device is not a FIDO2 device with HMAC-SECRET */))
goto finish;
}
r = -EAGAIN;
finish:
sym_fido_dev_info_free(&di, allocated);
return r;
}
#define FIDO2_SALT_SIZE 32
int fido2_generate_hmac_hash(

View File

@ -69,6 +69,18 @@ static inline void fido_cred_free_wrapper(fido_cred_t **p) {
sym_fido_cred_free(p);
}
int fido2_use_hmac_hash(
const char *device,
const char *rp_id,
const void *salt,
size_t salt_size,
const void *cid,
size_t cid_size,
char **pins,
bool up, /* user presence permitted */
void **ret_hmac,
size_t *ret_hmac_size);
int fido2_generate_hmac_hash(
const char *device,
const char *rp_id,