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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <p11-kit/p11-kit.h>
#include <p11-kit/uri.h>
#include "alloc-util.h"
#include "ask-password-api.h"
#include "cryptsetup-pkcs11.h"
#include "escape.h"
#include "fd-util.h"
#include "format-util.h"
#include "macro.h"
#include "memory-util.h"
#include "pkcs11-util.h"
#include "stat-util.h"
#include "strv.h"
#define KEY_FILE_SIZE_MAX (16U*1024U*1024U) /* 16 MiB */
static int load_key_file(
const char *key_file,
size_t key_file_size,
uint64_t key_file_offset,
void **ret_encrypted_key,
size_t *ret_encrypted_key_size) {
_cleanup_(erase_and_freep) char *buffer = NULL;
_cleanup_close_ int fd = -1;
ssize_t n;
int r;
assert(key_file);
assert(ret_encrypted_key);
assert(ret_encrypted_key_size);
fd = open(key_file, O_RDONLY|O_CLOEXEC);
if (fd < 0)
return log_error_errno(errno, "Failed to load encrypted PKCS#11 key: %m");
if (key_file_size == 0) {
struct stat st;
if (fstat(fd, &st) < 0)
return log_error_errno(errno, "Failed to stat key file: %m");
r = stat_verify_regular(&st);
if (r < 0)
return log_error_errno(r, "Key file is not a regular file: %m");
if (st.st_size == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Key file is empty, refusing.");
if ((uint64_t) st.st_size > KEY_FILE_SIZE_MAX) {
char buf1[FORMAT_BYTES_MAX], buf2[FORMAT_BYTES_MAX];
return log_error_errno(SYNTHETIC_ERRNO(ERANGE),
"Key file larger (%s) than allowed maximum size (%s), refusing.",
format_bytes(buf1, sizeof(buf1), st.st_size),
format_bytes(buf2, sizeof(buf2), KEY_FILE_SIZE_MAX));
}
if (key_file_offset >= (uint64_t) st.st_size)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Key file offset too large for file, refusing.");
key_file_size = st.st_size - key_file_offset;
}
buffer = malloc(key_file_size);
if (!buffer)
return log_oom();
if (key_file_offset > 0)
n = pread(fd, buffer, key_file_size, key_file_offset);
else
n = read(fd, buffer, key_file_size);
if (n < 0)
return log_error_errno(errno, "Failed to read PKCS#11 key file: %m");
if (n == 0)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Empty encrypted key found, refusing.");
*ret_encrypted_key = TAKE_PTR(buffer);
*ret_encrypted_key_size = (size_t) n;
return 0;
}
struct pkcs11_callback_data {
const char *friendly_name;
usec_t until;
void *encrypted_key;
size_t encrypted_key_size;
void *decrypted_key;
size_t decrypted_key_size;
};
static void pkcs11_callback_data_release(struct pkcs11_callback_data *data) {
free(data->decrypted_key);
free(data->encrypted_key);
}
static int pkcs11_callback(
CK_FUNCTION_LIST *m,
CK_SESSION_HANDLE session,
CK_SLOT_ID slot_id,
const CK_SLOT_INFO *slot_info,
const CK_TOKEN_INFO *token_info,
P11KitUri *uri,
void *userdata) {
struct pkcs11_callback_data *data = userdata;
CK_OBJECT_HANDLE object;
int r;
assert(m);
assert(slot_info);
assert(token_info);
assert(uri);
assert(data);
/* Called for every token matching our URI */
r = pkcs11_token_login(
m,
session,
slot_id,
token_info,
data->friendly_name,
"drive-harddisk",
"pkcs11-pin",
data->until,
NULL);
if (r < 0)
return r;
/* We are likely called during early boot, where entropy is scarce. Mix some data from the PKCS#11
* token, if it supports that. It should be cheap, given that we already are talking to it anyway and
* shouldn't hurt. */
(void) pkcs11_token_acquire_rng(m, session);
r = pkcs11_token_find_private_key(m, session, uri, &object);
if (r < 0)
return r;
r = pkcs11_token_decrypt_data(
m,
session,
object,
data->encrypted_key,
data->encrypted_key_size,
&data->decrypted_key,
&data->decrypted_key_size);
if (r < 0)
return r;
return 1;
}
int decrypt_pkcs11_key(
const char *friendly_name,
const char *pkcs11_uri,
const char *key_file,
size_t key_file_size,
uint64_t key_file_offset,
usec_t until,
void **ret_decrypted_key,
size_t *ret_decrypted_key_size) {
_cleanup_(pkcs11_callback_data_release) struct pkcs11_callback_data data = {
.friendly_name = friendly_name,
.until = until,
};
int r;
assert(friendly_name);
assert(pkcs11_uri);
assert(key_file);
assert(ret_decrypted_key);
assert(ret_decrypted_key_size);
/* The functions called here log about all errors, except for EAGAIN which means "token not found right now" */
r = load_key_file(key_file, key_file_size, key_file_offset, &data.encrypted_key, &data.encrypted_key_size);
if (r < 0)
return r;
r = pkcs11_find_token(pkcs11_uri, pkcs11_callback, &data);
if (r < 0)
return r;
*ret_decrypted_key = TAKE_PTR(data.decrypted_key);
*ret_decrypted_key_size = data.decrypted_key_size;
return 0;
}
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