src/cryptsetup/cryptsetup-pkcs11.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#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 "fileio.h"
#include "format-util.h"
#include "hexdecoct.h"
#include "json.h"
#include "macro.h"
#include "memory-util.h"
#include "parse-util.h"
#include "pkcs11-util.h"
#include "random-util.h"
#include "stat-util.h"
#include "strv.h"

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;
        bool free_encrypted_key;
        bool headless;
};

static void pkcs11_callback_data_release(struct pkcs11_callback_data *data) {
        erase_and_free(data->decrypted_key);

        if (data->free_encrypted_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",
                        "cryptsetup.pkcs11-pin",
                        data->until,
                        data->headless,
                        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 0;
}

int decrypt_pkcs11_key(
                const char *volume_name,
                const char *friendly_name,
                const char *pkcs11_uri,
                const char *key_file,         /* We either expect key_file and associated parameters to be set (for file keys) … */
                size_t key_file_size,
                uint64_t key_file_offset,
                const void *key_data,         /* … or key_data and key_data_size (for literal keys) */
                size_t key_data_size,
                usec_t until,
                bool headless,
                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,
                .headless = headless,
        };
        int r;

        assert(friendly_name);
        assert(pkcs11_uri);
        assert(key_file || key_data);
        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" */

        if (key_data) {
                data.encrypted_key = (void*) key_data;
                data.encrypted_key_size = key_data_size;

                data.free_encrypted_key = false;
        } else {
                _cleanup_free_ char *bindname = NULL;

                /* If we read the key via AF_UNIX, make this client recognizable */
                if (asprintf(&bindname, "@%" PRIx64"/cryptsetup-pkcs11/%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**) &data.encrypted_key, &data.encrypted_key_size);
                if (r < 0)
                        return r;

                data.free_encrypted_key = true;
        }

        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;
}

int find_pkcs11_auto_data(
                struct crypt_device *cd,
                char **ret_uri,
                void **ret_encrypted_key,
                size_t *ret_encrypted_key_size,
                int *ret_keyslot) {

        _cleanup_free_ char *uri = NULL;
        _cleanup_free_ void *key = NULL;
        int r, keyslot = -1;
        size_t key_size = 0;

        assert(cd);
        assert(ret_uri);
        assert(ret_encrypted_key);
        assert(ret_encrypted_key_size);
        assert(ret_keyslot);

        /* Loads PKCS#11 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;

                r = cryptsetup_get_token_as_json(cd, token, "systemd-pkcs11", &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");

                if (uri)
                        return log_error_errno(SYNTHETIC_ERRNO(ENOTUNIQ),
                                               "Multiple PKCS#11 tokens enrolled, cannot automatically determine token.");

                w = json_variant_by_key(v, "pkcs11-uri");
                if (!w || !json_variant_is_string(w))
                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
                                               "PKCS#11 token data lacks 'pkcs11-uri' field.");

                uri = strdup(json_variant_string(w));
                if (!uri)
                        return log_oom();

                if (!pkcs11_uri_valid(uri))
                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
                                               "PKCS#11 token data contains invalid PKCS#11 URI.");

                w = json_variant_by_key(v, "pkcs11-key");
                if (!w || !json_variant_is_string(w))
                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
                                               "PKCS#11 token data lacks 'pkcs11-key' field.");

                assert(!key);
                assert(key_size == 0);
                r = unbase64mem(json_variant_string(w), SIZE_MAX, &key, &key_size);
                if (r < 0)
                        return log_error_errno(r, "Failed to decode base64 encoded key.");

                assert(keyslot < 0);
                keyslot = cryptsetup_get_keyslot_from_token(v);
                if (keyslot < 0)
                        return log_error_errno(keyslot, "Failed to extract keyslot index from PKCS#11 JSON data: %m");
        }

        if (!uri)
                return log_error_errno(SYNTHETIC_ERRNO(ENXIO),
                                       "No valid PKCS#11 token data found.");

        log_info("Automatically discovered security PKCS#11 token '%s' unlocks volume.", uri);

        *ret_uri = TAKE_PTR(uri);
        *ret_encrypted_key = TAKE_PTR(key);
        *ret_encrypted_key_size = key_size;
        *ret_keyslot = keyslot;
        return 0;
}