luks2-tpm2.c

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

#include "alloc-util.h"
#include "ask-password-api.h"
#include "env-util.h"
#include "hexdecoct.h"
#include "json.h"
#include "log.h"
#include "luks2-tpm2.h"
#include "parse-util.h"
#include "random-util.h"
#include "sha256.h"
#include "strv.h"
#include "tpm2-util.h"

int acquire_luks2_key(
                const char *device,
                uint32_t hash_pcr_mask,
                uint16_t pcr_bank,
                const struct iovec *pubkey,
                uint32_t pubkey_pcr_mask,
                const char *signature_path,
                const char *pin,
                const char *pcrlock_path,
                uint16_t primary_alg,
                const struct iovec *blob,
                const struct iovec *policy_hash,
                const struct iovec *salt,
                const struct iovec *srk,
                const struct iovec *pcrlock_nv,
                TPM2Flags flags,
                struct iovec *ret_decrypted_key) {

        _cleanup_(json_variant_unrefp) JsonVariant *signature_json = NULL;
        _cleanup_free_ char *auto_device = NULL;
        _cleanup_(erase_and_freep) char *b64_salted_pin = NULL;
        int r;

        assert(iovec_is_valid(salt));
        assert(ret_decrypted_key);

        if (!device) {
                r = tpm2_find_device_auto(&auto_device);
                if (r == -ENODEV)
                        return -EAGAIN; /* Tell the caller to wait for a TPM2 device to show up */
                if (r < 0)
                        return log_error_errno(r, "Could not find TPM2 device: %m");

                device = auto_device;
        }

        if ((flags & TPM2_FLAGS_USE_PIN) && !pin)
                return -ENOANO;

        if (pin && iovec_is_set(salt)) {
                uint8_t salted_pin[SHA256_DIGEST_SIZE] = {};
                CLEANUP_ERASE(salted_pin);
                r = tpm2_util_pbkdf2_hmac_sha256(pin, strlen(pin), salt->iov_base, salt->iov_len, salted_pin);
                if (r < 0)
                        return log_error_errno(r, "Failed to perform PBKDF2: %m");

                r = base64mem(salted_pin, sizeof(salted_pin), &b64_salted_pin);
                if (r < 0)
                        return log_error_errno(r, "Failed to base64 encode salted pin: %m");
                pin = b64_salted_pin;
        }

        if (pubkey_pcr_mask != 0) {
                r = tpm2_load_pcr_signature(signature_path, &signature_json);
                if (r < 0)
                        return log_error_errno(r, "Failed to load PCR signature: %m");
        }

        _cleanup_(tpm2_pcrlock_policy_done) Tpm2PCRLockPolicy pcrlock_policy = {};
        if (FLAGS_SET(flags, TPM2_FLAGS_USE_PCRLOCK)) {
                r = tpm2_pcrlock_policy_load(pcrlock_path, &pcrlock_policy);
                if (r < 0)
                        return r;
                if (r == 0) {
                        /* Not found? Then search among passed credentials */
                        r = tpm2_pcrlock_policy_from_credentials(srk, pcrlock_nv, &pcrlock_policy);
                        if (r < 0)
                                return r;
                        if (r == 0)
                                return log_error_errno(SYNTHETIC_ERRNO(EREMOTE), "Couldn't find pcrlock policy for volume.");
                }
        }

        _cleanup_(tpm2_context_unrefp) Tpm2Context *tpm2_context = NULL;
        r = tpm2_context_new_or_warn(device, &tpm2_context);
        if (r < 0)
                return r;

        r = tpm2_unseal(tpm2_context,
                        hash_pcr_mask,
                        pcr_bank,
                        pubkey,
                        pubkey_pcr_mask,
                        signature_json,
                        pin,
                        FLAGS_SET(flags, TPM2_FLAGS_USE_PCRLOCK) ? &pcrlock_policy : NULL,
                        primary_alg,
                        blob,
                        policy_hash,
                        srk,
                        ret_decrypted_key);
        if (r < 0)
                return log_error_errno(r, "Failed to unseal secret using TPM2: %m");

        return r;
}