tpm2: add tpm2_policy_authorize()
This adds functions to get the digest for a PolicyAuthorize operation. For building a policy hash, this provides a function to calculate the hash; and for building a policy hash to satisfy the authPolicy for an existing object, this provides a function to perform PolicyAuthorize with an existing session.
This commit is contained in:
Dan Streetman
@@ -2077,6 +2077,203 @@ static int tpm2_policy_pcr(
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return tpm2_get_policy_digest(c, session, ret_policy_digest);
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}
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/* Extend 'digest' with the PolicyAuthorize calculated hash. */
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int tpm2_calculate_policy_authorize(
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const TPM2B_PUBLIC *public,
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const TPM2B_DIGEST *policy_ref,
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TPM2B_DIGEST *digest) {
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TPM2_CC command = TPM2_CC_PolicyAuthorize;
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TSS2_RC rc;
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int r;
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assert(public);
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assert(digest);
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assert(digest->size == SHA256_DIGEST_SIZE);
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r = dlopen_tpm2();
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if (r < 0)
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return log_error_errno(r, "TPM2 support not installed: %m");
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uint8_t buf[sizeof(command)];
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size_t offset = 0;
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rc = sym_Tss2_MU_TPM2_CC_Marshal(command, buf, sizeof(buf), &offset);
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if (rc != TSS2_RC_SUCCESS)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Failed to marshal PolicyAuthorize command: %s", sym_Tss2_RC_Decode(rc));
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if (offset != sizeof(command))
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Offset 0x%zx wrong after marshalling PolicyAuthorize command", offset);
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TPM2B_NAME name = {};
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r = tpm2_calculate_name(&public->publicArea, &name);
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if (r < 0)
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return r;
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/* PolicyAuthorize does not use the previous hash value; we must zero and then extend it. */
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zero(digest->buffer);
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struct iovec data[] = {
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IOVEC_MAKE(buf, offset),
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IOVEC_MAKE(name.name, name.size),
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};
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r = tpm2_digest_many(TPM2_ALG_SHA256, digest, data, ELEMENTSOF(data), /* extend= */ true);
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if (r < 0)
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return r;
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/* PolicyAuthorize requires hashing twice; this is either an extension or rehashing. */
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if (policy_ref)
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r = tpm2_digest_many_digests(TPM2_ALG_SHA256, digest, policy_ref, 1, /* extend= */ true);
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else
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r = tpm2_digest_rehash(TPM2_ALG_SHA256, digest);
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if (r < 0)
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return r;
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tpm2_log_debug_digest(digest, "PolicyAuthorize calculated digest");
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return 0;
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}
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static int tpm2_policy_authorize(
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Tpm2Context *c,
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const Tpm2Handle *session,
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TPML_PCR_SELECTION *pcr_selection,
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const TPM2B_PUBLIC *public,
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const void *fp,
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size_t fp_size,
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JsonVariant *signature_json,
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TPM2B_DIGEST **ret_policy_digest) {
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TSS2_RC rc;
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int r;
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assert(c);
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assert(session);
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assert(pcr_selection);
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assert(public);
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assert(fp && fp_size > 0);
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log_debug("Adding PCR signature policy.");
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_cleanup_tpm2_handle_ Tpm2Handle *pubkey_handle = NULL;
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r = tpm2_handle_new(c, &pubkey_handle);
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if (r < 0)
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return r;
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/* Load the key into the TPM */
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rc = sym_Esys_LoadExternal(
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c->esys_context,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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NULL,
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public,
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#if HAVE_TSS2_ESYS3
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/* tpm2-tss >= 3.0.0 requires a ESYS_TR_RH_* constant specifying the requested
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* hierarchy, older versions need TPM2_RH_* instead. */
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ESYS_TR_RH_OWNER,
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#else
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TPM2_RH_OWNER,
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#endif
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&pubkey_handle->esys_handle);
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if (rc != TSS2_RC_SUCCESS)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Failed to load public key into TPM: %s", sym_Tss2_RC_Decode(rc));
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/* Acquire the "name" of what we just loaded */
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_cleanup_(Esys_Freep) TPM2B_NAME *pubkey_name = NULL;
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r = tpm2_get_name(c, pubkey_handle, &pubkey_name);
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if (r < 0)
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return r;
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/* If we have a signature, proceed with verifying the PCR digest */
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const TPMT_TK_VERIFIED *check_ticket;
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_cleanup_(Esys_Freep) TPMT_TK_VERIFIED *check_ticket_buffer = NULL;
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_cleanup_(Esys_Freep) TPM2B_DIGEST *approved_policy = NULL;
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if (signature_json) {
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r = tpm2_policy_pcr(
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c,
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session,
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pcr_selection,
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&approved_policy);
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if (r < 0)
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return r;
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_cleanup_free_ void *signature_raw = NULL;
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size_t signature_size;
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r = find_signature(
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signature_json,
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pcr_selection,
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fp, fp_size,
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approved_policy->buffer,
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approved_policy->size,
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&signature_raw,
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&signature_size);
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if (r < 0)
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return r;
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/* TPM2_VerifySignature() will only verify the RSA part of the RSA+SHA256 signature,
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* hence we need to do the SHA256 part ourselves, first */
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TPM2B_DIGEST signature_hash = *approved_policy;
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r = tpm2_digest_rehash(TPM2_ALG_SHA256, &signature_hash);
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if (r < 0)
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return r;
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TPMT_SIGNATURE policy_signature = {
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.sigAlg = TPM2_ALG_RSASSA,
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.signature.rsassa = {
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.hash = TPM2_ALG_SHA256,
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.sig.size = signature_size,
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},
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};
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if (signature_size > sizeof(policy_signature.signature.rsassa.sig.buffer))
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE), "Signature larger than buffer.");
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memcpy(policy_signature.signature.rsassa.sig.buffer, signature_raw, signature_size);
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rc = sym_Esys_VerifySignature(
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c->esys_context,
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pubkey_handle->esys_handle,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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&signature_hash,
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&policy_signature,
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&check_ticket_buffer);
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if (rc != TSS2_RC_SUCCESS)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Failed to validate signature in TPM: %s", sym_Tss2_RC_Decode(rc));
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check_ticket = check_ticket_buffer;
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} else {
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/* When enrolling, we pass a NULL ticket */
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static const TPMT_TK_VERIFIED check_ticket_null = {
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.tag = TPM2_ST_VERIFIED,
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.hierarchy = TPM2_RH_OWNER,
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};
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check_ticket = &check_ticket_null;
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}
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rc = sym_Esys_PolicyAuthorize(
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c->esys_context,
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session->esys_handle,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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approved_policy,
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/* policyRef= */ &(const TPM2B_NONCE) {},
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pubkey_name,
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check_ticket);
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if (rc != TSS2_RC_SUCCESS)
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return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
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"Failed to push Authorize policy into TPM: %s", sym_Tss2_RC_Decode(rc));
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return tpm2_get_policy_digest(c, session, ret_policy_digest);
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}
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static int tpm2_build_sealing_policy(
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Tpm2Context *c,
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const Tpm2Handle *session,
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@@ -91,6 +91,7 @@ static inline int tpm2_digest_init(TPMI_ALG_HASH alg, TPM2B_DIGEST *digest) {
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int tpm2_calculate_name(const TPMT_PUBLIC *public, TPM2B_NAME *ret_name);
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int tpm2_calculate_policy_auth_value(TPM2B_DIGEST *digest);
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int tpm2_calculate_policy_authorize(const TPM2B_PUBLIC *public, const TPM2B_DIGEST *policy_ref, TPM2B_DIGEST *digest);
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int tpm2_calculate_policy_pcr(const TPML_PCR_SELECTION *pcr_selection, const TPM2B_DIGEST pcr_values[], size_t pcr_values_count, TPM2B_DIGEST *digest);
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int tpm2_seal(const char *device, uint32_t hash_pcr_mask, const void *pubkey, size_t pubkey_size, uint32_t pubkey_pcr_mask, const char *pin, void **ret_secret, size_t *ret_secret_size, void **ret_blob, size_t *ret_blob_size, void **ret_pcr_hash, size_t *ret_pcr_hash_size, uint16_t *ret_pcr_bank, uint16_t *ret_primary_alg, void **ret_srk_buf, size_t *ret_srk_buf_size);
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@@ -700,6 +700,18 @@ TEST(calculate_policy_auth_value) {
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assert_se(digest_check(&d, "759ebd5ed65100e0b4aa2d04b4b789c2672d92ecc9cdda4b5fa16a303132e008"));
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}
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TEST(calculate_policy_authorize) {
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TPM2B_PUBLIC public;
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TPM2B_DIGEST d;
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tpm2b_public_init(&public);
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digest_init_sha256(&d, "0000000000000000000000000000000000000000000000000000000000000000");
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assert_se(tpm2_calculate_policy_authorize(&public, NULL, &d) == 0);
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assert_se(digest_check(&d, "95213a3784eaab04f427bc7e8851c2f1df0903be8e42428ec25dcefd907baff1"));
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assert_se(tpm2_calculate_policy_authorize(&public, NULL, &d) == 0);
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assert_se(digest_check(&d, "95213a3784eaab04f427bc7e8851c2f1df0903be8e42428ec25dcefd907baff1"));
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}
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TEST(calculate_policy_pcr) {
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TPML_PCR_SELECTION pcr_selection;
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TPM2B_DIGEST pcr_values[16];
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