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https://github.com/systemd/systemd
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Merge pull request #26357 from ddstreet/tpm2_policy_session
Tpm2 policy session
This commit is contained in:
Luca Boccassi
GitHub
commit
3be6943e07
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@ -52,6 +52,7 @@ TSS2_RC (*sym_Esys_PolicyPCR)(ESYS_CONTEXT *esysContext, ESYS_TR policySession,
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TSS2_RC (*sym_Esys_ReadPublic)(ESYS_CONTEXT *esysContext, ESYS_TR objectHandle, ESYS_TR shandle1, ESYS_TR shandle2, ESYS_TR shandle3, TPM2B_PUBLIC **outPublic, TPM2B_NAME **name, TPM2B_NAME **qualifiedName);
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TSS2_RC (*sym_Esys_StartAuthSession)(ESYS_CONTEXT *esysContext, ESYS_TR tpmKey, ESYS_TR bind, ESYS_TR shandle1, ESYS_TR shandle2, ESYS_TR shandle3, const TPM2B_NONCE *nonceCaller, TPM2_SE sessionType, const TPMT_SYM_DEF *symmetric, TPMI_ALG_HASH authHash, ESYS_TR *sessionHandle) = NULL;
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TSS2_RC (*sym_Esys_Startup)(ESYS_CONTEXT *esysContext, TPM2_SU startupType) = NULL;
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TSS2_RC (*sym_Esys_TRSess_GetAttributes)(ESYS_CONTEXT *esysContext, ESYS_TR session, TPMA_SESSION *flags);
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TSS2_RC (*sym_Esys_TRSess_SetAttributes)(ESYS_CONTEXT *esysContext, ESYS_TR session, TPMA_SESSION flags, TPMA_SESSION mask);
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TSS2_RC (*sym_Esys_TR_GetName)(ESYS_CONTEXT *esysContext, ESYS_TR handle, TPM2B_NAME **name);
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TSS2_RC (*sym_Esys_TR_Deserialize)(ESYS_CONTEXT *esys_context, uint8_t const *buffer, size_t buffer_size, ESYS_TR *esys_handle);
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@ -93,6 +94,7 @@ int dlopen_tpm2(void) {
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DLSYM_ARG(Esys_ReadPublic),
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DLSYM_ARG(Esys_StartAuthSession),
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DLSYM_ARG(Esys_Startup),
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DLSYM_ARG(Esys_TRSess_GetAttributes),
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DLSYM_ARG(Esys_TRSess_SetAttributes),
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DLSYM_ARG(Esys_TR_FromTPMPublic),
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DLSYM_ARG(Esys_TR_GetName),
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@ -1393,6 +1395,20 @@ static void hash_pin(const char *pin, size_t len, TPM2B_AUTH *auth) {
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sha256_finish_ctx(&hash, auth->buffer);
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}
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static bool tpm2_is_encryption_session(Tpm2Context *c, const Tpm2Handle *session) {
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TPMA_SESSION flags = 0;
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TSS2_RC rc;
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assert(c);
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assert(session);
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rc = sym_Esys_TRSess_GetAttributes(c->esys_context, session->esys_handle, &flags);
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if (rc != TSS2_RC_SUCCESS)
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return false;
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return (flags & TPMA_SESSION_DECRYPT) && (flags & TPMA_SESSION_ENCRYPT);
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}
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static int tpm2_make_encryption_session(
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Tpm2Context *c,
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const Tpm2Handle *primary,
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@ -1476,6 +1492,59 @@ static int tpm2_make_encryption_session(
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return 0;
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}
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static int tpm2_make_policy_session(
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Tpm2Context *c,
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const Tpm2Handle *primary,
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const Tpm2Handle *encryption_session,
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bool trial,
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Tpm2Handle **ret_session) {
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static const TPMT_SYM_DEF symmetric = {
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.algorithm = TPM2_ALG_AES,
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.keyBits.aes = 128,
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.mode.aes = TPM2_ALG_CFB,
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};
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TPM2_SE session_type = trial ? TPM2_SE_TRIAL : TPM2_SE_POLICY;
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TSS2_RC rc;
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int r;
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assert(c);
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assert(primary);
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assert(encryption_session);
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assert(ret_session);
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if (!tpm2_is_encryption_session(c, encryption_session))
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return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
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"Missing encryption session");
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log_debug("Starting policy session.");
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_cleanup_tpm2_handle_ Tpm2Handle *session = NULL;
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r = tpm2_handle_new(c, &session);
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if (r < 0)
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return r;
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rc = sym_Esys_StartAuthSession(
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c->esys_context,
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primary->esys_handle,
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ESYS_TR_NONE,
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encryption_session->esys_handle,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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NULL,
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session_type,
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&symmetric,
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TPM2_ALG_SHA256,
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&session->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 open session in TPM: %s", sym_Tss2_RC_Decode(rc));
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*ret_session = TAKE_PTR(session);
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return 0;
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}
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static int openssl_pubkey_to_tpm2_pubkey(
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const void *pubkey,
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size_t pubkey_size,
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@ -1693,87 +1762,36 @@ static int find_signature(
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#endif
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}
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static int tpm2_make_policy_session(
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static int tpm2_build_sealing_policy(
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Tpm2Context *c,
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const Tpm2Handle *primary,
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const Tpm2Handle *parent_session,
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TPM2_SE session_type,
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const Tpm2Handle *session,
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uint32_t hash_pcr_mask,
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uint16_t pcr_bank, /* If UINT16_MAX, pick best bank automatically, otherwise specify bank explicitly. */
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uint16_t pcr_bank,
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const void *pubkey,
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size_t pubkey_size,
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uint32_t pubkey_pcr_mask,
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JsonVariant *signature_json,
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bool use_pin,
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Tpm2Handle **ret_session,
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TPM2B_DIGEST **ret_policy_digest,
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TPMI_ALG_HASH *ret_pcr_bank) {
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TPM2B_DIGEST **ret_policy_digest) {
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static const TPMT_SYM_DEF symmetric = {
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.algorithm = TPM2_ALG_AES,
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.keyBits.aes = 128,
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.mode.aes = TPM2_ALG_CFB,
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};
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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(pubkey || pubkey_size == 0);
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assert(pubkey_pcr_mask == 0 || pubkey_size > 0);
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log_debug("Starting authentication session.");
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/* So apparently some TPM implementations don't implement trial mode correctly. To avoid issues let's
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* avoid it when it is easy to. At the moment we only really need trial mode for the signed PCR
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* policies (since only then we need to shove PCR values into the policy that don't match current
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* state anyway), hence if we have none of those we don't need to bother. Hence, let's patch in
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* TPM2_SE_POLICY even if trial mode is requested unless a pubkey PCR mask is specified that is
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* non-zero, i.e. signed PCR policy is requested.
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*
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* One day we should switch to calculating policy hashes client side when trial mode is requested, to
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* avoid this mess. */
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if (session_type == TPM2_SE_TRIAL && pubkey_pcr_mask == 0)
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session_type = TPM2_SE_POLICY;
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log_debug("Building sealing policy.");
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if ((hash_pcr_mask | pubkey_pcr_mask) != 0) {
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/* We are told to configure a PCR policy of some form, let's determine/validate the PCR bank to use. */
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if (pcr_bank != UINT16_MAX) {
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r = tpm2_pcr_mask_good(c, pcr_bank, hash_pcr_mask|pubkey_pcr_mask);
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if (r < 0)
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return r;
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if (r == 0)
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log_warning("Selected TPM2 PCRs are not initialized on this system, most likely due to a firmware issue. PCR policy is effectively not enforced. Proceeding anyway.");
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} else {
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/* No bank configured, pick automatically. Some TPM2 devices only can do SHA1. If we
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* detect that use that, but preferably use SHA256 */
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r = tpm2_get_best_pcr_bank(c, hash_pcr_mask|pubkey_pcr_mask, &pcr_bank);
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if (r < 0)
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return r;
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}
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r = tpm2_pcr_mask_good(c, pcr_bank, hash_pcr_mask|pubkey_pcr_mask);
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if (r < 0)
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return r;
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if (r == 0)
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log_warning("Selected TPM2 PCRs are not initialized on this system.");
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}
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_cleanup_tpm2_handle_ Tpm2Handle *session = NULL;
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r = tpm2_handle_new(c, &session);
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if (r < 0)
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return r;
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rc = sym_Esys_StartAuthSession(
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c->esys_context,
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primary->esys_handle,
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ESYS_TR_NONE,
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parent_session->esys_handle,
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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NULL,
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session_type,
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&symmetric,
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TPM2_ALG_SHA256,
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&session->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 open session in TPM: %s", sym_Tss2_RC_Decode(rc));
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if (pubkey_pcr_mask != 0) {
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_cleanup_free_ void *fp = NULL;
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size_t fp_size = 0;
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@ -1954,12 +1972,6 @@ static int tpm2_make_policy_session(
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if (r < 0)
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return r;
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if (ret_session)
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*ret_session = TAKE_PTR(session);
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if (ret_pcr_bank)
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*ret_pcr_bank = pcr_bank;
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return 0;
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}
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@ -2032,33 +2044,57 @@ int tpm2_seal(const char *device,
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if (r < 0)
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return r;
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TPMI_ALG_HASH pcr_bank = 0;
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if (hash_pcr_mask | pubkey_pcr_mask) {
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/* Some TPM2 devices only can do SHA1. Prefer SHA256 but allow SHA1. */
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r = tpm2_get_best_pcr_bank(c, hash_pcr_mask|pubkey_pcr_mask, &pcr_bank);
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if (r < 0)
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return r;
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}
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_cleanup_tpm2_handle_ Tpm2Handle *primary = NULL;
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r = tpm2_make_primary(c, /* alg = */0, !!ret_srk_buf, &primary_alg, &primary);
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if (r < 0)
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return r;
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/* we cannot use the bind key before its created */
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_cleanup_tpm2_handle_ Tpm2Handle *session = NULL;
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r = tpm2_make_encryption_session(c, primary, &TPM2_HANDLE_NONE, NULL, &session);
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_cleanup_tpm2_handle_ Tpm2Handle *encryption_session = NULL;
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r = tpm2_make_encryption_session(c, primary, &TPM2_HANDLE_NONE, NULL, &encryption_session);
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if (r < 0)
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return r;
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/* So apparently some TPM implementations don't implement trial mode correctly. To avoid issues let's
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* avoid it when it is easy to. At the moment we only really need trial mode for the signed PCR
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* policies (since only then we need to shove PCR values into the policy that don't match current
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* state anyway), hence if we have none of those we don't need to bother. Hence, let's patch in
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* TPM2_SE_POLICY even if trial mode is requested unless a pubkey PCR mask is specified that is
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* non-zero, i.e. signed PCR policy is requested.
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*
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* One day we should switch to calculating policy hashes client side when trial mode is requested, to
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* avoid this mess. */
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bool trial = (pubkey_pcr_mask != 0);
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_cleanup_tpm2_handle_ Tpm2Handle *policy_session = NULL;
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r = tpm2_make_policy_session(
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c,
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primary,
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encryption_session,
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trial,
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&policy_session);
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if (r < 0)
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return r;
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_cleanup_(Esys_Freep) TPM2B_DIGEST *policy_digest = NULL;
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TPMI_ALG_HASH pcr_bank;
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r = tpm2_make_policy_session(
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r = tpm2_build_sealing_policy(
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c,
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primary,
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session,
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TPM2_SE_TRIAL,
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policy_session,
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hash_pcr_mask,
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/* pcr_bank= */ UINT16_MAX,
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pcr_bank,
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pubkey, pubkey_size,
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pubkey_pcr_mask,
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/* signature_json= */ NULL,
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!!pin,
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/* ret_session= */ NULL,
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&policy_digest,
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&pcr_bank);
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&policy_digest);
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if (r < 0)
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return r;
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@ -2099,7 +2135,7 @@ int tpm2_seal(const char *device,
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rc = sym_Esys_Create(
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c->esys_context,
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primary->esys_handle,
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session->esys_handle, /* use HMAC session to enable parameter encryption */
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encryption_session->esys_handle, /* use HMAC session to enable parameter encryption */
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ESYS_TR_NONE,
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ESYS_TR_NONE,
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&hmac_sensitive,
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@ -2317,8 +2353,8 @@ int tpm2_unseal(const char *device,
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sym_Tss2_RC_Decode(rc));
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}
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_cleanup_tpm2_handle_ Tpm2Handle *hmac_session = NULL;
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r = tpm2_make_encryption_session(c, primary, hmac_key, pin, &hmac_session);
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_cleanup_tpm2_handle_ Tpm2Handle *encryption_session = NULL;
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r = tpm2_make_encryption_session(c, primary, hmac_key, pin, &encryption_session);
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if (r < 0)
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return r;
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@ -2328,17 +2364,22 @@ int tpm2_unseal(const char *device,
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r = tpm2_make_policy_session(
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c,
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primary,
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hmac_session,
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TPM2_SE_POLICY,
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encryption_session,
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/* trial= */ false,
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&policy_session);
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if (r < 0)
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return r;
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r = tpm2_build_sealing_policy(
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c,
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policy_session,
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hash_pcr_mask,
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pcr_bank,
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pubkey, pubkey_size,
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pubkey_pcr_mask,
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signature,
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!!pin,
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&policy_session,
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&policy_digest,
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/* ret_pcr_bank= */ NULL);
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&policy_digest);
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if (r < 0)
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return r;
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@ -2356,7 +2397,7 @@ int tpm2_unseal(const char *device,
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c->esys_context,
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hmac_key->esys_handle,
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policy_session->esys_handle,
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hmac_session->esys_handle, /* use HMAC session to enable parameter encryption */
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encryption_session->esys_handle, /* use HMAC session to enable parameter encryption */
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ESYS_TR_NONE,
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&unsealed);
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if (rc == TSS2_RC_SUCCESS)
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@ -56,6 +56,7 @@ extern TSS2_RC (*sym_Esys_PolicyGetDigest)(ESYS_CONTEXT *esysContext, ESYS_TR po
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extern TSS2_RC (*sym_Esys_PolicyPCR)(ESYS_CONTEXT *esysContext, ESYS_TR policySession, ESYS_TR shandle1, ESYS_TR shandle2, ESYS_TR shandle3, const TPM2B_DIGEST *pcrDigest, const TPML_PCR_SELECTION *pcrs);
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extern TSS2_RC (*sym_Esys_StartAuthSession)(ESYS_CONTEXT *esysContext, ESYS_TR tpmKey, ESYS_TR bind, ESYS_TR shandle1, ESYS_TR shandle2, ESYS_TR shandle3, const TPM2B_NONCE *nonceCaller, TPM2_SE sessionType, const TPMT_SYM_DEF *symmetric, TPMI_ALG_HASH authHash, ESYS_TR *sessionHandle);
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extern TSS2_RC (*sym_Esys_Startup)(ESYS_CONTEXT *esysContext, TPM2_SU startupType);
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extern TSS2_RC (*sym_Esys_TRSess_GetAttributes)(ESYS_CONTEXT *esysContext, ESYS_TR session, TPMA_SESSION *flags);
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extern TSS2_RC (*sym_Esys_TRSess_SetAttributes)(ESYS_CONTEXT *esysContext, ESYS_TR session, TPMA_SESSION flags, TPMA_SESSION mask);
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extern TSS2_RC (*sym_Esys_TR_GetName)(ESYS_CONTEXT *esysContext, ESYS_TR handle, TPM2B_NAME **name);
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extern TSS2_RC (*sym_Esys_TR_SetAuth)(ESYS_CONTEXT *esysContext, ESYS_TR handle, TPM2B_AUTH const *authValue);
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