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wolfBoot
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Fixes for sealing/unsealing: 

* Fix for sealing policy, which was not being set on creation.
* Fix to clear the userWithAuth bit requiring policy
* Updated wolfTPM submodule with changes in https://github.com/wolfSSL/wolfTPM/pull/327
pull/403/head
David Garske 2024-02-02 15:51:08 -08:00
parent c6ac284ba0
commit 4408eeaa74
3 changed files with 28 additions and 7 deletions
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2
docs/TPM.md
View File

@ -15,7 +15,7 @@ In wolfBoot we support TPM based root of trust, sealing/unsealing, cryptographic
| `MEASURED_PCR_A=16` | `WOLFBOOT_MEASURED_PCR_A=16` | The PCR index to use. See [docs/measured_boot.md](/docs/measured_boot.md). |
| `WOLFBOOT_TPM_SEAL=1` | `WOLFBOOT_TPM_SEAL` | Enables support for sealing/unsealing based on PCR policy signed externally. |
| `WOLFBOOT_TPM_SEAL_NV_BASE=0x01400300` | `WOLFBOOT_TPM_SEAL_NV_BASE` | To override the default sealed blob storage location in the platform hierarchy. |
| `WOLFBOOT_TPM_SEAL_AUTH=secret` | `WOLFBOOT_TPM_SEAL_AUTH` | Password for sealing/unsealing secrets |
| `WOLFBOOT_TPM_SEAL_AUTH=secret` | `WOLFBOOT_TPM_SEAL_AUTH` | Password for sealing/unsealing secrets, if omitted the PCR policy will be used |
## Root of Trust (ROT)

2
lib/wolfTPM

@ -1 +1 @@
Subproject commit 7c079dd3f0e40539519101cffd0c27c5d6c1777c
Subproject commit bc1415d0da8e882723cb1a4b2aca0764afa6aac0

25
src/tpm.c
View File

@ -788,6 +788,8 @@ int wolfBoot_seal_blob(const uint8_t* pubkey_hint,
/* build authorization policy based on public key */
/* digest here is input and output, must be zero'd */
uint32_t digestSz = TPM2_GetHashDigestSize(pcrAlg);
/* Create a new key for sealing using external signing auth */
wolfTPM2_GetKeyTemplate_KeySeal(&template, pcrAlg);
memset(template.authPolicy.buffer, 0, digestSz);
rc = wolfTPM2_PolicyAuthorizeMake(pcrAlg, &authKey.pub,
template.authPolicy.buffer, &digestSz, NULL, 0);
@ -800,8 +802,15 @@ int wolfBoot_seal_blob(const uint8_t* pubkey_hint,
wolfBoot_print_hexstr(template.authPolicy.buffer,
template.authPolicy.size, 0);
#endif
/* Create a new key for sealing using external signing auth */
wolfTPM2_GetKeyTemplate_KeySeal(&template, pcrAlg);
if (auth != NULL && authSz > 0) {
/* allow password based sealing */
template.objectAttributes |= TPMA_OBJECT_userWithAuth;
}
else {
/* disable password based sealing, require policy */
template.objectAttributes &= ~TPMA_OBJECT_userWithAuth;
}
rc = wolfTPM2_CreateKeySeal_ex(&wolftpm_dev, seal_blob,
&wolftpm_srk.handle, &template, auth, authSz,
pcrAlg, NULL, 0, secret, secret_sz);
@ -1005,9 +1014,21 @@ int wolfBoot_unseal_blob(const uint8_t* pubkey_hint,
wolfBoot_printf("Loaded seal blob to 0x%x\n",
(uint32_t)seal_blob->handle.hndl);
#endif
/* if using password auth, set it otherwise use policy auth */
if (auth != NULL && authSz > 0) {
seal_blob->handle.auth.size = authSz;
memcpy(seal_blob->handle.auth.buffer, auth, authSz);
wolfTPM2_SetAuthHandle(&wolftpm_dev, 0, &seal_blob->handle);
}
else {
/* use the policy session for unseal */
rc = wolfTPM2_SetAuthSession(&wolftpm_dev, 0, &policy_session,
(TPMA_SESSION_decrypt | TPMA_SESSION_encrypt |
TPMA_SESSION_continueSession));
/* set the sealed object name 0 (required) */
wolfTPM2_SetAuthHandleName(&wolftpm_dev, 0, &seal_blob->handle);
}
/* unseal */
unsealIn.itemHandle = seal_blob->handle.hndl;