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Merge pull request #30971 from ddstreet/tpm2_key_conversion

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Fix tpm unsealing when using RSA public key signatures
This commit is contained in:
Lennart Poettering
2024-01-17 13:36:47 +01:00
committed by GitHub
parent 5a702b6c81 fda3e84465
commit 66ea62b71e
2 changed files with 79 additions and 18 deletions
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src/shared/tpm2-util.c
+26 -4
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@@ -4196,6 +4196,11 @@ int tpm2_tpm2b_public_to_openssl_pkey(const TPM2B_PUBLIC *public, EVP_PKEY **ret
}
}
/* Be careful before changing anything in this function, as the TPM key "name" is calculated using the entire
* TPMT_PUBLIC (after marshalling), and that "name" is used (for example) to calculate the policy hash for
* the Authorize policy. So we must ensure this conversion of a PEM to TPM2B_PUBLIC does not change the
* "name", because it would break unsealing of previously-sealed objects that used (for example)
* tpm2_calculate_policy_authorize(). See bug #30546. */
int tpm2_tpm2b_public_from_openssl_pkey(const EVP_PKEY *pkey, TPM2B_PUBLIC *ret) {
int key_id, r;
@@ -4274,8 +4279,11 @@ int tpm2_tpm2b_public_from_openssl_pkey(const EVP_PKEY *pkey, TPM2B_PUBLIC *ret)
uint32_t exponent = 0;
memcpy(&exponent, e, e_size);
exponent = be32toh(exponent) >> (32 - e_size * 8);
if (exponent == TPM2_RSA_DEFAULT_EXPONENT)
exponent = 0;
/* TPM specification Part 2 ("Structures") section for TPMS_RSA_PARAMS states "An exponent of
* zero indicates that the exponent is the default of 2^16 + 1". However, we have no reason
* to special case it in our PEM->TPM2B_PUBLIC conversion, and doing so could break backwards
* compatibility, so even if it is the "default" value of 0x10001, we do not set it to 0. */
public.parameters.rsaDetail.exponent = exponent;
break;
@@ -5549,11 +5557,25 @@ int tpm2_unseal(Tpm2Context *c,
/* If we know the policy hash to expect, and it doesn't match, we can shortcut things here, and not
* wait until the TPM2 tells us to go away. */
if (iovec_is_set(known_policy_hash) &&
memcmp_nn(policy_digest->buffer, policy_digest->size, known_policy_hash->iov_base, known_policy_hash->iov_len) != 0)
if (iovec_is_set(known_policy_hash) && memcmp_nn(policy_digest->buffer,
policy_digest->size,
known_policy_hash->iov_base,
known_policy_hash->iov_len) != 0) {
#if HAVE_OPENSSL
if (iovec_is_set(pubkey) &&
pubkey_tpm2b.publicArea.type == TPM2_ALG_RSA &&
pubkey_tpm2b.publicArea.parameters.rsaDetail.exponent == TPM2_RSA_DEFAULT_EXPONENT) {
/* Due to bug #30546, if using RSA pubkey with the default exponent, we may
* need to set the exponent to the TPM special-case value of 0 and retry. */
log_debug("Policy hash mismatch, retrying with RSA pubkey exponent set to 0.");
pubkey_tpm2b.publicArea.parameters.rsaDetail.exponent = 0;
continue;
} else
#endif
return log_debug_errno(SYNTHETIC_ERRNO(EPERM),
"Current policy digest does not match stored policy digest, cancelling "
"TPM2 authentication attempt.");
}
log_debug("Unsealing HMAC key.");