I am trying to verify a signature using a public key from an X509
certificate generated with the tpm engine.
What i tried to do is to load the cert from the certificate file into a
X509 type variable using PEM_read_bio_X509 and convert it into an EVP_PKEY
type using X509_get_pubkey.
How do i then convert the EVP_PKEY into a public key usable with the
signature verification function Tspi_Hash_VerifySignature?
This is what i am trying and it does not seem to be working:
UINT32 convertPubKeyToByte(tpmArgs tpm, EVP_PKEY* pkey, BYTE** pkeyByte) {
int modulusLen;
int exponentLen;
BYTE *modulus = malloc(256);
BYTE *exponent = malloc(256);
BYTE *pubKeyByte = NULL;
RSA* rsa;
TSS_HKEY hKey;
TSS_FLAG initFlags;
TSS_RESULT result;
UINT32 pubKeySize;
rsa = EVP_PKEY_get1_RSA(pkey);
modulusLen = BN_bn2bin(rsa->n, (unsigned char*)modulus);
exponentLen = BN_bn2bin(rsa->e, (unsigned char*)exponent);
initFlags = TSS_KEY_TYPE_LEGACY |
TSS_KEY_SIZE_2048 |
TSS_KEY_NO_AUTHORIZATION |
TSS_KEY_MIGRATABLE;
result = Tspi_Context_CreateObject(tpm.hContext,
TSS_OBJECT_TYPE_RSAKEY,
initFlags,
&hKey);
DBG("Create key object", result);
result = Tspi_SetAttribUint32(hKey,
TSS_TSPATTRIB_KEY_INFO,
TSS_TSPATTRIB_KEYINFO_SIGSCHEME,
PADDING_SCHEME);
DBG("Set the key's padding type", result);
result = Tspi_SetAttribData(hKey,
TSS_TSPATTRIB_RSAKEY_INFO,
TSS_TSPATTRIB_KEYINFO_RSA_EXPONENT,
exponentLen,
exponent);
DBG("Set public key exponent", result);
result = Tspi_SetAttribData(hKey,
TSS_TSPATTRIB_RSAKEY_INFO,
TSS_TSPATTRIB_KEYINFO_RSA_MODULUS,
modulusLen,
modulus);
DBG("Set public key modulus", result);
result = Tspi_Key_LoadKey(hKey, tpm.hSRK);
DBG("Load key into TPM", result);
result = Tspi_Key_GetPubKey(hKey, &pubKeySize, &pubKeyByte);
DBG("Get public key blob", result);
return pubKeySize;
}
The errors i got from the above code are:
Load key into TPM returned 0x00000028. Unsupported key parameters.
Get public key blob returned 0x0000310e. The addressed key is not currently
loaded.
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