error_t tlsParseCertificate(TlsContext *context, const TlsCertificate *message, size_t length)
{
error_t error;
const uint8_t *p;
size_t n;
const char_t *pemCert;
size_t pemCertLength;
uint8_t *derCert;
size_t derCertSize;
size_t derCertLength;
//X.509 certificates
X509CertificateInfo *certInfo = NULL;
X509CertificateInfo *issuerCertInfo = NULL;
//Debug message
TRACE_INFO("Certificate message received (%" PRIuSIZE " bytes)...\r\n", length);
TRACE_DEBUG_ARRAY(" ", message, length);
//Check the length of the Certificate message
if(length < sizeof(TlsCertificate))
return ERROR_DECODING_FAILED;
//TLS operates as a client or a server?
if(context->entity == TLS_CONNECTION_END_CLIENT)
{
//Check current state
if(context->state != TLS_STATE_SERVER_CERTIFICATE)
return ERROR_UNEXPECTED_MESSAGE;
}
else
{
//Check current state
if(context->state != TLS_STATE_CLIENT_CERTIFICATE)
return ERROR_UNEXPECTED_MESSAGE;
}
//Update the hash value with the incoming handshake message
tlsUpdateHandshakeHash(context, message, length);
//Get the size occupied by the certificate list
n = LOAD24BE(message->certificateListLength);
//Remaining bytes to process
length -= sizeof(TlsCertificate);
//Ensure that the chain of certificates is valid
if(n > length)
return ERROR_DECODING_FAILED;
//Compute the length of the certificate list
length = n;
//The sender's certificate must come first in the list
p = message->certificateList;
//Start of exception handling block
do
{
//Assume an error...
error = ERROR_OUT_OF_MEMORY;
//Allocate a memory buffer to store X.509 certificate info
certInfo = osAllocMem(sizeof(X509CertificateInfo));
//Failed to allocate memory?
if(!certInfo) break;
//Allocate a memory buffer to store the parent certificate
issuerCertInfo = osAllocMem(sizeof(X509CertificateInfo));
//Failed to allocate memory?
if(!issuerCertInfo) break;
//TLS operates as a server?
if(context->entity == TLS_CONNECTION_END_SERVER)
{
//Empty certificate list?
if(!length)
{
//Check whether mutual authentication is required
if(context->clientAuthMode == TLS_CLIENT_AUTH_REQUIRED)
{
//If client authentication is required by the server for the handshake
//to continue, it may respond with a fatal handshake failure alert
error = ERROR_HANDSHAKE_FAILED;
break;
}
else
{
//Client authentication is optional
context->peerCertType = TLS_CERT_NONE;
//Exit immediately
error = NO_ERROR;
break;
}
}
}
//Each certificate is preceded by a 3-byte length field
if(length < 3)
{
//Report an error
error = ERROR_DECODING_FAILED;
break;
}
//Get the size occupied by the certificate
n = LOAD24BE(p);
//Jump to the beginning of the DER encoded certificate
p += 3;
length -= 3;
//Make sure that the certificate is valid
if(n > length)
{
//Report an error
error = ERROR_DECODING_FAILED;
break;
}
//Display ASN.1 structure
error = asn1DumpObject(p, n, 0);
//Any error to report?
if(error) break;
//Parse X.509 certificate
error = x509ParseCertificate(p, n, certInfo);
//Failed to parse the X.509 certificate?
if(error) break;
#if (TLS_CLIENT_SUPPORT == ENABLED)
//TLS operates as a client?
if(context->entity == TLS_CONNECTION_END_CLIENT)
{
//Check if the hostname must be verified
if(context->serverName != NULL)
{
//Point to the last character of the common name
int_t i = certInfo->subject.commonNameLen - 1;
//Point to the last character of the hostname
int_t j = strlen(context->serverName) - 1;
//Check the common name in the server certificate against
//the actual hostname that is being requested
while(i >= 0 && j >= 0)
{
//Wildcard certificate found?
if(certInfo->subject.commonName[i] == '*' && i == 0)
{
//The CN is acceptable
j = 0;
}
//Perform case insensitive character comparison
else if(tolower((uint8_t) certInfo->subject.commonName[i]) != context->serverName[j])
{
break;
}
//Compare previous characters
i--;
j--;
}
//If the host names do not match, reject the certificate
if(i >= 0 || j >= 0)
{
//Debug message
TRACE_WARNING("Server name mismatch!\r\n");
//Report an error
error = ERROR_BAD_CERTIFICATE;
break;
}
}
}
#endif
//The certificate contains a valid RSA public key?
if(!oidComp(certInfo->subjectPublicKeyInfo.oid, certInfo->subjectPublicKeyInfo.oidLen,
RSA_ENCRYPTION_OID, sizeof(RSA_ENCRYPTION_OID)))
{
//Retrieve the RSA public key
error = x509ReadRsaPublicKey(certInfo, &context->peerRsaPublicKey);
//Any error to report
if(error) break;
//Save the certificate type
context->peerCertType = TLS_CERT_RSA_SIGN;
}
//The certificate contains a valid DSA public key?
else if(!oidComp(certInfo->subjectPublicKeyInfo.oid, certInfo->subjectPublicKeyInfo.oidLen,
DSA_OID, sizeof(DSA_OID)))
{
//Retrieve the DSA public key
error = x509ReadDsaPublicKey(certInfo, &context->peerDsaPublicKey);
//Any error to report
if(error) break;
//Save the certificate type
context->peerCertType = TLS_CERT_DSS_SIGN;
}
//The certificate contains a valid EC public key?
else if(!oidComp(certInfo->subjectPublicKeyInfo.oid, certInfo->subjectPublicKeyInfo.oidLen,
EC_PUBLIC_KEY_OID, sizeof(EC_PUBLIC_KEY_OID)))
{
const EcCurveInfo *curveInfo;
//Retrieve EC domain parameters
curveInfo = ecGetCurveInfo(certInfo->subjectPublicKeyInfo.ecParams.namedCurve,
certInfo->subjectPublicKeyInfo.ecParams.namedCurveLen);
//Make sure the specified elliptic curve is supported
if(curveInfo == NULL)
{
//Report an error
error = ERROR_BAD_CERTIFICATE;
//Exit immediately
break;
}
//Load EC domain parameters
error = ecLoadDomainParameters(&context->peerEcParams, curveInfo);
//Any error to report?
if(error) break;
//Retrieve the EC public key
error = ecImport(&context->peerEcParams, &context->peerEcPublicKey,
certInfo->subjectPublicKeyInfo.ecPublicKey.q, certInfo->subjectPublicKeyInfo.ecPublicKey.qLen);
//Any error to report
if(error) break;
//Save the certificate type
context->peerCertType = TLS_CERT_ECDSA_SIGN;
}
//The certificate does not contain any valid public key?
else
{
//Report an error
error = ERROR_BAD_CERTIFICATE;
break;
}
//Next certificate
p += n;
length -= n;
//PKIX path validation
while(length > 0)
{
//Each certificate is preceded by a 3-byte length field
if(length < 3)
{
//Report an error
error = ERROR_DECODING_FAILED;
break;
}
//Get the size occupied by the certificate
n = LOAD24BE(p);
//Jump to the beginning of the DER encoded certificate
p += 3;
length -= 3;
//Ensure that the certificate is valid
if(n > length)
{
//Report an error
error = ERROR_DECODING_FAILED;
break;
}
//Display ASN.1 structure
error = asn1DumpObject(p, n, 0);
//Any error to report?
if(error) break;
//Parse X.509 certificate
error = x509ParseCertificate(p, n, issuerCertInfo);
//Failed to parse the X.509 certificate?
if(error) break;
//Validate current certificate
error = x509ValidateCertificate(certInfo, issuerCertInfo);
//Certificate validation failed?
if(error) break;
//Keep track of the issuer certificate
memcpy(certInfo, issuerCertInfo, sizeof(X509CertificateInfo));
//Next certificate
p += n;
length -= n;
}
//Propagate exception if necessary...
if(error) break;
//Point to the first trusted CA certificate
pemCert = context->trustedCaList;
//Get the total length, in bytes, of the trusted CA list
pemCertLength = context->trustedCaListLength;
//DER encoded certificate
derCert = NULL;
derCertSize = 0;
derCertLength = 0;
//Loop through the list
while(pemCertLength > 0)
{
//Decode PEM certificate
error = pemReadCertificate(&pemCert, &pemCertLength,
&derCert, &derCertSize, &derCertLength);
//Any error to report?
if(error) break;
//Parse X.509 certificate
error = x509ParseCertificate(derCert, derCertLength, issuerCertInfo);
//Failed to parse the X.509 certificate?
if(error) break;
//Validate the certificate with the current trusted CA
error = x509ValidateCertificate(certInfo, issuerCertInfo);
//Certificate validation succeeded?
if(!error) break;
}
//The certificate could not be matched with a known, trusted CA?
if(error == ERROR_END_OF_FILE)
error = ERROR_UNKNOWN_CA;
//Free previously allocated memory
osFreeMem(derCert);
//End of exception handling block
} while(0);
//Free previously allocated memory
osFreeMem(certInfo);
osFreeMem(issuerCertInfo);
//Clean up side effects
if(error)
{
//Release previously allocated memory
rsaFreePublicKey(&context->peerRsaPublicKey);
dsaFreePublicKey(&context->peerDsaPublicKey);
ecFreeDomainParameters(&context->peerEcParams);
ecFree(&context->peerEcPublicKey);
}
//TLS operates as a client or a server?
if(context->entity == TLS_CONNECTION_END_CLIENT)
{
//Update FSM state
if(context->keyExchMethod != TLS_KEY_EXCH_RSA)
context->state = TLS_STATE_SERVER_KEY_EXCHANGE;
else
context->state = TLS_STATE_CERTIFICATE_REQUEST;
}
else
{
//Prepare to receive ClientKeyExchange message...
context->state = TLS_STATE_CLIENT_KEY_EXCHANGE;
}
//Return status code
return error;
}
error_t tlsSendCertificate(TlsContext *context)
{
error_t error;
bool_t sendCert;
uint8_t *p;
size_t length;
const char_t *pemCert;
size_t pemCertLength;
uint8_t *derCert;
size_t derCertSize;
size_t derCertLength;
TlsCertificate *message;
//TLS operates as a client or a server?
if(context->entity == TLS_CONNECTION_END_CLIENT)
{
//The client must send a Certificate message if the server requests it
sendCert = context->clientCertRequested ? TRUE : FALSE;
#if (TLS_MAX_VERSION >= SSL_VERSION_3_0 && TLS_MIN_VERSION <= SSL_VERSION_3_0)
//SSL 3.0 currently selected?
if(context->version == SSL_VERSION_3_0)
{
//The server requests a certificate but no suitable certificate is available?
if(sendCert && context->cert == NULL)
{
//The client should send a no_certificate alert instead
error = tlsSendAlert(context, TLS_ALERT_LEVEL_WARNING, TLS_ALERT_NO_CERTIFICATE);
//Any error to report?
if(error) return error;
//Skip Certificate message...
sendCert = FALSE;
}
}
#endif
}
else
{
//The server must send a Certificate message whenever the agreed-upon
//key exchange method uses certificates for authentication
sendCert = (context->cert != NULL) ? TRUE : FALSE;
}
//Check whether a Certificate message must be sent
if(sendCert)
{
//Buffer where to format the message
p = context->txBuffer + sizeof(TlsRecord);
//Point to the Certificate message
message = (TlsCertificate *) p;
//Format message header
message->msgType = TLS_TYPE_CERTIFICATE;
//Point to the first certificate of the list
p = message->certificateList;
//Length of the certificate list in bytes
length = 0;
//Check whether a certificate is available
if(context->cert != NULL)
{
//Point to the certificate chain
pemCert = context->cert->certChain;
//Get the total length, in bytes, of the certificate chain
pemCertLength = context->cert->certChainLength;
}
else
{
//If no suitable certificate is available, the message
//contains an empty certificate list
pemCert = NULL;
pemCertLength = 0;
}
//DER encoded certificate
derCert = NULL;
derCertSize = 0;
derCertLength = 0;
//Parse the certificate chain
while(pemCertLength > 0)
{
//Decode PEM certificate
error = pemReadCertificate(&pemCert, &pemCertLength,
&derCert, &derCertSize, &derCertLength);
//Any error to report?
if(error) break;
//Total length of the certificate list
length += derCertLength + 3;
//Prevent the buffer from overflowing
if((length + sizeof(TlsCertificate)) > TLS_MAX_PROTOCOL_DATA_LENGTH)
return ERROR_MESSAGE_TOO_LONG;
//Each certificate is preceded by a 3-byte length field
STORE24BE(derCertLength, p);
//Copy the current certificate
memcpy(p + 3, derCert, derCertLength);
//Advance data pointer
p += derCertLength + 3;
}
//Free previously allocated memory
osFreeMem(derCert);
//A 3-byte length field shall precede the certificate list
STORE24BE(length, message->certificateListLength);
//Consider the 3-byte length field
length += 3;
//Fix message header
STORE24BE(length, message->length);
//Length of the complete handshake message
length += sizeof(TlsHandshake);
//Debug message
TRACE_INFO("Sending Certificate message (%" PRIuSIZE " bytes)...\r\n", length);
TRACE_DEBUG_ARRAY(" ", message, length);
//Send handshake message
error = tlsWriteProtocolData(context, length, TLS_TYPE_HANDSHAKE);
//Failed to send TLS record?
if(error) return error;
}
//Update FSM state
context->state = (context->entity == TLS_CONNECTION_END_CLIENT) ?
TLS_STATE_CLIENT_KEY_EXCHANGE : TLS_STATE_SERVER_KEY_EXCHANGE;
//Successful processing
return NO_ERROR;
}
error_t tlsAddCertificate(TlsContext *context, const char_t *certChain,
size_t certChainLength, const char_t *privateKey, size_t privateKeyLength)
{
error_t error;
const char_t *p;
size_t n;
uint8_t *derCert;
size_t derCertSize;
size_t derCertLength;
X509CertificateInfo *certInfo;
TlsCertificateType certType;
TlsSignatureAlgo certSignAlgo;
TlsHashAlgo certHashAlgo;
//Invalid TLS context?
if(context == NULL)
return ERROR_INVALID_PARAMETER;
//Check parameters
if(certChain == NULL || certChainLength == 0)
return ERROR_INVALID_PARAMETER;
if(privateKey == NULL || privateKeyLength == 0)
return ERROR_INVALID_PARAMETER;
//Make sure there is enough room to add the certificate
if(context->numCerts >= TLS_MAX_CERTIFICATES)
return ERROR_OUT_OF_RESOURCES;
//Allocate a memory buffer to store X.509 certificate info
certInfo = osMemAlloc(sizeof(X509CertificateInfo));
//Failed to allocate memory?
if(!certInfo) return ERROR_OUT_OF_MEMORY;
//Point to the beginning of the certificate chain
p = certChain;
n = certChainLength;
//DER encoded certificate
derCert = NULL;
derCertSize = 0;
derCertLength = 0;
//Start of exception handling block
do
{
//Decode end entity certificate
error = pemReadCertificate(&p, &n, &derCert, &derCertSize, &derCertLength);
//Any error to report?
if(error) break;
//Parse X.509 certificate
error = x509ParseCertificate(derCert, derCertLength, certInfo);
//Failed to parse the X.509 certificate?
if(error) break;
//Retrieve the signature algorithm that has been used to sign the certificate
error = tlsGetCertificateType(certInfo, &certType, &certSignAlgo, &certHashAlgo);
//The specified signature algorithm is not supported?
if(error) break;
//End of exception handling block
} while(0);
//Check whether the certificate is acceptable
if(!error)
{
//Point to the structure that describes the certificate
TlsCertDesc *cert = &context->certs[context->numCerts];
//Save the certificate chain and the corresponding private key
cert->certChain = certChain;
cert->certChainLength = certChainLength;
cert->privateKey = privateKey;
cert->privateKeyLength = privateKeyLength;
cert->type = certType;
cert->signAlgo = certSignAlgo;
cert->hashAlgo = certHashAlgo;
//Update the number of certificate
context->numCerts++;
}
//Release previously allocated memory
osMemFree(derCert);
osMemFree(certInfo);
//Return status code
return error;
}
