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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Secure Component */
/** */
/** X.509 Digital Certificates */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_x509.h"
static UCHAR generated_hash[64]; /* We need to be able to hold the entire generated hash - SHA-512 = 64 bytes. */
static UCHAR decrypted_signature[512]; /* This needs to hold the entire decrypted data - RSA 2048-bit key = 256 bytes. */
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_x509_certificate_verify PORTABLE C */
/* 6.1.6 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function verifies a certificate by checking its signature */
/* against its issuer's public key. */
/* */
/* INPUT */
/* */
/* store Pointer to certificate store */
/* certificate Pointer to certificate */
/* issuer_certificate Pointer to issuer certificate */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* [nx_crypto_init] Crypto initialization */
/* [nx_crypto_operation] Crypto operation */
/* _nx_secure_x509_pkcs7_decode Decode the PKCS#7 signature */
/* _nx_secure_x509_find_certificate_methods */
/* Find certificate methods */
/* _nx_secure_x509_find_curve_method Find named curve used */
/* _nx_secure_x509_asn1_tlv_block_parse Parse ASN.1 block */
/* */
/* CALLED BY */
/* */
/* _nx_secure_x509_certificate_chain_verify */
/* Verify cert against stores */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Timothy Stapko Initial Version 6.0 */
/* 09-30-2020 Timothy Stapko Modified comment(s), update */
/* ECC find curve method, */
/* add KeyUsage check, */
/* resulting in version 6.1 */
/* 04-02-2021 Timothy Stapko Modified comment(s), */
/* removed dependency on TLS, */
/* resulting in version 6.1.6 */
/* */
/**************************************************************************/
UINT _nx_secure_x509_certificate_verify(NX_SECURE_X509_CERTIFICATE_STORE *store,
NX_SECURE_X509_CERT *certificate,
NX_SECURE_X509_CERT *issuer_certificate)
{
UINT status;
UINT oid_length;
const UCHAR *oid;
UINT decrypted_hash_length;
const UCHAR *decrypted_hash;
const UCHAR *certificate_verify_data;
UINT verify_data_length;
const UCHAR *signature_data;
UINT signature_length;
UINT compare_result;
UINT hash_length;
const NX_CRYPTO_METHOD *hash_method;
const NX_CRYPTO_METHOD *public_cipher_method;
NX_SECURE_X509_CRYPTO *crypto_methods;
VOID *handler = NX_CRYPTO_NULL;
#ifndef NX_SECURE_X509_DISABLE_KEY_USAGE_CHECK
USHORT key_usage_bitfield = 0;
#endif
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
NX_SECURE_EC_PUBLIC_KEY *ec_pubkey;
const NX_CRYPTO_METHOD *curve_method;
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
NX_CRYPTO_PARAMETER_NOT_USED(store);
#ifndef NX_SECURE_X509_DISABLE_KEY_USAGE_CHECK
/* Before we do any crypto verification, we need to check the KeyUsage extension. */
status = _nx_secure_x509_key_usage_extension_parse(issuer_certificate, &key_usage_bitfield);
/* If extension is not present, we don't need to verify per RFC 5280. */
if(NX_SECURE_X509_SUCCESS == status)
{
/* The issuer cert has a KeyUsage extension - check the KeyCertSign bit. */
if(!(key_usage_bitfield & NX_SECURE_X509_KEY_USAGE_KEY_CERT_SIGN))
{
return(NX_SECURE_X509_KEY_USAGE_ERROR);
}
}
#endif
/* Get working pointers to relevant data. */
certificate_verify_data = certificate -> nx_secure_x509_certificate_data;
verify_data_length = certificate -> nx_secure_x509_certificate_data_length;
signature_data = certificate -> nx_secure_x509_signature_data;
signature_length = certificate -> nx_secure_x509_signature_data_length;
/* Find certificate crypto methods for this certificate. */
status = _nx_secure_x509_find_certificate_methods(certificate, (USHORT)certificate -> nx_secure_x509_signature_algorithm, &crypto_methods);
if (status != NX_SECURE_X509_SUCCESS)
{
return(status);
}
/* Assign local pointers for the crypto methods. */
hash_method = crypto_methods -> nx_secure_x509_hash_method;
public_cipher_method = crypto_methods -> nx_secure_x509_public_cipher_method;
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
NX_SECURE_MEMSET(decrypted_signature, 0, sizeof(decrypted_signature));
if (hash_method -> nx_crypto_init)
{
status = hash_method -> nx_crypto_init((NX_CRYPTO_METHOD*)hash_method,
NX_CRYPTO_NULL,
0,
&handler,
certificate -> nx_secure_x509_hash_metadata_area,
certificate -> nx_secure_x509_hash_metadata_size);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
/* We need to generate a hash of this certificate in order to verify it against our trusted store. */
if (hash_method -> nx_crypto_operation != NX_CRYPTO_NULL)
{
status = hash_method -> nx_crypto_operation(NX_CRYPTO_VERIFY,
handler,
(NX_CRYPTO_METHOD*)hash_method,
NX_CRYPTO_NULL,
0,
(UCHAR *)certificate_verify_data,
verify_data_length,
NX_CRYPTO_NULL,
generated_hash,
sizeof(generated_hash),
certificate -> nx_secure_x509_hash_metadata_area,
certificate -> nx_secure_x509_hash_metadata_size,
NX_CRYPTO_NULL, NX_CRYPTO_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
return(status);
}
}
if (hash_method -> nx_crypto_cleanup)
{
status = hash_method -> nx_crypto_cleanup(certificate -> nx_secure_x509_hash_metadata_area);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
hash_length = (hash_method -> nx_crypto_ICV_size_in_bits >> 3);
/* Perform a public-key decryption operation on the extracted signature from the certificate.
* In this case, the operation is doing a "reverse decryption", using the public key to decrypt, rather
* than the private. This allows us to tie a trusted root certificate to a signature of a certificate
* signed by that root CA's private key. when combined with a hash method, this is the basic digital
* signature operation. */
if (public_cipher_method -> nx_crypto_algorithm == NX_CRYPTO_KEY_EXCHANGE_RSA ||
public_cipher_method -> nx_crypto_algorithm == NX_CRYPTO_DIGITAL_SIGNATURE_RSA)
{
/* Make sure the public algorithm of the issuer certificate is RSA. */
if (issuer_certificate -> nx_secure_x509_public_algorithm != NX_SECURE_TLS_X509_TYPE_RSA)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(NX_SECURE_X509_WRONG_SIGNATURE_METHOD);
}
if (public_cipher_method -> nx_crypto_init != NX_CRYPTO_NULL)
{
/* Initialize the crypto method with public key. */
status = public_cipher_method -> nx_crypto_init((NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)issuer_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus,
(NX_CRYPTO_KEY_SIZE)(issuer_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_modulus_length << 3),
&handler,
certificate -> nx_secure_x509_public_cipher_metadata_area,
certificate -> nx_secure_x509_public_cipher_metadata_size);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
if (public_cipher_method -> nx_crypto_operation != NX_CRYPTO_NULL)
{
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_DECRYPT,
handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)issuer_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_exponent,
(NX_CRYPTO_KEY_SIZE)(issuer_certificate -> nx_secure_x509_public_key.rsa_public_key.nx_secure_rsa_public_exponent_length << 3),
(UCHAR *)signature_data,
signature_length,
NX_CRYPTO_NULL,
decrypted_signature,
sizeof(decrypted_signature),
certificate -> nx_secure_x509_public_cipher_metadata_area,
certificate -> nx_secure_x509_public_cipher_metadata_size,
NX_CRYPTO_NULL, NX_CRYPTO_NULL);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
if (public_cipher_method -> nx_crypto_cleanup)
{
status = public_cipher_method -> nx_crypto_cleanup(certificate -> nx_secure_x509_public_cipher_metadata_area);
if(status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
NX_SECURE_MEMSET(decrypted_signature, 0, sizeof(decrypted_signature));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
/* Decode the decrypted signature, which should be in PKCS#7 format. */
status = _nx_secure_x509_pkcs7_decode(decrypted_signature, signature_length, &oid, &oid_length,
&decrypted_hash, &decrypted_hash_length);
#ifdef NX_SECURE_KEY_CLEAR
if(status != NX_SECURE_X509_SUCCESS || decrypted_hash_length != hash_length)
{
/* Clear secrets state on errors. */
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
NX_SECURE_MEMSET(decrypted_signature, 0, sizeof(decrypted_signature));
}
#endif /* NX_SECURE_KEY_CLEAR */
if (status != NX_SECURE_X509_SUCCESS)
{
return(status);
}
if (decrypted_hash_length != hash_length)
{
return(NX_SECURE_X509_WRONG_SIGNATURE_METHOD);
}
/* Compare generated hash with decrypted hash. */
compare_result = (UINT)NX_SECURE_MEMCMP(generated_hash, decrypted_hash, decrypted_hash_length);
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
NX_SECURE_MEMSET(decrypted_signature, 0, sizeof(decrypted_signature));
#endif /* NX_SECURE_KEY_CLEAR */
/* If the comparision worked, return success. */
if (compare_result == 0)
{
return(NX_SECURE_X509_SUCCESS);
}
}
#ifdef NX_SECURE_ENABLE_ECC_CIPHERSUITE
else if (public_cipher_method -> nx_crypto_algorithm == NX_CRYPTO_DIGITAL_SIGNATURE_ECDSA)
{
/* Make sure the public algorithm of the issuer certificate is EC. */
if (issuer_certificate -> nx_secure_x509_public_algorithm != NX_SECURE_TLS_X509_TYPE_EC)
{
return(NX_SECURE_X509_WRONG_SIGNATURE_METHOD);
}
/* Verify the ECDSA signature. */
ec_pubkey = &issuer_certificate -> nx_secure_x509_public_key.ec_public_key;
/* Find out which named curve the remote certificate is using. */
status = _nx_secure_x509_find_curve_method((USHORT)(ec_pubkey -> nx_secure_ec_named_curve), &curve_method);
#ifdef NX_SECURE_KEY_CLEAR
if(status != NX_SECURE_X509_SUCCESS || curve_method == NX_CRYPTO_NULL)
{
/* Clear secrets on errors. */
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
}
#endif /* NX_SECURE_KEY_CLEAR */
if(status != NX_SECURE_X509_SUCCESS)
{
return(status);
}
if (curve_method == NX_CRYPTO_NULL)
{
/* The issuer certificate is using an unsupported curve. */
return(NX_SECURE_X509_UNSUPPORTED_PUBLIC_CIPHER);
}
if (public_cipher_method -> nx_crypto_init != NX_CRYPTO_NULL)
{
status = public_cipher_method -> nx_crypto_init((NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)ec_pubkey -> nx_secure_ec_public_key,
(NX_CRYPTO_KEY_SIZE)(ec_pubkey -> nx_secure_ec_public_key_length << 3),
&handler,
certificate -> nx_secure_x509_public_cipher_metadata_area,
certificate -> nx_secure_x509_public_cipher_metadata_size);
if (status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
}
if (public_cipher_method -> nx_crypto_operation == NX_CRYPTO_NULL)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(NX_SECURE_X509_MISSING_CRYPTO_ROUTINE);
}
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_EC_CURVE_SET, handler,
(NX_CRYPTO_METHOD*)public_cipher_method, NX_CRYPTO_NULL, 0,
(UCHAR *)curve_method, sizeof(NX_CRYPTO_METHOD *), NX_CRYPTO_NULL,
NX_CRYPTO_NULL, 0,
certificate -> nx_secure_x509_public_cipher_metadata_area,
certificate -> nx_secure_x509_public_cipher_metadata_size,
NX_CRYPTO_NULL, NX_CRYPTO_NULL);
if (status != NX_CRYPTO_SUCCESS)
{
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
return(status);
}
status = public_cipher_method -> nx_crypto_operation(NX_CRYPTO_VERIFY, handler,
(NX_CRYPTO_METHOD*)public_cipher_method,
(UCHAR *)ec_pubkey -> nx_secure_ec_public_key,
(NX_CRYPTO_KEY_SIZE)(ec_pubkey -> nx_secure_ec_public_key_length << 3),
generated_hash,
hash_method -> nx_crypto_ICV_size_in_bits >> 3,
NX_CRYPTO_NULL,
(UCHAR *)signature_data,
signature_length,
certificate -> nx_secure_x509_public_cipher_metadata_area,
certificate -> nx_secure_x509_public_cipher_metadata_size,
NX_CRYPTO_NULL, NX_CRYPTO_NULL);
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
if (status == NX_CRYPTO_SUCCESS)
{
return(NX_SECURE_X509_SUCCESS);
}
}
#endif /* NX_SECURE_ENABLE_ECC_CIPHERSUITE */
else
{
return(NX_SECURE_X509_UNSUPPORTED_PUBLIC_CIPHER);
}
#ifdef NX_SECURE_KEY_CLEAR
NX_SECURE_MEMSET(generated_hash, 0, sizeof(generated_hash));
#endif /* NX_SECURE_KEY_CLEAR */
/* Comparison failed, return error. */
return(NX_SECURE_X509_CERTIFICATE_SIG_CHECK_FAILED);
}