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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"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_x509_certificate_chain_verify PORTABLE C */
/* 6.1.6 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function verifies a certificate chain (built using the service */
/* nx_secure_certificate_chain_build) by checking each issuer back to */
/* a certificate in the trusted store of the given X509 store. */
/* */
/* INPUT */
/* */
/* store Pointer to certificate store */
/* certificate Pointer to cert chain */
/* */
/* OUTPUT */
/* */
/* status Completion status */
/* */
/* CALLS */
/* */
/* _nx_secure_x509_certificate_verify Verify a certificate */
/* _nx_secure_x509_store_certificate_find */
/* Find a cert in a store */
/* _nx_secure_x509_distinguished_name_compare */
/* Compare distinguished name */
/* */
/* CALLED BY */
/* */
/* _nx_secure_tls_remote_certificate_verify */
/* Verify the server certificate */
/* _nx_secure_x509_crl_revocation_check Check revocation in crl */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Timothy Stapko Initial Version 6.0 */
/* 09-30-2020 Timothy Stapko Modified comment(s), */
/* 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_chain_verify(NX_SECURE_X509_CERTIFICATE_STORE *store,
NX_SECURE_X509_CERT *certificate)
{
UINT status;
NX_SECURE_X509_CERT *current_certificate;
NX_SECURE_X509_CERT *issuer_certificate;
UINT issuer_location = NX_SECURE_X509_CERT_LOCATION_NONE;
INT compare_result;
/* Process, following X509 basic certificate authentication (RFC 5280):
* 1. Last certificate in chain is the end entity - start with it.
* 2. Build chain from issuer to issuer - linked list of issuers. Find in stores: [ Remote, Trusted ]
* 3. Walk list from end certificate back to a root CA in the trusted store, verifying each signature.
* Additionally, any policy enforcement should be done at each step.
*/
/* Get working pointer to certificate chain entry. */
current_certificate = certificate;
if (current_certificate == NX_CRYPTO_NULL)
{
#ifdef NX_CRYPTO_STANDALONE_ENABLE
return(NX_CRYPTO_PTR_ERROR);
#else
return(NX_PTR_ERROR);
#endif /* NX_CRYPTO_STANDALONE_ENABLE */
}
while (current_certificate != NX_CRYPTO_NULL)
{
/* Check the certificate expiration against the current time. */
/* See if the certificate is self-signed or not. */
compare_result = _nx_secure_x509_distinguished_name_compare(¤t_certificate -> nx_secure_x509_distinguished_name,
¤t_certificate -> nx_secure_x509_issuer, NX_SECURE_X509_NAME_ALL_FIELDS);
if (compare_result != 0)
{
/* Find the certificate issuer in the store. */
status = _nx_secure_x509_store_certificate_find(store, ¤t_certificate -> nx_secure_x509_issuer, 0, &issuer_certificate, &issuer_location);
if (status != NX_SECURE_X509_SUCCESS)
{
return(NX_SECURE_X509_ISSUER_CERTIFICATE_NOT_FOUND);
}
}
else
{
#ifndef NX_SECURE_ALLOW_SELF_SIGNED_CERTIFICATES
/* The certificate is self-signed. If we don't allow that, return error. */
return(NX_SECURE_X509_INVALID_SELF_SIGNED_CERT);
#else
/* Certificate is self-signed and we are configured to accept them. */
issuer_certificate = current_certificate;
#endif
}
/* Verify the current certificate against its issuer certificate. */
status = _nx_secure_x509_certificate_verify(store, current_certificate, issuer_certificate);
if (status != 0)
{
return(status);
}
else
{
/* The comparison passed, so we have a valid issuer. If the issuer is in the trusted
store, our chain verification is complete. If the issuer is not in the trusted store,
then continue the verification process. */
if (issuer_location == NX_SECURE_X509_CERT_LOCATION_TRUSTED)
{
return(NX_SECURE_X509_SUCCESS);
}
#ifdef NX_SECURE_ALLOW_SELF_SIGNED_CERTIFICATES
/* Certificate is self-signed and we are configured to accept them. */
if (issuer_certificate == current_certificate)
{
/* Check for self-signed certificate in trusted store. */
status = _nx_secure_x509_store_certificate_find(store, ¤t_certificate -> nx_secure_x509_distinguished_name, 0, &issuer_certificate, &issuer_location);
if(status == NX_SECURE_X509_SUCCESS && issuer_location == NX_SECURE_X509_CERT_LOCATION_TRUSTED)
{
return(NX_SECURE_X509_SUCCESS);
}
/* Self-signed certificate is not trusted. */
return(NX_SECURE_X509_CHAIN_VERIFY_FAILURE);
}
#endif
}
/* Advance our working pointer to the next entry in the list. */
current_certificate = issuer_certificate;
} /* End while. */
/* Certificate is valid. */
return(NX_SECURE_X509_CHAIN_VERIFY_FAILURE);
}