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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 - PKCS#7 parsing */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SECURE_SOURCE_CODE
#include "nx_secure_x509.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_secure_x509_pkcs7_decode PORTABLE C */
/* 6.1.6 */
/* AUTHOR */
/* */
/* Timothy Stapko, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function decodes a PKCS#7 (RFC 5652) certificate signature */
/* and returns a pointer to the encapsulated hash for signature */
/* verification by the caller. Also returned is the OID for the */
/* signature algorithm. */
/* */
/* INPUT */
/* */
/* signature_pointer Pointer to PCKS#7 signature */
/* signature_length Length of entire signagure */
/* signature_oid Pointer to signature OID */
/* signature_oid_length Return length of OID */
/* hash_data Pointer to hash data */
/* hash_length Return length of hash */
/* */
/* OUTPUT */
/* */
/* status Signature validity status */
/* */
/* CALLS */
/* */
/* _nx_secure_x509_asn1_tlv_block_parse Parse ASN.1 block */
/* */
/* CALLED BY */
/* */
/* _nx_secure_x509_certificate_verify Verify a certificate */
/* _nx_secure_x509_crl_verify Verify revocation list */
/* _nx_secure_tls_process_server_key_exchange */
/* Process ServerKeyExchange */
/* */
/* 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_pkcs7_decode(const UCHAR *signature_pointer, UINT signature_length,
const UCHAR **signature_oid, UINT *signature_oid_length,
const UCHAR **hash_data, UINT *hash_length)
{
UINT i;
USHORT tlv_type;
USHORT tlv_type_class;
ULONG tlv_length;
const UCHAR *tlv_data = NX_CRYPTO_NULL;
ULONG header_length;
ULONG seq_length;
UINT status;
const UCHAR *signature_data = NX_CRYPTO_NULL;
ULONG remaining_length;
/* Certificate signatures encrypted with RSA use PKCS#7 encoding (RFC 5652) which
* has the following format:
* 1 byte header (0x00)
* Padding type byte (should be < 2)
* <Padding>
* 1 byte padding terminator (always 0x00)
* ASN.1 encoded signature
* Signature Sequence
* OID sequence
* signature algorithm OID(s) (can be multiple)
* NULL ASN.1 object terminator
* Octet string of hash value
* 1 byte end padding (0x01)
*/
signature_data = signature_pointer;
remaining_length = signature_length;
/* Check padding type. */
if (signature_data[1] >= 2)
{
/* Invalid PKCS#7 encoding or decryption failure. */
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
/* Loop through padding - skip the first 2 bytes of padding type.
* Also ensure that we don't run past the end of the buffer if
* the NULL terminator isn't found. */
i = 2;
while (i < signature_length)
{
if (signature_data[i] == 0x00)
{
break;
}
i++;
}
/* Skip over the padding null-terminator. */
i++;
/* Make sure we actually saw a NULL byte. */
if (i >= signature_length)
{
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
/* Advance our working pointer. */
signature_data = &signature_data[i];
remaining_length -= i;
/* Now we have our ASN.1-encoded signature. */
status = _nx_secure_x509_asn1_tlv_block_parse(signature_data, &remaining_length, &tlv_type, &tlv_type_class, &tlv_length, &tlv_data, &header_length);
/* Make sure we parsed a proper ASN.1 sequence. */
if (status != 0 || tlv_type != NX_SECURE_ASN_TAG_SEQUENCE || tlv_type_class != NX_SECURE_ASN_TAG_CLASS_UNIVERSAL)
{
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
/* Advance our working pointer and adjust remaining length. */
signature_data = tlv_data;
remaining_length = tlv_length;
/* Next up is the OID sequence. */
status = _nx_secure_x509_asn1_tlv_block_parse(signature_data, &remaining_length, &tlv_type, &tlv_type_class, &tlv_length, &tlv_data, &header_length);
/* Make sure we parsed a proper ASN.1 sequence. */
if (status != 0 || tlv_type != NX_SECURE_ASN_TAG_SEQUENCE || tlv_type_class != NX_SECURE_ASN_TAG_CLASS_UNIVERSAL)
{
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
signature_data = tlv_data;
seq_length = tlv_length;
/* Next we parse the OID(s). */
do
{
/* Parse at least 1 OID. */
status = _nx_secure_x509_asn1_tlv_block_parse(signature_data, &seq_length, &tlv_type, &tlv_type_class, &tlv_length, &tlv_data, &header_length);
/* Make sure we parsed a proper ASN.1 sequence. */
if (status != 0 || tlv_type_class != NX_SECURE_ASN_TAG_CLASS_UNIVERSAL)
{
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
/* Adjust our buffer pointer. */
signature_data = &signature_data[tlv_length + header_length];
/* If we see a NULL tag, we are at the end of the list. */
if (tlv_type == NX_SECURE_ASN_TAG_NULL)
{
break;
}
/* Save off the OID. */
*signature_oid = tlv_data;
*signature_oid_length = tlv_length;
} while (tlv_type == NX_SECURE_ASN_TAG_OID);
/* Finally, we should be at the signature hash itself. */
status = _nx_secure_x509_asn1_tlv_block_parse(signature_data, &remaining_length, &tlv_type, &tlv_type_class, &tlv_length, &tlv_data, &header_length);
/* Make sure we parsed a proper ASN.1 sequence. */
if (status != 0 || tlv_type != NX_SECURE_ASN_TAG_OCTET_STRING || tlv_type_class != NX_SECURE_ASN_TAG_CLASS_UNIVERSAL)
{
return(NX_SECURE_X509_PKCS7_PARSING_FAILED);
}
/* Return pointer to hash data and its length. */
*hash_data = tlv_data;
*hash_length = tlv_length;
/* Signature is valid. */
return(NX_SECURE_X509_SUCCESS);
}