pkcs8_key_format.c

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/**
 * @file pkcs8_key_format.c
 * @brief PKCS #8 key formatting
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2010-2025 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneCRYPTO Open.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * @author Oryx Embedded SARL (www.oryx-embedded.com)
 * @version 2.5.0
 **/
 
//Switch to the appropriate trace level
#define TRACE_LEVEL CRYPTO_TRACE_LEVEL
 
//Dependencies
#include "core/crypto.h"
#include "pkix/pkcs8_key_format.h"
#include "pkix/x509_key_format.h"
#include "encoding/asn1.h"
#include "encoding/oid.h"
#include "ecc/ec_misc.h"
#include "debug.h"
 
//Check crypto library configuration
#if (PEM_SUPPORT == ENABLED)
 
 
/**
 * @brief Format an RSA private key
 * @param[in] privateKey Pointer to the RSA private key
 * @param[out] output Buffer where to store the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatRsaPrivateKey(const RsaPrivateKey *privateKey,
   uint8_t *output, size_t *written)
{
   error_t error;
   size_t n;
   Asn1Tag tag;
 
   //Export the RSA private key to ASN.1 format
   error = x509ExportRsaPrivateKey(privateKey, output, &n);
 
   //Check status code
   if(!error)
   {
      //The RSAPrivateKey structure is encapsulated within an octet string
      tag.constructed = FALSE;
      tag.objClass = ASN1_CLASS_UNIVERSAL;
      tag.objType = ASN1_TYPE_OCTET_STRING;
      tag.length = n;
      tag.value = output;
 
      //Write PrivateKey structure
      error = asn1WriteTag(&tag, FALSE, output, written);
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Format a DSA private key
 * @param[in] privateKey Pointer to the RSA private key
 * @param[out] output Buffer where to store the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatDsaPrivateKey(const DsaPrivateKey *privateKey,
   uint8_t *output, size_t *written)
{
   error_t error;
   size_t n;
   Asn1Tag tag;
 
   //Export the DSA private key to ASN.1 format
   error = x509ExportDsaPrivateKey(privateKey, output, &n);
 
   //Check status code
   if(!error)
   {
      //The DSAPrivateKey structure is encapsulated within an octet string
      tag.constructed = FALSE;
      tag.objClass = ASN1_CLASS_UNIVERSAL;
      tag.objType = ASN1_TYPE_OCTET_STRING;
      tag.length = n;
      tag.value = output;
 
      //Write PrivateKey structure
      error = asn1WriteTag(&tag, FALSE, output, written);
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Format an EC private key
 * @param[in] privateKey EC private key
 * @param[out] output Buffer where to format the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatEcPrivateKey(const EcPrivateKey *privateKey,
   uint8_t *output, size_t *written)
{
#if (EC_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   size_t length;
   uint8_t *p;
   Asn1Tag tag;
 
   //Point to the buffer where to write the ASN.1 structure
   p = output;
   //Length of the ASN.1 structure
   length = 0;
 
   //Format Version field (refer to RFC 5915, section 3)
   error = asn1WriteInt32(1, FALSE, p, &n);
   //Any error to report?
   if(error)
      return error;
 
   //Update the length of the ECPrivateKey structure
   length += n;
 
   //If the output parameter is NULL, then the function calculates the
   //length of the resulting PEM file without copying any data
   if(output != NULL)
   {
      //Advance data pointer
      p += n;
 
      //The PrivateKey field is an octet string of length ceiling (log2(n)/8)
      //(refer to RFC 5915, section 3)
      error = ecExportPrivateKey(privateKey, p, &n);
      //Any error to report?
      if(error)
         return error;
   }
 
   //Format PrivateKey field
   tag.constructed = FALSE;
   tag.objClass = ASN1_CLASS_UNIVERSAL;
   tag.objType = ASN1_TYPE_OCTET_STRING;
   tag.length = n;
   tag.value = p;
 
   //Write the corresponding ASN.1 tag
   error = asn1WriteTag(&tag, FALSE, p, &n);
   //Any error to report?
   if(error)
      return error;
 
   //Update the length of the ECPrivateKey structure
   n = tag.totalLength;
   length += n;
 
   //Advance data pointer
   if(output != NULL)
      p += n;
 
   //The public key is optional
   if(privateKey->q.curve != NULL)
   {
      //Format PublicKey field
      error = pkcs8FormatEcPublicKey(&privateKey->q, p, &n);
      //Any error to report?
      if(error)
         return error;
 
      //Update the length of the ECPrivateKey structure
      length += n;
   }
 
   //Format ECPrivateKey field
   tag.constructed = TRUE;
   tag.objClass = ASN1_CLASS_UNIVERSAL;
   tag.objType = ASN1_TYPE_SEQUENCE;
   tag.length = length;
   tag.value = output;
 
   //Write the corresponding ASN.1 tag
   error = asn1WriteTag(&tag, FALSE, output, &n);
   //Any error to report?
   if(error)
      return error;
 
   //Get the length of the ECPrivateKey structure
   n = tag.totalLength;
 
   //The PrivateKey field is an octet string whose contents are the value
   //of the private key
   tag.constructed = FALSE;
   tag.objClass = ASN1_CLASS_UNIVERSAL;
   tag.objType = ASN1_TYPE_OCTET_STRING;
   tag.length = n;
   tag.value = output;
 
   //Write the corresponding ASN.1 tag
   error = asn1WriteTag(&tag, FALSE, output, &n);
   //Any error to report?
   if(error)
      return error;
 
   //Total number of bytes that have been written
   *written = tag.totalLength;
 
   //Successful processing
   return NO_ERROR;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Format an EC public key
 * @param[in] publicKey EC public key
 * @param[out] output Buffer where to format the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatEcPublicKey(const EcPublicKey *publicKey,
   uint8_t *output, size_t *written)
{
#if (EC_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   Asn1Tag tag;
 
   //The bit string shall contain an initial octet which encodes the number
   //of unused bits in the final subsequent octet
   output[0] = 0;
 
   //Format ECPublicKey structure
   error = ecExportPublicKey(publicKey, output + 1, &n,
      EC_PUBLIC_KEY_FORMAT_X963);
 
   //Check status code
   if(!error)
   {
      //The public key is encapsulated within a bit string
      tag.constructed = FALSE;
      tag.objClass = ASN1_CLASS_UNIVERSAL;
      tag.objType = ASN1_TYPE_BIT_STRING;
      tag.length = n + 1;
      tag.value = output;
 
      //Write the corresponding ASN.1 tag
      error = asn1WriteTag(&tag, FALSE, output, &n);
   }
 
   //Check status code
   if(!error)
   {
      //Explicit tagging shall be used to encode the public key
      tag.constructed = TRUE;
      tag.objClass = ASN1_CLASS_CONTEXT_SPECIFIC;
      tag.objType = 1;
      tag.length = n;
      tag.value = output;
 
      //Write the corresponding ASN.1 tag
      error = asn1WriteTag(&tag, FALSE, output, written);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Format an EdDSA private key
 * @param[in] privateKey EdDSA private key
 * @param[out] output Buffer where to format the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatEddsaPrivateKey(const EddsaPrivateKey *privateKey,
   uint8_t *output, size_t *written)
{
#if (ED25519_SUPPORT == ENABLED || ED448_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   Asn1Tag tag;
 
   //Export the EdDSA private key to ASN.1 format
   error = x509ExportEddsaPrivateKey(privateKey, output, &n);
 
   //Check status code
   if(!error)
   {
      //The CurvePrivateKey structure is encapsulated within an octet string
      tag.constructed = FALSE;
      tag.objClass = ASN1_CLASS_UNIVERSAL;
      tag.objType = ASN1_TYPE_OCTET_STRING;
      tag.length = n;
      tag.value = output;
 
      //Write PrivateKey structure
      error = asn1WriteTag(&tag, FALSE, output, written);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Format an EdDSA public key
 * @param[in] publicKey EdDSA public key
 * @param[out] output Buffer where to format the ASN.1 structure
 * @param[out] written Length of the resulting ASN.1 structure
 * @return Error code
 **/
 
error_t pkcs8FormatEddsaPublicKey(const EddsaPublicKey *publicKey,
   uint8_t *output, size_t *written)
{
#if (ED25519_SUPPORT == ENABLED || ED448_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   Asn1Tag tag;
 
   //The bit string shall contain an initial octet which encodes the number
   //of unused bits in the final subsequent octet
   output[0] = 0;
 
   //Format EdDSA public key
   error = eddsaExportPublicKey(publicKey, output + 1, &n);
 
   //Check status code
   if(!error)
   {
      //Explicit tagging shall be used to encode the public key
      tag.constructed = TRUE;
      tag.objClass = ASN1_CLASS_CONTEXT_SPECIFIC;
      tag.objType = 1;
      tag.length = n + 1;
      tag.value = output;
 
      //Write the corresponding ASN.1 tag
      error = asn1WriteTag(&tag, FALSE, output, written);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
#endif