ssh_key_import.c

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/**
 * @file ssh_key_import.c
 * @brief SSH key file import functions
 *
 * @section License
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 *
 * Copyright (C) 2019-2025 Oryx Embedded SARL. All rights reserved.
 *
 * This file is part of CycloneSSH 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 SSH_TRACE_LEVEL
 
//Dependencies
#include "ssh/ssh.h"
#include "ssh/ssh_key_import.h"
#include "ssh/ssh_key_parse.h"
#include "ssh/ssh_key_decrypt.h"
#include "ssh/ssh_misc.h"
#include "encoding/base64.h"
#include "pkix/pem_import.h"
#include "ecc/ec_misc.h"
#include "debug.h"
 
//Check SSH stack configuration
#if (SSH_SUPPORT == ENABLED)
 
 
/**
 * @brief List of supported key types
 **/
 
static const SshKeyType sshKeyTypes[] =
{
#if (SSH_RSA_SIGN_SUPPORT == ENABLED)
   {"ssh-rsa", X509_KEY_TYPE_RSA, NULL},
#endif
#if (SSH_DSA_SIGN_SUPPORT == ENABLED)
   {"ssh-dss", X509_KEY_TYPE_DSA, NULL},
#endif
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED && SSH_NISTP256_SUPPORT == ENABLED)
   {"ecdsa-sha2-nistp256", X509_KEY_TYPE_EC, "secp256r1"},
#endif
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED && SSH_NISTP384_SUPPORT == ENABLED)
   {"ecdsa-sha2-nistp384", X509_KEY_TYPE_EC, "secp384r1"},
#endif
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED && SSH_NISTP521_SUPPORT == ENABLED)
   {"ecdsa-sha2-nistp521", X509_KEY_TYPE_EC, "secp521r1"},
#endif
#if (SSH_ED25519_SIGN_SUPPORT == ENABLED)
   {"ssh-ed25519", X509_KEY_TYPE_ED25519, NULL},
#endif
#if (SSH_ED448_SIGN_SUPPORT == ENABLED)
   {"ssh-ed448", X509_KEY_TYPE_ED448, NULL},
#endif
};
 
 
/**
 * @brief Decode an SSH public key file containing an RSA public key
 * @param[out] publicKey RSA public key resulting from the parsing process
 * @param[in] input Pointer to the SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return Error code
 **/
 
error_t sshImportRsaPublicKey(RsaPublicKey *publicKey, const char_t *input,
   size_t length)
{
#if (SSH_RSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *buffer;
   SshRsaHostKey hostKey;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(publicKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse RSA host key structure
            error = sshParseRsaHostKey(buffer, n, &hostKey);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA public key
            error = sshImportRsaHostKey(publicKey, &hostKey);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the public key file (PEM format)
      error = pemImportRsaPublicKey(publicKey, input, length);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      rsaFreePublicKey(publicKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH public key file containing a DSA public key
 * @param[out] publicKey DSA public key resulting from the parsing process
 * @param[in] input Pointer to the SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return Error code
 **/
 
error_t sshImportDsaPublicKey(DsaPublicKey *publicKey, const char_t *input,
   size_t length)
{
#if (SSH_DSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *buffer;
   SshDsaHostKey hostKey;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(publicKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse DSA host key structure
            error = sshParseDsaHostKey(buffer, n, &hostKey);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA public key
            error = sshImportDsaHostKey(publicKey, &hostKey);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the public key file (PEM format)
      error = pemImportDsaPublicKey(publicKey, input, length);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      dsaFreePublicKey(publicKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH public key file containing an ECDSA public key
 * @param[out] publicKey ECDSA public key resulting from the parsing process
 * @param[in] input Pointer to the SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return Error code
 **/
 
error_t sshImportEcdsaPublicKey(EcPublicKey *publicKey, const char_t *input,
   size_t length)
{
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *buffer;
   SshEcdsaHostKey hostKey;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(publicKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse ECDSA host key structure
            error = sshParseEcdsaHostKey(buffer, n, &hostKey);
         }
 
         //Check status code
         if(!error)
         {
            //Import ECDSA public key
            error = sshImportEcdsaHostKey(publicKey, &hostKey);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the public key file (PEM format)
      error = pemImportEcPublicKey(publicKey, input, length);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      ecFreePublicKey(publicKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH public key file containing an Ed25519 public key
 * @param[out] publicKey Ed25519 public key resulting from the parsing process
 * @param[in] input Pointer to the SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return Error code
 **/
 
error_t sshImportEd25519PublicKey(EddsaPublicKey *publicKey,
   const char_t *input, size_t length)
{
#if (SSH_ED25519_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *buffer;
   SshEddsaHostKey hostKey;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(publicKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse Ed25519 host key structure
            error = sshParseEd25519HostKey(buffer, n, &hostKey);
         }
 
         //Check status code
         if(!error)
         {
            //Import Ed25519 public key
            error = eddsaImportPublicKey(publicKey, ED25519_CURVE,
               hostKey.q.value, hostKey.q.length);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the public key file (PEM format)
      error = pemImportEddsaPublicKey(publicKey, input, length);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      eddsaFreePublicKey(publicKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH public key file containing an Ed448 public key
 * @param[out] publicKey Ed448 public key resulting from the parsing process
 * @param[in] input Pointer to the SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return Error code
 **/
 
error_t sshImportEd448PublicKey(EddsaPublicKey *publicKey,
   const char_t *input, size_t length)
{
#if (SSH_ED448_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *buffer;
   SshEddsaHostKey hostKey;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(publicKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse Ed448 host key structure
            error = sshParseEd448HostKey(buffer, n, &hostKey);
         }
 
         //Check status code
         if(!error)
         {
            //Import Ed448 public key
            error = eddsaImportPublicKey(publicKey, ED448_CURVE,
               hostKey.q.value, hostKey.q.length);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the public key file (PEM format)
      error = pemImportEddsaPublicKey(publicKey, input, length);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      eddsaFreePublicKey(publicKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH private key file containing an RSA private key
 * @param[out] privateKey RSA private key resulting from the parsing process
 * @param[in] input Pointer to the SSH private key file
 * @param[in] length Length of the SSH private key file
 * @param[in] password NULL-terminated string containing the password. This
 *   parameter is required if the private key is encrypted
 * @return Error code
 **/
 
error_t sshImportRsaPrivateKey(RsaPrivateKey *privateKey, const char_t *input,
   size_t length, const char_t *password)
{
#if (SSH_RSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *data;
   uint8_t *buffer;
   Mpi t;
   SshPrivateKeyHeader privateKeyHeader;
   SshRsaPrivateKey privateKeyInfo;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(privateKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the private key structure
   error = sshDecodeOpenSshPrivateKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the private key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Initialize multiple precision integer
         mpiInit(&t);
 
         //Decode the content of the private key file (OpenSSH format)
         error = sshDecodeOpenSshPrivateKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse private key header
            error = sshParseOpenSshPrivateKeyHeader(buffer, n,
               &privateKeyHeader);
         }
 
         //Check status code
         if(!error)
         {
            //Point to the encrypted data
            data = (uint8_t *) privateKeyHeader.encrypted.value;
            n = privateKeyHeader.encrypted.length;
 
            //Perform decryption operation
            error = sshDecryptOpenSshPrivateKey(&privateKeyHeader, password,
               data, data, n);
         }
 
         //Check status code
         if(!error)
         {
            //Parse RSA private key blob
            error = sshParseOpenSshRsaPrivateKey(data, n, &privateKeyInfo);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA modulus
            error = mpiImport(&privateKey->n, privateKeyInfo.n.value,
               privateKeyInfo.n.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA public exponent
            error = mpiImport(&privateKey->e, privateKeyInfo.e.value,
               privateKeyInfo.e.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA private exponent
            error = mpiImport(&privateKey->d, privateKeyInfo.d.value,
               privateKeyInfo.d.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA first factor
            error = mpiImport(&privateKey->p, privateKeyInfo.p.value,
               privateKeyInfo.p.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA second factor
            error = mpiImport(&privateKey->q, privateKeyInfo.q.value,
               privateKeyInfo.q.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import RSA CRT coefficient
            error = mpiImport(&privateKey->qinv, privateKeyInfo.qinv.value,
               privateKeyInfo.qinv.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Compute t = p - 1
            error = mpiSubInt(&t, &privateKey->p, 1);
         }
 
         //Check status code
         if(!error)
         {
            //Compute first factor's CRT exponent
            error = mpiMod(&privateKey->dp, &privateKey->d, &t);
         }
 
         //Check status code
         if(!error)
         {
            //Compute t = q - 1
            error = mpiSubInt(&t, &privateKey->q, 1);
         }
 
         //Check status code
         if(!error)
         {
            //Compute second factor's CRT exponent
            error = mpiMod(&privateKey->dq, &privateKey->d, &t);
         }
 
         //Release multiple precision integers
         mpiFree(&t);
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the private key file (PEM format)
      error = pemImportRsaPrivateKey(privateKey, input, length, password);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      rsaFreePrivateKey(privateKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH private key file containing a DSA private key
 * @param[out] privateKey DSA private key resulting from the parsing process
 * @param[in] input Pointer to the SSH private key file
 * @param[in] length Length of the SSH private key file
 * @param[in] password NULL-terminated string containing the password. This
 *   parameter is required if the private key is encrypted
 * @return Error code
 **/
 
error_t sshImportDsaPrivateKey(DsaPrivateKey *privateKey, const char_t *input,
   size_t length, const char_t *password)
{
#if (SSH_DSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *data;
   uint8_t *buffer;
   SshPrivateKeyHeader privateKeyHeader;
   SshDsaPrivateKey privateKeyInfo;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(privateKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the private key structure
   error = sshDecodeOpenSshPrivateKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the private key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the private key file (OpenSSH format)
         error = sshDecodeOpenSshPrivateKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse private key header
            error = sshParseOpenSshPrivateKeyHeader(buffer, n,
               &privateKeyHeader);
         }
 
         //Check status code
         if(!error)
         {
            //Point to the encrypted data
            data = (uint8_t *) privateKeyHeader.encrypted.value;
            n = privateKeyHeader.encrypted.length;
 
            //Perform decryption operation
            error = sshDecryptOpenSshPrivateKey(&privateKeyHeader, password,
               data, data, n);
         }
 
         //Check status code
         if(!error)
         {
            //Parse DSA private key blob
            error = sshParseOpenSshDsaPrivateKey(data, n, &privateKeyInfo);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA prime modulus
            error = mpiImport(&privateKey->params.p, privateKeyInfo.p.value,
               privateKeyInfo.p.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA group order
            error = mpiImport(&privateKey->params.q, privateKeyInfo.q.value,
               privateKeyInfo.q.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA group generator
            error = mpiImport(&privateKey->params.g, privateKeyInfo.g.value,
               privateKeyInfo.g.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA private key value
            error = mpiImport(&privateKey->x, privateKeyInfo.x.value,
               privateKeyInfo.x.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Check status code
         if(!error)
         {
            //Import DSA public key value
            error = mpiImport(&privateKey->y, privateKeyInfo.y.value,
               privateKeyInfo.y.length, MPI_FORMAT_BIG_ENDIAN);
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the private key file (PEM format)
      error = pemImportDsaPrivateKey(privateKey, input, length, password);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      dsaFreePrivateKey(privateKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH private key file containing an ECDSA private key
 * @param[out] privateKey ECDSA private key resulting from the parsing process
 * @param[in] input Pointer to the SSH private key file
 * @param[in] length Length of the SSH private key file
 * @param[in] password NULL-terminated string containing the password. This
 *   parameter is required if the private key is encrypted
 * @return Error code
 **/
 
error_t sshImportEcdsaPrivateKey(EcPrivateKey *privateKey, const char_t *input,
   size_t length, const char_t *password)
{
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *data;
   uint8_t *buffer;
   SshPrivateKeyHeader privateKeyHeader;
   SshEcdsaPrivateKey privateKeyInfo;
   const EcCurve *curve;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(privateKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the private key structure
   error = sshDecodeOpenSshPrivateKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the private key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the private key file (OpenSSH format)
         error = sshDecodeOpenSshPrivateKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse private key header
            error = sshParseOpenSshPrivateKeyHeader(buffer, n,
               &privateKeyHeader);
         }
 
         //Check status code
         if(!error)
         {
            //Point to the encrypted data
            data = (uint8_t *) privateKeyHeader.encrypted.value;
            n = privateKeyHeader.encrypted.length;
 
            //Perform decryption operation
            error = sshDecryptOpenSshPrivateKey(&privateKeyHeader, password,
               data, data, n);
         }
 
         //Check status code
         if(!error)
         {
            //Parse ECDSA private key blob
            error = sshParseOpenSshEcdsaPrivateKey(data, n, &privateKeyInfo);
         }
 
         //Check status code
         if(!error)
         {
            //Retrieve the elliptic curve that matches the specified key format
            //identifier
            curve = sshGetCurve(&privateKeyInfo.keyFormatId,
               &privateKeyInfo.curveName);
 
            //Make sure the key format identifier is acceptable
            if(curve != NULL)
            {
               //Import EC private key
               error = ecImportPrivateKey(privateKey, curve,
                  privateKeyInfo.d.value, privateKeyInfo.d.length);
 
               //Check status code
               if(!error)
               {
                  //Import EC public key
                  error = ecImportPublicKey(&privateKey->q, curve,
                     privateKeyInfo.q.value, privateKeyInfo.q.length,
                     EC_PUBLIC_KEY_FORMAT_X963);
               }
            }
            else
            {
               //Report an error
               error = ERROR_WRONG_IDENTIFIER;
            }
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the private key file (PEM format)
      error = pemImportEcPrivateKey(privateKey, input, length, password);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      ecFreePrivateKey(privateKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH private key file containing an Ed25519 private key
 * @param[out] privateKey Ed25519 private key resulting from the parsing process
 * @param[in] input Pointer to the SSH private key file
 * @param[in] length Length of the SSH private key file
 * @param[in] password NULL-terminated string containing the password. This
 *   parameter is required if the private key is encrypted
 * @return Error code
 **/
 
error_t sshImportEd25519PrivateKey(EddsaPrivateKey *privateKey,
   const char_t *input, size_t length, const char_t *password)
{
#if (SSH_ED25519_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *data;
   uint8_t *buffer;
   SshPrivateKeyHeader privateKeyHeader;
   SshEddsaPrivateKey privateKeyInfo;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(privateKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the private key structure
   error = sshDecodeOpenSshPrivateKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the private key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the private key file (OpenSSH format)
         error = sshDecodeOpenSshPrivateKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse private key header
            error = sshParseOpenSshPrivateKeyHeader(buffer, n,
               &privateKeyHeader);
         }
 
         //Check status code
         if(!error)
         {
            //Point to the encrypted data
            data = (uint8_t *) privateKeyHeader.encrypted.value;
            n = privateKeyHeader.encrypted.length;
 
            //Perform decryption operation
            error = sshDecryptOpenSshPrivateKey(&privateKeyHeader, password,
               data, data, n);
         }
 
         //Check status code
         if(!error)
         {
            //Parse Ed25519 private key blob
            error = sshParseOpenSshEd25519PrivateKey(data, n, &privateKeyInfo);
         }
 
         //Check status code
         if(!error)
         {
            //Import Ed25519 private key
            error = eddsaImportPrivateKey(privateKey, ED25519_CURVE,
               privateKeyInfo.d.value, ED25519_PRIVATE_KEY_LEN);
 
            //Check status code
            if(!error)
            {
               //Import Ed25519 public key
               error = eddsaImportPublicKey(&privateKey->q, ED25519_CURVE,
                  privateKeyInfo.q.value, privateKeyInfo.q.length);
            }
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the private key file (PEM format)
      error = pemImportEddsaPrivateKey(privateKey, input, length, password);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      eddsaFreePrivateKey(privateKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Decode an SSH private key file containing an Ed448 private key
 * @param[out] privateKey Ed448 private key resulting from the parsing process
 * @param[in] input Pointer to the SSH private key file
 * @param[in] length Length of the SSH private key file
 * @param[in] password NULL-terminated string containing the password. This
 *   parameter is required if the private key is encrypted
 * @return Error code
 **/
 
error_t sshImportEd448PrivateKey(EddsaPrivateKey *privateKey,
   const char_t *input, size_t length, const char_t *password)
{
#if (SSH_ED448_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t n;
   uint8_t *data;
   uint8_t *buffer;
   SshPrivateKeyHeader privateKeyHeader;
   SshEddsaPrivateKey privateKeyInfo;
 
   //Check parameters
   if(input == NULL && length != 0)
      return ERROR_INVALID_PARAMETER;
   if(privateKey == NULL)
      return ERROR_INVALID_PARAMETER;
 
   //Retrieve the length of the private key structure
   error = sshDecodeOpenSshPrivateKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      //Allocate a memory buffer to hold the private key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the private key file (OpenSSH format)
         error = sshDecodeOpenSshPrivateKeyFile(input, length, buffer, &n);
 
         //Check status code
         if(!error)
         {
            //Parse private key header
            error = sshParseOpenSshPrivateKeyHeader(buffer, n,
               &privateKeyHeader);
         }
 
         //Check status code
         if(!error)
         {
            //Point to the encrypted data
            data = (uint8_t *) privateKeyHeader.encrypted.value;
            n = privateKeyHeader.encrypted.length;
 
            //Perform decryption operation
            error = sshDecryptOpenSshPrivateKey(&privateKeyHeader, password,
               data, data, n);
         }
 
         //Check status code
         if(!error)
         {
            //Parse Ed448 private key blob
            error = sshParseOpenSshEd448PrivateKey(data, n, &privateKeyInfo);
         }
 
         //Check status code
         if(!error)
         {
            //Import Ed448 private key
            error = eddsaImportPrivateKey(privateKey, ED448_CURVE,
               privateKeyInfo.d.value, ED448_PRIVATE_KEY_LEN);
 
            //Check status code
            if(!error)
            {
               //Import Ed448 public key
               error = eddsaImportPublicKey(&privateKey->q, ED448_CURVE,
                  privateKeyInfo.q.value, privateKeyInfo.q.length);
            }
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
      else
      {
         //Failed to allocate memory
         error = ERROR_OUT_OF_MEMORY;
      }
   }
   else
   {
      //Decode the content of the private key file (PEM format)
      error = pemImportEddsaPrivateKey(privateKey, input, length, password);
   }
 
   //Any error to report?
   if(error)
   {
      //Clean up side effects
      eddsaFreePrivateKey(privateKey);
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Import an RSA host key
 * @param[out] publicKey Pointer to the RSA public key
 * @param[in] hostKey Pointer to the host key structure
 * @return Error code
 **/
 
error_t sshImportRsaHostKey(RsaPublicKey *publicKey,
   const SshRsaHostKey *hostKey)
{
#if (SSH_RSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   uint_t k;
 
   //Import RSA public exponent
   error = mpiImport(&publicKey->e, hostKey->e.value, hostKey->e.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Import RSA modulus
   error = mpiImport(&publicKey->n, hostKey->n.value, hostKey->n.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Get the length of the modulus, in bits
   k = mpiGetBitLength(&publicKey->n);
 
   //Applications should enforce minimum and maximum key sizes
   if(k < SSH_MIN_RSA_MODULUS_SIZE || k > SSH_MAX_RSA_MODULUS_SIZE)
      return ERROR_INVALID_KEY_LENGTH;
 
   //Successful processing
   return NO_ERROR;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Import a DSA host key
 * @param[out] publicKey Pointer to the DSA public key
 * @param[in] hostKey Pointer to the host key structure
 * @return Error code
 **/
 
error_t sshImportDsaHostKey(DsaPublicKey *publicKey,
   const SshDsaHostKey *hostKey)
{
#if (SSH_DSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   size_t k;
 
   //Import DSA prime modulus
   error = mpiImport(&publicKey->params.p, hostKey->p.value, hostKey->p.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Import DSA group order
   error = mpiImport(&publicKey->params.q, hostKey->q.value, hostKey->q.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Import DSA group generator
   error = mpiImport(&publicKey->params.g, hostKey->g.value, hostKey->g.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Import DSA public key value
   error = mpiImport(&publicKey->y, hostKey->y.value, hostKey->y.length,
      MPI_FORMAT_BIG_ENDIAN);
   //Any error to report?
   if(error)
      return error;
 
   //Get the length of the modulus, in bits
   k = mpiGetBitLength(&publicKey->params.p);
 
   //Applications should enforce minimum and maximum key sizes
   if(k < SSH_MIN_DSA_MODULUS_SIZE || k > SSH_MAX_DSA_MODULUS_SIZE)
      return ERROR_INVALID_KEY_LENGTH;
 
   //Successful processing
   return NO_ERROR;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Import a ECDSA host key
 * @param[out] publicKey Pointer to the ECDSA public key
 * @param[in] hostKey Pointer to the host key structure
 * @return Error code
 **/
 
error_t sshImportEcdsaHostKey(EcPublicKey *publicKey,
   const SshEcdsaHostKey *hostKey)
{
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED)
   error_t error;
   const EcCurve *curve;
 
   //Retrieve the elliptic curve that matches the specified key format
   //identifier
   curve = sshGetCurve(&hostKey->keyFormatId, &hostKey->curveName);
 
   //Make sure the key format identifier is acceptable
   if(curve != NULL)
   {
      //Import EC public key
      error = ecImportPublicKey(publicKey, curve, hostKey->q.value,
         hostKey->q.length, EC_PUBLIC_KEY_FORMAT_X963);
   }
   else
   {
      //Report an error
      error = ERROR_WRONG_IDENTIFIER;
   }
 
   //Return status code
   return error;
#else
   //Not implemented
   return ERROR_NOT_IMPLEMENTED;
#endif
}
 
 
/**
 * @brief Get SSH public key type
 * @param[in] input SSH public key file
 * @param[in] length Length of the SSH public key file
 * @return SSH public key type
 **/
 
const char_t *sshGetPublicKeyType(const char_t *input, size_t length)
{
   error_t error;
   uint_t i;
   size_t n;
   const char_t *keyType;
 
   //Initialize key type
   keyType = NULL;
 
   //Retrieve the length of the public key structure
   error = sshDecodePublicKeyFile(input, length, NULL, &n);
 
   //Check status code
   if(!error)
   {
      uint8_t *buffer;
      SshString keyFormatId;
 
      //Allocate a memory buffer to hold the public key structure
      buffer = sshAllocMem(n);
 
      //Successful memory allocation?
      if(buffer != NULL)
      {
         //Decode the content of the public key file (SSH2 or OpenSSH format)
         error = sshDecodePublicKeyFile(input, length, buffer, &n);
 
         //Check status
         if(!error)
         {
            //Decode key format identifier
            error = sshParseString(buffer, n, &keyFormatId);
         }
 
         //Check status
         if(!error)
         {
            //Loop through the list of supported key types
            for(i = 0; i < arraysize(sshKeyTypes); i++)
            {
               //Matching identifier?
               if(sshCompareString(&keyFormatId, sshKeyTypes[i].identifier))
               {
                  keyType = sshKeyTypes[i].identifier;
                  break;
               }
            }
         }
 
         //Release previously allocated memory
         sshFreeMem(buffer);
      }
   }
   else
   {
#if (SSH_ECDSA_SIGN_SUPPORT == ENABLED)
      X509KeyType type;
      const EcCurve *curve;
 
      //Extract the type of the public key (PEM format)
      type = pemGetPublicKeyType(input, length);
 
      //Extract the elliptic curve parameters
      if(type == X509_KEY_TYPE_EC)
      {
         curve = pemGetPublicKeyCurve(input, length);
      }
      else
      {
         curve = NULL;
      }
 
      //Loop through the list of supported key types
      for(i = 0; i < arraysize(sshKeyTypes); i++)
      {
         //Matching key type?
         if(sshKeyTypes[i].type == type)
         {
            //EC public key?
            if(type == X509_KEY_TYPE_EC)
            {
               //Check curve name
               if(osStrcmp(sshKeyTypes[i].curveName, curve->name) == 0)
               {
                  keyType = sshKeyTypes[i].identifier;
                  break;
               }
            }
            else
            {
               keyType = sshKeyTypes[i].identifier;
               break;
            }
         }
      }
#else
      X509KeyType type;
 
      //Extract the type of the public key (PEM format)
      type = pemGetPublicKeyType(input, length);
 
      //Loop through the list of supported key types
      for(i = 0; i < arraysize(sshKeyTypes); i++)
      {
         //Matching key type?
         if(sshKeyTypes[i].type == type)
         {
            keyType = sshKeyTypes[i].identifier;
            break;
         }
      }
#endif
   }
 
   //Return key type
   return keyType;
}
 
 
/**
 * @brief Decode SSH public key file (SSH2 or OpenSSH format)
 * @param[in] input SSH public key file to decode
 * @param[in] inputLen Length of the SSH public key file to decode
 * @param[out] output Pointer to the decoded data (optional parameter)
 * @param[out] outputLen Length of the decoded data
 **/
 
error_t sshDecodePublicKeyFile(const char_t *input, size_t inputLen,
   uint8_t *output, size_t *outputLen)
{
   error_t error;
 
   //Decode SSH public key file (SSH2 format)
   error = sshDecodeSsh2PublicKeyFile(input, inputLen, output, outputLen);
 
   //Check status code
   if(error)
   {
      //Decode SSH public key file (OpenSSH format)
      error = sshDecodeOpenSshPublicKeyFile(input, inputLen, output, outputLen);
   }
 
   //Return status code
   return error;
}
 
 
/**
 * @brief Decode SSH public key file (SSH2 format)
 * @param[in] input SSH public key file to decode
 * @param[in] inputLen Length of the SSH public key file to decode
 * @param[out] output Pointer to the decoded data (optional parameter)
 * @param[out] outputLen Length of the decoded data
 **/
 
error_t sshDecodeSsh2PublicKeyFile(const char_t *input, size_t inputLen,
   uint8_t *output, size_t *outputLen)
{
   error_t error;
   int_t i;
   int_t n;
   bool_t separatorChar;
   bool_t backslashChar;
   bool_t continuationLine;
   const char_t *p;
 
   //The first line of a conforming key file must be a begin marker (refer to
   //RFC 4716, section 3.2)
   i = sshSearchMarker(input, inputLen, "---- BEGIN SSH2 PUBLIC KEY ----", 31);
   //Begin marker not found?
   if(i < 0)
      return ERROR_INVALID_SYNTAX;
 
   //Advance the pointer over the marker
   i += 31;
 
   //The last line of a conforming key file must be an end marker (refer to
   //RFC 4716, section 3.2)
   n = sshSearchMarker(input + i, inputLen - i, "---- END SSH2 PUBLIC KEY ----", 29);
   //End marker not found?
   if(n < 0)
      return ERROR_INVALID_SYNTAX;
 
   //Point to the key file header
   p = input + i;
   i = 0;
 
   //Initialize flags
   separatorChar = FALSE;
   backslashChar = FALSE;
   continuationLine = FALSE;
 
   //The key file header section consists of multiple lines
   while(i < n)
   {
      //End of line detected?
      if(p[i] == '\n' || (i + 1) == n)
      {
         //A line that is not a continuation line and that has no ':' in it
         //is the first line of the Base64-encoded body (refer to RFC 4716,
         //section 3.3)
         if(!continuationLine && !separatorChar)
         {
            break;
         }
 
         //A line is continued if the last character in the line is a '\'
         continuationLine = backslashChar;
 
         //Reset flags
         separatorChar = FALSE;
         backslashChar = FALSE;
 
         //Point to the next line
         p += i + 1;
         n -= i + 1;
         i = 0;
      }
      else
      {
         //Check current character
         if(p[i] == ':')
         {
            //A ':' character is used to separate header name and value
            separatorChar = TRUE;
            backslashChar = FALSE;
         }
         else if(p[i] == '\\')
         {
            //A backslash is used at the end of a continued line
            backslashChar = TRUE;
         }
         else if(p[i] == '\r')
         {
            //Discard current character
         }
         else
         {
            //The current line is not a continued line
            backslashChar = FALSE;
         }
 
         //Next character
         i++;
      }
   }
 
   //The body of the SSH public key file is Base64-encoded
   error = base64Decode(p, n, output, outputLen);
   //Failed to decode the file?
   if(error)
      return error;
 
   //Sanity check
   if(*outputLen == 0)
      return ERROR_INVALID_SYNTAX;
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Decode SSH public key file (OpenSSH format)
 * @param[in] input SSH public key file to decode
 * @param[in] inputLen Length of the SSH public key file to decode
 * @param[out] output Pointer to the decoded data (optional parameter)
 * @param[out] outputLen Length of the decoded data
 **/
 
error_t sshDecodeOpenSshPublicKeyFile(const char_t *input, size_t inputLen,
   uint8_t *output, size_t *outputLen)
{
   error_t error;
   size_t i;
   size_t j;
   size_t n;
   const char_t *keyType;
 
   //Initialize key type
   keyType = NULL;
 
   //Loop through the list of identifiers
   for(i = 0; i < arraysize(sshKeyTypes); i++)
   {
      //Get the length of the identifier
      n = osStrlen(sshKeyTypes[i].identifier);
 
      //Matching identifier?
      if(inputLen > n && osMemcmp(input, sshKeyTypes[i].identifier, n) == 0)
      {
         keyType = sshKeyTypes[i].identifier;
         break;
      }
   }
 
   //Unrecognized key type?
   if(keyType == NULL)
      return ERROR_INVALID_SYNTAX;
 
   //Get the length of the identifier string
   i = osStrlen(keyType);
 
   //The identifier must be followed by a whitespace character
   if(input[i] != ' ' && input[i] != '\t')
      return ERROR_INVALID_SYNTAX;
 
   //Skip whitespace characters
   while(i < inputLen && (input[i] == ' ' || input[i] == '\t'))
   {
      i++;
   }
 
   //Point to the public key
   j = i;
 
   //The public key may be followed by a whitespace character and a comment
   while(j < inputLen && (input[j] != ' ' && input[j] != '\t'))
   {
      j++;
   }
 
   //The public key is Base64-encoded
   error = base64Decode(input + i, j - i, output, outputLen);
   //Failed to decode the file?
   if(error)
      return error;
 
   //Sanity check
   if(*outputLen == 0)
      return ERROR_INVALID_SYNTAX;
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Decode SSH private key file (OpenSSH format)
 * @param[in] input SSH public key file to decode
 * @param[in] inputLen Length of the SSH private key file to decode
 * @param[out] output Pointer to the decoded data (optional parameter)
 * @param[out] outputLen Length of the decoded data
 **/
 
error_t sshDecodeOpenSshPrivateKeyFile(const char_t *input, size_t inputLen,
   uint8_t *output, size_t *outputLen)
{
   error_t error;
   int_t i;
   int_t n;
 
   //The first line of the private key file must be a begin marker
   i = sshSearchMarker(input, inputLen,
      "-----BEGIN OPENSSH PRIVATE KEY-----", 35);
   //Begin marker not found?
   if(i < 0)
      return ERROR_INVALID_SYNTAX;
 
   //Advance the pointer over the marker
   i += 35;
 
   //The last line of the private key file must be an end marker
   n = sshSearchMarker(input + i, inputLen - i,
      "-----END OPENSSH PRIVATE KEY-----", 33);
   //End marker not found?
   if(n < 0)
      return ERROR_INVALID_SYNTAX;
 
   //The body of the SSH private key file is Base64-encoded
   error = base64Decode(input + i, n, output, outputLen);
   //Failed to decode the file?
   if(error)
      return error;
 
   //Sanity check
   if(*outputLen == 0)
      return ERROR_INVALID_SYNTAX;
 
   //Successful processing
   return NO_ERROR;
}
 
 
/**
 * @brief Search a string for a given marker
 * @param[in] s String to search
 * @param[in] sLen Length of the string to search
 * @param[in] marker String containing the marker to search for
 * @param[in] markerLen Length of the marker
 * @return The index of the first occurrence of the marker in the string,
 *   or -1 if the marker does not appear in the string
 **/
 
int_t sshSearchMarker(const char_t *s, size_t sLen, const char_t *marker,
   size_t markerLen)
{
   size_t i;
   size_t j;
 
   //Loop through input string
   for(i = 0; (i + markerLen) <= sLen; i++)
   {
      //Compare current substring with the given marker
      for(j = 0; j < markerLen; j++)
      {
         if(s[i + j] != marker[j])
            break;
      }
 
      //Check whether the marker has been found
      if(j == markerLen)
         return i;
   }
 
   //The marker does not appear in the string
   return -1;
}
 
#endif