/* mppe.c - MPPE key implementation
*
* Copyright (c) 2020 Eivind Naess. All rights reserved.
* Copyright (c) 2008-2024 Paul Mackerras. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in
*    the documentation and/or other materials provided with the
*    distribution.
*
* 3. The name(s) of the authors of this software must not be used to
*    endorse or promote products derived from this software without
*    prior written permission.
*
* THE AUTHORS OF THIS SOFTWARE DISCLAIM ALL WARRANTIES WITH REGARD TO
* THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS, IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
* SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
* AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
* OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <string.h>


#include "pppd-private.h"
#include "fsm.h"
#include "ccp.h"
#include "chap_ms.h"
#include "mppe.h"
#include "crypto.h"

u_char mppe_send_key[MPPE_MAX_KEY_SIZE];
u_char mppe_recv_key[MPPE_MAX_KEY_SIZE];
int mppe_keys_set = 0;

void
mppe_set_keys(u_char *send_key, u_char *recv_key, int keylen)
{
       int length = keylen;
       if (length > MPPE_MAX_KEY_SIZE)
               length = MPPE_MAX_KEY_SIZE;

       if (send_key) {
           BCOPY(send_key, mppe_send_key, length);
           BZERO(send_key, keylen);
       }

       if (recv_key) {
           BCOPY(recv_key, mppe_recv_key, length);
           BZERO(recv_key, keylen);
       }

       mppe_keys_set = length;
}

bool
mppe_keys_isset()
{
       return !!mppe_keys_set;
}

int
mppe_get_recv_key(u_char *recv_key, int length)
{
       if (mppe_keys_isset()) {
               if (length > mppe_keys_set)
                       length = mppe_keys_set;
               BCOPY(mppe_recv_key, recv_key, length);
               return length;
       }
       return 0;
}

int
mppe_get_send_key(u_char *send_key, int length)
{
       if (mppe_keys_isset()) {
               if (length > mppe_keys_set)
                       length = mppe_keys_set;
               BCOPY(mppe_send_key, send_key, length);
               return length;
       }
       return 0;
}

void
mppe_clear_keys(void)
{
       mppe_keys_set = 0;
       BZERO(mppe_send_key, sizeof(mppe_send_key));
       BZERO(mppe_recv_key, sizeof(mppe_recv_key));
}

/*
* Set mppe_xxxx_key from the NTPasswordHashHash.
* RFC 2548 (RADIUS support) requires us to export this function (ugh).
*/
void
mppe_set_chapv1(unsigned char *rchallenge, unsigned char *PasswordHashHash)
{
   PPP_MD_CTX *ctx;
   u_char Digest[SHA_DIGEST_LENGTH];
   unsigned int DigestLen;

   ctx = PPP_MD_CTX_new();
   if (ctx != NULL) {

       if (PPP_DigestInit(ctx, PPP_sha1())) {

           if (PPP_DigestUpdate(ctx, PasswordHashHash, MD4_DIGEST_LENGTH)) {

               if (PPP_DigestUpdate(ctx, PasswordHashHash, MD4_DIGEST_LENGTH)) {

                   if (PPP_DigestUpdate(ctx, rchallenge, 8)) {

                       DigestLen = SHA_DIGEST_LENGTH;
                       PPP_DigestFinal(ctx, Digest, &DigestLen);
                   }
               }
           }
       }

       PPP_MD_CTX_free(ctx);
   }


   /* Same key in both directions. */
   mppe_set_keys(Digest, Digest, sizeof(Digest));
}

/*
* Set mppe_xxxx_key from MS-CHAPv2 credentials. (see RFC 3079)
*
* This helper function used in the Winbind module, which gets the
* NTHashHash from the server.
*/
void
mppe_set_chapv2(unsigned char *PasswordHashHash, unsigned char *NTResponse,
       int IsServer)
{
   PPP_MD_CTX *ctx;

   u_char      MasterKey[SHA_DIGEST_LENGTH];
   u_char      SendKey[SHA_DIGEST_LENGTH];
   u_char      RecvKey[SHA_DIGEST_LENGTH];
   unsigned int KeyLen;

   u_char SHApad1[40] =
       { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
   u_char SHApad2[40] =
       { 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
         0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
         0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
         0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2 };

   /* "This is the MPPE Master Key" */
   u_char Magic1[27] =
       { 0x54, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74,
         0x68, 0x65, 0x20, 0x4d, 0x50, 0x50, 0x45, 0x20, 0x4d,
         0x61, 0x73, 0x74, 0x65, 0x72, 0x20, 0x4b, 0x65, 0x79 };
   /* "On the client side, this is the send key; "
      "on the server side, it is the receive key." */
   u_char Magic2[84] =
       { 0x4f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x69,
         0x65, 0x6e, 0x74, 0x20, 0x73, 0x69, 0x64, 0x65, 0x2c, 0x20,
         0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
         0x65, 0x20, 0x73, 0x65, 0x6e, 0x64, 0x20, 0x6b, 0x65, 0x79,
         0x3b, 0x20, 0x6f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x73,
         0x65, 0x72, 0x76, 0x65, 0x72, 0x20, 0x73, 0x69, 0x64, 0x65,
         0x2c, 0x20, 0x69, 0x74, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
         0x65, 0x20, 0x72, 0x65, 0x63, 0x65, 0x69, 0x76, 0x65, 0x20,
         0x6b, 0x65, 0x79, 0x2e };
   /* "On the client side, this is the receive key; "
      "on the server side, it is the send key." */
   u_char Magic3[84] =
       { 0x4f, 0x6e, 0x20, 0x74, 0x68, 0x65, 0x20, 0x63, 0x6c, 0x69,
         0x65, 0x6e, 0x74, 0x20, 0x73, 0x69, 0x64, 0x65, 0x2c, 0x20,
         0x74, 0x68, 0x69, 0x73, 0x20, 0x69, 0x73, 0x20, 0x74, 0x68,
         0x65, 0x20, 0x72, 0x65, 0x63, 0x65, 0x69, 0x76, 0x65, 0x20,
         0x6b, 0x65, 0x79, 0x3b, 0x20, 0x6f, 0x6e, 0x20, 0x74, 0x68,
         0x65, 0x20, 0x73, 0x65, 0x72, 0x76, 0x65, 0x72, 0x20, 0x73,
         0x69, 0x64, 0x65, 0x2c, 0x20, 0x69, 0x74, 0x20, 0x69, 0x73,
         0x20, 0x74, 0x68, 0x65, 0x20, 0x73, 0x65, 0x6e, 0x64, 0x20,
         0x6b, 0x65, 0x79, 0x2e };
   u_char *s;

   ctx = PPP_MD_CTX_new();
   if (ctx != NULL) {

       if (PPP_DigestInit(ctx, PPP_sha1())) {

           if (PPP_DigestUpdate(ctx, PasswordHashHash, MD4_DIGEST_LENGTH)) {

               if (PPP_DigestUpdate(ctx, NTResponse, 24)) {

                   if (PPP_DigestUpdate(ctx, Magic1, sizeof(Magic1))) {

                       KeyLen = SHA_DIGEST_LENGTH;
                       PPP_DigestFinal(ctx, MasterKey, &KeyLen);
                   }
               }
           }
       }

       PPP_MD_CTX_free(ctx);
   }

   /*
    * generate send key
    */
   if (IsServer)
       s = Magic3;
   else
       s = Magic2;

   ctx = PPP_MD_CTX_new();
   if (ctx != NULL) {

       if (PPP_DigestInit(ctx, PPP_sha1())) {

           if (PPP_DigestUpdate(ctx, MasterKey, 16)) {

               if (PPP_DigestUpdate(ctx, SHApad1, sizeof(SHApad1))) {

                   if (PPP_DigestUpdate(ctx, s, 84)) {

                       if (PPP_DigestUpdate(ctx, SHApad2, sizeof(SHApad2))) {

                           KeyLen = SHA_DIGEST_LENGTH;
                           PPP_DigestFinal(ctx, SendKey, &KeyLen);
                       }
                   }
               }
           }
       }

       PPP_MD_CTX_free(ctx);
   }


   /*
    * generate recv key
    */
   if (IsServer)
       s = Magic2;
   else
       s = Magic3;

   ctx = PPP_MD_CTX_new();
   if (ctx != NULL) {

       if (PPP_DigestInit(ctx, PPP_sha1())) {

           if (PPP_DigestUpdate(ctx, MasterKey, 16)) {

               if (PPP_DigestUpdate(ctx, SHApad1, sizeof(SHApad1))) {

                   if (PPP_DigestUpdate(ctx, s, 84)) {

                       if (PPP_DigestUpdate(ctx, SHApad2, sizeof(SHApad2))) {

                           KeyLen = SHA_DIGEST_LENGTH;
                           PPP_DigestFinal(ctx, RecvKey, &KeyLen);
                       }
                   }
               }
           }
       }

       PPP_MD_CTX_free(ctx);
   }

   mppe_set_keys(SendKey, RecvKey, SHA_DIGEST_LENGTH);
}

#ifndef UNIT_TEST

/*
* Set MPPE options from plugins.
*/
void
mppe_set_enc_types(int policy, int types)
{
   /* Early exit for unknown policies. */
   if (policy != MPPE_ENC_POL_ENC_ALLOWED &&
       policy != MPPE_ENC_POL_ENC_REQUIRED)
       return;

   /* Don't modify MPPE if it's optional and wasn't already configured. */
   if (policy == MPPE_ENC_POL_ENC_ALLOWED && !ccp_wantoptions[0].mppe)
       return;

   /*
    * Disable undesirable encryption types.  Note that we don't ENABLE
    * any encryption types, to avoid overriding manual configuration.
    */
   switch(types) {
       case MPPE_ENC_TYPES_RC4_40:
           ccp_wantoptions[0].mppe &= ~MPPE_OPT_128;   /* disable 128-bit */
           break;
       case MPPE_ENC_TYPES_RC4_128:
           ccp_wantoptions[0].mppe &= ~MPPE_OPT_40;    /* disable 40-bit */
           break;
       default:
           break;
   }
}

#endif

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