path: root/src/qmail-dkim.cpp

/*****************************************************************************
*  Copyright 2005 Alt-N Technologies, Ltd. 
*
*  Licensed under the Apache License, Version 2.0 (the "License"); 
*  you may not use this file except in compliance with the License. 
*  You may obtain a copy of the License at 
*
*      http://www.apache.org/licenses/LICENSE-2.0 
*
*  This code incorporates intellectual property owned by Yahoo! and licensed 
*  pursuant to the Yahoo! DomainKeys Patent License Agreement.
*
*  Unless required by applicable law or agreed to in writing, software 
*  distributed under the License is distributed on an "AS IS" BASIS, 
*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
*  See the License for the specific language governing permissions and 
*  limitations under the License.
*
*  Changes done by ¢feh@fehcom.de obeying the above license
*
*  Comment: Awful mixture of C and C++ making use of the worst parts of it.
*           Style: Partial Hungarian notation (see Torvalds comments)
*           C++: Obsolete classes, allocators, virtual constructors w/o destructors
*           C: Stdio interface routines
*           OpenSSL: Brain demaged EVP_Digest calls with memory leaks.
*           Network: Sigh, exchanged internal DNS routines by fehQlibs resolver
*
*****************************************************************************/
#include <unistd.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include "dkim.h"
extern "C" {
#include "dns.h"
}

// change these to your selector name, domain name, etc
#define MYRSASELECTOR "default"
#define MYECCSELECTOR "eddy"
#define MYDOMAIN      ""  //"bardenhagen.com"
#define MYIDENTITY    ""  //"dkimtest@bardenhagen.com"

#define strnicmp strncasecmp
#define FDLOG    stderr /* writing to another FD requires a method */

int DKIM_CALL SignThisHeader(const char *szHeader)
{
  if (strnicmp(szHeader, "X-", 2) == 0) {
    return 0;
  }
  return 1;
}

int DKIM_CALL SelectorCallback(const char *szFQDN, char *szBuffer, int nBufLen)
{
  return 0;
}

void usage()
{
  char version[] = "1.4.0";
  fprintf(FDLOG, "qmail-dkim %s \n", version);
  fprintf(
      FDLOG,
      "Usage: qmail-dkim [-h|-v|-s] [tags] <msgfile> [<RSAkeyfile> <outfile> <Ed25519keyfile>]\n\n");
  fprintf(FDLOG, "Options:\n\t-h show this help\n");
  fprintf(FDLOG, "\t-s sign the message \n");
  fprintf(FDLOG, "\t-v verify the message\n");
  fprintf(FDLOG, "\t-V verify the message and write result to output file (Pass/Fail)\n\n");
  fprintf(FDLOG, "These tags are available:\n");
  fprintf(
      FDLOG,
      "\t-c<canonicalization>   - r=relaxed [DEFAULT], s=simple, t=relaxed/simple, u=simple/relaxed\n");
  fprintf(
      FDLOG,
      "\t-d<sdid>               - Signing Domain Identifier (if not provided it will be determined from "
      "the sender/from header)\n");
  fprintf(
      FDLOG,
      "\t-i<auid>               - Agent User Identifier, usually the sender's email address "
      "(optional)\n");
  fprintf(FDLOG, "\t-l                     - include body length tag (optional)\n");
  fprintf(FDLOG, "\t-q                     - include query method tag\n");
  fprintf(FDLOG, "\t-t                     - include a timestamp tag (optional)\n");
  fprintf(
      FDLOG,
      "\t-x<expire_time>        - the expire time in seconds since epoch (optional, DEFAULT = current "
      "time + 604800)\n");
  fprintf(FDLOG, "\t-y<selector>           - set RSA selector (DEFAULT: default)\n");
  fprintf(FDLOG, "\t-Y<selector>           - set Ed25519 selector (DEFAULT: default)\n");
  fprintf(
      FDLOG,
      "\t-z<hash>               - set signature algorithm type (1=rsa-sha1, 2=rsa-sha256, 3=both, "
      "4=ed25519, 5=hybrid)\n");
}

int main(int argc, char *argv[])
{
  int n;
  const char *RSAKeyFile = "rsa.pem";
  const char *ECCKeyFile = "ed25519.pem";
  const char *MsgFile = "test.msg";
  const char *OutFile = "signed.msg";
  int nKeyLen;
  char RSAPrivKey[4196];  // storge for private key FILE including header and DER envelope
  char ECCPrivKey[128];
  char Buffer[1000];
  int BufLen;
  char szSignature[8192];
  time_t t;
  DKIMContext ctxt;
  DKIMSignOptions opts = {0};

  opts.nHash = DKIM_HASH_SHA256;  // default

  time(&t);

  opts.nCanon = DKIM_SIGN_RELAXED;
  opts.nIncludeBodyLengthTag = 0;
  opts.nIncludeQueryMethod = 0;
  opts.nIncludeTimeStamp = 0;
  opts.expireTime = t + 604800;  // expires in 1 week
  strcpy(opts.szSelector, MYRSASELECTOR);
  strcpy(opts.szSelectorE, MYECCSELECTOR);
  strcpy(opts.szDomain, MYDOMAIN);
  strcpy(opts.szIdentity, MYIDENTITY);
  opts.pfnHeaderCallback = SignThisHeader;
  strcpy(opts.szRequiredHeaders, "NonExistant");
  opts.nIncludeCopiedHeaders = 0;

  int nArgParseState = 0;
  bool bSign = true;
  bool bRes = false;

  if (argc < 2) {
    usage();
    exit(1);
  }

  for (n = 1; n < argc; n++) {
    if (argv[n][0] == '-' && strlen(argv[n]) > 1) {
      switch (argv[n][1]) {
        case 'c':  // canonicalization
          if (argv[n][2] == 'r') {
            opts.nCanon = DKIM_SIGN_RELAXED;
          } else if (argv[n][2] == 's') {
            opts.nCanon = DKIM_SIGN_SIMPLE;
          } else if (argv[n][2] == 't') {
            opts.nCanon = DKIM_SIGN_RELAXED_SIMPLE;
          } else if (argv[n][2] == 'u') {
            opts.nCanon = DKIM_SIGN_SIMPLE_RELAXED;
          }
          break;
        case 'd': strncpy(opts.szDomain, (const char *)(argv[n] + 2), sizeof(opts.szDomain) - 1); break;
        case 'l':  // body length tag
          opts.nIncludeBodyLengthTag = 1;
          break;
        case 'h': usage(); return 0;
        case 'i':  // identity
          if (argv[n][2] == '-') {
            opts.szIdentity[0] = '\0';
          } else {
            strncpy(opts.szIdentity, argv[n] + 2, sizeof(opts.szIdentity) - 1);
          }
          break;
        case 'q':  // query method tag
          opts.nIncludeQueryMethod = 1;
          break;
        case 's':  // sign with and use potentially Ed25519 private key
          bSign = true;
          break;
        case 't':  // timestamp tag
          opts.nIncludeTimeStamp = 1;
          break;
        case 'v':  // verify
          bSign = false;
          break;
        case 'V':  // verify and write result to OutFile
          bSign = false;
          bRes = true;
          break;
        case 'x':  // expire time
          if (argv[n][2] == '-') {
            opts.expireTime = 0;
          } else {
            opts.expireTime = t + atoi(argv[n] + 2);
          }
          break;
        case 'y': strncpy(opts.szSelector, argv[n] + 2, sizeof(opts.szSelector) - 1); break;
        case 'Y': strncpy(opts.szSelectorE, argv[n] + 2, sizeof(opts.szSelectorE) - 1); break;
        case 'z':  // sign w/ sha1, sha256, both, ed25519, hybrid
          opts.nHash = atoi(&argv[n][2]);
      }
    } else {
      switch (nArgParseState) {
        case 0: MsgFile = argv[n]; break;
        case 1: RSAKeyFile = argv[n]; break;
        case 2: OutFile = argv[n]; break;
        case 3: ECCKeyFile = argv[n]; break;
      }
      nArgParseState++;
    }
  }

  /** Go for DKIM signing ... **/

  if (bSign) {
    if (opts.nHash != 4) {
      FILE *RSAPrivKeyFP = fopen(RSAKeyFile, "r");
      if (RSAPrivKeyFP == NULL) {
#ifdef SHOWLOG
        fprintf(FDLOG, " qmail-dkim: can't open private key file (%s) \n", RSAKeyFile);
#endif
        exit(1);
      }
      nKeyLen = fread(
          RSAPrivKey,
          1,
          sizeof(RSAPrivKey),
          RSAPrivKeyFP);  // we read sizeof(RSAPrivKey) members with size of 1 byte each; sigh
#ifdef SHOWLOG
      fprintf(FDLOG, " qmail-dkim: private key file (%s) - length %i \n", RSAKeyFile, nKeyLen);
#endif
      if (nKeyLen >= sizeof(RSAPrivKey)) { /* (TC9) on return, we get the number of members read!  */
#ifdef SHOWLOG
        fprintf(
            FDLOG,
            " qmail-dkim: private key buffer isn't big enough for private key length %i \n",
            nKeyLen);
#endif
        exit(1);
      }
      RSAPrivKey[nKeyLen] = '\0';
      fclose(RSAPrivKeyFP);
    }

    /** Ed25519 signing **/

    if (opts.nHash == 4 || opts.nHash == 5) {
      FILE *ECCPrivKeyFP = fopen(ECCKeyFile, "r");
      if (ECCPrivKeyFP == NULL) {
#ifdef SHOWLOG
        fprintf(FDLOG, " qmail-dkim: can't open Ed25519 private key file (%s) \n", ECCKeyFile);
#endif
        exit(1);
      }
      nKeyLen = fread(ECCPrivKey, 1, sizeof(ECCPrivKey), ECCPrivKeyFP);
#ifdef SHOWLOG
      fprintf(FDLOG, " qmail-dkim: Ed25519 private key file (%s) - length %i \n", ECCKeyFile, nKeyLen);
#endif
      if (nKeyLen >= sizeof(ECCPrivKey)) {
#ifdef SHOWLOG
        fprintf(
            FDLOG,
            " qmail-dkim: ECC private key buffer isn't big enough for ECC private key length %i \n",
            nKeyLen);
#endif
        exit(1);
      }
      ECCPrivKey[nKeyLen] = '\0';
      fclose(ECCPrivKeyFP);
    }

    /** Input message for signing **/

    FILE *MsgFP = fopen(MsgFile, "rb");
    if (MsgFP == NULL) {
#ifdef SHOWLOG
      fprintf(FDLOG, " qmail-dkim: can't open msg file (%s) \n", MsgFile);
#endif
      exit(1);
    }

    n = DKIMSignInit(&ctxt, &opts);

    while (1) {
      BufLen = fread(Buffer, 1, sizeof(Buffer), MsgFP);
      if (BufLen > 0) {
        DKIMSignProcess(&ctxt, Buffer, BufLen);
      } else {
        break;
      }
    }
    fclose(MsgFP);

    char *pSig = NULL;

    /** Do the actual signing **/

    n = DKIMSignGetSig2(&ctxt, RSAPrivKey, ECCPrivKey, &pSig);

    strcpy(szSignature, pSig);

    DKIMSignFree(&ctxt);

    FILE *in = fopen(MsgFile, "rb");
    FILE *out = fopen(OutFile, "wb+");

#ifdef SHOWLOG
    fprintf(FDLOG, " outfile written %s \n", OutFile);
#endif

    fwrite(szSignature, 1, strlen(szSignature), out);
    fwrite("\r\n", 1, 2, out);

    while (1) {
      BufLen = fread(Buffer, 1, sizeof(Buffer), in);
      if (BufLen > 0) {
        fwrite(Buffer, 1, BufLen, out);
      } else {
        break;
      }
    }
    fclose(in);

  }

  /** Now go for verification **/

  else
  {
    FILE *in = fopen(MsgFile, "rb");
    if (in == NULL) {
      //#ifdef SHOWLOG
      fprintf(FDLOG, " qmail-dkim: can't open input file\n");
      //#endif
      return 0;  // bad option --  no CTX set up yet
    }

    DKIMVerifyOptions vopts = {0};
    vopts.pfnSelectorCallback = NULL;  //SelectorCallback;

    n = DKIMVerifyInit(&ctxt, &vopts);

    while (1) {
      BufLen = fread(Buffer, 1, sizeof(Buffer), in);
      if (BufLen > 0) {
        DKIMVerifyProcess(&ctxt, Buffer, BufLen);
      } else {
        break;
      }
    }

    n = DKIMVerifyResults(&ctxt);

    int nSigCount = 0;
    DKIMVerifyDetails *pDetails;
    char szPolicy[512];

    n = DKIMVerifyGetDetails(&ctxt, &nSigCount, &pDetails, szPolicy);

    for (int i = 0; i < nSigCount; i++) {
      const char s[] = "pass";
      const char f[] = "fail";
      const char *error = DKIM_ErrorResult(pDetails[i].nResult);
      if (!bRes) fprintf(FDLOG, " Signature #%d: ", i + 1);
      if (pDetails[i].nResult >= 0) {
        if (bRes) {
          _DKIM_ReportResult(OutFile, s, 0);
        } else
          printf(" Pass\n");
      } else {  // fail
        if (bRes) {
          _DKIM_ReportResult(OutFile, f, error);
        } else
          printf(" Fail %s \n", error);
      }
    }
    DKIMVerifyFree(&ctxt);
  }
  return 0;
}