path: root/src/qmail-dkverify.c

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/socket.h>
#include "sig.h"
#include "stralloc.h"
#include "buffer.h"
#include "error.h"
#include "auto_qmail.h"
#include "auto_queue.h"
#include "str.h"
#include "exit.h"
#include "uint_t.h"
#include "fd.h"
#include "open.h"
#include "fmt.h"
#include "fmtqfn.h"
#include "readwrite.h"
#include "getln.h"
#include "qmail.h"
#include "wait.h"
#include "byte.h"
#include "case.h"
#include "control.h"
#include "pathexec.h"
#include "env.h"
#include "logmsg.h"

#define WHO "qmail-dkverify"

/** @file  qmail-dkverify.c 
    @brief stub routine for DKIM signature verification and indication in received message

    Steps:
    ------
    a) Store message with CRLF
    b) Get DKIM signature from message - if given:
    c)   Call qmail-dkim for verification
    d)   Include results as appended header
    e) Queue the message for processing

  */

char inbuf[BUFSIZE_LINE];  
buffer bi = BUFFER_INIT(read,0,inbuf,sizeof(inbuf));    // read buffer 
char outbuf[BUFSIZE_MESS];
buffer bo = BUFFER_INIT(write,1,outbuf,sizeof(outbuf)); // output message 

void die(int e) { _exit(e); }
void die_pipe(char *fn) { unlink(fn); die(54); };
void die_write(char *fn) { unlink(fn); die(62); };
void die_read() { die(54); };
void out(char *s) { if (buffer_puts(&bo,s) == -1) _exit(111); }
void zero() { if (buffer_put(&bo,"\0",1) == -1) _exit(111); }
void zerodie() { zero(); buffer_flush(&bo); _exit(111); }

void temp_nomem() 
{
  out("ZOut of memory. (#4.3.0)\n");
  zerodie();
}
void temp_chdir() 
{
  out("ZUnable to switch to target directory. (#4.3.0)\n");
  zerodie();
}
void temp_create() 
{
  out("ZUnable to create DKIM stage file. (#4.3.0)\n");
  zerodie();
}
void temp_unlink() 
{
  out("ZUnable to unlink DKIM stage file. (#4.3.0)\n");
  zerodie();
}
void temp_read()
{
  out("ZUnable to read message. (#4.3.0)\n");
  zerodie();
}
void temp_socket()
{
  out("ZUnable to crate socket pair. (#4.3.0)\n");
  zerodie();
}
void temp_control()
{
  out("ZUnable to read control files. (#4.3.0)\n");
  zerodie();
}

static stralloc me = {0};
static stralloc senddomain = {0};
static stralloc dkheader = {0};
static stralloc fndkin = {0};
static stralloc fndkout = {0};
static stralloc result = {0};
 
void fnmake_dkim(unsigned long id) 
{ 
  fndkin.len = fmtqfn(fndkin.s,"queue/dkim/",id,1); 
  id += id;
  fndkout.len = fmtqfn(fndkout.s,"queue/dkim/",id,1); 
} 

void dkim_stage()
{
  int r;
  int fd;
  int in, out;
  struct stat st;
  char tmpbuf[BUFSIZE_MESS + 2];

  if (chdir(auto_queue) == -1) temp_chdir();

  if (!stralloc_ready(&fndkin,FMTQFN)) temp_nomem();
  if (!stralloc_ready(&fndkout,FMTQFN)) temp_nomem();

  fnmake_dkim(getpid());  // pre-staging
  fd = open_excl(fndkin.s);
  if (fd == -1) die_write(fndkin.s);

  buffer_init(&bi,read,0,inbuf,sizeof(inbuf));
  buffer_init(&bo,write,fd,outbuf,sizeof(outbuf));

  while ((r = buffer_get(&bi,inbuf,sizeof(inbuf)))) { // read into buffer
    if (r == -1) temp_read();

    for (in = out = 0; in < r; in++) {                // reconstruct CRLF (ok)
      if (inbuf[in] != '\n') {
        tmpbuf[out++] = inbuf[in];
      } else {
        tmpbuf[out++] = '\r';
        tmpbuf[out++] = '\n';
      }
    }
    if (out) buffer_put(&bo,tmpbuf,out);
  }

  if (buffer_flush(&bo) == -1) die(51);
  if (fstat(fd,&st) == -1) die_write(fndkin.s);
  if (fsync(fd) == -1) die_write(fndkin.s);
  if (close(fd) == -1) die_write(fndkin.s);
}

int mess_dkim()
{
  stralloc line = {0};
  int match;
  int fd;
  int at = 0;
  int ket = 0;
  int end = 0;
  int len = 0;
  int r = 0;
  int i;

  fd = open_read(fndkin.s);
  if (fd == -1) die_read(); 
  buffer_init(&bi,read,fd,inbuf,sizeof(inbuf));

  if (!stralloc_copys(&senddomain,"")) temp_nomem();
  
  for (;;) { 
    if (getln(&bi,&line,&match,'\n') == -1) temp_read();
    if (case_starts(line.s,"DKIM-Signature: ")) r = 1;
    if (r == 1) { 
      if (case_starts(line.s,"From: ")) {        // fallback: From
        at = str_chr(line.s,'@');
        if (at < line.len) {
          end = str_chr(line.s,'\n');            // From: user@senddomain\n
          ket = str_chr(line.s,'>');             // From: User <user@senddomain>
          len = (ket < end) ? ket : end;
          len -= at - 1;                         // From: User <user@>
          if (len > 0) {
            if (!stralloc_copyb(&senddomain,line.s + at + 1,len)) temp_nomem();
          } else
            if (!stralloc_copys(&senddomain,"unknown")) temp_nomem();
          r = 2;
        }
      }
      for (i = 0; i < line.len; ++i) {           // d=domain.tld
        if (*(line.s + i) == '=' && *(line.s + i - 1) == 'd') {
          ++i;                                   // gotcha
          while (*(line.s + i) != ';') {
            if (!stralloc_catb(&senddomain,line.s + i,1)) temp_nomem();
            i++;
            r = 3;
          }
        }
      }
    }
    if (r >= 2 || !match) break;
  }
  if (senddomain.len < 2) 
    if (!stralloc_copys(&senddomain,"unknown")) temp_nomem();
  if (!stralloc_0(&senddomain)) temp_nomem();

  return r;
}

int dkim_verify()
{
  int child;
  int wstat;
  char *(args[6]);
  int r = -1;

  args[0] = "qmail-dkim";
  args[1] = "-V";
  args[2] = fndkin.s;
  args[3] = "none";
  args[4] = fndkout.s;
  args[5] = 0;

  if (!(child = fork())) { 
    pathexec(args);
    if (errno) _exit(111);
    _exit(100);
  }

  wait_pid(&wstat,child);
  if (wait_crashed(wstat)) return 1;

  switch (r = wait_exitcode(wstat)) {
    case 10: return 1;
    default: return 0;
  }
}

int dkim_result(const char *me)
{
  int max = 64;
  int fd;
  int j;
  char ch;
  int r = 0; 

  if (!stralloc_copys(&result,"")) temp_nomem();

  if ((fd = open_read(fndkout.s)) == -1) return 0; // nothing to read
  while ((r = read(fd,inbuf,sizeof(inbuf))) > 0) 
    if (!stralloc_catb(&result,inbuf,r)) temp_nomem();

  if (!stralloc_0(&result)) temp_nomem();

  if (result.len > 2) {
    if (case_starts(result.s,"pass")) r = 0;
    if (case_starts(result.s,"fail")) r = 35;
  } else
    if (!stralloc_copys(&result,"unknown")) temp_nomem();

  if (!stralloc_copys(&dkheader,"X-Authentication-Results: ")) temp_nomem();
  if (!stralloc_cats(&dkheader,senddomain.s)) temp_nomem();
  if (!stralloc_cats(&dkheader,"; dkim=")) temp_nomem();

  for (j = 0; j < result.len; j++) {
    ch = result.s[j];
    if (ch == '\r' || ch == '\n' || ch == '\0') continue;
    if (j <= max) if (!stralloc_catb(&dkheader,&ch,1)) temp_nomem();
    if (ch == ' ' && (j > max)) {
      if (!stralloc_cats(&dkheader,"\n  ")) temp_nomem();
      max += max;
    }
  }

  if (!stralloc_cats(&dkheader,"; ")) temp_nomem();
  if (!stralloc_cats(&dkheader,me)) temp_nomem();
  if (!stralloc_0(&dkheader)) temp_nomem();

  return r;
}

int qmail_queue() 
{
  int fd;
  int r;
  int child;
  int wstat;
  int pi[2];
  char *(args[2]);
  char tmpbuf[BUFSIZE_MESS + 2];
  int in, out;

  if (pipe(pi) == -1) die_pipe(fndkin.s);

  args[0] = "qmail-queue";
  args[1] = 0;

  switch (child = vfork()) {
    case -1: 
      close(pi[0]); close(pi[1]); 
      die_write(fndkin.s); 
    case  0: 
      close(pi[1]);
      if (fd_move(0,pi[0]) == -1) die_pipe(fndkin.s);
      sig_pipedefault();
      pathexec(args);
      if (errno) _exit(111);
      _exit(100);
  }
  close(pi[0]);

  buffer_init(&bo,write,pi[1],outbuf,sizeof(outbuf));

  if (dkheader.len > 2) {                        // write DKIM header
    if (buffer_put(&bo,dkheader.s,dkheader.len - 1) == -1) die_write(fndkout.s);
    if (buffer_put(&bo,"\n",1) == -1) die_write(fndkout.s);
    if (buffer_flush(&bo) == -1) die_write(fndkout.s);
  }

  /* read/write message; we need to remove the CR (ok) */

  if ((fd = open_read(fndkin.s)) == -1) die_read();
  while ((r = read(fd,tmpbuf,sizeof(tmpbuf))) > 0) {
    for (in = 0, out = 0; in < r; ++in) {
      if (tmpbuf[in] == '\r') {
        buffer_put(&bo,&tmpbuf[out],in - out);
        out = in + 1;                            // \n to follow
      }
    }
  }

  if (buffer_flush(&bo) == -1) die_write(fndkin.s);
  close(pi[1]);

  wait_pid(&wstat,child);
  if (wait_crashed(wstat)) return 1;

  switch (r = wait_exitcode(wstat)) {
    case 10: return 1;
    default: return 0;
  }
}

void dkim_unlink()
{
  if (unlink(fndkin.s) == -1)
    if (errno != ENOENT) temp_unlink();
  if (unlink(fndkout.s) == -1)
    if (errno != ENOENT) temp_unlink();
}

int main()
{
  int r = 0;
  char *mode = 0;

  umask(033);
  if (chdir(auto_qmail) == -1) temp_chdir();
  if (control_init() == -1) temp_control();
  if (control_readline(&me,"control/me") == -1) temp_control();
  if (!stralloc_0(&me)) temp_nomem();

  dkim_stage();

  if (mess_dkim()) {
    dkim_verify(); 
    r = dkim_result(me.s);
  }

  /* we are done: call qmail-queue */

  mode = env_get("DKIM");
  if (!mode || *mode != '+') r = 0;

  qmail_queue();
  dkim_unlink();

  _exit(r);
}