yaid.c: Beef up `reply' with an extra token argument.

[yaid] / yaid.c

/* -*-c-*-
 *
 * Main daemon
 *
 * (c) 2012 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Yet Another Ident Daemon (YAID).
 *
 * YAID 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.
 *
 * YAID 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 YAID; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include "yaid.h"

/*----- Data structures ---------------------------------------------------*/

struct listen {
  const struct addrops *ao;
  sel_file f;
};

#define WRBUFSZ 1024
struct writebuf {
  size_t o, n;
  sel_file wr;
  void (*func)(int, void *);
  void *p;
  unsigned char buf[WRBUFSZ];
};

struct proxy {
  struct client *c;
  int fd;
  conn cn;
  selbuf b;
  struct writebuf wb;
  char nat[ADDRLEN];
};

struct client {
  selbuf b;
  int fd;
  struct query q;
  struct listen *l;
  struct writebuf wb;
  struct proxy *px;
};

/*----- Static variables --------------------------------------------------*/

static sel_state sel;

static policy_v policy = DA_INIT;
static fwatch polfw;

static unsigned char tokenbuf[4096];
static size_t tokenptr = sizeof(tokenbuf);
static int randfd;

/*----- Main code ---------------------------------------------------------*/

void logmsg(const struct query *q, int prio, const char *msg, ...)
{
  va_list ap;
  dstr d = DSTR_INIT;

  va_start(ap, msg);
  if (q) {
    dputsock(&d, q->ao, &q->s[L]);
    dstr_puts(&d, " <-> ");
    dputsock(&d, q->ao, &q->s[R]);
    dstr_puts(&d, ": ");
  }
  dstr_vputf(&d, msg, &ap);
  va_end(ap);
  fprintf(stderr, "yaid: %s\n", d.buf);
  dstr_destroy(&d);
}

static void write_out(int fd, unsigned mode, void *p)
{
  ssize_t n;
  struct writebuf *wb = p;

  if ((n = write(fd, wb->buf + wb->o, wb->n)) < 0) {
    if (errno == EAGAIN || errno == EWOULDBLOCK) return;
    wb->n = 0;
    sel_rmfile(&wb->wr);
    wb->func(errno, wb->p);
  }
  wb->o += n;
  wb->n -= n;
  if (!wb->n) {
    wb->o = 0;
    sel_rmfile(&wb->wr);
    wb->func(0, wb->p);
  }
}

static int queue_write(struct writebuf *wb, const void *p, size_t n)
{
  if (!n) return (0);
  if (wb->n - wb->o + n > WRBUFSZ) return (-1);
  if (wb->o) {
    memmove(wb->buf, wb->buf + wb->o, wb->n);
    wb->o = 0;
  }
  memcpy(wb->buf + wb->n, p, n);
  if (!wb->n) {
    sel_addfile(&wb->wr);
    sel_force(&wb->wr);
  }
  wb->n += n;
  return (0);
}

static void free_writebuf(struct writebuf *wb)
  { if (wb->n) sel_rmfile(&wb->wr); }

static void init_writebuf(struct writebuf *wb,
			  int fd, void (*func)(int, void *), void *p)
{
  sel_initfile(&sel, &wb->wr, fd, SEL_WRITE, write_out, wb);
  wb->func = func;
  wb->p = p;
  wb->n = wb->o = 0;
}

static void cancel_proxy(struct proxy *px)
{
  if (px->fd == -1)
    conn_kill(&px->cn);
  else {
    close(px->fd);
    selbuf_destroy(&px->b);
    free_writebuf(&px->wb);
  }
  selbuf_enable(&px->c->b);
  px->c->px = 0;
  xfree(px);
}

static void disconnect_client(struct client *c)
{
  close(c->fd);
  selbuf_destroy(&c->b);
  free_writebuf(&c->wb);
  if (c->px) cancel_proxy(c->px);
  xfree(c);
}

static void done_client_write(int err, void *p)
{
  struct client *c = p;

  if (!err)
    selbuf_enable(&c->b);
  else {
    logmsg(&c->q, LOG_ERR, "failed to send reply: %s", strerror(err));
    disconnect_client(c);
  }
}

static void write_to_client(struct client *c, const char *fmt, ...)
{
  va_list ap;
  char buf[WRBUFSZ];
  ssize_t n;

  va_start(ap, fmt);
  n = vsnprintf(buf, sizeof(buf), fmt, ap);
  if (n < 0) {
    logmsg(&c->q, LOG_ERR, "failed to format output: %s", strerror(errno));
    disconnect_client(c);
    return;
  } else if (n > sizeof(buf)) {
    logmsg(&c->q, LOG_ERR, "output too long for client send buffer");
    disconnect_client(c);
    return;
  }

  selbuf_disable(&c->b);
  if (queue_write(&c->wb, buf, n)) {
    logmsg(&c->q, LOG_ERR, "write buffer overflow");
    disconnect_client(c);
  }
}

static void reply(struct client *c, const char *ty,
		  const char *tok0, const char *tok1)
{
  write_to_client(c, "%u,%u:%s:%s%s%s\r\n",
		  c->q.s[L].port, c->q.s[R].port, ty,
		  tok0, tok1 ? ":" : "", tok1 ? tok1 : "");
}

const char *const errtok[] = {
#define DEFTOK(err, tok) tok,
  ERROR(DEFTOK)
#undef DEFTOK
};

static void reply_error(struct client *c, unsigned err)
{
  assert(err < E_LIMIT);
  reply(c, "ERROR", errtok[err], 0);
}

static void skipws(const char **pp)
  { while (isspace((unsigned char )**pp)) (*pp)++; }

static int idtoken(const char **pp, char *q, size_t n)
{
  const char *p = *pp;

  skipws(&p);
  n--;
  for (;;) {
    if (*p == ':' || *p <= 32 || *p >= 127) break;
    if (!n) return (-1);
    *q++ = *p++;
    n--;
  }
  *q++ = 0;
  *pp = p;
  return (0);
}

static int unum(const char **pp, unsigned *ii, unsigned min, unsigned max)
{
  char *q;
  unsigned long i;
  int e;

  skipws(pp);
  if (!isdigit((unsigned char)**pp)) return (-1);
  e = errno; errno = 0;
  i = strtoul(*pp, &q, 10);
  if (errno) return (-1);
  *pp = q;
  errno = e;
  if (i < min || i > max) return (-1);
  *ii = i;
  return (0);
}

static void proxy_line(char *line, size_t sz, void *p)
{
  struct proxy *px = p;
  char buf[1024];
  const char *q = line;
  unsigned lp, rp;

  while (sz && isspace((unsigned char)line[sz - 1])) sz--;
  printf("received proxy line from %s: %s\n", px->nat, line);

  if (unum(&q, &lp, 1, 65535)) goto syntax;
  skipws(&q); if (*q != ',') goto syntax; q++;
  if (unum(&q, &rp, 1, 65535)) goto syntax;
  skipws(&q); if (*q != ':') goto syntax; q++;
  if (lp != px->c->q.u.nat.port || rp != px->c->q.s[R].port) goto syntax;
  if (idtoken(&q, buf, sizeof(buf))) goto syntax;
  skipws(&q); if (*q != ':') goto syntax; q++;
  if (strcmp(buf, "ERROR") == 0) {
    skipws(&q);
    logmsg(&px->c->q, LOG_ERR, "proxy error from %s: %s", px->nat, q);
    reply(px->c, "ERROR", q, 0);
  } else if (strcmp(buf, "USERID") == 0) {
    if (idtoken(&q, buf, sizeof(buf))) goto syntax;
    skipws(&q); if (*q != ':') goto syntax; q++;
    skipws(&q);
    logmsg(&px->c->q, LOG_ERR, "user `%s'; proxy = %s, os = %s",
	   q, px->nat, buf);
    reply(px->c, "USERID", buf, q);
  } else
    goto syntax;
  goto done;

syntax:
  logmsg(&px->c->q, LOG_ERR, "failed to parse response from %s", px->nat);
  reply_error(px->c, E_UNKNOWN);
done:
  cancel_proxy(px);
}

static void done_proxy_write(int err, void *p)
{
  struct proxy *px = p;

  if (err) {
    logmsg(&px->c->q, LOG_ERR, "failed to proxy query to %s: %s",
	   px->nat, strerror(errno));
    reply_error(px->c, E_UNKNOWN);
    cancel_proxy(px);
    return;
  }
  selbuf_enable(&px->b);
}

static void proxy_connected(int fd, void *p)
{
  struct proxy *px = p;
  char buf[16];
  int n;

  if (fd < 0) {
    logmsg(&px->c->q, LOG_ERR,
	   "failed to make %s proxy connection to %s: %s",
	   px->c->l->ao->name, px->nat, strerror(errno));
    reply_error(px->c, E_UNKNOWN);
    cancel_proxy(px);
    return;
  }

  px->fd = fd;
  selbuf_init(&px->b, &sel, fd, proxy_line, px);
  selbuf_setsize(&px->b, 1024);
  selbuf_disable(&px->b);
  init_writebuf(&px->wb, fd, done_proxy_write, px);

  n = sprintf(buf, "%u,%u\r\n", px->c->q.u.nat.port, px->c->q.s[R].port);
  queue_write(&px->wb, buf, n);
}

static void proxy_query(struct client *c)
{
  struct socket s;
  struct sockaddr_storage ss;
  size_t ssz;
  struct proxy *px;
  int fd;

  px = xmalloc(sizeof(*px));
  inet_ntop(c->q.ao->af, &c->q.u.nat.addr, px->nat, sizeof(px->nat));

  if ((fd = socket(c->q.ao->af, SOCK_STREAM, 0)) < 0) {
    logmsg(&c->q, LOG_ERR, "failed to make %s socket for proxy: %s",
	   c->l->ao->name, strerror(errno));
    goto err_0;
  }

  if (fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0)) {
    logmsg(&c->q, LOG_ERR, "failed to set %s proxy socket nonblocking: %s",
	   c->l->ao->name, strerror(errno));
    goto err_1;
  }

  s = c->q.u.nat;
  s.port = 113;
  c->l->ao->socket_to_sockaddr(&s, &ss, &ssz);
  selbuf_disable(&c->b);
  if (conn_init(&px->cn, &sel, fd, (struct sockaddr *)&ss, ssz,
		proxy_connected, px)) {
    logmsg(&c->q, LOG_ERR, "failed to make %s proxy connection to %s: %s",
	   c->l->ao->name, px->nat, strerror(errno));
    goto err_2;
  }

  c->px = px; px->c = c;
  px->fd = -1;
  return;

err_2:
  selbuf_enable(&c->b);
err_1:
  close(px->fd);
err_0:
  xfree(px);
  reply_error(c, E_UNKNOWN);
}

static const struct policy default_policy = POLICY_INIT(A_NAME);

static void user_token(char *p)
{
  static const char tokmap[64] =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789.-";
  unsigned a = 0;
  unsigned b = 0;
  int i;
#define TOKENSZ 8

  if (tokenptr + TOKENSZ >= sizeof(tokenbuf)) {
    if (read(randfd, tokenbuf, sizeof(tokenbuf)) < sizeof(tokenbuf))
      die(1, "unexpected short read or error from `/dev/urandom'");
    tokenptr = 0;
  }

  for (i = 0; i < TOKENSZ; i++) {
    a = (a << 8) | tokenbuf[tokenptr++]; b += 8;
    while (b >= 6) {
      b -= 6;
      *p++ = tokmap[(a >> b) & 0x3f];
    }
  }
  if (b)
    *p++ = tokmap[(a << (6 - b)) & 0x3f];
  *p++ = 0;
}

static void client_line(char *line, size_t len, void *p)
{
  struct client *c = p;
  const char *q;
  struct passwd *pw = 0;
  const struct policy *pol;
  dstr d = DSTR_INIT;
  struct policy upol = POLICY_INIT(A_LIMIT);
  struct policy_file pf;
  char buf[16];
  int i;

  c->q.s[L].port = c->q.s[R].port = 0;
  if (!line) {
    disconnect_client(c);
    return;
  }

  if (fwatch_update(&polfw, "yaid.policy")) {
    logmsg(0, LOG_INFO, "reload master policy file `%s'", "yaid.policy");
    load_policy_file("yaid.policy", &policy);
  }

  q = line;
  if (unum(&q, &c->q.s[L].port, 1, 65535)) goto bad;
  skipws(&q); if (*q != ',') goto bad; q++;
  if (unum(&q, &c->q.s[R].port, 1, 65535)) goto bad;
  skipws(&q); if (*q) goto bad;

  identify(&c->q);
  switch (c->q.resp) {
    case R_UID:
      if ((pw = getpwuid(c->q.u.uid)) == 0) {
	logmsg(&c->q, LOG_ERR, "no passwd entry for user %d", c->q.u.uid);
	reply_error(c, E_NOUSER);
	return;
      }
      break;
    case R_NAT:
      proxy_query(c);
      return;
    case R_ERROR:
      /* Should already be logged. */
      reply_error(c, c->q.u.error);
      return;
    default:
      abort();
  }

  for (i = 0; i < DA_LEN(&policy); i++) {
    pol = &DA(&policy)[i];
    if (!match_policy(pol, &c->q)) continue;
    if (pol->act.act != A_USER)
      goto match;
    DRESET(&d);
    dstr_putf(&d, "%s/.yaid.policy", pw->pw_dir);
    if (open_policy_file(&pf, d.buf, "user policy file", &c->q))
      continue;
    while (!read_policy_file(&pf)) {
      if (pf.lno > 100) {
	logmsg(&c->q, LOG_ERR, "%s:%d: user policy file too long",
	       pf.name, pf.lno);
	break;
      }
      if (!match_policy(&pf.p, &c->q)) continue;
      if (!(pol->act.u.user & (1 << pf.p.act.act))) {
	logmsg(&c->q, LOG_ERR,
	       "%s:%d: user action forbidden by global policy",
	       pf.name, pf.lno);
	continue;
      }
      upol = pf.p; pol = &upol;
      init_policy(&pf.p);
      close_policy_file(&pf);
      goto match;
    }
    close_policy_file(&pf);
  }
  pol = &default_policy;

match:
  DDESTROY(&d);
  switch (pol->act.act) {
    case A_NAME:
      logmsg(&c->q, LOG_INFO, "user `%s' (%d)", pw->pw_name, c->q.u.uid);
      reply(c, "USERID", "UNIX", pw->pw_name);
      break;
    case A_TOKEN:
      user_token(buf);
      logmsg(&c->q, LOG_INFO, "user `%s' (%d); token = %s",
	     pw->pw_name, c->q.u.uid, buf);
      reply(c, "USERID", "OTHER", buf);
      break;
    case A_DENY:
      logmsg(&c->q, LOG_INFO, "user `%s' (%d); denying",
	     pw->pw_name, c->q.u.uid);
      break;
    case A_HIDE:
      logmsg(&c->q, LOG_INFO, "user `%s' (%d); hiding",
	     pw->pw_name, c->q.u.uid);
      reply_error(c, E_HIDDEN);
      break;
    case A_LIE:
      logmsg(&c->q, LOG_INFO, "user `%s' (%d); lie = `%s'",
	     pw->pw_name, c->q.u.uid, pol->act.u.lie);
      reply(c, "USERID", "UNIX", pol->act.u.lie);
      break;
    default:
      abort();
  }

  free_policy(&upol);
  return;

bad:
  logmsg(&c->q, LOG_ERR, "failed to parse query from client");
  disconnect_client(c);
}

static void accept_client(int fd, unsigned mode, void *p)
{
  struct listen *l = p;
  struct client *c;
  struct sockaddr_storage ssr, ssl;
  size_t ssz = sizeof(ssr);
  int sk;

  if ((sk = accept(fd, (struct sockaddr *)&ssr, &ssz)) < 0) {
    if (errno != EAGAIN && errno == EWOULDBLOCK) {
      logmsg(0, LOG_ERR, "failed to accept incoming %s connection: %s",
	     l->ao->name, strerror(errno));
    }
    return;
  }

  c = xmalloc(sizeof(*c));
  c->l = l;
  c->q.ao = l->ao;
  l->ao->sockaddr_to_addr(&ssr, &c->q.s[R].addr);
  ssz = sizeof(ssl);
  if (getsockname(sk, (struct sockaddr *)&ssl, &ssz)) {
    logmsg(0, LOG_ERR,
	   "failed to read local address for incoming %s connection: %s",
	   l->ao->name, strerror(errno));
    close(sk);
    xfree(c);
    return;
  }
  l->ao->sockaddr_to_addr(&ssl, &c->q.s[L].addr);
  c->q.s[L].port = c->q.s[R].port = 0;

  /* logmsg(&c->q, LOG_INFO, "accepted %s connection", l->ao->name); */

  selbuf_init(&c->b, &sel, sk, client_line, c);
  selbuf_setsize(&c->b, 1024);
  c->fd = sk;
  c->px = 0;
  init_writebuf(&c->wb, sk, done_client_write, c);
}

static int make_listening_socket(const struct addrops *ao, int port)
{
  int fd;
  int yes = 1;
  struct socket s;
  struct sockaddr_storage ss;
  struct listen *l;
  size_t ssz;

  if ((fd = socket(ao->af, SOCK_STREAM, 0)) < 0) {
    if (errno == EAFNOSUPPORT) return (-1);
    die(1, "failed to create %s listening socket: %s",
	ao->name, strerror(errno));
  }
  setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(yes));
  s.addr = *ao->any;
  s.port = port;
  ao->socket_to_sockaddr(&s, &ss, &ssz);
  if (ao->init_listen_socket(fd)) {
    die(1, "failed to initialize %s listening socket: %s",
	ao->name, strerror(errno));
  }
  if (bind(fd, (struct sockaddr *)&ss, ssz)) {
    die(1, "failed to bind %s listening socket: %s",
	ao->name, strerror(errno));
  }
  if (fdflags(fd, O_NONBLOCK, O_NONBLOCK, 0, 0)) {
    die(1, "failed to set %s listening socket nonblocking: %s",
	ao->name, strerror(errno));
  }
  if (listen(fd, 5))
    die(1, "failed to listen for %s: %s", ao->name, strerror(errno));

  l = xmalloc(sizeof(*l));
  l->ao = ao;
  sel_initfile(&sel, &l->f, fd, SEL_READ, accept_client, l);
  sel_addfile(&l->f);

  return (0);
}

int main(int argc, char *argv[])
{
  int port = 113;
  const struct addrops *ao;
  int any = 0;

  ego(argv[0]);

  fwatch_init(&polfw, "yaid.policy");
  init_sys();
  if (load_policy_file("yaid.policy", &policy))
    exit(1);
  { int i;
    for (i = 0; i < DA_LEN(&policy); i++)
      print_policy(&DA(&policy)[i]);
  }

  if ((randfd = open("/dev/urandom", O_RDONLY)) < 0) {
    die(1, "failed to open `/dev/urandom' for reading: %s",
	strerror(errno));
  }

  sel_init(&sel);
  for (ao = addroptab; ao->name; ao++)
    if (!make_listening_socket(ao, port)) any = 1;
  if (!any)
    die(1, "no IP protocols supported");

  for (;;)
    if (sel_select(&sel)) die(1, "select failed: %s", strerror(errno));

  return (0);
}

/*----- That's all, folks -------------------------------------------------*/