X-Git-Url: https://git.distorted.org.uk/~mdw/tripe/blobdiff_plain/e6b06b6b61b4b877937d4a56ba704d3f18154dc2..786989941b7b4504f0234c4a318f929802e981ad:/server/tun-slip.c?ds=sidebyside

diff --git a/server/tun-slip.c b/server/tun-slip.c
new file mode 100644
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--- /dev/null
+++ b/server/tun-slip.c
@@ -0,0 +1,450 @@
+/* -*-c-*-
+ *
+ * $Id$
+ *
+ * Tunnel packets via SLIP
+ *
+ * (c) 2005 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of Trivial IP Encryption (TrIPE).
+ *
+ * TrIPE 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.
+ * 
+ * TrIPE 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 TrIPE; if not, write to the Free Software Foundation,
+ * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#define TUN_INTERNALS
+
+#include "tripe.h"
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct slipif {
+  struct slipif *next;			/* Next one in the list */
+  int ifd, ofd;				/* File descriptors to talk on */
+  char *name;				/* Interface name */
+  pid_t kid;				/* Child process id */
+  unsigned f;				/* Various flags */
+#   define F_INUSE 1u			/*   Interface is in use */
+#   define F_DYNAMIC 2u			/*   Interface found dynamically */
+} slipif;
+
+struct tunnel {
+  const tunnel_ops *ops;		/* Pointer to operations */
+  slipif *sl;				/* My interface record */
+  sel_file f;				/* Selector for SLIP tty */
+  struct peer *p;			/* Pointer to my peer */
+  unsigned st;				/* Current parser state */
+#   define ST_ESC 1u			/*   Last saw an escape character */
+#   define ST_BAD 2u			/*   This packet is malformed */
+#   define ST_EOF 4u			/*   File descriptor reported EOF */
+  size_t n;				/* Number of bytes used in buffer */
+  octet buf[PKBUFSZ];			/* Buffer for incoming data */
+};  
+
+/*----- Static variables --------------------------------------------------*/
+
+static slipif *slipifs;			/* List of available interfaces */
+static const char *slipcmd;		/* Script to make new interfaces */
+
+/*----- Main code ---------------------------------------------------------*/
+
+#define SL_END 0xc0
+#define SL_ESC 0xdb
+#define SL_ESCEND 0xdc
+#define SL_ESCESC 0xdd
+
+/* --- @t_read@ --- *
+ *
+ * Arguments:	@int fd@ = file descriptor to read
+ *		@unsigned mode@ = what's happened
+ *		@void *v@ = pointer to tunnel block
+ *
+ * Returns:	---
+ *
+ * Use:		Reads data from the tunnel.
+ */
+
+static void t_read(int fd, unsigned mode, void *v)
+{
+  tunnel *t = v;
+  ssize_t n;
+  const octet *p, *l, *ll;
+  octet *q;
+  unsigned st;
+  octet o;
+  buf b;
+
+  /* --- Read the input data --- */
+
+  n = read(fd, buf_t, sizeof(buf_t));
+  if (n < 0) {
+    if (errno == EINTR ||
+#if defined(EWOULDBLOCK) && EWOULDBLOCK != EAGAIN
+	errno == EWOULDBLOCK ||
+#endif
+	errno == EAGAIN)
+      return;
+    a_warn("TUN", "%s", t->sl->name, "read-error", "?ERRNO", A_END);
+    return;
+  }
+  if (!n) {
+    a_warn("TUN", "%s", t->sl->name, "slip", "eof", A_END);
+    t->st = ST_EOF;
+    sel_rmfile(&t->f);
+    return;
+  }
+  IF_TRACING(T_TUNNEL, {
+    trace_block(T_PACKET, "tun-slip: SLIP-encapsulated data",
+		buf_t, n);
+  })
+
+  /* --- Decapsulate the packet --- */
+
+  for (p = buf_t, l = p + n, st = t->st,
+       q = t->buf + t->n, ll = t->buf + sizeof(t->buf);
+       p < l;
+       p++) {
+    o = *p;
+    switch (o) {
+      case SL_END:
+	if (st & ST_BAD)
+	  ;
+	else if (st & ST_ESC)
+	  a_warn("TUN", "%s", t->sl->name, "slip", "escape-end", A_END);
+	else if (q == t->buf) {
+	  T( trace(T_TUNNEL, "tun-slip: empty packet"); )
+	} else {
+	  IF_TRACING(T_TUNNEL, {
+	    trace(T_TUNNEL, "tun-slip: packet arrived");
+	    trace_block(T_PACKET, "tun-slip: packet contents",
+			t->buf, q - t->buf);
+	  })
+	  buf_init(&b, t->buf, q - t->buf);
+	  p_tun(t->p, &b);
+	}
+	q = t->buf;
+	st &= ~(ST_ESC | ST_BAD);
+	break;
+      case SL_ESC:
+	if ((st & ST_ESC) && !(st & ST_BAD)) {
+	  a_warn("TUN", "%s", t->sl->name, "slip", "bad-escape", A_END);
+	  st |= ST_BAD;
+	} else
+	  st |= ST_ESC;
+	break;
+      case SL_ESCEND:
+	if (st & ST_ESC)
+	  o = SL_END;
+	goto emit;
+      case SL_ESCESC:
+	if (st & ST_ESC)
+	  o = SL_ESC;
+	goto emit;
+      default:
+	if ((st & ST_ESC) && !(st & ST_BAD)) {
+	  a_warn("TUN", "%s", t->sl->name, "slip", "bad-escape", A_END);
+	  st |= ST_BAD;
+	}
+      emit:
+	if (!(st & ST_BAD)) {
+	  if (q < ll)
+	    *q++ = o;
+	  else {
+	    a_warn("TUN", "%s", t->sl->name, "slip", "overflow", A_END);
+	    st |= ST_BAD;
+	  }
+	}
+	st &= ~ST_ESC;
+	break;
+    }
+  }
+
+  t->n = q - t->buf;
+  t->st = st;
+}
+
+/* --- @t_init@ --- *
+ *
+ * Arguments:	---
+ *
+ * Returns:	---
+ *
+ * Use:		Initializes the tunneling system.  Maybe this will require
+ *		opening file descriptors or something.
+ */
+
+static void t_init(void)
+{
+  char *p, *q;
+  dstr d = DSTR_INIT;
+  slipif *sl, **tail = &slipifs;
+  unsigned long uli, ulo;
+  size_t n;
+
+  if ((p = getenv("TRIPE_SLIPIF")) == 0)
+    return;
+
+  /* --- Build the list of available interfaces --- */
+
+  dstr_puts(&d, p);
+
+  p = d.buf;
+  for (;;) {
+    if (*p == '/' || *p == '.') {
+      slipcmd = p;
+      T( trace(T_TUNNEL, "tun-slip: declared slip command `%s'", slipcmd); )
+      break;
+    }
+    uli = strtoul(p, &q, 0);
+    if (uli > INT_MAX || q == p)
+      goto whine;
+    if (*q != ',')
+      ulo = uli;
+    else {
+      p = q + 1;
+      ulo = strtoul(p, &q, 0);
+      if (ulo > INT_MAX || q == p)
+	goto whine;
+    }
+    if (*q != '=' || (n = strcspn(q + 1, ":")) == 0)
+      goto whine;
+    sl = CREATE(slipif);
+    sl->next = 0;
+    sl->ifd = uli;
+    fdflags(sl->ifd, O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
+    fdflags(sl->ofd, O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
+    sl->ofd = ulo;
+    sl->name = xmalloc(n + 1);
+    sl->kid = -1;
+    sl->f = 0;
+    memcpy(sl->name, q + 1, n);
+    sl->name[n] = 0;
+    *tail = sl;
+    tail = &sl->next;
+    T( trace(T_TUNNEL, "tun-slip: declared slipif %d,%d=%s",
+	     sl->ifd, sl->ofd, sl->name); )
+    p = q + n + 1;
+    if (!*p)
+      break;
+    p++;
+  }
+  return;
+
+whine:
+  moan("bad slip interface list");
+}
+
+/* --- @t_create@ --- *
+ *
+ * Arguments:	@peer *p@ = pointer to peer block
+ *
+ * Returns:	A tunnel block if it worked, or null on failure.
+ *
+ * Use:		Initializes a new tunnel.
+ */
+
+static tunnel *t_create(peer *p)
+{
+  slipif *sl = 0;
+  int pin[2] = { -1, -1 }, pout[2] = { -1, -1 };
+  pid_t kid = -1;
+  dstr d = DSTR_INIT;
+  unsigned char ch;
+  tunnel *t;
+  static const char end[] = { SL_END, SL_END };
+
+  /* --- Try to find a spare static interface --- */
+
+  for (sl = slipifs; sl; sl = sl->next) {
+    if (!(sl->f & F_INUSE)) {
+      T( trace(T_TUNNEL, "tun-slip: %s using static slipif %s",
+	       p_name(p), sl->name); )
+      goto found;
+    }
+  }
+
+  /* --- If no dynamic interfaces are available, give up --- */
+
+  if (!slipcmd) {
+    a_warn("TUN", "-", "slip", "no-slip-interfaces", A_END);
+    goto fail;
+  }
+
+  /* --- Fork off a child process to create a dynamic SLIP interface --- */
+
+  if (pipe(pin) || pipe(pout)) {
+    a_warn("TUN", "-", "slip", "pipe-error", "?ERRNO", A_END);
+    goto fail;
+  }
+  if ((kid = fork()) < 0) {
+    a_warn("TUN", "-", "slip", "fork-error", "?ERRNO", A_END);
+    goto fail;
+  }
+  if (!kid) {
+    close(pin[1]);
+    close(pout[0]);
+    dup2(pin[0], STDIN_FILENO);
+    dup2(pout[1], STDOUT_FILENO);
+    execlp(slipcmd, slipcmd, p_name(p), (char *)0);
+    _exit(127);
+  }
+
+  /* --- Read the interface name --- */
+
+  sl = CREATE(slipif);
+  close(pin[0]); pin[0] = -1;
+  close(pout[1]); pout[1] = -1;
+  for (;;) {
+    errno = EIO;
+    if (read(pout[0], &ch, 1) != 1 || ch == SL_END) {
+      a_warn("TUN", "-", "slip", "read-ifname-failed", "?ERRNO", A_END);
+      goto fail;
+    }
+    if (ch == '\n')
+      break;
+    DPUTC(&d, (char)ch);
+  }
+  DPUTZ(&d);
+  sl->name = xstrdup(d.buf);
+  sl->ifd = pout[0];
+  sl->ofd = pin[1];
+  sl->kid = kid;
+  sl->next = 0;
+  sl->f = F_DYNAMIC;
+  T( trace(T_TUNNEL, "tun-slip: %s using dynamic slipif %s",
+	   p_name(p), sl->name); )
+  fdflags(pout[0], O_NONBLOCK, O_NONBLOCK, FD_CLOEXEC, FD_CLOEXEC);
+  fdflags(pin[1], O_NONBLOCK, 0, FD_CLOEXEC, FD_CLOEXEC);
+
+  /* --- Set up the new tunnel --- */
+
+found:
+  t = CREATE(tunnel);
+  t->ops = &tun_slip;
+  t->p = p;
+  t->sl = sl;
+  t->st = 0;
+  t->n = 0;
+  sl->f |= F_INUSE;
+  sel_initfile(&sel, &t->f, sl->ifd, SEL_READ, t_read, t);
+  sel_addfile(&t->f);
+  write(sl->ofd, end, sizeof(end));
+  dstr_destroy(&d);
+  return (t);
+
+  /* --- Tidy up after a failure --- */
+
+fail:
+#define CLOSE(fd) do if (fd != -1) close(fd); while (0)
+  CLOSE(pin[0]); CLOSE(pout[0]);
+  CLOSE(pin[1]); CLOSE(pout[1]);
+#undef CLOSE
+  if (kid != -1) kill(kid, SIGTERM);
+  if (sl && (sl->f & F_DYNAMIC)) DESTROY(sl);
+  dstr_destroy(&d);
+  return (0);
+}
+
+/* --- @t_ifname@ --- *
+ *
+ * Arguments:	@tunnel *t@ = pointer to tunnel block
+ *
+ * Returns:	A pointer to the tunnel's interface name.
+ */
+
+static const char *t_ifname(tunnel *t) { return (t->sl->name); }
+
+/* --- @t_inject@ --- *
+ *
+ * Arguments:	@tunnel *t@ = pointer to tunnel block
+ *		@buf *b@ = buffer to send
+ *
+ * Returns:	---
+ *
+ * Use:		Injects a packet into the local network stack.
+ */
+
+static void t_inject(tunnel *t, buf *b)
+{
+  octet buf[PKBUFSZ * 2 + 2];
+  const octet *p, *l;
+  octet *q;
+
+  IF_TRACING(T_TUNNEL, {
+    trace(T_TUNNEL, "tun-slip: inject decrypted packet");
+    trace_block(T_PACKET, "tun-slip: packet contents", BBASE(b), BLEN(b));
+  })
+
+  q = buf;
+  *q++ = SL_END;
+  for (p = BBASE(b), l = BCUR(b); p < l; p++) {
+    switch (*p) {
+      case SL_END: *q++ = SL_ESC; *q++ = SL_ESCEND; break;
+      case SL_ESC: *q++ = SL_ESC; *q++ = SL_ESCESC; break;
+      default: *q++ = *p; break;
+    }
+  }
+  *q++ = SL_END;
+  IF_TRACING(T_TUNNEL, {
+    trace_block(T_PACKET, "tun-slip: SLIP-encapsulated contents",
+		buf, q - buf);
+  })
+  write(t->sl->ofd, buf, q - buf);
+}
+
+/* --- @t_destroy@ --- *
+ *
+ * Arguments:	@tunnel *t@ = pointer to tunnel block
+ *
+ * Returns:	---
+ *
+ * Use:		Destroys a tunnel.
+ */
+
+static void t_destroy(tunnel *t)
+{
+  slipif *sl = t->sl;
+
+  /* --- If it reported EOF, leave it out-of-action --- */
+
+  if (!(t->st & ST_EOF)) {
+    sel_rmfile(&t->f);
+    sl->f &= ~F_INUSE;
+  }
+  if (sl && (sl->f & F_DYNAMIC)) {
+    T( trace(T_TUNNEL, "tun-slip: releasing dynamic slipif %s", sl->name); )
+    close(sl->ofd);
+    close(sl->ifd);
+    kill(sl->kid, SIGTERM);
+    xfree(sl->name);
+    DESTROY(sl);
+  }
+  DESTROY(t);
+}
+
+const tunnel_ops tun_slip = {
+  "slip",
+  t_init,
+  t_create,
+  t_ifname,
+  t_inject,
+  t_destroy
+};
+
+/*----- That's all, folks -------------------------------------------------*/