Add GnuTLS infrastructure

Add configure.ac section to detect GnuTLS

Add buffer.[ch] and crypto-gnutls.[ch] from
  https://github.com/abligh/tlsproxy

Add Makefile.am changes to link these new files in

Signed-off-by: Alex Bligh <alex@alex.org.uk>
(cherry picked from commit aac8f6a)
[wouter: updated to cooperate with server-side GnuTLS support that already exists]
Signed-off-by: Wouter Verhelst <w@uter.be>

Makefile.am

@@ -19,3 +19,8 @@ nbd_server_LDADD = @GLIB_LIBS@ libnbdsrv.la libcliserv.la @GnuTLS_LIBS@
 nbd_trdump_LDADD = libcliserv.la
 make_integrityhuge_SOURCES = make-integrityhuge.c cliserv.h nbd.h nbd-debug.h
 EXTRA_DIST = maketr CodingStyle autogen.sh README.md support/genver.sh
+TLSSRC = crypto-gnutls.c crypto-gnutls.h buffer.c buffer.h
+if GNUTLS
+nbd_client_SOURCES += $(TLSSRC)
+nbd_server_SOURCES += $(TLSSRC)
+endif

buffer.c

@@ -0,0 +1,225 @@
+/*
+
+The MIT License (MIT)
+
+Copyright (c) 2016 Wrymouth Innovation Ltd
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+*/
+
+#include <sys/types.h>
+
+#include "buffer.h"
+
+typedef struct buffer
+{
+  char *buf;
+  ssize_t size;
+  ssize_t hwm;
+  ssize_t ridx;
+  ssize_t widx;
+  int empty;
+} buffer_t;
+
+/* the buffer is organised internally as follows:
+ *
+ * * There are b->size bytes in the buffer.
+ *
+ * * Bytes are at offsets 0 to b->size-1
+ * 
+ * * b->ridx points to the first readable byte
+ *
+ * * b->widx points to the first empty space
+ *
+ * * b->ridx < b->widx indicates a non-wrapped buffer:
+ *
+ *     0       ridx     widx            size
+ *     |       |        |               |
+ *     V       V        V               V
+ *     ........XXXXXXXXX................
+ *
+ * * b->ridx > b->widx indicates a wrapped buffer:
+ *
+ *     0       widx     ridx            size
+ *     |       |        |               |
+ *     V       V        V               V
+ *     XXXXXXXX.........XXXXXXXXXXXXXXXX
+ *
+ * * b->ridx == b->widx indicates a FULL buffer:
+ *
+ * * b->ridx == b->widx indicates a wrapped buffer:
+ *
+ *     0       widx == ridx            size
+ *     |       |                       |
+ *     V       V                       V
+ *     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
+ *
+ * An empty buffer is indicated by empty=1
+ *
+ */
+
+buffer_t *
+bufNew (ssize_t size, ssize_t hwm)
+{
+  buffer_t *b = calloc (1, sizeof (buffer_t));
+  b->buf = calloc (1, size);
+  b->size = size;
+  b->hwm = hwm;
+  b->empty = 1;
+  return b;
+}
+
+
+void
+bufFree (buffer_t * b)
+{
+  free (b->buf);
+  free (b);
+}
+
+/* get a maximal span to read. Returns 0 if buffer
+ * is empty
+ */
+ssize_t
+bufGetReadSpan (buffer_t * b, void **addr)
+{
+  if (b->empty)
+    {
+      *addr = NULL;
+      return 0;
+    }
+  *addr = &(b->buf[b->ridx]);
+  ssize_t len = b->widx - b->ridx;
+  if (len <= 0)
+    len = b->size - b->ridx;
+  return len;
+}
+
+/* get a maximal span to write. Returns 0 id buffer is full
+ */
+ssize_t
+bufGetWriteSpan (buffer_t * b, void **addr)
+{
+  if (b->empty)
+    {
+      *addr = b->buf;
+      b->ridx = 0;
+      b->widx = 0;
+      return b->size;
+    }
+  if (b->ridx == b->widx)
+    {
+      *addr = NULL;
+      return 0;
+    }
+  *addr = &(b->buf[b->widx]);
+  ssize_t len = b->ridx - b->widx;
+  if (len <= 0)
+    len = b->size - b->widx;
+  return len;
+}
+
+/* mark size bytes as read */
+void
+bufDoneRead (buffer_t * b, ssize_t size)
+{
+  while (!b->empty && (size > 0))
+    {
+      /* empty can't occur here, so equal pointers means full */
+      ssize_t len = b->widx - b->ridx;
+      if (len <= 0)
+	len = b->size - b->ridx;
+
+      /* len is the number of bytes in one read span */
+      if (len > size)
+	len = size;
+
+      b->ridx += len;
+      if (b->ridx >= b->size)
+	b->ridx = 0;
+
+      if (b->ridx == b->widx)
+	{
+	  b->ridx = 0;
+	  b->widx = 0;
+	  b->empty = 1;
+	}
+
+      size -= len;
+    }
+}
+
+/* mark size bytes as written */
+void
+bufDoneWrite (buffer_t * b, ssize_t size)
+{
+  while ((b->empty || (b->ridx != b->widx)) && (size > 0))
+    {
+      /* full can't occur here, so equal pointers means empty */
+      ssize_t len = b->ridx - b->widx;
+      if (len <= 0)
+	len = b->size - b->widx;
+
+      /* len is the number of bytes in one write span */
+      if (len > size)
+	len = size;
+
+      b->widx += len;
+      if (b->widx >= b->size)
+	b->widx = 0;
+
+      /* it can't be empty as we've written at least one byte */
+      b->empty = 0;
+
+      size -= len;
+    }
+}
+
+int
+bufIsEmpty (buffer_t * b)
+{
+  return b->empty;
+}
+
+int
+bufIsFull (buffer_t * b)
+{
+  return !b->empty && (b->ridx == b->widx);
+}
+
+int
+bufIsOverHWM (buffer_t * b)
+{
+  return bufGetCount (b) > b->hwm;
+}
+
+ssize_t
+bufGetFree (buffer_t * b)
+{
+  return b->size - bufGetCount (b);
+}
+
+ssize_t
+bufGetCount (buffer_t * b)
+{
+  if (b->empty)
+    return 0;
+  return b->widx - b->ridx + ((b->ridx < b->widx) ? 0 : b->size);
+}

buffer.h

@@ -0,0 +1,45 @@
+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 Wrymouth Innovation Ltd
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#ifndef __TLSPROXY_BUFFERS_H
+#define __TLSPROXY_BUFFERS_H
+
+#include <stdlib.h>
+#include <sys/types.h>
+
+typedef struct buffer buffer_t;
+
+buffer_t *bufNew (ssize_t size, ssize_t hwm);
+void bufFree (buffer_t * b);
+ssize_t bufGetReadSpan (buffer_t * b, void **addr);
+ssize_t bufGetWriteSpan (buffer_t * b, void **addr);
+void bufDoneRead (buffer_t * b, ssize_t size);
+void bufDoneWrite (buffer_t * b, ssize_t size);
+int bufIsEmpty (buffer_t * b);
+int bufIsFull (buffer_t * b);
+int bufIsOverHWM (buffer_t * b);
+ssize_t bufGetFree (buffer_t * b);
+ssize_t bufGetCount (buffer_t * b);
+
+#endif

configure.ac

@@ -121,6 +121,7 @@ AC_CHECK_SIZEOF(unsigned long long int)
 AC_STRUCT_DIRENT_D_TYPE
 AC_CHECK_FUNCS([llseek alarm gethostbyname inet_ntoa memset socket strerror strstr mkstemp fdatasync])
 HAVE_FL_PH=no
+
 AC_CHECK_FUNC(fallocate,
   [
     AC_CHECK_HEADERS([linux/falloc.h])
@@ -211,6 +212,7 @@ dnl fi
 
 PKG_CHECK_MODULES(GnuTLS, [gnutls >= 3.3.0],[HAVE_GNUTLS=1],[HAVE_GNUTLS=0])
 AC_DEFINE(HAVE_GNUTLS, $HAVE_GNUTLS, [Define to 1 if you have a GnuTLS version of 3.3 or above])
+AM_CONDITIONAL([GNUTLS], [test "x$HAVE_GNUTLS" = "x1"])
 
 AC_CHECK_HEADERS([winioctl.h], [], [],
 [#include <io.h>