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initial commit

git-svn-id: file:///home/ps/projects/saop@1 8c280a3b-b034-0410-b168-b83d87712a00
ps 14 years ago
commit
61b6bef780
7 changed files with 1020 additions and 0 deletions
  1. 9 0
      Makefile
  2. 561 0
      base64.c
  3. 56 0
      base64.h
  4. 197 0
      saop.c
  5. 19 0
      saoprc.example
  6. 141 0
      utils.c
  7. 37 0
      utils.h

+ 9 - 0
Makefile

@@ -0,0 +1,9 @@
+OBJS=utils.o saop.o base64.o
+CFLAGS=-Wall -Wshadow -Werror -ggdb
+
+all:saop
+
+saop: $(OBJS)
+
+clean:
+	rm -f $(OBJS) saop saop.exe

+ 561 - 0
base64.c

@@ -0,0 +1,561 @@
+/* -*- buffer-read-only: t -*- vi: set ro: */
+/* DO NOT EDIT! GENERATED AUTOMATICALLY! */
+/* base64.c -- Encode binary data using printable characters.
+   Copyright (C) 1999, 2000, 2001, 2004, 2005, 2006, 2007 Free Software
+   Foundation, Inc.
+
+   This program 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, or (at your option)
+   any later version.
+
+   This program 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 this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+/* Written by Simon Josefsson.  Partially adapted from GNU MailUtils
+ * (mailbox/filter_trans.c, as of 2004-11-28).  Improved by review
+ * from Paul Eggert, Bruno Haible, and Stepan Kasal.
+ *
+ * See also RFC 3548 <http://www.ietf.org/rfc/rfc3548.txt>.
+ *
+ * Be careful with error checking.  Here is how you would typically
+ * use these functions:
+ *
+ * bool ok = base64_decode_alloc (in, inlen, &out, &outlen);
+ * if (!ok)
+ *   FAIL: input was not valid base64
+ * if (out == NULL)
+ *   FAIL: memory allocation error
+ * OK: data in OUT/OUTLEN
+ *
+ * size_t outlen = base64_encode_alloc (in, inlen, &out);
+ * if (out == NULL && outlen == 0 && inlen != 0)
+ *   FAIL: input too long
+ * if (out == NULL)
+ *   FAIL: memory allocation error
+ * OK: data in OUT/OUTLEN.
+ *
+ */
+
+/*#include <config.h>*/
+
+/* Get prototype. */
+#include "base64.h"
+
+/* Get malloc. */
+#include <stdlib.h>
+
+/* Get UCHAR_MAX. */
+#include <limits.h>
+
+#include <string.h>
+
+/* C89 compliant way to cast 'char' to 'unsigned char'. */
+static unsigned char
+to_uchar (char ch)
+{
+  return ch;
+}
+
+/* Base64 encode IN array of size INLEN into OUT array of size OUTLEN.
+   If OUTLEN is less than BASE64_LENGTH(INLEN), write as many bytes as
+   possible.  If OUTLEN is larger than BASE64_LENGTH(INLEN), also zero
+   terminate the output buffer. */
+void
+base64_encode (const char *in, size_t inlen,
+	       char *out, size_t outlen)
+{
+     static const char b64str[] =
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+  while (inlen && outlen)
+    {
+      *out++ = b64str[(to_uchar (in[0]) >> 2) & 0x3f];
+      if (!--outlen)
+	break;
+      *out++ = b64str[((to_uchar (in[0]) << 4)
+		       + (--inlen ? to_uchar (in[1]) >> 4 : 0))
+		      & 0x3f];
+      if (!--outlen)
+	break;
+      *out++ =
+	(inlen
+	 ? b64str[((to_uchar (in[1]) << 2)
+		   + (--inlen ? to_uchar (in[2]) >> 6 : 0))
+		  & 0x3f]
+	 : '=');
+      if (!--outlen)
+	break;
+      *out++ = inlen ? b64str[to_uchar (in[2]) & 0x3f] : '=';
+      if (!--outlen)
+	break;
+      if (inlen)
+	inlen--;
+      if (inlen)
+	in += 3;
+    }
+
+  if (outlen)
+    *out = '\0';
+}
+
+/* Allocate a buffer and store zero terminated base64 encoded data
+   from array IN of size INLEN, returning BASE64_LENGTH(INLEN), i.e.,
+   the length of the encoded data, excluding the terminating zero.  On
+   return, the OUT variable will hold a pointer to newly allocated
+   memory that must be deallocated by the caller.  If output string
+   length would overflow, 0 is returned and OUT is set to NULL.  If
+   memory allocation failed, OUT is set to NULL, and the return value
+   indicates length of the requested memory block, i.e.,
+   BASE64_LENGTH(inlen) + 1. */
+size_t
+base64_encode_alloc (const char *in, size_t inlen, char **out)
+{
+  size_t outlen = 1 + BASE64_LENGTH (inlen);
+
+  /* Check for overflow in outlen computation.
+   *
+   * If there is no overflow, outlen >= inlen.
+   *
+   * If the operation (inlen + 2) overflows then it yields at most +1, so
+   * outlen is 0.
+   *
+   * If the multiplication overflows, we lose at least half of the
+   * correct value, so the result is < ((inlen + 2) / 3) * 2, which is
+   * less than (inlen + 2) * 0.66667, which is less than inlen as soon as
+   * (inlen > 4).
+   */
+  if (inlen > outlen)
+    {
+      *out = NULL;
+      return 0;
+    }
+
+  *out = (char *)malloc (outlen);
+  if (!*out)
+    return outlen;
+
+  base64_encode (in, inlen, *out, outlen);
+
+  return outlen - 1;
+}
+
+/* With this approach this file works independent of the charset used
+   (think EBCDIC).  However, it does assume that the characters in the
+   Base64 alphabet (A-Za-z0-9+/) are encoded in 0..255.  POSIX
+   1003.1-2001 require that char and unsigned char are 8-bit
+   quantities, though, taking care of that problem.  But this may be a
+   potential problem on non-POSIX C99 platforms.
+
+   IBM C V6 for AIX mishandles "#define B64(x) ...'x'...", so use "_"
+   as the formal parameter rather than "x".  */
+#define B64(_)					\
+  ((_) == 'A' ? 0				\
+   : (_) == 'B' ? 1				\
+   : (_) == 'C' ? 2				\
+   : (_) == 'D' ? 3				\
+   : (_) == 'E' ? 4				\
+   : (_) == 'F' ? 5				\
+   : (_) == 'G' ? 6				\
+   : (_) == 'H' ? 7				\
+   : (_) == 'I' ? 8				\
+   : (_) == 'J' ? 9				\
+   : (_) == 'K' ? 10				\
+   : (_) == 'L' ? 11				\
+   : (_) == 'M' ? 12				\
+   : (_) == 'N' ? 13				\
+   : (_) == 'O' ? 14				\
+   : (_) == 'P' ? 15				\
+   : (_) == 'Q' ? 16				\
+   : (_) == 'R' ? 17				\
+   : (_) == 'S' ? 18				\
+   : (_) == 'T' ? 19				\
+   : (_) == 'U' ? 20				\
+   : (_) == 'V' ? 21				\
+   : (_) == 'W' ? 22				\
+   : (_) == 'X' ? 23				\
+   : (_) == 'Y' ? 24				\
+   : (_) == 'Z' ? 25				\
+   : (_) == 'a' ? 26				\
+   : (_) == 'b' ? 27				\
+   : (_) == 'c' ? 28				\
+   : (_) == 'd' ? 29				\
+   : (_) == 'e' ? 30				\
+   : (_) == 'f' ? 31				\
+   : (_) == 'g' ? 32				\
+   : (_) == 'h' ? 33				\
+   : (_) == 'i' ? 34				\
+   : (_) == 'j' ? 35				\
+   : (_) == 'k' ? 36				\
+   : (_) == 'l' ? 37				\
+   : (_) == 'm' ? 38				\
+   : (_) == 'n' ? 39				\
+   : (_) == 'o' ? 40				\
+   : (_) == 'p' ? 41				\
+   : (_) == 'q' ? 42				\
+   : (_) == 'r' ? 43				\
+   : (_) == 's' ? 44				\
+   : (_) == 't' ? 45				\
+   : (_) == 'u' ? 46				\
+   : (_) == 'v' ? 47				\
+   : (_) == 'w' ? 48				\
+   : (_) == 'x' ? 49				\
+   : (_) == 'y' ? 50				\
+   : (_) == 'z' ? 51				\
+   : (_) == '0' ? 52				\
+   : (_) == '1' ? 53				\
+   : (_) == '2' ? 54				\
+   : (_) == '3' ? 55				\
+   : (_) == '4' ? 56				\
+   : (_) == '5' ? 57				\
+   : (_) == '6' ? 58				\
+   : (_) == '7' ? 59				\
+   : (_) == '8' ? 60				\
+   : (_) == '9' ? 61				\
+   : (_) == '+' ? 62				\
+   : (_) == '/' ? 63				\
+   : -1)
+
+static const signed char b64[0x100] = {
+  B64 (0), B64 (1), B64 (2), B64 (3),
+  B64 (4), B64 (5), B64 (6), B64 (7),
+  B64 (8), B64 (9), B64 (10), B64 (11),
+  B64 (12), B64 (13), B64 (14), B64 (15),
+  B64 (16), B64 (17), B64 (18), B64 (19),
+  B64 (20), B64 (21), B64 (22), B64 (23),
+  B64 (24), B64 (25), B64 (26), B64 (27),
+  B64 (28), B64 (29), B64 (30), B64 (31),
+  B64 (32), B64 (33), B64 (34), B64 (35),
+  B64 (36), B64 (37), B64 (38), B64 (39),
+  B64 (40), B64 (41), B64 (42), B64 (43),
+  B64 (44), B64 (45), B64 (46), B64 (47),
+  B64 (48), B64 (49), B64 (50), B64 (51),
+  B64 (52), B64 (53), B64 (54), B64 (55),
+  B64 (56), B64 (57), B64 (58), B64 (59),
+  B64 (60), B64 (61), B64 (62), B64 (63),
+  B64 (64), B64 (65), B64 (66), B64 (67),
+  B64 (68), B64 (69), B64 (70), B64 (71),
+  B64 (72), B64 (73), B64 (74), B64 (75),
+  B64 (76), B64 (77), B64 (78), B64 (79),
+  B64 (80), B64 (81), B64 (82), B64 (83),
+  B64 (84), B64 (85), B64 (86), B64 (87),
+  B64 (88), B64 (89), B64 (90), B64 (91),
+  B64 (92), B64 (93), B64 (94), B64 (95),
+  B64 (96), B64 (97), B64 (98), B64 (99),
+  B64 (100), B64 (101), B64 (102), B64 (103),
+  B64 (104), B64 (105), B64 (106), B64 (107),
+  B64 (108), B64 (109), B64 (110), B64 (111),
+  B64 (112), B64 (113), B64 (114), B64 (115),
+  B64 (116), B64 (117), B64 (118), B64 (119),
+  B64 (120), B64 (121), B64 (122), B64 (123),
+  B64 (124), B64 (125), B64 (126), B64 (127),
+  B64 (128), B64 (129), B64 (130), B64 (131),
+  B64 (132), B64 (133), B64 (134), B64 (135),
+  B64 (136), B64 (137), B64 (138), B64 (139),
+  B64 (140), B64 (141), B64 (142), B64 (143),
+  B64 (144), B64 (145), B64 (146), B64 (147),
+  B64 (148), B64 (149), B64 (150), B64 (151),
+  B64 (152), B64 (153), B64 (154), B64 (155),
+  B64 (156), B64 (157), B64 (158), B64 (159),
+  B64 (160), B64 (161), B64 (162), B64 (163),
+  B64 (164), B64 (165), B64 (166), B64 (167),
+  B64 (168), B64 (169), B64 (170), B64 (171),
+  B64 (172), B64 (173), B64 (174), B64 (175),
+  B64 (176), B64 (177), B64 (178), B64 (179),
+  B64 (180), B64 (181), B64 (182), B64 (183),
+  B64 (184), B64 (185), B64 (186), B64 (187),
+  B64 (188), B64 (189), B64 (190), B64 (191),
+  B64 (192), B64 (193), B64 (194), B64 (195),
+  B64 (196), B64 (197), B64 (198), B64 (199),
+  B64 (200), B64 (201), B64 (202), B64 (203),
+  B64 (204), B64 (205), B64 (206), B64 (207),
+  B64 (208), B64 (209), B64 (210), B64 (211),
+  B64 (212), B64 (213), B64 (214), B64 (215),
+  B64 (216), B64 (217), B64 (218), B64 (219),
+  B64 (220), B64 (221), B64 (222), B64 (223),
+  B64 (224), B64 (225), B64 (226), B64 (227),
+  B64 (228), B64 (229), B64 (230), B64 (231),
+  B64 (232), B64 (233), B64 (234), B64 (235),
+  B64 (236), B64 (237), B64 (238), B64 (239),
+  B64 (240), B64 (241), B64 (242), B64 (243),
+  B64 (244), B64 (245), B64 (246), B64 (247),
+  B64 (248), B64 (249), B64 (250), B64 (251),
+  B64 (252), B64 (253), B64 (254), B64 (255)
+};
+
+#if UCHAR_MAX == 255
+# define uchar_in_range(c) true
+#else
+# define uchar_in_range(c) ((c) <= 255)
+#endif
+
+/* Return true if CH is a character from the Base64 alphabet, and
+   false otherwise.  Note that '=' is padding and not considered to be
+   part of the alphabet.  */
+bool
+isbase64 (char ch)
+{
+  return uchar_in_range (to_uchar (ch)) && 0 <= b64[to_uchar (ch)];
+}
+
+/* Initialize decode-context buffer, CTX.  */
+void
+base64_decode_ctx_init (struct base64_decode_context *ctx)
+{
+  ctx->i = 0;
+}
+
+/* If CTX->i is 0 or 4, there are four or more bytes in [*IN..IN_END), and
+   none of those four is a newline, then return *IN.  Otherwise, copy up to
+   4 - CTX->i non-newline bytes from that range into CTX->buf, starting at
+   index CTX->i and setting CTX->i to reflect the number of bytes copied,
+   and return CTX->buf.  In either case, advance *IN to point to the byte
+   after the last one processed, and set *N_NON_NEWLINE to the number of
+   verified non-newline bytes accessible through the returned pointer.  */
+static char *
+get_4 (struct base64_decode_context *ctx,
+       char const **in, char const *in_end,
+       size_t *n_non_newline)
+{
+  if (ctx->i == 4)
+    ctx->i = 0;
+
+  if (ctx->i == 0)
+    {
+      char const *t = *in;
+      if (4 <= in_end - *in && memchr (t, '\n', 4) == NULL)
+	{
+	  /* This is the common case: no newline.  */
+	  *in += 4;
+	  *n_non_newline = 4;
+	  return (char *) t;
+	}
+    }
+
+  {
+    /* Copy non-newline bytes into BUF.  */
+    char const *p = *in;
+    while (p < in_end)
+      {
+	char c = *p++;
+	if (c != '\n')
+	  {
+	    ctx->buf[ctx->i++] = c;
+	    if (ctx->i == 4)
+	      break;
+	  }
+      }
+
+    *in = p;
+    *n_non_newline = ctx->i;
+    return ctx->buf;
+  }
+}
+
+#define return_false				\
+  do						\
+    {						\
+      *outp = out;				\
+      return false;				\
+    }						\
+  while (false)
+
+/* Decode up to four bytes of base64-encoded data, IN, of length INLEN
+   into the output buffer, *OUT, of size *OUTLEN bytes.  Return true if
+   decoding is successful, false otherwise.  If *OUTLEN is too small,
+   as many bytes as possible are written to *OUT.  On return, advance
+   *OUT to point to the byte after the last one written, and decrement
+   *OUTLEN to reflect the number of bytes remaining in *OUT.  */
+static bool
+decode_4 (char const *in, size_t inlen,
+	  char **outp, size_t *outleft)
+{
+  char *out = *outp;
+  if (inlen < 2)
+    return false;
+
+  if (!isbase64 (in[0]) || !isbase64 (in[1]))
+    return false;
+
+  if (*outleft)
+    {
+      *out++ = ((b64[to_uchar (in[0])] << 2)
+		| (b64[to_uchar (in[1])] >> 4));
+      --*outleft;
+    }
+
+  if (inlen == 2)
+    return_false;
+
+  if (in[2] == '=')
+    {
+      if (inlen != 4)
+	return_false;
+
+      if (in[3] != '=')
+	return_false;
+    }
+  else
+    {
+      if (!isbase64 (in[2]))
+	return_false;
+
+      if (*outleft)
+	{
+	  *out++ = (((b64[to_uchar (in[1])] << 4) & 0xf0)
+		    | (b64[to_uchar (in[2])] >> 2));
+	  --*outleft;
+	}
+
+      if (inlen == 3)
+	return_false;
+
+      if (in[3] == '=')
+	{
+	  if (inlen != 4)
+	    return_false;
+	}
+      else
+	{
+	  if (!isbase64 (in[3]))
+	    return_false;
+
+	  if (*outleft)
+	    {
+	      *out++ = (((b64[to_uchar (in[2])] << 6) & 0xc0)
+			| b64[to_uchar (in[3])]);
+	      --*outleft;
+	    }
+	}
+    }
+
+  *outp = out;
+  return true;
+}
+
+/* Decode base64-encoded input array IN of length INLEN to output array
+   OUT that can hold *OUTLEN bytes.  The input data may be interspersed
+   with newlines.  Return true if decoding was successful, i.e. if the
+   input was valid base64 data, false otherwise.  If *OUTLEN is too
+   small, as many bytes as possible will be written to OUT.  On return,
+   *OUTLEN holds the length of decoded bytes in OUT.  Note that as soon
+   as any non-alphabet, non-newline character is encountered, decoding
+   is stopped and false is returned.  If INLEN is zero, then process
+   only whatever data is stored in CTX.
+
+   Initially, CTX must have been initialized via base64_decode_ctx_init.
+   Subsequent calls to this function must reuse whatever state is recorded
+   in that buffer.  It is necessary for when a quadruple of base64 input
+   bytes spans two input buffers.  */
+
+bool
+base64_decode (struct base64_decode_context *ctx,
+	       const char *in, size_t inlen,
+	       char *out, size_t *outlen)
+{
+  size_t outleft = *outlen;
+  bool flush_ctx = inlen == 0;
+
+  while (true)
+    {
+      size_t outleft_save = outleft;
+      if (ctx->i == 0 && !flush_ctx)
+	{
+	  while (true)
+	    {
+	      /* Save a copy of outleft, in case we need to re-parse this
+		 block of four bytes.  */
+	      outleft_save = outleft;
+	      if (!decode_4 (in, inlen, &out, &outleft))
+		break;
+
+	      in += 4;
+	      inlen -= 4;
+	    }
+	}
+
+      if (inlen == 0 && !flush_ctx)
+	break;
+
+      /* Handle the common case of 72-byte wrapped lines.
+	 This also handles any other multiple-of-4-byte wrapping.  */
+      if (inlen && *in == '\n')
+	{
+	  ++in;
+	  --inlen;
+	  continue;
+	}
+
+      /* Restore OUT and OUTLEFT.  */
+      out -= outleft_save - outleft;
+      outleft = outleft_save;
+
+      {
+	char const *in_end = in + inlen;
+	char const *non_nl = get_4 (ctx, &in, in_end, &inlen);
+
+	/* If the input is empty or consists solely of newlines (0 non-newlines),
+	   then we're done.  Likewise if there are fewer than 4 bytes when not
+	   flushing context.  */
+	if (inlen == 0 || (inlen < 4 && !flush_ctx))
+	  {
+	    inlen = 0;
+	    break;
+	  }
+	if (!decode_4 (non_nl, inlen, &out, &outleft))
+	  break;
+
+	inlen = in_end - in;
+      }
+    }
+
+  *outlen -= outleft;
+
+  return inlen == 0;
+}
+
+/* Allocate an output buffer in *OUT, and decode the base64 encoded
+   data stored in IN of size INLEN to the *OUT buffer.  On return, the
+   size of the decoded data is stored in *OUTLEN.  OUTLEN may be NULL,
+   if the caller is not interested in the decoded length.  *OUT may be
+   NULL to indicate an out of memory error, in which case *OUTLEN
+   contains the size of the memory block needed.  The function returns
+   true on successful decoding and memory allocation errors.  (Use the
+   *OUT and *OUTLEN parameters to differentiate between successful
+   decoding and memory error.)  The function returns false if the
+   input was invalid, in which case *OUT is NULL and *OUTLEN is
+   undefined. */
+bool
+base64_decode_alloc (struct base64_decode_context *ctx,
+		     const char *in, size_t inlen, char **out,
+		     size_t *outlen)
+{
+  /* This may allocate a few bytes too many, depending on input,
+     but it's not worth the extra CPU time to compute the exact size.
+     The exact size is 3 * inlen / 4, minus 1 if the input ends
+     with "=" and minus another 1 if the input ends with "==".
+     Dividing before multiplying avoids the possibility of overflow.  */
+  size_t needlen = 3 * (inlen / 4) + 2;
+
+  *out = (char *)malloc (needlen);
+  if (!*out)
+    return true;
+
+  if (!base64_decode (ctx, in, inlen, *out, &needlen))
+    {
+      free (*out);
+      *out = NULL;
+      return false;
+    }
+
+  if (outlen)
+    *outlen = needlen;
+
+  return true;
+}

+ 56 - 0
base64.h

@@ -0,0 +1,56 @@
+/* -*- buffer-read-only: t -*- vi: set ro: */
+/* DO NOT EDIT! GENERATED AUTOMATICALLY! */
+/* base64.h -- Encode binary data using printable characters.
+   Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
+   Written by Simon Josefsson.
+
+   This program 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, or (at your option)
+   any later version.
+
+   This program 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 this program; if not, write to the Free Software Foundation,
+   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
+
+#ifndef BASE64_H
+# define BASE64_H
+
+/* Get size_t. */
+# include <stddef.h>
+
+/* Get bool. */
+# include <stdbool.h>
+
+/* This uses that the expression (n+(k-1))/k means the smallest
+   integer >= n/k, i.e., the ceiling of n/k.  */
+# define BASE64_LENGTH(inlen) ((((inlen) + 2) / 3) * 4)
+
+struct base64_decode_context
+{
+  unsigned int i;
+  char buf[4];
+};
+
+bool isbase64 (char ch);
+
+void base64_encode (const char * in, size_t inlen,
+			   char * out, size_t outlen);
+
+extern size_t base64_encode_alloc (const char *in, size_t inlen, char **out);
+
+void base64_decode_ctx_init (struct base64_decode_context *ctx);
+bool base64_decode (struct base64_decode_context *ctx,
+			   const char * in, size_t inlen,
+			   char * out, size_t *outlen);
+
+bool base64_decode_alloc (struct base64_decode_context *ctx,
+				 const char *in, size_t inlen,
+				 char **out, size_t *outlen);
+
+#endif /* BASE64_H */

+ 197 - 0
saop.c

@@ -0,0 +1,197 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <ctype.h>
+#include "base64.h"
+#include "utils.h"
+
+#ifndef WIN32
+  #define CONFIGFILE "saoprc"
+#else
+  #define CONFIGFILE "saop.cfg"
+#endif /* WIN32 */
+
+int quit=0;
+void handle_connection(int);
+int authenticate_with_pop3(char *,char *,char *,unsigned long);
+void read_config(char *);
+
+struct
+{
+  unsigned short listen_port;
+  char smtp_server[512];
+  unsigned short smtp_port;
+  char pop3_server[512];
+  unsigned short pop3_port;
+}
+config={25,"localhost",2525,"localhost",110};
+
+int main(int argc,char **argv)
+{
+  int fd_server,fd;
+
+  read_config(CONFIGFILE);
+
+  if(-1==(fd_server=create_listening_socket(config.listen_port))) exit(-1);
+
+  while(!quit)
+    if(can_read(fd_server,1))
+    {
+      if(-1!=(fd=accept(fd_server,NULL,0)))
+        handle_connection(fd);
+    }
+  close(fd_server);
+
+  return 0;
+}
+
+void handle_connection(int outside)
+{
+  int inside;
+  char *line;
+  int added_auth_line=0;
+  char *user=NULL,*pass=NULL;
+  size_t boguslen;
+  struct base64_decode_context b64ctx;
+
+  if(-1==(inside=create_connected_socket(config.smtp_server,config.smtp_port))) { exit(-1); }
+
+  while(1)
+  {
+    if(can_read(outside,0.01))
+    {
+      line=read_string(outside);
+
+      if(NULL==line) break; /* reached end of message */
+
+      if(!cmp(line,"AUTH LOGIN"))
+      {
+        /* perform authentication */
+        /* get username */
+        write_string(outside,"334 VXNlcm5hbWU6");    /* Username: in base64 */
+        if(NULL==(line=read_string(outside))) break; /* someone dropped the connection */
+        condfree(user);
+        base64_decode_ctx_init(&b64ctx);
+        base64_decode_alloc(&b64ctx,line,strlen(line),&user,&boguslen);
+
+        /* get password */
+        write_string(outside,"334 UGFzc3dvcmQ6");    /* Password: in base64 */
+        if(NULL==(line=read_string(outside))) break; /* someone dropped the connection */
+        condfree(pass);
+        base64_decode_ctx_init(&b64ctx);
+        base64_decode_alloc(&b64ctx,line,strlen(line),&pass,&boguslen);
+
+        if(authenticate_with_pop3(user,pass,config.pop3_server,config.pop3_port))
+          write_string(outside,"235 Authentication Successful");
+        else
+          write_string(outside,"535 Authentication Failed");
+        condfree(user);
+        condfree(pass);
+        line[0]='\0';
+      }
+      if(*line)
+        write_string(inside,line);
+    }
+
+    if(can_read(inside,0.01))
+    {
+      line=read_string(inside);
+
+      if(NULL==line) break; /* reached end of message */
+
+      /*
+       * we have to process some lines of the ehlo response:
+       *  -remove PIPELINING, TLS and STARTTLS
+       *  -change all auth lines to AUTH LOGIN to only support login
+       */
+      if(!cmp(line,"250")&&(!cmp(line+4,"PIPELINING")||!cmp(line+4,"TLS")||!cmp(line+4,"STARTTLS")))
+      {
+        if('-'==line[3])
+          line[0]='\0';
+        else
+          if(!added_auth_line)
+            line="250 AUTH LOGIN";
+          else
+            line="250 X-NOEXTENSION";
+      }
+      else if(!cmp(line,"250")&&!cmp(line+4,"AUTH"))
+      {
+        if('-'==line[3])
+          line="250-AUTH LOGIN";
+        added_auth_line=1;
+      }
+      else if(!cmp(line,"250 ")&&!added_auth_line)
+        write_string(outside,"250-AUTH LOGIN");
+
+      if(*line)
+        write_string(outside,line);
+    }
+  }
+
+  close(outside);
+  close(inside);
+}
+
+int authenticate_with_pop3(char *user,char *pass,char *server,unsigned long port)
+{
+  int fd;
+  char *line=NULL;
+  char tmpline[1024];
+
+  if(-1==(fd=create_connected_socket(server,port))) { printf("Error connecting to pop3 server\n"); return 0; }
+
+  /* read pop3 banner */
+  line=read_string(fd);
+  if(NULL==line||!cmp(line,"-ERR")) { close(fd); return 0; }
+
+  /* check user */
+  snprintf(tmpline,sizeof(tmpline),"USER %s",user);
+  write_string(fd,tmpline);
+  line=read_string(fd);
+  if(NULL==line||!cmp(line,"-ERR")) { close(fd); return 0; }
+
+  /* check password */
+  snprintf(tmpline,sizeof(tmpline),"PASS %s",pass);
+  write_string(fd,tmpline);
+  line=read_string(fd);
+  if(NULL==line||!cmp(line,"-ERR")) { close(fd); return 0; }
+
+  close(fd);
+  return 1;
+}
+
+void read_config(char *file)
+{
+  char line[1024]={0};
+  FILE *f;
+  unsigned long i,j=0;
+
+  f=fopen(file,"r");
+
+  if(NULL==f)
+  {
+    printf("No config file found, continuing with defaults.");
+    return;
+  }
+  while(!feof(f))
+  {
+    fgets(line,sizeof(line),f);
+    if('#'!=line[0]&&'\0'!=line[0]&&'\r'!=line[0]&&'\n'!=line[0])
+    {
+      for(i=0;i<strlen(line);i++)
+        if(!isspace(line[i])&&'\r'!=line[i]&&'\n'!=line[i])
+          line[i]=line[j++];
+      line[j]='\0';
+      #define PROCESS_CONFIG_OPTION_STR(x,y) if(!cmp(line,x "=")) strncpy(config.y,line+strlen(x "="),sizeof(config.y)); else
+      #define PROCESS_CONFIG_OPTION_INT(x,y) if(!cmp(line,x "=")) config.y=atoi(line+strlen(x "=")); else
+      PROCESS_CONFIG_OPTION_INT("listen_port",listen_port)
+      PROCESS_CONFIG_OPTION_STR("smtp_server",smtp_server)
+      PROCESS_CONFIG_OPTION_INT("smtp_port",smtp_port)
+      PROCESS_CONFIG_OPTION_STR("pop3_server",pop3_server)
+      PROCESS_CONFIG_OPTION_INT("pop3_port",pop3_port)
+      printf("Option line %s not recognized\n",line); /* keep in mind this line comes after an else, so it won't get executed normally */
+    }
+  }
+  fclose(f);
+}

+ 19 - 0
saoprc.example

@@ -0,0 +1,19 @@
+#default config file
+
+#address to listen at
+#listen_port = 25
+
+#real smtp server
+#smtp_server = localhost
+
+#port of the real smtp server
+#smtp_port = 2525
+
+#pop3 server against to which authenticate
+#pop3_server = localhost
+
+#port of the pop3 server
+#pop3_port = 110
+
+#local domains file list
+#local_domains = localdomains

+ 141 - 0
utils.c

@@ -0,0 +1,141 @@
+#include "utils.h"
+
+/**
+ * reads a string as safely as possible.
+ *
+ * it will read one byte at a time until a '\\n' is read.
+ * we store one char at a time in a static buffer, and when
+ * we find a '\\n', we do an strndup of the buffer.
+ * it might be possible in this special case to just use
+ * a static buffer, return a pointer to it and never assign 
+ * any memory with strndup or in any other way.
+ *
+ * @param fd fd to read from
+ *
+ * @return a pointer to the read string
+ */
+char *read_string(int fd)
+{
+  char chr;
+  static char buffer[BUFLEN]={0};
+  int i;
+
+  assert(fd>=0);
+  /* read one byte at a time */
+  for(i=0;i<BUFLEN-1;i++)
+  {
+    if(recv(fd,&chr,1,MSG_NOSIGNAL)!=1) return NULL;
+    if(10==chr) break;
+    if(chr!=13)
+      buffer[i]=chr;
+    else
+      i--; /* HACK HACK HACK */
+  }
+
+  /* finalize string */
+  buffer[i]='\0';
+
+  /* return a new string with new mem */
+  return buffer;
+}
+
+/**
+ * create a new listening socket.
+ *
+ * with following options:
+ * - SO_REUSEADDR
+ * - INADDR_ANY
+ *
+ * @param port the port to listen on
+ *
+ * @return the new socket fd
+ */
+int create_listening_socket(unsigned int port)
+{
+  int fd_server;
+  struct sockaddr_in address;
+  int i;
+
+  /* create socket */
+  if(-1==(fd_server=socket(PF_INET,SOCK_STREAM,0))) { perror("Error creating socket"); return -1; }
+
+  /* set option for the socket: SO_REUSEADDR (will reuse address between invocations of the same program) */
+  i=1;
+  if(-1==setsockopt(fd_server,SOL_SOCKET,SO_REUSEADDR,(void *)&i,sizeof(i))) { perror("Error configuring socket reuse"); close(fd_server); return -1; }
+
+  /* bind to address :ANY */
+  address.sin_family=AF_INET;
+  address.sin_addr.s_addr=INADDR_ANY;
+  address.sin_port=htons(port);
+
+  if(-1==bind(fd_server,(struct sockaddr *)&address,sizeof(address))) { perror("Error binding to address"); close(fd_server); return -1; }
+
+  /* listen on socket */
+  if(-1==listen(fd_server,10)) { perror("Error listening on socket"); close(fd_server); return -1; }
+
+  return fd_server; 
+}
+
+/**
+ * create a socket that is connected to an address.
+ *
+ * @param address address to connect to
+ * @param port port to connect to
+ *
+ * @return fd of the opened connection
+ */
+int create_connected_socket(char *address,unsigned int port)
+{
+  int fd;
+  struct sockaddr_in addr;
+
+  /* create socket */
+  if(-1==(fd=socket(PF_INET,SOCK_STREAM,0))) { perror("Error creating socket"); return -1; }
+
+  /* fill address structure */
+  addr.sin_family=AF_INET;
+  addr.sin_addr.s_addr=resolve(address);
+  addr.sin_port=htons(port);
+
+  /* connect to remote host */
+  if(-1==connect(fd,(struct sockaddr *)&addr,sizeof(addr))) { perror("Error connecting to host"); return -1; }
+
+  return fd;
+}
+
+unsigned long resolve(char *address)
+{
+  struct hostent *resolved;
+  struct in_addr addr;
+
+  if(NULL==(resolved=gethostbyname(address))) { perror("Error resolving"); return 0; }
+
+  memcpy(&addr,resolved->h_addr,sizeof(addr));
+  return addr.s_addr;
+}
+
+/**
+ * whether a fd does have data waiting or not.
+ *
+ * @param fd fd to ask
+ * @param time time to wait for data
+ *
+ * @return 1 on data waiting to be read, else return 0
+ */
+unsigned char can_read(int fd,float time)
+{
+  fd_set rfd;
+  struct timeval timeout;
+
+  assert(fd>=0);
+
+  /* configure timeout */
+  timeout.tv_sec=(int)time;
+  timeout.tv_usec=(time-(int)time)*1000000;
+
+  /* configure rfd */
+  FD_ZERO(&rfd);
+  FD_SET(fd,&rfd);
+
+  return (0==select(fd+1,&rfd,NULL,NULL,&timeout))?0:1;
+}

+ 37 - 0
utils.h

@@ -0,0 +1,37 @@
+#ifndef UTILS_H
+#define UTILS_H
+
+#include <assert.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#ifdef WIN32
+  #include <winsock2.h>
+  #include <ws2tcpip.h>
+#else
+  #include <sys/socket.h>
+  #include <netdb.h>
+  #include <arpa/inet.h>
+  #include <netinet/in.h>
+  #include <sys/select.h>
+#endif /* WIN32 */
+
+#define BUFLEN 512 /* max length of strings */
+
+#ifndef MSG_NOSIGNAL
+  #define MSG_NOSIGNAL 0
+#endif /* MSG_NOSIGNAL */
+
+/* utility macros */
+#define cmp(x,y) strncasecmp(x,y,strlen(y))
+#define write_string(x,y) do { send(x,y,strlen(y),MSG_NOSIGNAL); send(x,"\r\n",2,MSG_NOSIGNAL); } while(0)
+#define condfree(x) do { if(NULL!=x) free(x); x=NULL; } while(0)
+#define safestrdup(x,y) do { assert(NULL!=y); if(NULL==(x=strndup(y,strlen(y)))) { perror("Error duplicating string"); exit(-1); } } while(0)
+
+char *read_string(int);
+int create_listening_socket(unsigned int);
+int create_connected_socket(char *,unsigned int);
+unsigned long resolve(char *);
+unsigned char can_read(int,float);
+
+#endif /* UTILS_H */