/* base64.c -- Encode binary data using printable characters.

   Copyright (C) 1999-2001, 2004-2006, 2009-2016 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 3, 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, see <http://www.gnu.org/licenses/>.  */

/* 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 4648 <http://www.ietf.org/rfc/rfc4648.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;

}

static const char b64c[64] =

  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/* Base64 encode IN array of size INLEN into OUT array. OUT needs

   to be of length >= BASE64_LENGTH(INLEN), and INLEN needs to be

   a multiple of 3.  */

static void

base64_encode_fast (const char *restrict in, size_t inlen, char *restrict out)

{

  while (inlen)

    {

      *out++ = b64c[to_uchar (in[0]) >> 2];

      *out++ = b64c[((to_uchar (in[0]) << 4) + (to_uchar (in[1]) >> 4)) & 0x3f];

      *out++ = b64c[((to_uchar (in[1]) << 2) + (to_uchar (in[2]) >> 6)) & 0x3f];

      *out++ = b64c[to_uchar (in[2]) & 0x3f];

      inlen -= 3;

      in += 3;

    }

}

/* 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 *restrict in, size_t inlen,

               char *restrict out, size_t outlen)

{

  /* Note this outlen constraint can be enforced at compile time.

     I.E. that the output buffer is exactly large enough to hold

     the encoded inlen bytes.  The inlen constraints (of corresponding

     to outlen, and being a multiple of 3) can change at runtime

     at the end of input.  However the common case when reading

     large inputs is to have both constraints satisfied, so we depend

     on both in base_encode_fast().  */

  if (outlen % 4 == 0 && inlen == outlen / 4 * 3)

    {

      base64_encode_fast (in, inlen, out);

      return;

    }

  while (inlen && outlen)

    {

      *out++ = b64c[to_uchar (in[0]) >> 2];

      if (!--outlen)

        break;

      *out++ = b64c[((to_uchar (in[0]) << 4)

                       + (--inlen ? to_uchar (in[1]) >> 4 : 0))

                      & 0x3f];

      if (!--outlen)

        break;

      *out++ =

        (inlen

         ? b64c[((to_uchar (in[1]) << 2)

                   + (--inlen ? to_uchar (in[2]) >> 6 : 0))

                  & 0x3f]

         : '=');

      if (!--outlen)

        break;

      *out++ = inlen ? b64c[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 = 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 *restrict *in, char const *restrict 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 *restrict in, size_t inlen,

          char *restrict *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.

   If CTX is NULL then newlines are treated as garbage and the input

   buffer is processed as a unit.  */

bool

base64_decode_ctx (struct base64_decode_context *ctx,

                   const char *restrict in, size_t inlen,

                   char *restrict out, size_t *outlen)

{

  size_t outleft = *outlen;

  bool ignore_newlines = ctx != NULL;

  bool flush_ctx = false;

  unsigned int ctx_i = 0;

  if (ignore_newlines)

    {

      ctx_i = ctx->i;

      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' && ignore_newlines)

        {

          ++in;

          --inlen;

          continue;

        }

      /* Restore OUT and OUTLEFT.  */

      out -= outleft_save - outleft;

      outleft = outleft_save;

      {

        char const *in_end = in + inlen;

        char const *non_nl;

        if (ignore_newlines)

          non_nl = get_4 (ctx, &in, in_end, &inlen);

        else

          non_nl = in;  /* Might have nl in this case. */

        /* 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 and not treating newlines as garbage.  */

        if (inlen == 0 || (inlen < 4 && !flush_ctx && ignore_newlines))

          {

            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_ctx (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 + (ctx ? ctx->i : 0)) / 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) + 3;

  *out = malloc (needlen);

  if (!*out)

    return true;

  if (!base64_decode_ctx (ctx, in, inlen, *out, &needlen))

    {

      free (*out);

      *out = NULL;

      return false;

    }

  if (outlen)

    *outlen = needlen;

  return true;

}