gnupg/common/b64enc.c

/* b64enc.c - Simple Base64 encoder.
 * Copyright (C) 2001, 2003, 2004, 2008, 2010,
 *               2011 Free Software Foundation, Inc.
 * Copyright (C) 2001, 2003, 2004, 2008, 2010,
 *               2011 g10 Code GmbH
 *
 * This file is part of GnuPG.
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This file 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 Lesser General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses/>.
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>

#include "i18n.h"
#include "util.h"

#define B64ENC_DID_HEADER   1
#define B64ENC_DID_TRAILER  2
#define B64ENC_NO_LINEFEEDS 16
#define B64ENC_USE_PGPCRC   32

/* The base-64 character list */
static unsigned char bintoasc[64] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                    "abcdefghijklmnopqrstuvwxyz"
                                    "0123456789+/";

/* Stuff required to create the OpenPGP CRC.  This crc_table has been
   created using this code:

   #include <stdio.h>
   #include <stdint.h>

   #define CRCPOLY 0x864CFB

   int
   main (void)
   {
     int i, j;
     uint32_t t;
     uint32_t crc_table[256];

     crc_table[0] = 0;
     for (i=j=0; j < 128; j++ )
       {
         t = crc_table[j];
         if ( (t & 0x00800000) )
           {
             t <<= 1;
             crc_table[i++] = t ^ CRCPOLY;
             crc_table[i++] = t;
   	}
         else
           {
             t <<= 1;
             crc_table[i++] = t;
             crc_table[i++] = t ^ CRCPOLY;
   	}
       }

     puts ("static const u32 crc_table[256] = {");
     for (i=j=0; i < 256; i++)
       {
         printf ("%s 0x%08lx", j? "":" ", (unsigned long)crc_table[i]);
         if (i != 255)
           {
             putchar (',');
             if ( ++j > 5)
               {
                 j = 0;
                 putchar ('\n');
               }
           }
       }
     puts ("\n};");
     return 0;
   }
*/
#define CRCINIT 0xB704CE
static const u32 crc_table[256] = {
  0x00000000, 0x00864cfb, 0x018ad50d, 0x010c99f6, 0x0393e6e1, 0x0315aa1a,
  0x021933ec, 0x029f7f17, 0x07a18139, 0x0727cdc2, 0x062b5434, 0x06ad18cf,
  0x043267d8, 0x04b42b23, 0x05b8b2d5, 0x053efe2e, 0x0fc54e89, 0x0f430272,
  0x0e4f9b84, 0x0ec9d77f, 0x0c56a868, 0x0cd0e493, 0x0ddc7d65, 0x0d5a319e,
  0x0864cfb0, 0x08e2834b, 0x09ee1abd, 0x09685646, 0x0bf72951, 0x0b7165aa,
  0x0a7dfc5c, 0x0afbb0a7, 0x1f0cd1e9, 0x1f8a9d12, 0x1e8604e4, 0x1e00481f,
  0x1c9f3708, 0x1c197bf3, 0x1d15e205, 0x1d93aefe, 0x18ad50d0, 0x182b1c2b,
  0x192785dd, 0x19a1c926, 0x1b3eb631, 0x1bb8faca, 0x1ab4633c, 0x1a322fc7,
  0x10c99f60, 0x104fd39b, 0x11434a6d, 0x11c50696, 0x135a7981, 0x13dc357a,
  0x12d0ac8c, 0x1256e077, 0x17681e59, 0x17ee52a2, 0x16e2cb54, 0x166487af,
  0x14fbf8b8, 0x147db443, 0x15712db5, 0x15f7614e, 0x3e19a3d2, 0x3e9fef29,
  0x3f9376df, 0x3f153a24, 0x3d8a4533, 0x3d0c09c8, 0x3c00903e, 0x3c86dcc5,
  0x39b822eb, 0x393e6e10, 0x3832f7e6, 0x38b4bb1d, 0x3a2bc40a, 0x3aad88f1,
  0x3ba11107, 0x3b275dfc, 0x31dced5b, 0x315aa1a0, 0x30563856, 0x30d074ad,
  0x324f0bba, 0x32c94741, 0x33c5deb7, 0x3343924c, 0x367d6c62, 0x36fb2099,
  0x37f7b96f, 0x3771f594, 0x35ee8a83, 0x3568c678, 0x34645f8e, 0x34e21375,
  0x2115723b, 0x21933ec0, 0x209fa736, 0x2019ebcd, 0x228694da, 0x2200d821,
  0x230c41d7, 0x238a0d2c, 0x26b4f302, 0x2632bff9, 0x273e260f, 0x27b86af4,
  0x252715e3, 0x25a15918, 0x24adc0ee, 0x242b8c15, 0x2ed03cb2, 0x2e567049,
  0x2f5ae9bf, 0x2fdca544, 0x2d43da53, 0x2dc596a8, 0x2cc90f5e, 0x2c4f43a5,
  0x2971bd8b, 0x29f7f170, 0x28fb6886, 0x287d247d, 0x2ae25b6a, 0x2a641791,
  0x2b688e67, 0x2beec29c, 0x7c3347a4, 0x7cb50b5f, 0x7db992a9, 0x7d3fde52,
  0x7fa0a145, 0x7f26edbe, 0x7e2a7448, 0x7eac38b3, 0x7b92c69d, 0x7b148a66,
  0x7a181390, 0x7a9e5f6b, 0x7801207c, 0x78876c87, 0x798bf571, 0x790db98a,
  0x73f6092d, 0x737045d6, 0x727cdc20, 0x72fa90db, 0x7065efcc, 0x70e3a337,
  0x71ef3ac1, 0x7169763a, 0x74578814, 0x74d1c4ef, 0x75dd5d19, 0x755b11e2,
  0x77c46ef5, 0x7742220e, 0x764ebbf8, 0x76c8f703, 0x633f964d, 0x63b9dab6,
  0x62b54340, 0x62330fbb, 0x60ac70ac, 0x602a3c57, 0x6126a5a1, 0x61a0e95a,
  0x649e1774, 0x64185b8f, 0x6514c279, 0x65928e82, 0x670df195, 0x678bbd6e,
  0x66872498, 0x66016863, 0x6cfad8c4, 0x6c7c943f, 0x6d700dc9, 0x6df64132,
  0x6f693e25, 0x6fef72de, 0x6ee3eb28, 0x6e65a7d3, 0x6b5b59fd, 0x6bdd1506,
  0x6ad18cf0, 0x6a57c00b, 0x68c8bf1c, 0x684ef3e7, 0x69426a11, 0x69c426ea,
  0x422ae476, 0x42aca88d, 0x43a0317b, 0x43267d80, 0x41b90297, 0x413f4e6c,
  0x4033d79a, 0x40b59b61, 0x458b654f, 0x450d29b4, 0x4401b042, 0x4487fcb9,
  0x461883ae, 0x469ecf55, 0x479256a3, 0x47141a58, 0x4defaaff, 0x4d69e604,
  0x4c657ff2, 0x4ce33309, 0x4e7c4c1e, 0x4efa00e5, 0x4ff69913, 0x4f70d5e8,
  0x4a4e2bc6, 0x4ac8673d, 0x4bc4fecb, 0x4b42b230, 0x49ddcd27, 0x495b81dc,
  0x4857182a, 0x48d154d1, 0x5d26359f, 0x5da07964, 0x5cace092, 0x5c2aac69,
  0x5eb5d37e, 0x5e339f85, 0x5f3f0673, 0x5fb94a88, 0x5a87b4a6, 0x5a01f85d,
  0x5b0d61ab, 0x5b8b2d50, 0x59145247, 0x59921ebc, 0x589e874a, 0x5818cbb1,
  0x52e37b16, 0x526537ed, 0x5369ae1b, 0x53efe2e0, 0x51709df7, 0x51f6d10c,
  0x50fa48fa, 0x507c0401, 0x5542fa2f, 0x55c4b6d4, 0x54c82f22, 0x544e63d9,
  0x56d11cce, 0x56575035, 0x575bc9c3, 0x57dd8538
};


static gpg_error_t
enc_start (struct b64state *state, FILE *fp, estream_t stream,
           const char *title)
{
  memset (state, 0, sizeof *state);
  state->fp = fp;
  state->stream = stream;
  state->lasterr = 0;
  if (title && !*title)
    state->flags |= B64ENC_NO_LINEFEEDS;
  else if (title)
    {
      if (!strncmp (title, "PGP ", 4))
        {
          state->flags |= B64ENC_USE_PGPCRC;
          state->crc = CRCINIT;
        }
      state->title = xtrystrdup (title);
      if (!state->title)
        state->lasterr = gpg_error_from_syserror ();
    }
  return state->lasterr;
}


/* Prepare for base-64 writing to the stream FP.  If TITLE is not NULL
   and not an empty string, this string will be used as the title for
   the armor lines, with TITLE being an empty string, we don't write
   the header lines and furthermore even don't write any linefeeds.
   If TITLE starts with "PGP " the OpenPGP CRC checksum will be
   written as well.  With TITLE being NULL, we merely don't write
   header but make sure that lines are not too long. Note, that we
   don't write any output unless at least one byte get written using
   b64enc_write. */
gpg_error_t
b64enc_start (struct b64state *state, FILE *fp, const char *title)
{
  return enc_start (state, fp, NULL, title);
}

/* Same as b64enc_start but takes an estream.  */
gpg_error_t
b64enc_start_es (struct b64state *state, estream_t fp, const char *title)
{
  return enc_start (state, NULL, fp, title);
}


static int
my_fputs (const char *string, struct b64state *state)
{
  if (state->stream)
    return es_fputs (string, state->stream);
  else
    return fputs (string, state->fp);
}


/* Write NBYTES from BUFFER to the Base 64 stream identified by
   STATE. With BUFFER and NBYTES being 0, merely do a fflush on the
   stream. */
gpg_error_t
b64enc_write (struct b64state *state, const void *buffer, size_t nbytes)
{
  unsigned char radbuf[4];
  int idx, quad_count;
  const unsigned char *p;

  if (state->lasterr)
    return state->lasterr;

  if (!nbytes)
    {
      if (buffer)
        if (state->stream? es_fflush (state->stream) : fflush (state->fp))
          goto write_error;
      return 0;
    }

  if (!(state->flags & B64ENC_DID_HEADER))
    {
      if (state->title)
        {
          if ( my_fputs ("-----BEGIN ", state) == EOF
               || my_fputs (state->title, state) == EOF
               || my_fputs ("-----\n", state) == EOF)
            goto write_error;
          if ( (state->flags & B64ENC_USE_PGPCRC)
               && my_fputs ("\n", state) == EOF)
            goto write_error;
        }

      state->flags |= B64ENC_DID_HEADER;
    }

  idx = state->idx;
  quad_count = state->quad_count;
  assert (idx < 4);
  memcpy (radbuf, state->radbuf, idx);

  if ( (state->flags & B64ENC_USE_PGPCRC) )
    {
      size_t n;
      u32 crc = state->crc;

      for (p=buffer, n=nbytes; n; p++, n-- )
        crc = ((u32)crc << 8) ^ crc_table[((crc >> 16)&0xff) ^ *p];
      state->crc = (crc & 0x00ffffff);
    }

  for (p=buffer; nbytes; p++, nbytes--)
    {
      radbuf[idx++] = *p;
      if (idx > 2)
        {
          char tmp[4];

          tmp[0] = bintoasc[(*radbuf >> 2) & 077];
          tmp[1] = bintoasc[(((*radbuf<<4)&060)|((radbuf[1] >> 4)&017))&077];
          tmp[2] = bintoasc[(((radbuf[1]<<2)&074)|((radbuf[2]>>6)&03))&077];
          tmp[3] = bintoasc[radbuf[2]&077];
          if (state->stream)
            {
              for (idx=0; idx < 4; idx++)
                es_putc (tmp[idx], state->stream);
              idx = 0;
              if (es_ferror (state->stream))
                goto write_error;
            }
          else
            {
              for (idx=0; idx < 4; idx++)
                putc (tmp[idx], state->fp);
              idx = 0;
              if (ferror (state->fp))
                goto write_error;
            }
          if (++quad_count >= (64/4))
            {
              quad_count = 0;
              if (!(state->flags & B64ENC_NO_LINEFEEDS)
                  && my_fputs ("\n", state) == EOF)
                goto write_error;
            }
        }
    }
  memcpy (state->radbuf, radbuf, idx);
  state->idx = idx;
  state->quad_count = quad_count;
  return 0;

 write_error:
  state->lasterr = gpg_error_from_syserror ();
  if (state->title)
    {
      xfree (state->title);
      state->title = NULL;
    }
  return state->lasterr;
}


gpg_error_t
b64enc_finish (struct b64state *state)
{
  gpg_error_t err = 0;
  unsigned char radbuf[4];
  int idx, quad_count;
  char tmp[4];

  if (state->lasterr)
    return state->lasterr;

  if (!(state->flags & B64ENC_DID_HEADER))
    goto cleanup;

  /* Flush the base64 encoding */
  idx = state->idx;
  quad_count = state->quad_count;
  assert (idx < 4);
  memcpy (radbuf, state->radbuf, idx);

  if (idx)
    {
      tmp[0] = bintoasc[(*radbuf>>2)&077];
      if (idx == 1)
        {
          tmp[1] = bintoasc[((*radbuf << 4) & 060) & 077];
          tmp[2] = '=';
          tmp[3] = '=';
        }
      else
        {
          tmp[1] = bintoasc[(((*radbuf<<4)&060)|((radbuf[1]>>4)&017))&077];
          tmp[2] = bintoasc[((radbuf[1] << 2) & 074) & 077];
          tmp[3] = '=';
        }
      if (state->stream)
        {
          for (idx=0; idx < 4; idx++)
            es_putc (tmp[idx], state->stream);
          if (es_ferror (state->stream))
            goto write_error;
        }
      else
        {
          for (idx=0; idx < 4; idx++)
            putc (tmp[idx], state->fp);
          if (ferror (state->fp))
            goto write_error;
        }

      if (++quad_count >= (64/4))
        {
          quad_count = 0;
          if (!(state->flags & B64ENC_NO_LINEFEEDS)
              && my_fputs ("\n", state) == EOF)
            goto write_error;
        }
    }

  /* Finish the last line and write the trailer. */
  if (quad_count
      && !(state->flags & B64ENC_NO_LINEFEEDS)
      && my_fputs ("\n", state) == EOF)
    goto write_error;

  if ( (state->flags & B64ENC_USE_PGPCRC) )
    {
      /* Write the CRC.  */
      my_fputs ("=", state);
      radbuf[0] = state->crc >>16;
      radbuf[1] = state->crc >> 8;
      radbuf[2] = state->crc;
      tmp[0] = bintoasc[(*radbuf>>2)&077];
      tmp[1] = bintoasc[(((*radbuf<<4)&060)|((radbuf[1]>>4)&017))&077];
      tmp[2] = bintoasc[(((radbuf[1]<<2)&074)|((radbuf[2]>>6)&03))&077];
      tmp[3] = bintoasc[radbuf[2]&077];
      if (state->stream)
        {
          for (idx=0; idx < 4; idx++)
            es_putc (tmp[idx], state->stream);
          if (es_ferror (state->stream))
            goto write_error;
        }
      else
        {
          for (idx=0; idx < 4; idx++)
            putc (tmp[idx], state->fp);
          if (ferror (state->fp))
            goto write_error;
        }
      if (!(state->flags & B64ENC_NO_LINEFEEDS)
          && my_fputs ("\n", state) == EOF)
        goto write_error;
    }

  if (state->title)
    {
      if ( my_fputs ("-----END ", state) == EOF
           || my_fputs (state->title, state) == EOF
           || my_fputs ("-----\n", state) == EOF)
        goto write_error;
    }

  goto cleanup;

 write_error:
  err = gpg_error_from_syserror ();

 cleanup:
  if (state->title)
    {
      xfree (state->title);
      state->title = NULL;
    }
  state->fp = NULL;
  state->stream = NULL;
  state->lasterr = err;
  return err;
}