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b64dec.c
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/* b64dec.c - Simple Base64 decoder.
* Copyright (C) 2008, 2011 Free Software Foundation, Inc.
* Copyright (C) 2008, 2011, 2016 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/>.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include "i18n.h"
#include "util.h"
/* The reverse base-64 list used for base-64 decoding. */
static unsigned char const asctobin[128] =
{
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
0x3c, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e,
0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16,
0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff
};
enum decoder_states
{
s_init, s_idle, s_lfseen, s_beginseen, s_waitheader, s_waitblank, s_begin,
s_b64_0, s_b64_1, s_b64_2, s_b64_3,
s_waitendtitle, s_waitend
};
/* Initialize the context for the base64 decoder. If TITLE is NULL a
plain base64 decoding is done. If it is the empty string the
decoder will skip everything until a "-----BEGIN " line has been
seen, decoding ends at a "----END " line. */
gpg_error_t
b64dec_start (struct b64state *state, const char *title)
{
memset (state, 0, sizeof *state);
if (title)
{
state->title = xtrystrdup (title);
if (!state->title)
state->lasterr = gpg_error_from_syserror ();
else
state->idx = s_init;
}
else
state->idx = s_b64_0;
return state->lasterr;
}
/* Do in-place decoding of base-64 data of LENGTH in BUFFER. Stores the
new length of the buffer at R_NBYTES. */
gpg_error_t
b64dec_proc (struct b64state *state, void *buffer, size_t length,
size_t *r_nbytes)
{
enum decoder_states ds = state->idx;
unsigned char val = state->radbuf[0];
int pos = state->quad_count;
char *d, *s;
if (state->lasterr)
return state->lasterr;
if (state->stop_seen)
{
*r_nbytes = 0;
state->lasterr = gpg_error (GPG_ERR_EOF);
xfree (state->title);
state->title = NULL;
return state->lasterr;
}
for (s=d=buffer; length && !state->stop_seen; length--, s++)
{
again:
switch (ds)
{
case s_idle:
if (*s == '\n')
{
ds = s_lfseen;
pos = 0;
}
break;
case s_init:
ds = s_lfseen;
/* fall through */
case s_lfseen:
if (*s != "-----BEGIN "[pos])
{
ds = s_idle;
goto again;
}
else if (pos == 10)
{
pos = 0;
ds = s_beginseen;
}
else
pos++;
break;
case s_beginseen:
if (*s != "PGP "[pos])
ds = s_begin; /* Not a PGP armor. */
else if (pos == 3)
ds = s_waitheader;
else
pos++;
break;
case s_waitheader:
if (*s == '\n')
ds = s_waitblank;
break;
case s_waitblank:
if (*s == '\n')
ds = s_b64_0; /* blank line found. */
else if (*s == ' ' || *s == '\r' || *s == '\t')
; /* Ignore spaces. */
else
{
/* Armor header line. Note that we don't care that our
* FSM accepts a header prefixed with spaces. */
ds = s_waitheader; /* Wait for next header. */
}
break;
case s_begin:
if (*s == '\n')
ds = s_b64_0;
break;
case s_b64_0:
case s_b64_1:
case s_b64_2:
case s_b64_3:
{
int c;
if (*s == '-' && state->title)
{
/* Not a valid Base64 character: assume end
header. */
ds = s_waitend;
}
else if (*s == '=')
{
/* Pad character: stop */
if (ds == s_b64_1)
*d++ = val;
ds = state->title? s_waitendtitle : s_waitend;
}
else if (*s == '\n' || *s == ' ' || *s == '\r' || *s == '\t')
; /* Skip white spaces. */
else if ( (*s & 0x80)
|| (c = asctobin[*(unsigned char *)s]) == 255)
{
/* Skip invalid encodings. */
state->invalid_encoding = 1;
}
else if (ds == s_b64_0)
{
val = c << 2;
ds = s_b64_1;
}
else if (ds == s_b64_1)
{
val |= (c>>4)&3;
*d++ = val;
val = (c<<4)&0xf0;
ds = s_b64_2;
}
else if (ds == s_b64_2)
{
val |= (c>>2)&15;
*d++ = val;
val = (c<<6)&0xc0;
ds = s_b64_3;
}
else
{
val |= c&0x3f;
*d++ = val;
ds = s_b64_0;
}
}
break;
case s_waitendtitle:
if (*s == '-')
ds = s_waitend;
break;
case s_waitend:
if ( *s == '\n')
state->stop_seen = 1;
break;
default:
BUG();
}
}
state->idx = ds;
state->radbuf[0] = val;
state->quad_count = pos;
*r_nbytes = (d -(char*) buffer);
return 0;
}
/* This function needs to be called before releasing the decoder
state. It may return an error code in case an encoding error has
been found during decoding. */
gpg_error_t
b64dec_finish (struct b64state *state)
{
xfree (state->title);
state->title = NULL;
if (state->lasterr)
return state->lasterr;
return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0;
}

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