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gnupg2/common/convert.c

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/* convert.c - Hex conversion functions.
* Copyright (C) 2006, 2008 Free Software Foundation, Inc.
*
* This file is part of GnuPG.
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of either
*
* - the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 3 of the License, or (at
* your option) any later version.
*
* or
*
* - the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* or both in parallel, as here.
*
* 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 General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include "util.h"
#define tohex(n) ((n) < 10 ? ((n) + '0') : (((n) - 10) + 'A'))
/* Convert STRING consisting of hex characters into its binary
representation and store that at BUFFER. BUFFER needs to be of
LENGTH bytes. The function checks that the STRING will convert
exactly to LENGTH bytes. The string is delimited by either end of
string or a white space character. The function returns -1 on
error or the length of the parsed string. */
int
hex2bin (const char *string, void *buffer, size_t length)
{
int i;
const char *s = string;
for (i=0; i < length; )
{
if (!hexdigitp (s) || !hexdigitp (s+1))
return -1; /* Invalid hex digits. */
((unsigned char*)buffer)[i++] = xtoi_2 (s);
s += 2;
}
if (*s && (!isascii (*s) || !isspace (*s)) )
return -1; /* Not followed by Nul or white space. */
if (i != length)
return -1; /* Not of expected length. */
if (*s)
s++; /* Skip the delimiter. */
return s - string;
}
/* Convert STRING consisting of hex characters into its binary representation
and store that at BUFFER. BUFFER needs to be of LENGTH bytes. The
function check that the STRING will convert exactly to LENGTH
bytes. Colons between the hex digits are allowed, if one colon
has been given a colon is expected very 2 characters. The string
is delimited by either end of string or a white space character.
The function returns -1 on error or the length of the parsed
string. */
int
hexcolon2bin (const char *string, void *buffer, size_t length)
{
int i;
const char *s = string;
int need_colon = 0;
for (i=0; i < length; )
{
if (i==1 && *s == ':') /* Skip colons between hex digits. */
{
need_colon = 1;
s++;
}
else if (need_colon && *s == ':')
s++;
else if (need_colon)
return -1; /* Colon expected. */
if (!hexdigitp (s) || !hexdigitp (s+1))
return -1; /* Invalid hex digits. */
((unsigned char*)buffer)[i++] = xtoi_2 (s);
s += 2;
}
if (*s == ':')
return -1; /* Trailing colons are not allowed. */
if (*s && (!isascii (*s) || !isspace (*s)) )
return -1; /* Not followed by Nul or white space. */
if (i != length)
return -1; /* Not of expected length. */
if (*s)
s++; /* Skip the delimiter. */
return s - string;
}
static char *
do_bin2hex (const void *buffer, size_t length, char *stringbuf, int with_colon)
{
const unsigned char *s;
char *p;
if (!stringbuf)
{
/* Not really correct for with_colon but we don't care about the
one wasted byte. */
size_t n = with_colon? 3:2;
size_t nbytes = n * length + 1;
if (length && (nbytes-1) / n != length)
{
gpg_err_set_errno (ENOMEM);
return NULL;
}
stringbuf = xtrymalloc (nbytes);
if (!stringbuf)
return NULL;
}
for (s = buffer, p = stringbuf; length; length--, s++)
{
if (with_colon && s != buffer)
*p++ = ':';
*p++ = tohex ((*s>>4)&15);
*p++ = tohex (*s&15);
}
*p = 0;
return stringbuf;
}
/* Convert LENGTH bytes of data in BUFFER into hex encoding and store
that at the provided STRINGBUF. STRINGBUF must be allocated of at
least (2*LENGTH+1) bytes or be NULL so that the function mallocs an
appropriate buffer. Returns STRINGBUF or NULL on error (which may
only occur if STRINGBUF has been NULL and the internal malloc
failed). */
char *
bin2hex (const void *buffer, size_t length, char *stringbuf)
{
return do_bin2hex (buffer, length, stringbuf, 0);
}
/* Convert LENGTH bytes of data in BUFFER into hex encoding and store
that at the provided STRINGBUF. STRINGBUF must be allocated of at
least (3*LENGTH+1) bytes or be NULL so that the function mallocs an
appropriate buffer. Returns STRINGBUF or NULL on error (which may
only occur if STRINGBUF has been NULL and the internal malloc
failed). */
char *
bin2hexcolon (const void *buffer, size_t length, char *stringbuf)
{
return do_bin2hex (buffer, length, stringbuf, 1);
}
/* Convert HEXSTRING consisting of hex characters into string and
store that at BUFFER. HEXSTRING is either delimited by end of
string or a white space character. The function makes sure that
the resulting string in BUFFER is terminated by a Nul byte. Note
that the returned string may include embedded Nul bytes; the extra
Nul byte at the end is used to make sure tha the result can always
be used as a C-string.
BUFSIZE is the available length of BUFFER; if the converted result
plus a possible required extra Nul character does not fit into this
buffer, the function returns NULL and won't change the existing
content of BUFFER. In-place conversion is possible as long as
BUFFER points to HEXSTRING.
If BUFFER is NULL and BUFSIZE is 0 the function scans HEXSTRING but
does not store anything. This may be used to find the end of
HEXSTRING.
On success the function returns a pointer to the next character
after HEXSTRING (which is either end-of-string or a the next white
space). If BUFLEN is not NULL the number of valid vytes in BUFFER
is stored there (an extra Nul byte is not counted); this will even
be done if BUFFER has been passed as NULL. */
const char *
hex2str (const char *hexstring, char *buffer, size_t bufsize, size_t *buflen)
{
const char *s = hexstring;
int idx, count;
int need_nul = 0;
if (buflen)
*buflen = 0;
for (s=hexstring, count=0; hexdigitp (s) && hexdigitp (s+1); s += 2, count++)
;
if (*s && (!isascii (*s) || !isspace (*s)) )
{
gpg_err_set_errno (EINVAL);
return NULL; /* Not followed by Nul or white space. */
}
/* We need to append a nul character. However we don't want that if
the hexstring already ends with "00". */
need_nul = ((s == hexstring) || !(s[-2] == '0' && s[-1] == '0'));
if (need_nul)
count++;
if (buffer)
{
if (count > bufsize)
{
gpg_err_set_errno (EINVAL);
return NULL; /* Too long. */
}
for (s=hexstring, idx=0; hexdigitp (s) && hexdigitp (s+1); s += 2)
((unsigned char*)buffer)[idx++] = xtoi_2 (s);
if (need_nul)
buffer[idx] = 0;
}
if (buflen)
*buflen = count - need_nul;
return s;
}
/* Same as hex2str but this function allocated a new string. Returns
NULL on error. If R_COUNT is not NULL, the number of scanned bytes
will be stored there. ERRNO is set on error. */
char *
hex2str_alloc (const char *hexstring, size_t *r_count)
{
const char *tail;
size_t nbytes;
char *result;
tail = hex2str (hexstring, NULL, 0, &nbytes);
if (!tail)
{
if (r_count)
*r_count = 0;
return NULL;
}
if (r_count)
*r_count = tail - hexstring;
result = xtrymalloc (nbytes+1);
if (!result)
return NULL;
if (!hex2str (hexstring, result, nbytes+1, NULL))
BUG ();
return result;
}
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