/*
* fmt_rfc2047.c -- decode RFC-2047 header format
*
* $Id: fmt_rfc2047.c,v 1.4 2005/11/06 21:54:40 pm215 Exp $
*
* This code is Copyright (c) 2002, by the authors of nmh. See the
* COPYRIGHT file in the root directory of the nmh distribution for
* complete copyright information.
*/
#include <h/mh.h>
#ifdef HAVE_ICONV
# include <iconv.h>
# include <errno.h>
#endif
static signed char hexindex[] = {
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
0, 1, 2, 3, 4, 5, 6, 7, 8, 9,-1,-1,-1,-1,-1,-1,
-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,10,11,12,13,14,15,-1,-1,-1,-1,-1,-1,-1,-1,-1,
-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1
};
static signed char index_64[128] = {
-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,62, -1,-1,-1,63,
52,53,54,55, 56,57,58,59, 60,61,-1,-1, -1,-1,-1,-1,
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10, 11,12,13,14,
15,16,17,18, 19,20,21,22, 23,24,25,-1, -1,-1,-1,-1,
-1,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
41,42,43,44, 45,46,47,48, 49,50,51,-1, -1,-1,-1,-1
};
#define char64(c) (((unsigned char) (c) > 127) ? -1 : index_64[(unsigned char) (c)])
static int
unqp (unsigned char byte1, unsigned char byte2)
{
if (hexindex[byte1] == -1 || hexindex[byte2] == -1)
return -1;
return (hexindex[byte1] << 4 | hexindex[byte2]);
}
/* Check if character is linear whitespace */
#define is_lws(c) ((c) == ' ' || (c) == '\t' || (c) == '\n')
/*
* Decode the string as a RFC-2047 header field
*/
/* Add character to the destination buffer, and bomb out if it fills up */
#define ADDCHR(C) do { *q++ = (C); dstlen--; if (!dstlen) goto buffull; } while (0)
int
decode_rfc2047 (char *str, char *dst, size_t dstlen)
{
char *p, *q, *pp;
char *startofmime, *endofmime;
int c, quoted_printable;
int encoding_found = 0; /* did we decode anything? */
int between_encodings = 0; /* are we between two encodings? */
int equals_pending = 0; /* is there a '=' pending? */
int whitespace = 0; /* how much whitespace between encodings? */
#ifdef HAVE_ICONV
int use_iconv = 0; /* are we converting encoding with iconv? */
iconv_t cd;
int fromutf8 = 0;
char *saveq, *convbuf = NULL;
size_t savedstlen;
#endif
if (!str)
return 0;
/*
* Do a quick and dirty check for the '=' character.
* This should quickly eliminate many cases.
*/
if (!strchr (str, '='))
return 0;
for (p = str, q = dst; *p; p++) {
/* reset iconv */
#ifdef HAVE_ICONV
if (use_iconv) {
iconv_close(cd);
use_iconv = 0;
}
#endif
/*
* If we had an '=' character pending from
* last iteration, then add it first.
*/
if (equals_pending) {
ADDCHR('=');
equals_pending = 0;
between_encodings = 0; /* we have added non-whitespace text */
}
if (*p != '=') {
/* count linear whitespace while between encodings */
if (between_encodings && is_lws(*p))
whitespace++;
else
between_encodings = 0; /* we have added non-whitespace text */
ADDCHR(*p);
continue;
}
equals_pending = 1; /* we have a '=' pending */
/* Check for initial =? */
if (*p == '=' && p[1] && p[1] == '?' && p[2]) {
startofmime = p + 2;
/* Scan ahead for the next '?' character */
for (pp = startofmime; *pp && *pp != '?'; pp++)
;
if (!*pp)
continue;
/* Check if character set can be handled natively */
if (!check_charset(startofmime, pp - startofmime)) {
#ifdef HAVE_ICONV
/* .. it can't. We'll use iconv then. */
*pp = '\0';
cd = iconv_open(get_charset(), startofmime);
fromutf8 = !strcasecmp(startofmime, "UTF-8");
*pp = '?';
if (cd == (iconv_t)-1) continue;
use_iconv = 1;
#else
continue;
#endif
}
startofmime = pp + 1;
/* Check for valid encoding type */
if (*startofmime != 'B' && *startofmime != 'b' &&
*startofmime != 'Q' && *startofmime != 'q')
continue;
/* Is encoding quoted printable or base64? */
quoted_printable = (*startofmime == 'Q' || *startofmime == 'q');
startofmime++;
/* Check for next '?' character */
if (*startofmime != '?')
continue;
startofmime++;
/*
* Scan ahead for the ending ?=
*
* While doing this, we will also check if encoded
* word has any embedded linear whitespace.
*/
endofmime = NULL;
for (pp = startofmime; *pp && *(pp+1); pp++) {
if (is_lws(*pp)) {
break;
} else if (*pp == '?' && pp[1] == '=') {
endofmime = pp;
break;
}
}
if (is_lws(*pp) || endofmime == NULL)
continue;
/*
* We've found an encoded word, so we can drop
* the '=' that was pending
*/
equals_pending = 0;
/*
* If we are between two encoded words separated only by
* linear whitespace, then we ignore the whitespace.
* We will roll back the buffer the number of whitespace
* characters we've seen since last encoded word.
*/
if (between_encodings) {
q -= whitespace;
dstlen += whitespace;
}
#ifdef HAVE_ICONV
if (use_iconv) {
saveq = q;
savedstlen = dstlen;
if (!(q = convbuf = (char *)malloc(endofmime - startofmime)))
continue;
}
/* ADDCHR2 is for adding characters when q is or might be convbuf:
* in this case on buffer-full we want to run iconv before returning.
* I apologise for the dreadful name.
*/
#define ADDCHR2(C) do { *q++ = (C); dstlen--; if (!dstlen) goto iconvbuffull; } while (0)
#else
#define ADDCHR2(C) ADDCHR(C)
#endif
/* Now decode the text */
if (quoted_printable) {
for (pp = startofmime; pp < endofmime; pp++) {
if (*pp == '=') {
c = unqp (pp[1], pp[2]);
if (c == -1)
continue;
if (c != 0)
*q++ = c;
pp += 2;
} else if (*pp == '_') {
ADDCHR2(' ');
} else {
ADDCHR2(*pp);
}
}
} else {
/* base64 */
int c1, c2, c3, c4;
pp = startofmime;
while (pp < endofmime) {
/* 6 + 2 bits */
while ((pp < endofmime) &&
((c1 = char64(*pp)) == -1)) {
pp++;
}
if (pp < endofmime) {
pp++;
}
while ((pp < endofmime) &&
((c2 = char64(*pp)) == -1)) {
pp++;
}
if (pp < endofmime && c1 != -1 && c2 != -1) {
ADDCHR2((c1 << 2) | (c2 >> 4));
pp++;
}
/* 4 + 4 bits */
while ((pp < endofmime) &&
((c3 = char64(*pp)) == -1)) {
pp++;
}
if (pp < endofmime && c2 != -1 && c3 != -1) {
ADDCHR2(((c2 & 0xF) << 4) | (c3 >> 2));
pp++;
}
/* 2 + 6 bits */
while ((pp < endofmime) &&
((c4 = char64(*pp)) == -1)) {
pp++;
}
if (pp < endofmime && c3 != -1 && c4 != -1) {
ADDCHR2(((c3 & 0x3) << 6) | (c4));
pp++;
}
}
}
#ifdef HAVE_ICONV
iconvbuffull:
/* NB that the string at convbuf is not necessarily NUL terminated here:
* q points to the first byte after the valid part.
*/
/* Convert to native character set */
if (use_iconv) {
size_t inbytes = q - convbuf;
ICONV_CONST char *start = convbuf;
while (inbytes) {
if (iconv(cd, &start, &inbytes, &saveq, &savedstlen) ==
(size_t)-1) {
if (errno != EILSEQ) break;
/* character couldn't be converted. we output a `?'
* and try to carry on which won't work if
* either encoding was stateful */
iconv (cd, 0, 0, &saveq, &savedstlen);
if (!savedstlen)
break;
*saveq++ = '?';
savedstlen--;
if (!savedstlen)
break;
/* skip to next input character */
if (fromutf8) {
for (start++;(start < q) && ((*start & 192) == 128);start++)
inbytes--;
} else
start++, inbytes--;
if (start >= q)
break;
}
}
q = saveq;
/* Stop now if (1) we hit the end of the buffer trying to do
* MIME decoding and have just iconv-converted a partial string
* or (2) our iconv-conversion hit the end of the buffer.
*/
if (!dstlen || !savedstlen)
goto buffull;
dstlen = savedstlen;
free(convbuf);
}
#endif
/*
* Now that we are done decoding this particular
* encoded word, advance string to trailing '='.
*/
p = endofmime + 1;
encoding_found = 1; /* we found (at least 1) encoded word */
between_encodings = 1; /* we have just decoded something */
whitespace = 0; /* re-initialize amount of whitespace */
}
}
#ifdef HAVE_ICONV
if (use_iconv) iconv_close(cd);
#endif
/* If an equals was pending at end of string, add it now. */
if (equals_pending)
ADDCHR('=');
*q = '\0';
return encoding_found;
buffull:
/* q is currently just off the end of the buffer, so rewind to NUL terminate */
q--;
*q = '\0';
return encoding_found;
}
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