ascmagic.c revision 299236 
1/*
2 * Copyright (c) Ian F. Darwin 1986-1995.
3 * Software written by Ian F. Darwin and others;
4 * maintained 1995-present by Christos Zoulas and others.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice immediately at the beginning of the file, without modification,
11 *    this list of conditions, and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
20 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28/*
29 * ASCII magic -- try to detect text encoding.
30 *
31 * Extensively modified by Eric Fischer <enf@pobox.com> in July, 2000,
32 * to handle character codes other than ASCII on a unified basis.
33 */
34
35#include "file.h"
36
37#ifndef	lint
38FILE_RCSID("@(#)$File: ascmagic.c,v 1.92 2015/04/09 20:01:41 christos Exp $")
39#endif	/* lint */
40
41#include "magic.h"
42#include <string.h>
43#include <memory.h>
44#include <ctype.h>
45#include <stdlib.h>
46#ifdef HAVE_UNISTD_H
47#include <unistd.h>
48#endif
49
50#define MAXLINELEN 300	/* longest sane line length */
51#define ISSPC(x) ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' \
52		  || (x) == 0x85 || (x) == '\f')
53
54private unsigned char *encode_utf8(unsigned char *, size_t, unichar *, size_t);
55private size_t trim_nuls(const unsigned char *, size_t);
56
57/*
58 * Undo the NUL-termination kindly provided by process()
59 * but leave at least one byte to look at
60 */
61private size_t
62trim_nuls(const unsigned char *buf, size_t nbytes)
63{
64	while (nbytes > 1 && buf[nbytes - 1] == '\0')
65		nbytes--;
66
67	return nbytes;
68}
69
70protected int
71file_ascmagic(struct magic_set *ms, const unsigned char *buf, size_t nbytes,
72	int text)
73{
74	unichar *ubuf = NULL;
75	size_t ulen = 0;
76	int rv = 1;
77
78	const char *code = NULL;
79	const char *code_mime = NULL;
80	const char *type = NULL;
81
82	if (ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))
83		return 0;
84
85	nbytes = trim_nuls(buf, nbytes);
86
87	/* If file doesn't look like any sort of text, give up. */
88	if (file_encoding(ms, buf, nbytes, &ubuf, &ulen, &code, &code_mime,
89	    &type) == 0)
90		rv = 0;
91        else
92		rv = file_ascmagic_with_encoding(ms, buf, nbytes, ubuf, ulen, code,
93						 type, text);
94
95	free(ubuf);
96
97	return rv;
98}
99
100protected int
101file_ascmagic_with_encoding(struct magic_set *ms, const unsigned char *buf,
102    size_t nbytes, unichar *ubuf, size_t ulen, const char *code,
103    const char *type, int text)
104{
105	unsigned char *utf8_buf = NULL, *utf8_end;
106	size_t mlen, i;
107	int rv = -1;
108	int mime = ms->flags & MAGIC_MIME;
109
110	const char *subtype = NULL;
111	const char *subtype_mime = NULL;
112
113	int has_escapes = 0;
114	int has_backspace = 0;
115	int seen_cr = 0;
116
117	int n_crlf = 0;
118	int n_lf = 0;
119	int n_cr = 0;
120	int n_nel = 0;
121	int executable = 0;
122
123	size_t last_line_end = (size_t)-1;
124	int has_long_lines = 0;
125
126	if (ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))
127		return 0;
128
129	nbytes = trim_nuls(buf, nbytes);
130
131	/* If we have fewer than 2 bytes, give up. */
132	if (nbytes <= 1) {
133		rv = 0;
134		goto done;
135	}
136
137	if (ulen > 0 && (ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
138		/* Convert ubuf to UTF-8 and try text soft magic */
139		/* malloc size is a conservative overestimate; could be
140		   improved, or at least realloced after conversion. */
141		mlen = ulen * 6;
142		if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
143			file_oomem(ms, mlen);
144			goto done;
145		}
146		if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
147		    == NULL)
148			goto done;
149		if ((rv = file_softmagic(ms, utf8_buf,
150		    (size_t)(utf8_end - utf8_buf), 0, NULL,
151		    TEXTTEST, text)) == 0)
152			rv = -1;
153	}
154
155	/* Now try to discover other details about the file. */
156	for (i = 0; i < ulen; i++) {
157		if (ubuf[i] == '\n') {
158			if (seen_cr)
159				n_crlf++;
160			else
161				n_lf++;
162			last_line_end = i;
163		} else if (seen_cr)
164			n_cr++;
165
166		seen_cr = (ubuf[i] == '\r');
167		if (seen_cr)
168			last_line_end = i;
169
170		if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
171			n_nel++;
172			last_line_end = i;
173		}
174
175		/* If this line is _longer_ than MAXLINELEN, remember it. */
176		if (i > last_line_end + MAXLINELEN)
177			has_long_lines = 1;
178
179		if (ubuf[i] == '\033')
180			has_escapes = 1;
181		if (ubuf[i] == '\b')
182			has_backspace = 1;
183	}
184
185	/* Beware, if the data has been truncated, the final CR could have
186	   been followed by a LF.  If we have HOWMANY bytes, it indicates
187	   that the data might have been truncated, probably even before
188	   this function was called. */
189	if (seen_cr && nbytes < HOWMANY)
190		n_cr++;
191
192	if (strcmp(type, "binary") == 0) {
193		rv = 0;
194		goto done;
195	}
196	if (mime) {
197		if (!file_printedlen(ms) && (mime & MAGIC_MIME_TYPE) != 0) {
198			if (subtype_mime) {
199				if (file_printf(ms, "%s", subtype_mime) == -1)
200					goto done;
201			} else {
202				if (file_printf(ms, "text/plain") == -1)
203					goto done;
204			}
205		}
206	} else {
207		if (file_printedlen(ms)) {
208			switch (file_replace(ms, " text$", ", ")) {
209			case 0:
210				switch (file_replace(ms, " text executable$",
211				    ", ")) {
212				case 0:
213					if (file_printf(ms, ", ") == -1)
214						goto done;
215					break;
216				case -1:
217					goto done;
218				default:
219					executable = 1;
220					break;
221				}
222				break;
223			case -1:
224				goto done;
225			default:
226				break;
227			}
228		}
229
230		if (file_printf(ms, "%s", code) == -1)
231			goto done;
232
233		if (subtype) {
234			if (file_printf(ms, " %s", subtype) == -1)
235				goto done;
236		}
237
238		if (file_printf(ms, " %s", type) == -1)
239			goto done;
240
241		if (executable)
242			if (file_printf(ms, " executable") == -1)
243				goto done;
244
245		if (has_long_lines)
246			if (file_printf(ms, ", with very long lines") == -1)
247				goto done;
248
249		/*
250		 * Only report line terminators if we find one other than LF,
251		 * or if we find none at all.
252		 */
253		if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
254		    (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
255			if (file_printf(ms, ", with") == -1)
256				goto done;
257
258			if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
259				if (file_printf(ms, " no") == -1)
260					goto done;
261			} else {
262				if (n_crlf) {
263					if (file_printf(ms, " CRLF") == -1)
264						goto done;
265					if (n_cr || n_lf || n_nel)
266						if (file_printf(ms, ",") == -1)
267							goto done;
268				}
269				if (n_cr) {
270					if (file_printf(ms, " CR") == -1)
271						goto done;
272					if (n_lf || n_nel)
273						if (file_printf(ms, ",") == -1)
274							goto done;
275				}
276				if (n_lf) {
277					if (file_printf(ms, " LF") == -1)
278						goto done;
279					if (n_nel)
280						if (file_printf(ms, ",") == -1)
281							goto done;
282				}
283				if (n_nel)
284					if (file_printf(ms, " NEL") == -1)
285						goto done;
286			}
287
288			if (file_printf(ms, " line terminators") == -1)
289				goto done;
290		}
291
292		if (has_escapes)
293			if (file_printf(ms, ", with escape sequences") == -1)
294				goto done;
295		if (has_backspace)
296			if (file_printf(ms, ", with overstriking") == -1)
297				goto done;
298	}
299	rv = 1;
300done:
301	free(utf8_buf);
302
303	return rv;
304}
305
306/*
307 * Encode Unicode string as UTF-8, returning pointer to character
308 * after end of string, or NULL if an invalid character is found.
309 */
310private unsigned char *
311encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
312{
313	size_t i;
314	unsigned char *end = buf + len;
315
316	for (i = 0; i < ulen; i++) {
317		if (ubuf[i] <= 0x7f) {
318			if (end - buf < 1)
319				return NULL;
320			*buf++ = (unsigned char)ubuf[i];
321		} else if (ubuf[i] <= 0x7ff) {
322			if (end - buf < 2)
323				return NULL;
324			*buf++ = (unsigned char)((ubuf[i] >> 6) + 0xc0);
325			*buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
326		} else if (ubuf[i] <= 0xffff) {
327			if (end - buf < 3)
328				return NULL;
329			*buf++ = (unsigned char)((ubuf[i] >> 12) + 0xe0);
330			*buf++ = (unsigned char)(((ubuf[i] >> 6) & 0x3f) + 0x80);
331			*buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
332		} else if (ubuf[i] <= 0x1fffff) {
333			if (end - buf < 4)
334				return NULL;
335			*buf++ = (unsigned char)((ubuf[i] >> 18) + 0xf0);
336			*buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
337			*buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
338			*buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
339		} else if (ubuf[i] <= 0x3ffffff) {
340			if (end - buf < 5)
341				return NULL;
342			*buf++ = (unsigned char)((ubuf[i] >> 24) + 0xf8);
343			*buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
344			*buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
345			*buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
346			*buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
347		} else if (ubuf[i] <= 0x7fffffff) {
348			if (end - buf < 6)
349				return NULL;
350			*buf++ = (unsigned char)((ubuf[i] >> 30) + 0xfc);
351			*buf++ = (unsigned char)(((ubuf[i] >> 24) & 0x3f) + 0x80);
352			*buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
353			*buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
354			*buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
355			*buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
356		} else /* Invalid character */
357			return NULL;
358	}
359
360	return buf;
361}
362