cbc.c revision 81220 
1/* cbc.c: This file contains the encryption routines for the ed line editor */
2/*-
3 * Copyright (c) 1993 The Regents of the University of California.
4 * All rights reserved.
5 *
6 * Copyright (c) 1993 Andrew Moore, Talke Studio.
7 * All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. All advertising materials mentioning features or use of this software
18 *    must display the following acknowledgement:
19 *	This product includes software developed by the University of
20 *	California, Berkeley and its contributors.
21 * 4. Neither the name of the University nor the names of its contributors
22 *    may be used to endorse or promote products derived from this software
23 *    without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
28 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
35 * SUCH DAMAGE.
36 */
37
38#ifndef lint
39static const char rcsid[] =
40  "$FreeBSD: head/bin/ed/cbc.c 81220 2001-08-06 22:01:31Z mike $";
41#endif /* not lint */
42
43#include <sys/types.h>
44#include <errno.h>
45#include <pwd.h>
46#ifdef DES
47#include <time.h>
48#endif
49
50#include "ed.h"
51
52
53/*
54 * BSD and System V systems offer special library calls that do
55 * block move_liness and fills, so if possible we take advantage of them
56 */
57#define	MEMCPY(dest,src,len)	memcpy((dest),(src),(len))
58#define	MEMZERO(dest,len)	memset((dest), 0, (len))
59
60/* Hide the calls to the primitive encryption routines. */
61#define	DES_KEY(buf) \
62	if (des_setkey(buf)) \
63		des_error("des_setkey");
64#define	DES_XFORM(buf) \
65	if (des_cipher(buf, buf, 0L, (inverse ? -1 : 1))) \
66		des_error("des_cipher");
67
68/*
69 * read/write - no error checking
70 */
71#define	READ(buf, n, fp)	fread(buf, sizeof(char), n, fp)
72#define WRITE(buf, n, fp)	fwrite(buf, sizeof(char), n, fp)
73
74/*
75 * some things to make references easier
76 */
77typedef char Desbuf[8];
78#define	CHAR(x,i)	(x[i])
79#define	UCHAR(x,i)	(x[i])
80#define	BUFFER(x)	(x)
81#define	UBUFFER(x)	(x)
82
83/*
84 * global variables and related macros
85 */
86
87enum { 					/* encrypt, decrypt, authenticate */
88	MODE_ENCRYPT, MODE_DECRYPT, MODE_AUTHENTICATE
89} mode = MODE_ENCRYPT;
90
91Desbuf ivec;				/* initialization vector */
92Desbuf pvec;				/* padding vector */
93char bits[] = {				/* used to extract bits from a char */
94	'\200', '\100', '\040', '\020', '\010', '\004', '\002', '\001'
95};
96int pflag;				/* 1 to preserve parity bits */
97
98unsigned char des_buf[8];	/* shared buffer for get_des_char/put_des_char */
99int des_ct = 0;			/* count for get_des_char/put_des_char */
100int des_n = 0;			/* index for put_des_char/get_des_char */
101
102
103/* init_des_cipher: initialize DES */
104void
105init_des_cipher()
106{
107#ifdef DES
108	int i;
109
110	des_ct = des_n = 0;
111
112	/* initialize the initialization vector */
113	MEMZERO(ivec, 8);
114
115	/* initialize the padding vector */
116	for (i = 0; i < 8; i++)
117		CHAR(pvec, i) = (char) (arc4random() % 256);
118#endif
119}
120
121
122/* get_des_char: return next char in an encrypted file */
123int
124get_des_char(fp)
125	FILE *fp;
126{
127#ifdef DES
128	if (des_n >= des_ct) {
129		des_n = 0;
130		des_ct = cbc_decode(des_buf, fp);
131	}
132	return (des_ct > 0) ? des_buf[des_n++] : EOF;
133#else
134	return (getc(fp));
135#endif
136}
137
138
139/* put_des_char: write a char to an encrypted file; return char written */
140int
141put_des_char(c, fp)
142	int c;
143	FILE *fp;
144{
145#ifdef DES
146	if (des_n == sizeof des_buf) {
147		des_ct = cbc_encode(des_buf, des_n, fp);
148		des_n = 0;
149	}
150	return (des_ct >= 0) ? (des_buf[des_n++] = c) : EOF;
151#else
152	return (fputc(c, fp));
153#endif
154}
155
156
157/* flush_des_file: flush an encrypted file's output; return status */
158int
159flush_des_file(fp)
160	FILE *fp;
161{
162#ifdef DES
163	if (des_n == sizeof des_buf) {
164		des_ct = cbc_encode(des_buf, des_n, fp);
165		des_n = 0;
166	}
167	return (des_ct >= 0 && cbc_encode(des_buf, des_n, fp) >= 0) ? 0 : EOF;
168#else
169	return (fflush(fp));
170#endif
171}
172
173#ifdef DES
174/*
175 * get keyword from tty or stdin
176 */
177int
178get_keyword()
179{
180	char *p;			/* used to obtain the key */
181	Desbuf msgbuf;			/* I/O buffer */
182
183	/*
184	 * get the key
185	 */
186	if (*(p = getpass("Enter key: "))) {
187
188		/*
189		 * copy it, nul-padded, into the key area
190		 */
191		expand_des_key(BUFFER(msgbuf), p);
192		MEMZERO(p, _PASSWORD_LEN);
193		set_des_key(msgbuf);
194		MEMZERO(msgbuf, sizeof msgbuf);
195		return 1;
196	}
197	return 0;
198}
199
200
201/*
202 * print a warning message and, possibly, terminate
203 */
204void
205des_error(s)
206	const char *s;		/* the message */
207{
208	errmsg = s ? s : strerror(errno);
209}
210
211/*
212 * map a hex character to an integer
213 */
214int
215hex_to_binary(c, radix)
216	int c;			/* char to be converted */
217	int radix;		/* base (2 to 16) */
218{
219	switch(c) {
220	case '0':		return(0x0);
221	case '1':		return(0x1);
222	case '2':		return(radix > 2 ? 0x2 : -1);
223	case '3':		return(radix > 3 ? 0x3 : -1);
224	case '4':		return(radix > 4 ? 0x4 : -1);
225	case '5':		return(radix > 5 ? 0x5 : -1);
226	case '6':		return(radix > 6 ? 0x6 : -1);
227	case '7':		return(radix > 7 ? 0x7 : -1);
228	case '8':		return(radix > 8 ? 0x8 : -1);
229	case '9':		return(radix > 9 ? 0x9 : -1);
230	case 'A': case 'a':	return(radix > 10 ? 0xa : -1);
231	case 'B': case 'b':	return(radix > 11 ? 0xb : -1);
232	case 'C': case 'c':	return(radix > 12 ? 0xc : -1);
233	case 'D': case 'd':	return(radix > 13 ? 0xd : -1);
234	case 'E': case 'e':	return(radix > 14 ? 0xe : -1);
235	case 'F': case 'f':	return(radix > 15 ? 0xf : -1);
236	}
237	/*
238	 * invalid character
239	 */
240	return(-1);
241}
242
243/*
244 * convert the key to a bit pattern
245 */
246void
247expand_des_key(obuf, kbuf)
248	char *obuf;			/* bit pattern */
249	char *kbuf;			/* the key itself */
250{
251	int i, j;			/* counter in a for loop */
252	int nbuf[64];			/* used for hex/key translation */
253
254	/*
255	 * leading '0x' or '0X' == hex key
256	 */
257	if (kbuf[0] == '0' && (kbuf[1] == 'x' || kbuf[1] == 'X')) {
258		kbuf = &kbuf[2];
259		/*
260		 * now translate it, bombing on any illegal hex digit
261		 */
262		for (i = 0; kbuf[i] && i < 16; i++)
263			if ((nbuf[i] = hex_to_binary((int) kbuf[i], 16)) == -1)
264				des_error("bad hex digit in key");
265		while (i < 16)
266			nbuf[i++] = 0;
267		for (i = 0; i < 8; i++)
268			obuf[i] =
269			    ((nbuf[2*i]&0xf)<<4) | (nbuf[2*i+1]&0xf);
270		/* preserve parity bits */
271		pflag = 1;
272		return;
273	}
274	/*
275	 * leading '0b' or '0B' == binary key
276	 */
277	if (kbuf[0] == '0' && (kbuf[1] == 'b' || kbuf[1] == 'B')) {
278		kbuf = &kbuf[2];
279		/*
280		 * now translate it, bombing on any illegal binary digit
281		 */
282		for (i = 0; kbuf[i] && i < 16; i++)
283			if ((nbuf[i] = hex_to_binary((int) kbuf[i], 2)) == -1)
284				des_error("bad binary digit in key");
285		while (i < 64)
286			nbuf[i++] = 0;
287		for (i = 0; i < 8; i++)
288			for (j = 0; j < 8; j++)
289				obuf[i] = (obuf[i]<<1)|nbuf[8*i+j];
290		/* preserve parity bits */
291		pflag = 1;
292		return;
293	}
294	/*
295	 * no special leader -- ASCII
296	 */
297	(void)strncpy(obuf, kbuf, 8);
298}
299
300/*****************
301 * DES FUNCTIONS *
302 *****************/
303/*
304 * This sets the DES key and (if you're using the deszip version)
305 * the direction of the transformation.  This uses the Sun
306 * to map the 64-bit key onto the 56 bits that the key schedule
307 * generation routines use: the old way, which just uses the user-
308 * supplied 64 bits as is, and the new way, which resets the parity
309 * bit to be the same as the low-order bit in each character.  The
310 * new way generates a greater variety of key schedules, since many
311 * systems set the parity (high) bit of each character to 0, and the
312 * DES ignores the low order bit of each character.
313 */
314void
315set_des_key(buf)
316	Desbuf buf;				/* key block */
317{
318	int i, j;				/* counter in a for loop */
319	int par;				/* parity counter */
320
321	/*
322	 * if the parity is not preserved, flip it
323	 */
324	if (!pflag) {
325		for (i = 0; i < 8; i++) {
326			par = 0;
327			for (j = 1; j < 8; j++)
328				if ((bits[j]&UCHAR(buf, i)) != 0)
329					par++;
330			if ((par&01) == 01)
331				UCHAR(buf, i) = UCHAR(buf, i)&0177;
332			else
333				UCHAR(buf, i) = (UCHAR(buf, i)&0177)|0200;
334		}
335	}
336
337	DES_KEY(UBUFFER(buf));
338}
339
340
341/*
342 * This encrypts using the Cipher Block Chaining mode of DES
343 */
344int
345cbc_encode(msgbuf, n, fp)
346	char *msgbuf;
347	int n;
348	FILE *fp;
349{
350	int inverse = 0;	/* 0 to encrypt, 1 to decrypt */
351
352	/*
353	 * do the transformation
354	 */
355	if (n == 8) {
356		for (n = 0; n < 8; n++)
357			CHAR(msgbuf, n) ^= CHAR(ivec, n);
358		DES_XFORM(UBUFFER(msgbuf));
359		MEMCPY(BUFFER(ivec), BUFFER(msgbuf), 8);
360		return WRITE(BUFFER(msgbuf), 8, fp);
361	}
362	/*
363	 * at EOF or last block -- in either case, the last byte contains
364	 * the character representation of the number of bytes in it
365	 */
366/*
367	MEMZERO(msgbuf +  n, 8 - n);
368*/
369	/*
370	 *  Pad the last block randomly
371	 */
372	(void)MEMCPY(BUFFER(msgbuf + n), BUFFER(pvec), 8 - n);
373	CHAR(msgbuf, 7) = n;
374	for (n = 0; n < 8; n++)
375		CHAR(msgbuf, n) ^= CHAR(ivec, n);
376	DES_XFORM(UBUFFER(msgbuf));
377	return WRITE(BUFFER(msgbuf), 8, fp);
378}
379
380/*
381 * This decrypts using the Cipher Block Chaining mode of DES
382 */
383int
384cbc_decode(msgbuf, fp)
385	char *msgbuf;		/* I/O buffer */
386	FILE *fp;			/* input file descriptor */
387{
388	Desbuf tbuf;	/* temp buffer for initialization vector */
389	int n;			/* number of bytes actually read */
390	int c;			/* used to test for EOF */
391	int inverse = 1;	/* 0 to encrypt, 1 to decrypt */
392
393	if ((n = READ(BUFFER(msgbuf), 8, fp)) == 8) {
394		/*
395		 * do the transformation
396		 */
397		MEMCPY(BUFFER(tbuf), BUFFER(msgbuf), 8);
398		DES_XFORM(UBUFFER(msgbuf));
399		for (c = 0; c < 8; c++)
400			UCHAR(msgbuf, c) ^= UCHAR(ivec, c);
401		MEMCPY(BUFFER(ivec), BUFFER(tbuf), 8);
402		/*
403		 * if the last one, handle it specially
404		 */
405		if ((c = fgetc(fp)) == EOF) {
406			n = CHAR(msgbuf, 7);
407			if (n < 0 || n > 7) {
408				des_error("decryption failed (block corrupted)");
409				return EOF;
410			}
411		} else
412			(void)ungetc(c, fp);
413		return n;
414	}
415	if (n > 0)
416		des_error("decryption failed (incomplete block)");
417	else if (n < 0)
418		des_error("cannot read file");
419	return EOF;
420}
421#endif	/* DES */
422