2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 From: Arne Ansper <arne@cyber.ee>
15 I wrote function which took BIO* as argument, read data from it
16 and processed it. Then I wanted to store the input file in
17 encrypted form. OK I pushed BIO_f_cipher to the BIO stack
18 and everything was OK. BUT if user types wrong password
19 BIO_f_cipher outputs only garbage and my function crashes. Yes
20 I can and I should fix my function, but BIO_f_cipher is
21 easy way to add encryption support to many existing applications
22 and it's hard to debug and fix them all.
24 So I wanted another BIO which would catch the incorrect passwords and
25 file damages which cause garbage on BIO_f_cipher's output.
27 The easy way is to push the BIO_f_md and save the checksum at
28 the end of the file. However there are several problems with this
31 1) you must somehow separate checksum from actual data.
32 2) you need lot's of memory when reading the file, because you
33 must read to the end of the file and verify the checksum before
34 letting the application to read the data.
36 BIO_f_reliable tries to solve both problems, so that you can
37 read and write arbitrary long streams using only fixed amount
40 BIO_f_reliable splits data stream into blocks. Each block is prefixed
41 with it's length and suffixed with it's digest. So you need only
42 several Kbytes of memory to buffer single block before verifying
45 BIO_f_reliable goes further and adds several important capabilities:
47 1) the digest of the block is computed over the whole stream
48 -- so nobody can rearrange the blocks or remove or replace them.
50 2) to detect invalid passwords right at the start BIO_f_reliable
51 adds special prefix to the stream. In order to avoid known plain-text
52 attacks this prefix is generated as follows:
54 *) digest is initialized with random seed instead of
56 *) same seed is written to output
57 *) well-known text is then hashed and the output
58 of the digest is also written to output.
60 reader can now read the seed from stream, hash the same string
61 and then compare the digest output.
63 Bad things: BIO_f_reliable knows what's going on in EVP_Digest. I
64 initially wrote and tested this code on x86 machine and wrote the
65 digests out in machine-dependent order :( There are people using
66 this code and I cannot change this easily without making existing
67 data files unreadable.
74 #include "internal/cryptlib.h"
75 #include <openssl/buffer.h>
76 #include "internal/bio.h"
77 #include <openssl/evp.h>
78 #include <openssl/rand.h>
79 #include "internal/evp_int.h"
81 static int ok_write(BIO *h, const char *buf, int num);
82 static int ok_read(BIO *h, char *buf, int size);
83 static long ok_ctrl(BIO *h, int cmd, long arg1, void *arg2);
84 static int ok_new(BIO *h);
85 static int ok_free(BIO *data);
86 static long ok_callback_ctrl(BIO *h, int cmd, bio_info_cb *fp);
88 static __owur int sig_out(BIO *b);
89 static __owur int sig_in(BIO *b);
90 static __owur int block_out(BIO *b);
91 static __owur int block_in(BIO *b);
92 #define OK_BLOCK_SIZE (1024*4)
93 #define OK_BLOCK_BLOCK 4
94 #define IOBS (OK_BLOCK_SIZE+ OK_BLOCK_BLOCK+ 3*EVP_MAX_MD_SIZE)
95 #define WELLKNOWN "The quick brown fox jumped over the lazy dog's back."
97 typedef struct ok_struct {
102 int cont; /* <= 0 when finished */
105 int blockout; /* output block is ready */
106 int sigio; /* must process signature */
107 unsigned char buf[IOBS];
110 static const BIO_METHOD methods_ok = {
111 BIO_TYPE_CIPHER, "reliable",
122 const BIO_METHOD *BIO_f_reliable(void)
124 return (&methods_ok);
127 static int ok_new(BIO *bi)
131 ctx = OPENSSL_zalloc(sizeof(*ctx));
137 ctx->md = EVP_MD_CTX_new();
138 if (ctx->md == NULL) {
143 BIO_set_data(bi, ctx);
148 static int ok_free(BIO *a)
155 ctx = BIO_get_data(a);
157 EVP_MD_CTX_free(ctx->md);
158 OPENSSL_clear_free(ctx, sizeof(BIO_OK_CTX));
159 BIO_set_data(a, NULL);
165 static int ok_read(BIO *b, char *out, int outl)
174 ctx = BIO_get_data(b);
177 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
182 /* copy clean bytes to output buffer */
184 i = ctx->buf_len - ctx->buf_off;
187 memcpy(out, &(ctx->buf[ctx->buf_off]), i);
193 /* all clean bytes are out */
194 if (ctx->buf_len == ctx->buf_off) {
198 * copy start of the next block into proper place
200 if (ctx->buf_len_save - ctx->buf_off_save > 0) {
201 ctx->buf_len = ctx->buf_len_save - ctx->buf_off_save;
202 memmove(ctx->buf, &(ctx->buf[ctx->buf_off_save]),
211 /* output buffer full -- cancel */
215 /* no clean bytes in buffer -- fill it */
216 n = IOBS - ctx->buf_len;
217 i = BIO_read(next, &(ctx->buf[ctx->buf_len]), n);
220 break; /* nothing new */
224 /* no signature yet -- check if we got one */
225 if (ctx->sigio == 1) {
227 BIO_clear_retry_flags(b);
232 /* signature ok -- check if we got block */
233 if (ctx->sigio == 0) {
235 BIO_clear_retry_flags(b);
240 /* invalid block -- cancel */
246 BIO_clear_retry_flags(b);
247 BIO_copy_next_retry(b);
251 static int ok_write(BIO *b, const char *in, int inl)
260 ctx = BIO_get_data(b);
264 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
267 if (ctx->sigio && !sig_out(b))
271 BIO_clear_retry_flags(b);
272 n = ctx->buf_len - ctx->buf_off;
273 while (ctx->blockout && n > 0) {
274 i = BIO_write(next, &(ctx->buf[ctx->buf_off]), n);
276 BIO_copy_next_retry(b);
277 if (!BIO_should_retry(b))
285 /* at this point all pending data has been written */
287 if (ctx->buf_len == ctx->buf_off) {
288 ctx->buf_len = OK_BLOCK_BLOCK;
292 if ((in == NULL) || (inl <= 0))
295 n = (inl + ctx->buf_len > OK_BLOCK_SIZE + OK_BLOCK_BLOCK) ?
296 (int)(OK_BLOCK_SIZE + OK_BLOCK_BLOCK - ctx->buf_len) : inl;
298 memcpy(&ctx->buf[ctx->buf_len], in, n);
303 if (ctx->buf_len >= OK_BLOCK_SIZE + OK_BLOCK_BLOCK) {
305 BIO_clear_retry_flags(b);
311 BIO_clear_retry_flags(b);
312 BIO_copy_next_retry(b);
316 static long ok_ctrl(BIO *b, int cmd, long num, void *ptr)
325 ctx = BIO_get_data(b);
332 ctx->buf_len_save = 0;
333 ctx->buf_off_save = 0;
338 ret = BIO_ctrl(next, cmd, num, ptr);
340 case BIO_CTRL_EOF: /* More to read */
344 ret = BIO_ctrl(next, cmd, num, ptr);
346 case BIO_CTRL_PENDING: /* More to read in buffer */
347 case BIO_CTRL_WPENDING: /* More to read in buffer */
348 ret = ctx->blockout ? ctx->buf_len - ctx->buf_off : 0;
350 ret = BIO_ctrl(next, cmd, num, ptr);
353 /* do a final write */
354 if (ctx->blockout == 0)
358 while (ctx->blockout) {
359 i = ok_write(b, NULL, 0);
367 ctx->buf_off = ctx->buf_len = 0;
368 ctx->cont = (int)ret;
370 /* Finally flush the underlying BIO */
371 ret = BIO_ctrl(next, cmd, num, ptr);
373 case BIO_C_DO_STATE_MACHINE:
374 BIO_clear_retry_flags(b);
375 ret = BIO_ctrl(next, cmd, num, ptr);
376 BIO_copy_next_retry(b);
379 ret = (long)ctx->cont;
383 if (!EVP_DigestInit_ex(ctx->md, md, NULL))
388 if (BIO_get_init(b)) {
390 *ppmd = EVP_MD_CTX_md(ctx->md);
395 ret = BIO_ctrl(next, cmd, num, ptr);
401 static long ok_callback_ctrl(BIO *b, int cmd, bio_info_cb *fp)
413 ret = BIO_callback_ctrl(next, cmd, fp);
420 static void longswap(void *_ptr, size_t len)
429 if (is_endian.little) {
431 unsigned char *p = _ptr, c;
433 for (i = 0; i < len; i += 4) {
434 c = p[0], p[0] = p[3], p[3] = c;
435 c = p[1], p[1] = p[2], p[2] = c;
440 static int sig_out(BIO *b)
444 const EVP_MD *digest;
448 ctx = BIO_get_data(b);
450 digest = EVP_MD_CTX_md(md);
451 md_size = EVP_MD_size(digest);
452 md_data = EVP_MD_CTX_md_data(md);
454 if (ctx->buf_len + 2 * md_size > OK_BLOCK_SIZE)
457 if (!EVP_DigestInit_ex(md, digest, NULL))
460 * FIXME: there's absolutely no guarantee this makes any sense at all,
461 * particularly now EVP_MD_CTX has been restructured.
463 if (RAND_bytes(md_data, md_size) <= 0)
465 memcpy(&(ctx->buf[ctx->buf_len]), md_data, md_size);
466 longswap(&(ctx->buf[ctx->buf_len]), md_size);
467 ctx->buf_len += md_size;
469 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
471 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
473 ctx->buf_len += md_size;
478 BIO_clear_retry_flags(b);
482 static int sig_in(BIO *b)
486 unsigned char tmp[EVP_MAX_MD_SIZE];
488 const EVP_MD *digest;
492 ctx = BIO_get_data(b);
494 digest = EVP_MD_CTX_md(md);
495 md_size = EVP_MD_size(digest);
496 md_data = EVP_MD_CTX_md_data(md);
498 if ((int)(ctx->buf_len - ctx->buf_off) < 2 * md_size)
501 if (!EVP_DigestInit_ex(md, digest, NULL))
503 memcpy(md_data, &(ctx->buf[ctx->buf_off]), md_size);
504 longswap(md_data, md_size);
505 ctx->buf_off += md_size;
507 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
509 if (!EVP_DigestFinal_ex(md, tmp, NULL))
511 ret = memcmp(&(ctx->buf[ctx->buf_off]), tmp, md_size) == 0;
512 ctx->buf_off += md_size;
515 if (ctx->buf_len != ctx->buf_off) {
516 memmove(ctx->buf, &(ctx->buf[ctx->buf_off]),
517 ctx->buf_len - ctx->buf_off);
519 ctx->buf_len -= ctx->buf_off;
526 BIO_clear_retry_flags(b);
530 static int block_out(BIO *b)
535 const EVP_MD *digest;
538 ctx = BIO_get_data(b);
540 digest = EVP_MD_CTX_md(md);
541 md_size = EVP_MD_size(digest);
543 tl = ctx->buf_len - OK_BLOCK_BLOCK;
544 ctx->buf[0] = (unsigned char)(tl >> 24);
545 ctx->buf[1] = (unsigned char)(tl >> 16);
546 ctx->buf[2] = (unsigned char)(tl >> 8);
547 ctx->buf[3] = (unsigned char)(tl);
548 if (!EVP_DigestUpdate(md,
549 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
551 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
553 ctx->buf_len += md_size;
557 BIO_clear_retry_flags(b);
561 static int block_in(BIO *b)
565 unsigned long tl = 0;
566 unsigned char tmp[EVP_MAX_MD_SIZE];
569 ctx = BIO_get_data(b);
571 md_size = EVP_MD_size(EVP_MD_CTX_md(md));
573 assert(sizeof(tl) >= OK_BLOCK_BLOCK); /* always true */
582 if (ctx->buf_len < tl + OK_BLOCK_BLOCK + md_size)
585 if (!EVP_DigestUpdate(md,
586 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
588 if (!EVP_DigestFinal_ex(md, tmp, NULL))
590 if (memcmp(&(ctx->buf[tl + OK_BLOCK_BLOCK]), tmp, md_size) == 0) {
591 /* there might be parts from next block lurking around ! */
592 ctx->buf_off_save = tl + OK_BLOCK_BLOCK + md_size;
593 ctx->buf_len_save = ctx->buf_len;
594 ctx->buf_off = OK_BLOCK_BLOCK;
595 ctx->buf_len = tl + OK_BLOCK_BLOCK;
602 BIO_clear_retry_flags(b);