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",
113 /* TODO: Convert to new style read function */
124 const BIO_METHOD *BIO_f_reliable(void)
126 return (&methods_ok);
129 static int ok_new(BIO *bi)
133 ctx = OPENSSL_zalloc(sizeof(*ctx));
139 ctx->md = EVP_MD_CTX_new();
140 if (ctx->md == NULL) {
145 BIO_set_data(bi, ctx);
150 static int ok_free(BIO *a)
157 ctx = BIO_get_data(a);
159 EVP_MD_CTX_free(ctx->md);
160 OPENSSL_clear_free(ctx, sizeof(BIO_OK_CTX));
161 BIO_set_data(a, NULL);
167 static int ok_read(BIO *b, char *out, int outl)
176 ctx = BIO_get_data(b);
179 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
184 /* copy clean bytes to output buffer */
186 i = ctx->buf_len - ctx->buf_off;
189 memcpy(out, &(ctx->buf[ctx->buf_off]), i);
195 /* all clean bytes are out */
196 if (ctx->buf_len == ctx->buf_off) {
200 * copy start of the next block into proper place
202 if (ctx->buf_len_save - ctx->buf_off_save > 0) {
203 ctx->buf_len = ctx->buf_len_save - ctx->buf_off_save;
204 memmove(ctx->buf, &(ctx->buf[ctx->buf_off_save]),
213 /* output buffer full -- cancel */
217 /* no clean bytes in buffer -- fill it */
218 n = IOBS - ctx->buf_len;
219 i = BIO_read(next, &(ctx->buf[ctx->buf_len]), n);
222 break; /* nothing new */
226 /* no signature yet -- check if we got one */
227 if (ctx->sigio == 1) {
229 BIO_clear_retry_flags(b);
234 /* signature ok -- check if we got block */
235 if (ctx->sigio == 0) {
237 BIO_clear_retry_flags(b);
242 /* invalid block -- cancel */
248 BIO_clear_retry_flags(b);
249 BIO_copy_next_retry(b);
253 static int ok_write(BIO *b, const char *in, int inl)
262 ctx = BIO_get_data(b);
266 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
269 if (ctx->sigio && !sig_out(b))
273 BIO_clear_retry_flags(b);
274 n = ctx->buf_len - ctx->buf_off;
275 while (ctx->blockout && n > 0) {
276 i = BIO_write(next, &(ctx->buf[ctx->buf_off]), n);
278 BIO_copy_next_retry(b);
279 if (!BIO_should_retry(b))
287 /* at this point all pending data has been written */
289 if (ctx->buf_len == ctx->buf_off) {
290 ctx->buf_len = OK_BLOCK_BLOCK;
294 if ((in == NULL) || (inl <= 0))
297 n = (inl + ctx->buf_len > OK_BLOCK_SIZE + OK_BLOCK_BLOCK) ?
298 (int)(OK_BLOCK_SIZE + OK_BLOCK_BLOCK - ctx->buf_len) : inl;
300 memcpy(&ctx->buf[ctx->buf_len], in, n);
305 if (ctx->buf_len >= OK_BLOCK_SIZE + OK_BLOCK_BLOCK) {
307 BIO_clear_retry_flags(b);
313 BIO_clear_retry_flags(b);
314 BIO_copy_next_retry(b);
318 static long ok_ctrl(BIO *b, int cmd, long num, void *ptr)
327 ctx = BIO_get_data(b);
334 ctx->buf_len_save = 0;
335 ctx->buf_off_save = 0;
340 ret = BIO_ctrl(next, cmd, num, ptr);
342 case BIO_CTRL_EOF: /* More to read */
346 ret = BIO_ctrl(next, cmd, num, ptr);
348 case BIO_CTRL_PENDING: /* More to read in buffer */
349 case BIO_CTRL_WPENDING: /* More to read in buffer */
350 ret = ctx->blockout ? ctx->buf_len - ctx->buf_off : 0;
352 ret = BIO_ctrl(next, cmd, num, ptr);
355 /* do a final write */
356 if (ctx->blockout == 0)
360 while (ctx->blockout) {
361 i = ok_write(b, NULL, 0);
369 ctx->buf_off = ctx->buf_len = 0;
370 ctx->cont = (int)ret;
372 /* Finally flush the underlying BIO */
373 ret = BIO_ctrl(next, cmd, num, ptr);
375 case BIO_C_DO_STATE_MACHINE:
376 BIO_clear_retry_flags(b);
377 ret = BIO_ctrl(next, cmd, num, ptr);
378 BIO_copy_next_retry(b);
381 ret = (long)ctx->cont;
385 if (!EVP_DigestInit_ex(ctx->md, md, NULL))
390 if (BIO_get_init(b)) {
392 *ppmd = EVP_MD_CTX_md(ctx->md);
397 ret = BIO_ctrl(next, cmd, num, ptr);
403 static long ok_callback_ctrl(BIO *b, int cmd, bio_info_cb *fp)
415 ret = BIO_callback_ctrl(next, cmd, fp);
422 static void longswap(void *_ptr, size_t len)
431 if (is_endian.little) {
433 unsigned char *p = _ptr, c;
435 for (i = 0; i < len; i += 4) {
436 c = p[0], p[0] = p[3], p[3] = c;
437 c = p[1], p[1] = p[2], p[2] = c;
442 static int sig_out(BIO *b)
446 const EVP_MD *digest;
450 ctx = BIO_get_data(b);
452 digest = EVP_MD_CTX_md(md);
453 md_size = EVP_MD_size(digest);
454 md_data = EVP_MD_CTX_md_data(md);
456 if (ctx->buf_len + 2 * md_size > OK_BLOCK_SIZE)
459 if (!EVP_DigestInit_ex(md, digest, NULL))
462 * FIXME: there's absolutely no guarantee this makes any sense at all,
463 * particularly now EVP_MD_CTX has been restructured.
465 if (RAND_bytes(md_data, md_size) <= 0)
467 memcpy(&(ctx->buf[ctx->buf_len]), md_data, md_size);
468 longswap(&(ctx->buf[ctx->buf_len]), md_size);
469 ctx->buf_len += md_size;
471 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
473 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
475 ctx->buf_len += md_size;
480 BIO_clear_retry_flags(b);
484 static int sig_in(BIO *b)
488 unsigned char tmp[EVP_MAX_MD_SIZE];
490 const EVP_MD *digest;
494 ctx = BIO_get_data(b);
496 digest = EVP_MD_CTX_md(md);
497 md_size = EVP_MD_size(digest);
498 md_data = EVP_MD_CTX_md_data(md);
500 if ((int)(ctx->buf_len - ctx->buf_off) < 2 * md_size)
503 if (!EVP_DigestInit_ex(md, digest, NULL))
505 memcpy(md_data, &(ctx->buf[ctx->buf_off]), md_size);
506 longswap(md_data, md_size);
507 ctx->buf_off += md_size;
509 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
511 if (!EVP_DigestFinal_ex(md, tmp, NULL))
513 ret = memcmp(&(ctx->buf[ctx->buf_off]), tmp, md_size) == 0;
514 ctx->buf_off += md_size;
517 if (ctx->buf_len != ctx->buf_off) {
518 memmove(ctx->buf, &(ctx->buf[ctx->buf_off]),
519 ctx->buf_len - ctx->buf_off);
521 ctx->buf_len -= ctx->buf_off;
528 BIO_clear_retry_flags(b);
532 static int block_out(BIO *b)
537 const EVP_MD *digest;
540 ctx = BIO_get_data(b);
542 digest = EVP_MD_CTX_md(md);
543 md_size = EVP_MD_size(digest);
545 tl = ctx->buf_len - OK_BLOCK_BLOCK;
546 ctx->buf[0] = (unsigned char)(tl >> 24);
547 ctx->buf[1] = (unsigned char)(tl >> 16);
548 ctx->buf[2] = (unsigned char)(tl >> 8);
549 ctx->buf[3] = (unsigned char)(tl);
550 if (!EVP_DigestUpdate(md,
551 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
553 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
555 ctx->buf_len += md_size;
559 BIO_clear_retry_flags(b);
563 static int block_in(BIO *b)
567 unsigned long tl = 0;
568 unsigned char tmp[EVP_MAX_MD_SIZE];
571 ctx = BIO_get_data(b);
573 md_size = EVP_MD_size(EVP_MD_CTX_md(md));
575 assert(sizeof(tl) >= OK_BLOCK_BLOCK); /* always true */
584 if (ctx->buf_len < tl + OK_BLOCK_BLOCK + md_size)
587 if (!EVP_DigestUpdate(md,
588 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
590 if (!EVP_DigestFinal_ex(md, tmp, NULL))
592 if (memcmp(&(ctx->buf[tl + OK_BLOCK_BLOCK]), tmp, md_size) == 0) {
593 /* there might be parts from next block lurking around ! */
594 ctx->buf_off_save = tl + OK_BLOCK_BLOCK + md_size;
595 ctx->buf_len_save = ctx->buf_len;
596 ctx->buf_off = OK_BLOCK_BLOCK;
597 ctx->buf_len = tl + OK_BLOCK_BLOCK;
604 BIO_clear_retry_flags(b);