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",
112 /* TODO: Convert to new style write function */
115 /* TODO: Convert to new style read function */
126 const BIO_METHOD *BIO_f_reliable(void)
128 return (&methods_ok);
131 static int ok_new(BIO *bi)
135 ctx = OPENSSL_zalloc(sizeof(*ctx));
141 ctx->md = EVP_MD_CTX_new();
142 if (ctx->md == NULL) {
147 BIO_set_data(bi, ctx);
152 static int ok_free(BIO *a)
159 ctx = BIO_get_data(a);
161 EVP_MD_CTX_free(ctx->md);
162 OPENSSL_clear_free(ctx, sizeof(BIO_OK_CTX));
163 BIO_set_data(a, NULL);
169 static int ok_read(BIO *b, char *out, int outl)
178 ctx = BIO_get_data(b);
181 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
186 /* copy clean bytes to output buffer */
188 i = ctx->buf_len - ctx->buf_off;
191 memcpy(out, &(ctx->buf[ctx->buf_off]), i);
197 /* all clean bytes are out */
198 if (ctx->buf_len == ctx->buf_off) {
202 * copy start of the next block into proper place
204 if (ctx->buf_len_save - ctx->buf_off_save > 0) {
205 ctx->buf_len = ctx->buf_len_save - ctx->buf_off_save;
206 memmove(ctx->buf, &(ctx->buf[ctx->buf_off_save]),
215 /* output buffer full -- cancel */
219 /* no clean bytes in buffer -- fill it */
220 n = IOBS - ctx->buf_len;
221 i = BIO_read(next, &(ctx->buf[ctx->buf_len]), n);
224 break; /* nothing new */
228 /* no signature yet -- check if we got one */
229 if (ctx->sigio == 1) {
231 BIO_clear_retry_flags(b);
236 /* signature ok -- check if we got block */
237 if (ctx->sigio == 0) {
239 BIO_clear_retry_flags(b);
244 /* invalid block -- cancel */
250 BIO_clear_retry_flags(b);
251 BIO_copy_next_retry(b);
255 static int ok_write(BIO *b, const char *in, int inl)
264 ctx = BIO_get_data(b);
268 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
271 if (ctx->sigio && !sig_out(b))
275 BIO_clear_retry_flags(b);
276 n = ctx->buf_len - ctx->buf_off;
277 while (ctx->blockout && n > 0) {
278 i = BIO_write(next, &(ctx->buf[ctx->buf_off]), n);
280 BIO_copy_next_retry(b);
281 if (!BIO_should_retry(b))
289 /* at this point all pending data has been written */
291 if (ctx->buf_len == ctx->buf_off) {
292 ctx->buf_len = OK_BLOCK_BLOCK;
296 if ((in == NULL) || (inl <= 0))
299 n = (inl + ctx->buf_len > OK_BLOCK_SIZE + OK_BLOCK_BLOCK) ?
300 (int)(OK_BLOCK_SIZE + OK_BLOCK_BLOCK - ctx->buf_len) : inl;
302 memcpy(&ctx->buf[ctx->buf_len], in, n);
307 if (ctx->buf_len >= OK_BLOCK_SIZE + OK_BLOCK_BLOCK) {
309 BIO_clear_retry_flags(b);
315 BIO_clear_retry_flags(b);
316 BIO_copy_next_retry(b);
320 static long ok_ctrl(BIO *b, int cmd, long num, void *ptr)
329 ctx = BIO_get_data(b);
336 ctx->buf_len_save = 0;
337 ctx->buf_off_save = 0;
342 ret = BIO_ctrl(next, cmd, num, ptr);
344 case BIO_CTRL_EOF: /* More to read */
348 ret = BIO_ctrl(next, cmd, num, ptr);
350 case BIO_CTRL_PENDING: /* More to read in buffer */
351 case BIO_CTRL_WPENDING: /* More to read in buffer */
352 ret = ctx->blockout ? ctx->buf_len - ctx->buf_off : 0;
354 ret = BIO_ctrl(next, cmd, num, ptr);
357 /* do a final write */
358 if (ctx->blockout == 0)
362 while (ctx->blockout) {
363 i = ok_write(b, NULL, 0);
371 ctx->buf_off = ctx->buf_len = 0;
372 ctx->cont = (int)ret;
374 /* Finally flush the underlying BIO */
375 ret = BIO_ctrl(next, cmd, num, ptr);
377 case BIO_C_DO_STATE_MACHINE:
378 BIO_clear_retry_flags(b);
379 ret = BIO_ctrl(next, cmd, num, ptr);
380 BIO_copy_next_retry(b);
383 ret = (long)ctx->cont;
387 if (!EVP_DigestInit_ex(ctx->md, md, NULL))
392 if (BIO_get_init(b)) {
394 *ppmd = EVP_MD_CTX_md(ctx->md);
399 ret = BIO_ctrl(next, cmd, num, ptr);
405 static long ok_callback_ctrl(BIO *b, int cmd, bio_info_cb *fp)
417 ret = BIO_callback_ctrl(next, cmd, fp);
424 static void longswap(void *_ptr, size_t len)
433 if (is_endian.little) {
435 unsigned char *p = _ptr, c;
437 for (i = 0; i < len; i += 4) {
438 c = p[0], p[0] = p[3], p[3] = c;
439 c = p[1], p[1] = p[2], p[2] = c;
444 static int sig_out(BIO *b)
448 const EVP_MD *digest;
452 ctx = BIO_get_data(b);
454 digest = EVP_MD_CTX_md(md);
455 md_size = EVP_MD_size(digest);
456 md_data = EVP_MD_CTX_md_data(md);
458 if (ctx->buf_len + 2 * md_size > OK_BLOCK_SIZE)
461 if (!EVP_DigestInit_ex(md, digest, NULL))
464 * FIXME: there's absolutely no guarantee this makes any sense at all,
465 * particularly now EVP_MD_CTX has been restructured.
467 if (RAND_bytes(md_data, md_size) <= 0)
469 memcpy(&(ctx->buf[ctx->buf_len]), md_data, md_size);
470 longswap(&(ctx->buf[ctx->buf_len]), md_size);
471 ctx->buf_len += md_size;
473 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
475 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
477 ctx->buf_len += md_size;
482 BIO_clear_retry_flags(b);
486 static int sig_in(BIO *b)
490 unsigned char tmp[EVP_MAX_MD_SIZE];
492 const EVP_MD *digest;
496 ctx = BIO_get_data(b);
498 digest = EVP_MD_CTX_md(md);
499 md_size = EVP_MD_size(digest);
500 md_data = EVP_MD_CTX_md_data(md);
502 if ((int)(ctx->buf_len - ctx->buf_off) < 2 * md_size)
505 if (!EVP_DigestInit_ex(md, digest, NULL))
507 memcpy(md_data, &(ctx->buf[ctx->buf_off]), md_size);
508 longswap(md_data, md_size);
509 ctx->buf_off += md_size;
511 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
513 if (!EVP_DigestFinal_ex(md, tmp, NULL))
515 ret = memcmp(&(ctx->buf[ctx->buf_off]), tmp, md_size) == 0;
516 ctx->buf_off += md_size;
519 if (ctx->buf_len != ctx->buf_off) {
520 memmove(ctx->buf, &(ctx->buf[ctx->buf_off]),
521 ctx->buf_len - ctx->buf_off);
523 ctx->buf_len -= ctx->buf_off;
530 BIO_clear_retry_flags(b);
534 static int block_out(BIO *b)
539 const EVP_MD *digest;
542 ctx = BIO_get_data(b);
544 digest = EVP_MD_CTX_md(md);
545 md_size = EVP_MD_size(digest);
547 tl = ctx->buf_len - OK_BLOCK_BLOCK;
548 ctx->buf[0] = (unsigned char)(tl >> 24);
549 ctx->buf[1] = (unsigned char)(tl >> 16);
550 ctx->buf[2] = (unsigned char)(tl >> 8);
551 ctx->buf[3] = (unsigned char)(tl);
552 if (!EVP_DigestUpdate(md,
553 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
555 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
557 ctx->buf_len += md_size;
561 BIO_clear_retry_flags(b);
565 static int block_in(BIO *b)
569 unsigned long tl = 0;
570 unsigned char tmp[EVP_MAX_MD_SIZE];
573 ctx = BIO_get_data(b);
575 md_size = EVP_MD_size(EVP_MD_CTX_md(md));
577 assert(sizeof(tl) >= OK_BLOCK_BLOCK); /* always true */
586 if (ctx->buf_len < tl + OK_BLOCK_BLOCK + md_size)
589 if (!EVP_DigestUpdate(md,
590 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
592 if (!EVP_DigestFinal_ex(md, tmp, NULL))
594 if (memcmp(&(ctx->buf[tl + OK_BLOCK_BLOCK]), tmp, md_size) == 0) {
595 /* there might be parts from next block lurking around ! */
596 ctx->buf_off_save = tl + OK_BLOCK_BLOCK + md_size;
597 ctx->buf_len_save = ctx->buf_len;
598 ctx->buf_off = OK_BLOCK_BLOCK;
599 ctx->buf_len = tl + OK_BLOCK_BLOCK;
606 BIO_clear_retry_flags(b);