2 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (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
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 its length and suffixed with its 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 "crypto/evp.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 = {
113 /* TODO: Convert to new style write function */
116 /* TODO: Convert to new style read function */
127 const BIO_METHOD *BIO_f_reliable(void)
132 static int ok_new(BIO *bi)
136 if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL) {
137 EVPerr(EVP_F_OK_NEW, ERR_R_MALLOC_FAILURE);
143 ctx->md = EVP_MD_CTX_new();
144 if (ctx->md == NULL) {
149 BIO_set_data(bi, ctx);
154 static int ok_free(BIO *a)
161 ctx = BIO_get_data(a);
163 EVP_MD_CTX_free(ctx->md);
164 OPENSSL_clear_free(ctx, sizeof(BIO_OK_CTX));
165 BIO_set_data(a, NULL);
171 static int ok_read(BIO *b, char *out, int outl)
180 ctx = BIO_get_data(b);
183 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
188 /* copy clean bytes to output buffer */
190 i = ctx->buf_len - ctx->buf_off;
193 memcpy(out, &(ctx->buf[ctx->buf_off]), i);
199 /* all clean bytes are out */
200 if (ctx->buf_len == ctx->buf_off) {
204 * copy start of the next block into proper place
206 if (ctx->buf_len_save - ctx->buf_off_save > 0) {
207 ctx->buf_len = ctx->buf_len_save - ctx->buf_off_save;
208 memmove(ctx->buf, &(ctx->buf[ctx->buf_off_save]),
217 /* output buffer full -- cancel */
221 /* no clean bytes in buffer -- fill it */
222 n = IOBS - ctx->buf_len;
223 i = BIO_read(next, &(ctx->buf[ctx->buf_len]), n);
226 break; /* nothing new */
230 /* no signature yet -- check if we got one */
231 if (ctx->sigio == 1) {
233 BIO_clear_retry_flags(b);
238 /* signature ok -- check if we got block */
239 if (ctx->sigio == 0) {
241 BIO_clear_retry_flags(b);
246 /* invalid block -- cancel */
252 BIO_clear_retry_flags(b);
253 BIO_copy_next_retry(b);
257 static int ok_write(BIO *b, const char *in, int inl)
266 ctx = BIO_get_data(b);
270 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
273 if (ctx->sigio && !sig_out(b))
277 BIO_clear_retry_flags(b);
278 n = ctx->buf_len - ctx->buf_off;
279 while (ctx->blockout && n > 0) {
280 i = BIO_write(next, &(ctx->buf[ctx->buf_off]), n);
282 BIO_copy_next_retry(b);
283 if (!BIO_should_retry(b))
291 /* at this point all pending data has been written */
293 if (ctx->buf_len == ctx->buf_off) {
294 ctx->buf_len = OK_BLOCK_BLOCK;
298 if ((in == NULL) || (inl <= 0))
301 n = (inl + ctx->buf_len > OK_BLOCK_SIZE + OK_BLOCK_BLOCK) ?
302 (int)(OK_BLOCK_SIZE + OK_BLOCK_BLOCK - ctx->buf_len) : inl;
304 memcpy(&ctx->buf[ctx->buf_len], in, n);
309 if (ctx->buf_len >= OK_BLOCK_SIZE + OK_BLOCK_BLOCK) {
311 BIO_clear_retry_flags(b);
317 BIO_clear_retry_flags(b);
318 BIO_copy_next_retry(b);
322 static long ok_ctrl(BIO *b, int cmd, long num, void *ptr)
331 ctx = BIO_get_data(b);
338 ctx->buf_len_save = 0;
339 ctx->buf_off_save = 0;
344 ret = BIO_ctrl(next, cmd, num, ptr);
346 case BIO_CTRL_EOF: /* More to read */
350 ret = BIO_ctrl(next, cmd, num, ptr);
352 case BIO_CTRL_PENDING: /* More to read in buffer */
353 case BIO_CTRL_WPENDING: /* More to read in buffer */
354 ret = ctx->blockout ? ctx->buf_len - ctx->buf_off : 0;
356 ret = BIO_ctrl(next, cmd, num, ptr);
359 /* do a final write */
360 if (ctx->blockout == 0)
364 while (ctx->blockout) {
365 i = ok_write(b, NULL, 0);
373 ctx->buf_off = ctx->buf_len = 0;
374 ctx->cont = (int)ret;
376 /* Finally flush the underlying BIO */
377 ret = BIO_ctrl(next, cmd, num, ptr);
379 case BIO_C_DO_STATE_MACHINE:
380 BIO_clear_retry_flags(b);
381 ret = BIO_ctrl(next, cmd, num, ptr);
382 BIO_copy_next_retry(b);
385 ret = (long)ctx->cont;
389 if (!EVP_DigestInit_ex(ctx->md, md, NULL))
394 if (BIO_get_init(b)) {
396 *ppmd = EVP_MD_CTX_md(ctx->md);
401 ret = BIO_ctrl(next, cmd, num, ptr);
407 static long ok_callback_ctrl(BIO *b, int cmd, BIO_info_cb *fp)
416 return BIO_callback_ctrl(next, cmd, fp);
419 static void longswap(void *_ptr, size_t len)
428 if (is_endian.little) {
430 unsigned char *p = _ptr, c;
432 for (i = 0; i < len; i += 4) {
433 c = p[0], p[0] = p[3], p[3] = c;
434 c = p[1], p[1] = p[2], p[2] = c;
439 static int sig_out(BIO *b)
443 const EVP_MD *digest;
447 ctx = BIO_get_data(b);
449 digest = EVP_MD_CTX_md(md);
450 md_size = EVP_MD_size(digest);
451 md_data = EVP_MD_CTX_md_data(md);
453 if (ctx->buf_len + 2 * md_size > OK_BLOCK_SIZE)
456 if (!EVP_DigestInit_ex(md, digest, NULL))
459 * FIXME: there's absolutely no guarantee this makes any sense at all,
460 * particularly now EVP_MD_CTX has been restructured.
462 if (RAND_bytes(md_data, md_size) <= 0)
464 memcpy(&(ctx->buf[ctx->buf_len]), md_data, md_size);
465 longswap(&(ctx->buf[ctx->buf_len]), md_size);
466 ctx->buf_len += md_size;
468 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
470 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
472 ctx->buf_len += md_size;
477 BIO_clear_retry_flags(b);
481 static int sig_in(BIO *b)
485 unsigned char tmp[EVP_MAX_MD_SIZE];
487 const EVP_MD *digest;
491 ctx = BIO_get_data(b);
493 digest = EVP_MD_CTX_md(md);
494 md_size = EVP_MD_size(digest);
495 md_data = EVP_MD_CTX_md_data(md);
497 if ((int)(ctx->buf_len - ctx->buf_off) < 2 * md_size)
500 if (!EVP_DigestInit_ex(md, digest, NULL))
502 memcpy(md_data, &(ctx->buf[ctx->buf_off]), md_size);
503 longswap(md_data, md_size);
504 ctx->buf_off += md_size;
506 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
508 if (!EVP_DigestFinal_ex(md, tmp, NULL))
510 ret = memcmp(&(ctx->buf[ctx->buf_off]), tmp, md_size) == 0;
511 ctx->buf_off += md_size;
514 if (ctx->buf_len != ctx->buf_off) {
515 memmove(ctx->buf, &(ctx->buf[ctx->buf_off]),
516 ctx->buf_len - ctx->buf_off);
518 ctx->buf_len -= ctx->buf_off;
525 BIO_clear_retry_flags(b);
529 static int block_out(BIO *b)
534 const EVP_MD *digest;
537 ctx = BIO_get_data(b);
539 digest = EVP_MD_CTX_md(md);
540 md_size = EVP_MD_size(digest);
542 tl = ctx->buf_len - OK_BLOCK_BLOCK;
543 ctx->buf[0] = (unsigned char)(tl >> 24);
544 ctx->buf[1] = (unsigned char)(tl >> 16);
545 ctx->buf[2] = (unsigned char)(tl >> 8);
546 ctx->buf[3] = (unsigned char)(tl);
547 if (!EVP_DigestUpdate(md,
548 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
550 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
552 ctx->buf_len += md_size;
556 BIO_clear_retry_flags(b);
560 static int block_in(BIO *b)
564 unsigned long tl = 0;
565 unsigned char tmp[EVP_MAX_MD_SIZE];
568 ctx = BIO_get_data(b);
570 md_size = EVP_MD_size(EVP_MD_CTX_md(md));
572 assert(sizeof(tl) >= OK_BLOCK_BLOCK); /* always true */
581 if (ctx->buf_len < tl + OK_BLOCK_BLOCK + md_size)
584 if (!EVP_DigestUpdate(md,
585 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
587 if (!EVP_DigestFinal_ex(md, tmp, NULL))
589 if (memcmp(&(ctx->buf[tl + OK_BLOCK_BLOCK]), tmp, md_size) == 0) {
590 /* there might be parts from next block lurking around ! */
591 ctx->buf_off_save = tl + OK_BLOCK_BLOCK + md_size;
592 ctx->buf_len_save = ctx->buf_len;
593 ctx->buf_off = OK_BLOCK_BLOCK;
594 ctx->buf_len = tl + OK_BLOCK_BLOCK;
601 BIO_clear_retry_flags(b);