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 = {
123 const BIO_METHOD *BIO_f_reliable(void)
125 return (&methods_ok);
128 static int ok_new(BIO *bi)
132 ctx = OPENSSL_zalloc(sizeof(*ctx));
138 ctx->md = EVP_MD_CTX_new();
139 if (ctx->md == NULL) {
144 BIO_set_data(bi, ctx);
149 static int ok_free(BIO *a)
156 ctx = BIO_get_data(a);
158 EVP_MD_CTX_free(ctx->md);
159 OPENSSL_clear_free(ctx, sizeof(BIO_OK_CTX));
160 BIO_set_data(a, NULL);
166 static int ok_read(BIO *b, char *out, int outl)
175 ctx = BIO_get_data(b);
178 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
183 /* copy clean bytes to output buffer */
185 i = ctx->buf_len - ctx->buf_off;
188 memcpy(out, &(ctx->buf[ctx->buf_off]), i);
194 /* all clean bytes are out */
195 if (ctx->buf_len == ctx->buf_off) {
199 * copy start of the next block into proper place
201 if (ctx->buf_len_save - ctx->buf_off_save > 0) {
202 ctx->buf_len = ctx->buf_len_save - ctx->buf_off_save;
203 memmove(ctx->buf, &(ctx->buf[ctx->buf_off_save]),
212 /* output buffer full -- cancel */
216 /* no clean bytes in buffer -- fill it */
217 n = IOBS - ctx->buf_len;
218 i = BIO_read(next, &(ctx->buf[ctx->buf_len]), n);
221 break; /* nothing new */
225 /* no signature yet -- check if we got one */
226 if (ctx->sigio == 1) {
228 BIO_clear_retry_flags(b);
233 /* signature ok -- check if we got block */
234 if (ctx->sigio == 0) {
236 BIO_clear_retry_flags(b);
241 /* invalid block -- cancel */
247 BIO_clear_retry_flags(b);
248 BIO_copy_next_retry(b);
252 static int ok_write(BIO *b, const char *in, int inl)
261 ctx = BIO_get_data(b);
265 if ((ctx == NULL) || (next == NULL) || (BIO_get_init(b) == 0))
268 if (ctx->sigio && !sig_out(b))
272 BIO_clear_retry_flags(b);
273 n = ctx->buf_len - ctx->buf_off;
274 while (ctx->blockout && n > 0) {
275 i = BIO_write(next, &(ctx->buf[ctx->buf_off]), n);
277 BIO_copy_next_retry(b);
278 if (!BIO_should_retry(b))
286 /* at this point all pending data has been written */
288 if (ctx->buf_len == ctx->buf_off) {
289 ctx->buf_len = OK_BLOCK_BLOCK;
293 if ((in == NULL) || (inl <= 0))
296 n = (inl + ctx->buf_len > OK_BLOCK_SIZE + OK_BLOCK_BLOCK) ?
297 (int)(OK_BLOCK_SIZE + OK_BLOCK_BLOCK - ctx->buf_len) : inl;
299 memcpy(&ctx->buf[ctx->buf_len], in, n);
304 if (ctx->buf_len >= OK_BLOCK_SIZE + OK_BLOCK_BLOCK) {
306 BIO_clear_retry_flags(b);
312 BIO_clear_retry_flags(b);
313 BIO_copy_next_retry(b);
317 static long ok_ctrl(BIO *b, int cmd, long num, void *ptr)
326 ctx = BIO_get_data(b);
333 ctx->buf_len_save = 0;
334 ctx->buf_off_save = 0;
339 ret = BIO_ctrl(next, cmd, num, ptr);
341 case BIO_CTRL_EOF: /* More to read */
345 ret = BIO_ctrl(next, cmd, num, ptr);
347 case BIO_CTRL_PENDING: /* More to read in buffer */
348 case BIO_CTRL_WPENDING: /* More to read in buffer */
349 ret = ctx->blockout ? ctx->buf_len - ctx->buf_off : 0;
351 ret = BIO_ctrl(next, cmd, num, ptr);
354 /* do a final write */
355 if (ctx->blockout == 0)
359 while (ctx->blockout) {
360 i = ok_write(b, NULL, 0);
368 ctx->buf_off = ctx->buf_len = 0;
369 ctx->cont = (int)ret;
371 /* Finally flush the underlying BIO */
372 ret = BIO_ctrl(next, cmd, num, ptr);
374 case BIO_C_DO_STATE_MACHINE:
375 BIO_clear_retry_flags(b);
376 ret = BIO_ctrl(next, cmd, num, ptr);
377 BIO_copy_next_retry(b);
380 ret = (long)ctx->cont;
384 if (!EVP_DigestInit_ex(ctx->md, md, NULL))
389 if (BIO_get_init(b)) {
391 *ppmd = EVP_MD_CTX_md(ctx->md);
396 ret = BIO_ctrl(next, cmd, num, ptr);
402 static long ok_callback_ctrl(BIO *b, int cmd, BIO_info_cb *fp)
414 ret = BIO_callback_ctrl(next, cmd, fp);
421 static void longswap(void *_ptr, size_t len)
430 if (is_endian.little) {
432 unsigned char *p = _ptr, c;
434 for (i = 0; i < len; i += 4) {
435 c = p[0], p[0] = p[3], p[3] = c;
436 c = p[1], p[1] = p[2], p[2] = c;
441 static int sig_out(BIO *b)
445 const EVP_MD *digest;
449 ctx = BIO_get_data(b);
451 digest = EVP_MD_CTX_md(md);
452 md_size = EVP_MD_size(digest);
453 md_data = EVP_MD_CTX_md_data(md);
455 if (ctx->buf_len + 2 * md_size > OK_BLOCK_SIZE)
458 if (!EVP_DigestInit_ex(md, digest, NULL))
461 * FIXME: there's absolutely no guarantee this makes any sense at all,
462 * particularly now EVP_MD_CTX has been restructured.
464 if (RAND_bytes(md_data, md_size) <= 0)
466 memcpy(&(ctx->buf[ctx->buf_len]), md_data, md_size);
467 longswap(&(ctx->buf[ctx->buf_len]), md_size);
468 ctx->buf_len += md_size;
470 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
472 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
474 ctx->buf_len += md_size;
479 BIO_clear_retry_flags(b);
483 static int sig_in(BIO *b)
487 unsigned char tmp[EVP_MAX_MD_SIZE];
489 const EVP_MD *digest;
493 ctx = BIO_get_data(b);
495 digest = EVP_MD_CTX_md(md);
496 md_size = EVP_MD_size(digest);
497 md_data = EVP_MD_CTX_md_data(md);
499 if ((int)(ctx->buf_len - ctx->buf_off) < 2 * md_size)
502 if (!EVP_DigestInit_ex(md, digest, NULL))
504 memcpy(md_data, &(ctx->buf[ctx->buf_off]), md_size);
505 longswap(md_data, md_size);
506 ctx->buf_off += md_size;
508 if (!EVP_DigestUpdate(md, WELLKNOWN, strlen(WELLKNOWN)))
510 if (!EVP_DigestFinal_ex(md, tmp, NULL))
512 ret = memcmp(&(ctx->buf[ctx->buf_off]), tmp, md_size) == 0;
513 ctx->buf_off += md_size;
516 if (ctx->buf_len != ctx->buf_off) {
517 memmove(ctx->buf, &(ctx->buf[ctx->buf_off]),
518 ctx->buf_len - ctx->buf_off);
520 ctx->buf_len -= ctx->buf_off;
527 BIO_clear_retry_flags(b);
531 static int block_out(BIO *b)
536 const EVP_MD *digest;
539 ctx = BIO_get_data(b);
541 digest = EVP_MD_CTX_md(md);
542 md_size = EVP_MD_size(digest);
544 tl = ctx->buf_len - OK_BLOCK_BLOCK;
545 ctx->buf[0] = (unsigned char)(tl >> 24);
546 ctx->buf[1] = (unsigned char)(tl >> 16);
547 ctx->buf[2] = (unsigned char)(tl >> 8);
548 ctx->buf[3] = (unsigned char)(tl);
549 if (!EVP_DigestUpdate(md,
550 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
552 if (!EVP_DigestFinal_ex(md, &(ctx->buf[ctx->buf_len]), NULL))
554 ctx->buf_len += md_size;
558 BIO_clear_retry_flags(b);
562 static int block_in(BIO *b)
566 unsigned long tl = 0;
567 unsigned char tmp[EVP_MAX_MD_SIZE];
570 ctx = BIO_get_data(b);
572 md_size = EVP_MD_size(EVP_MD_CTX_md(md));
574 assert(sizeof(tl) >= OK_BLOCK_BLOCK); /* always true */
583 if (ctx->buf_len < tl + OK_BLOCK_BLOCK + md_size)
586 if (!EVP_DigestUpdate(md,
587 (unsigned char *)&(ctx->buf[OK_BLOCK_BLOCK]), tl))
589 if (!EVP_DigestFinal_ex(md, tmp, NULL))
591 if (memcmp(&(ctx->buf[tl + OK_BLOCK_BLOCK]), tmp, md_size) == 0) {
592 /* there might be parts from next block lurking around ! */
593 ctx->buf_off_save = tl + OK_BLOCK_BLOCK + md_size;
594 ctx->buf_len_save = ctx->buf_len;
595 ctx->buf_off = OK_BLOCK_BLOCK;
596 ctx->buf_len = tl + OK_BLOCK_BLOCK;
603 BIO_clear_retry_flags(b);