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evp/bio_enc.c: refine non-overlapping logic.

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RT#4628

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Andy Polyakov 2016-08-21 23:30:37 +02:00
parent 2e929e538c
commit c1a7dcbe16
1 changed files with 42 additions and 27 deletions
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69
crypto/evp/bio_enc.c
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@ -27,7 +27,8 @@ static int enc_new(BIO *h);
static int enc_free(BIO *data);
static long enc_callback_ctrl(BIO *h, int cmd, bio_info_cb *fps);
#define ENC_BLOCK_SIZE (1024*4)
#define BUF_OFFSET (EVP_MAX_BLOCK_LENGTH*2)
#define ENC_MIN_CHUNK (256)
#define BUF_OFFSET (ENC_MIN_CHUNK + EVP_MAX_BLOCK_LENGTH)
typedef struct enc_struct {
int buf_len;
@ -36,11 +37,12 @@ typedef struct enc_struct {
int finished;
int ok; /* bad decrypt */
EVP_CIPHER_CTX *cipher;
unsigned char *read_start, *read_end;
/*
* buf is larger than ENC_BLOCK_SIZE because EVP_DecryptUpdate can return
* up to a block more data than is presented to it
*/
unsigned char buf[ENC_BLOCK_SIZE + BUF_OFFSET + 2];
unsigned char buf[BUF_OFFSET + ENC_BLOCK_SIZE];
} BIO_ENC_CTX;
static const BIO_METHOD methods_enc = {
@ -75,6 +77,7 @@ static int enc_new(BIO *bi)
}
ctx->cont = 1;
ctx->ok = 1;
ctx->read_end = ctx->read_start = &(ctx->buf[BUF_OFFSET]);
BIO_set_data(bi, ctx);
BIO_set_init(bi, 1);
@ -102,7 +105,7 @@ static int enc_free(BIO *a)
static int enc_read(BIO *b, char *out, int outl)
{
int ret = 0, i;
int ret = 0, i, blocksize;
BIO_ENC_CTX *ctx;
BIO *next;
@ -130,27 +133,24 @@ static int enc_read(BIO *b, char *out, int outl)
}
}
blocksize = EVP_CIPHER_CTX_block_size(ctx->cipher);
if (blocksize == 1)
blocksize = 0;
/*
* At this point, we have room of outl bytes and an empty buffer, so we
* should read in some more.
*/
while (outl > 0) {
int buf_len;
if (ctx->cont <= 0)
break;
buf_len = outl + EVP_MAX_BLOCK_LENGTH - 1;
buf_len -= buf_len % EVP_MAX_BLOCK_LENGTH;
if (buf_len > ENC_BLOCK_SIZE) {
buf_len = ENC_BLOCK_SIZE;
if (ctx->read_start == ctx->read_end) { /* time to read more data */
ctx->read_end = ctx->read_start = &(ctx->buf[BUF_OFFSET]);
ctx->read_end += BIO_read(next, ctx->read_start, ENC_BLOCK_SIZE);
}
/*
* read in at IV offset, read the EVP_Cipher documentation about why
*/
i = BIO_read(next, &(ctx->buf[BUF_OFFSET]), buf_len);
i = ctx->read_end - ctx->read_start;
if (i <= 0) {
/* Should be continue next time we are called? */
@ -164,26 +164,41 @@ static int enc_read(BIO *b, char *out, int outl)
ret = (ret == 0) ? i : ret;
break;
}
} else if (outl >= EVP_MAX_BLOCK_LENGTH) {
if (!EVP_CipherUpdate(ctx->cipher,
(unsigned char *)out, &buf_len,
&(ctx->buf[BUF_OFFSET]), i)) {
BIO_clear_retry_flags(b);
return 0;
}
ret += buf_len;
outl -= buf_len;
out += buf_len;
continue;
} else {
if (outl > ENC_MIN_CHUNK) {
/*
* Depending on flags block cipher decrypt can write
* one extra block and then back off, i.e. output buffer
* has to accommodate extra block...
*/
int j = outl - blocksize, buf_len;
if (!EVP_CipherUpdate(ctx->cipher,
(unsigned char *)out, &buf_len,
ctx->read_start, i > j ? j : i)) {
BIO_clear_retry_flags(b);
return 0;
}
ret += buf_len;
out += buf_len;
outl -= buf_len;
if ((i -= j) <= 0) {
ctx->read_start = ctx->read_end;
continue;
}
ctx->read_start += j;
}
if (i > ENC_MIN_CHUNK)
i = ENC_MIN_CHUNK;
if (!EVP_CipherUpdate(ctx->cipher,
ctx->buf, &ctx->buf_len,
&(ctx->buf[BUF_OFFSET]), i)) {
ctx->read_start, i)) {
BIO_clear_retry_flags(b);
ctx->ok = 0;
return 0;
}
ctx->read_start += i;
ctx->cont = 1;
/*
* Note: it is possible for EVP_CipherUpdate to decrypt zero