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move hmac setting to flags on cipher context

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This commit is contained in:
Stephen Lombardo 2012-07-17 16:19:40 -04:00
parent dbbbb7cca7
commit 7a9b9e39a1
2 changed files with 31 additions and 14 deletions
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8
src/crypto.h
View File

@ -56,10 +56,14 @@
#define PBKDF2_ITER 4000
#endif
#ifndef DEFAULT_USE_HMAC
#define DEFAULT_USE_HMAC 1
/* possible flags for cipher_ctx->flags */
#define CIPHER_FLAG_HMAC 0x01
#ifndef DEFAULT_CIPHER_FLAGS
#define DEFAULT_CIPHER_FLAGS CIPHER_FLAG_HMAC
#endif
/* by default, sqlcipher will use a reduced number of iterations to generate
the HMAC key / or transform a raw cipher key
*/

37
src/crypto_impl.c
View File

@ -63,7 +63,7 @@ typedef struct {
int pass_sz;
int reserve_sz;
int hmac_sz;
int use_hmac;
unsigned int flags;
unsigned char *key;
unsigned char *hmac_key;
char *pass;
@ -79,7 +79,7 @@ int sqlcipher_cipher_ctx_key_derive(codec_ctx *, cipher_ctx *);
/* prototype for pager HMAC function */
int sqlcipher_page_hmac(cipher_ctx *, Pgno, unsigned char *, int, unsigned char *);
static int default_use_hmac = DEFAULT_USE_HMAC;
static unsigned int default_flags = DEFAULT_CIPHER_FLAGS;
struct codec_ctx {
int kdf_salt_sz;
@ -185,6 +185,10 @@ int sqlcipher_cipher_ctx_init(cipher_ctx **iCtx) {
ctx->hmac_key = (unsigned char *) sqlcipher_malloc(EVP_MAX_KEY_LENGTH);
if(ctx->key == NULL) return SQLITE_NOMEM;
if(ctx->hmac_key == NULL) return SQLITE_NOMEM;
/* setup default flags */
ctx->flags = default_flags;
return SQLITE_OK;
}
@ -216,7 +220,7 @@ int sqlcipher_cipher_ctx_cmp(cipher_ctx *c1, cipher_ctx *c2) {
&& c1->fast_kdf_iter == c2->fast_kdf_iter
&& c1->key_sz == c2->key_sz
&& c1->pass_sz == c2->pass_sz
&& c1->use_hmac == c2->use_hmac
&& c1->flags == c2->flags
&& c1->hmac_sz == c2->hmac_sz
&& (
c1->pass == c2->pass
@ -339,7 +343,8 @@ int sqlcipher_codec_ctx_set_fast_kdf_iter(codec_ctx *ctx, int fast_kdf_iter, int
/* set the global default flag for HMAC */
void sqlcipher_set_default_use_hmac(int use) {
default_use_hmac = use;
if(use) default_flags |= CIPHER_FLAG_HMAC;
else default_flags &= ~CIPHER_FLAG_HMAC;
}
/* set the codec flag for whether this individual database should be using hmac */
@ -356,7 +361,15 @@ int sqlcipher_codec_ctx_set_use_hmac(codec_ctx *ctx, int use) {
CODEC_TRACE(("sqlcipher_codec_ctx_set_use_hmac: use=%d block_sz=%d md_size=%d reserve=%d\n",
use, ctx->read_ctx->block_sz, ctx->read_ctx->hmac_sz, reserve));
ctx->write_ctx->use_hmac = ctx->read_ctx->use_hmac = use;
if(use) {
ctx->write_ctx->flags |= CIPHER_FLAG_HMAC;
ctx->read_ctx->flags |= CIPHER_FLAG_HMAC;
} else {
ctx->write_ctx->flags &= ~CIPHER_FLAG_HMAC;
ctx->read_ctx->flags &= ~CIPHER_FLAG_HMAC;
}
ctx->write_ctx->reserve_sz = ctx->read_ctx->reserve_sz = reserve;
return SQLITE_OK;
@ -449,9 +462,9 @@ int sqlcipher_codec_ctx_init(codec_ctx **iCtx, Db *pDb, Pager *pPager, sqlite3_f
if((rc = sqlcipher_codec_ctx_set_fast_kdf_iter(ctx, FAST_PBKDF2_ITER, 0)) != SQLITE_OK) return rc;
if((rc = sqlcipher_codec_ctx_set_pass(ctx, zKey, nKey, 0)) != SQLITE_OK) return rc;
/* Use HMAC signatures by default. Note that codec_set_use_hmac will implicity call
codec_set_page_size to set the default */
if((rc = sqlcipher_codec_ctx_set_use_hmac(ctx, default_use_hmac)) != SQLITE_OK) return rc;
/* Note that use_hmac is a special case that requires recalculation of page size
so we call set_use_hmac to perform setup */
if((rc = sqlcipher_codec_ctx_set_use_hmac(ctx, default_flags & CIPHER_FLAG_HMAC)) != SQLITE_OK) return rc;
if((rc = sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx)) != SQLITE_OK) return rc;
@ -524,7 +537,7 @@ int sqlcipher_page_cipher(codec_ctx *ctx, int for_ctx, Pgno pgno, int mode, int
iv_in = in + size;
/* hmac will be written immediately after the initialization vector. the remainder of the page reserve will contain
random bytes. note, these pointers are only valid when use_hmac is true */
random bytes. note, these pointers are only valid when using hmac */
hmac_in = in + size + c_ctx->iv_sz;
hmac_out = out + size + c_ctx->iv_sz;
out_start = out; /* note the original position of the output buffer pointer, as out will be rewritten during encryption */
@ -546,7 +559,7 @@ int sqlcipher_page_cipher(codec_ctx *ctx, int for_ctx, Pgno pgno, int mode, int
memcpy(iv_out, iv_in, c_ctx->iv_sz); /* copy the iv from the input to output buffer */
}
if(c_ctx->use_hmac && (mode == CIPHER_DECRYPT)) {
if((c_ctx->flags & CIPHER_FLAG_HMAC) && (mode == CIPHER_DECRYPT)) {
if(sqlcipher_page_hmac(c_ctx, pgno, in, size + c_ctx->iv_sz, hmac_out) != SQLITE_OK) {
memset(out, 0, page_sz);
CODEC_TRACE(("codec_cipher: hmac operations failed for pgno=%d\n", pgno));
@ -585,7 +598,7 @@ int sqlcipher_page_cipher(codec_ctx *ctx, int for_ctx, Pgno pgno, int mode, int
EVP_CIPHER_CTX_cleanup(&c_ctx->ectx);
assert(size == csz);
if(c_ctx->use_hmac && (mode == CIPHER_ENCRYPT)) {
if((c_ctx->flags & CIPHER_FLAG_HMAC) && (mode == CIPHER_ENCRYPT)) {
sqlcipher_page_hmac(c_ctx, pgno, out_start, size + c_ctx->iv_sz, hmac_out);
}
@ -630,7 +643,7 @@ int sqlcipher_cipher_ctx_key_derive(codec_ctx *ctx, cipher_ctx *c_ctx) {
/* if this context is setup to use hmac checks, generate a seperate and different
key for HMAC. In this case, we use the output of the previous KDF as the input to
this KDF run. This ensures a distinct but predictable HMAC key. */
if(c_ctx->use_hmac) {
if(c_ctx->flags & CIPHER_FLAG_HMAC) {
int i;
/* start by copying the kdf key into the hmac salt slot