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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 #define PBKDF2_ITER 4000
#endif #endif
#ifndef DEFAULT_USE_HMAC /* possible flags for cipher_ctx->flags */
#define DEFAULT_USE_HMAC 1 #define CIPHER_FLAG_HMAC 0x01
#ifndef DEFAULT_CIPHER_FLAGS
#define DEFAULT_CIPHER_FLAGS CIPHER_FLAG_HMAC
#endif #endif
/* by default, sqlcipher will use a reduced number of iterations to generate /* by default, sqlcipher will use a reduced number of iterations to generate
the HMAC key / or transform a raw cipher key 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 pass_sz;
int reserve_sz; int reserve_sz;
int hmac_sz; int hmac_sz;
int use_hmac; unsigned int flags;
unsigned char *key; unsigned char *key;
unsigned char *hmac_key; unsigned char *hmac_key;
char *pass; char *pass;
@ -79,7 +79,7 @@ int sqlcipher_cipher_ctx_key_derive(codec_ctx *, cipher_ctx *);
/* prototype for pager HMAC function */ /* prototype for pager HMAC function */
int sqlcipher_page_hmac(cipher_ctx *, Pgno, unsigned char *, int, unsigned char *); 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 { struct codec_ctx {
int kdf_salt_sz; 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); ctx->hmac_key = (unsigned char *) sqlcipher_malloc(EVP_MAX_KEY_LENGTH);
if(ctx->key == NULL) return SQLITE_NOMEM; if(ctx->key == NULL) return SQLITE_NOMEM;
if(ctx->hmac_key == NULL) return SQLITE_NOMEM; if(ctx->hmac_key == NULL) return SQLITE_NOMEM;
/* setup default flags */
ctx->flags = default_flags;
return SQLITE_OK; 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->fast_kdf_iter == c2->fast_kdf_iter
&& c1->key_sz == c2->key_sz && c1->key_sz == c2->key_sz
&& c1->pass_sz == c2->pass_sz && c1->pass_sz == c2->pass_sz
&& c1->use_hmac == c2->use_hmac && c1->flags == c2->flags
&& c1->hmac_sz == c2->hmac_sz && c1->hmac_sz == c2->hmac_sz
&& ( && (
c1->pass == c2->pass 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 */ /* set the global default flag for HMAC */
void sqlcipher_set_default_use_hmac(int use) { 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 */ /* 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", 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)); 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; ctx->write_ctx->reserve_sz = ctx->read_ctx->reserve_sz = reserve;
return SQLITE_OK; 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_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; 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 /* Note that use_hmac is a special case that requires recalculation of page size
codec_set_page_size to set the default */ so we call set_use_hmac to perform setup */
if((rc = sqlcipher_codec_ctx_set_use_hmac(ctx, default_use_hmac)) != SQLITE_OK) return rc; 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; 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; iv_in = in + size;
/* hmac will be written immediately after the initialization vector. the remainder of the page reserve will contain /* 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_in = in + size + c_ctx->iv_sz;
hmac_out = out + 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 */ 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 */ 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) { if(sqlcipher_page_hmac(c_ctx, pgno, in, size + c_ctx->iv_sz, hmac_out) != SQLITE_OK) {
memset(out, 0, page_sz); memset(out, 0, page_sz);
CODEC_TRACE(("codec_cipher: hmac operations failed for pgno=%d\n", pgno)); 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); EVP_CIPHER_CTX_cleanup(&c_ctx->ectx);
assert(size == csz); 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); 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 /* 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 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. */ 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; int i;
/* start by copying the kdf key into the hmac salt slot /* start by copying the kdf key into the hmac salt slot