signalapp/sqlcipher
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refactor calculation of reserve space

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This commit is contained in:
Stephen Lombardo 2011-02-17 01:49:01 -05:00
parent 3aefd5e5de
commit ffcb4f7fd9
1 changed files with 9 additions and 10 deletions
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19
src/crypto.c
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@ -55,6 +55,7 @@ typedef struct {
int kdf_iter;
int key_sz;
int iv_sz;
int block_sz;
int pass_sz;
int reserve_sz;
int hmac_sz;
@ -400,18 +401,15 @@ int codec_set_use_hmac(sqlite3* db, int nDb, int use) {
sqlite3pager_get_codec(pDb->pBt->pBt->pPager, (void **) &ctx);
reserve = EVP_MAX_IV_LENGTH; /* base reserve size will be IV only */
/* calculate the amount of reserve needed to include an hmac and pad so that it is evenly
divisible by the max IV size */
if(use) {
int md_size = ctx->read_ctx->hmac_sz;
if(use) reserve += ctx->read_ctx->hmac_sz; /* if reserve will include hmac, update that size */
reserve += ((md_size % EVP_MAX_IV_LENGTH) == 0)
? md_size
: ((md_size / EVP_MAX_IV_LENGTH) + 1) * EVP_MAX_IV_LENGTH;
/* calculate the amount of reserve needed in even increments of the cipher block size */
CODEC_TRACE(("codec_set_use_hmac: EVP_MAX_IV_LENGTH=%d md_size=%d reserve=%d\n",
EVP_MAX_IV_LENGTH, md_size, reserve));
}
reserve = ((reserve % ctx->read_ctx->block_sz) == 0) ? reserve :
((reserve / ctx->read_ctx->block_sz) + 1) * ctx->read_ctx->block_sz;
CODEC_TRACE(("codec_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;
ctx->write_ctx->reserve_sz = ctx->read_ctx->reserve_sz = reserve;
@ -473,6 +471,7 @@ int codec_set_cipher_name(sqlite3* db, int nDb, const char *cipher_name, int for
c_ctx->evp_cipher = (EVP_CIPHER *) EVP_get_cipherbyname(cipher_name);
c_ctx->key_sz = EVP_CIPHER_key_length(c_ctx->evp_cipher);
c_ctx->iv_sz = EVP_CIPHER_iv_length(c_ctx->evp_cipher);
c_ctx->block_sz = EVP_CIPHER_block_size(c_ctx->evp_cipher);
c_ctx->hmac_sz = EVP_MD_size(EVP_sha1());
c_ctx->derive_key = 1;