int sqlcipher_codec_key_copy(codec_ctx *ctx, int source) {
if(source == CIPHER_READ_CTX) {
return sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx);
} else {
return sqlcipher_cipher_ctx_copy(ctx->read_ctx, ctx->write_ctx);
}
}
int sqlcipher_codec_ctx_init(codec_ctx **iCtx, Db *pDb, Pager *pPager, sqlite3_file *fd, const void *zKey, int nKey) {
int rc;
codec_ctx *ctx;
*iCtx = sqlcipher_malloc(sizeof(codec_ctx));
ctx = *iCtx;
if(ctx == NULL) return SQLITE_NOMEM;
ctx->pBt = pDb->pBt; /* assign pointer to database btree structure */
/* allocate space for salt data. Then read the first 16 bytes
directly off the database file. This is the salt for the
key derivation function. If we get a short read allocate
a new random salt value */
ctx->kdf_salt_sz = FILE_HEADER_SZ;
ctx->kdf_salt = sqlcipher_malloc(ctx->kdf_salt_sz);
if(ctx->kdf_salt == NULL) return SQLITE_NOMEM;
/* allocate space for separate hmac salt data. We want the
HMAC derivation salt to be different than the encryption
key derivation salt */
ctx->hmac_kdf_salt = sqlcipher_malloc(ctx->kdf_salt_sz);
if(ctx->hmac_kdf_salt == NULL) return SQLITE_NOMEM;
/*
Always overwrite page size and set to the default because the first page of the database
in encrypted and thus sqlite can't effectively determine the pagesize. this causes an issue in
cases where bytes 16 & 17 of the page header are a power of 2 as reported by John Lehman
*/
if((rc = sqlcipher_codec_ctx_set_pagesize(ctx, SQLITE_DEFAULT_PAGE_SIZE)) != SQLITE_OK) return rc;
if((rc = sqlcipher_cipher_ctx_init(&ctx->read_ctx)) != SQLITE_OK) return rc;
if((rc = sqlcipher_cipher_ctx_init(&ctx->write_ctx)) != SQLITE_OK) return rc;
if(fd == NULL || sqlite3OsRead(fd, ctx->kdf_salt, FILE_HEADER_SZ, 0) != SQLITE_OK) {
ctx->need_kdf_salt = 1;
}
if((rc = sqlcipher_codec_ctx_set_cipher(ctx, CIPHER, 0)) != SQLITE_OK) return rc;
if((rc = sqlcipher_codec_ctx_set_kdf_iter(ctx, default_kdf_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;
/* 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;
return SQLITE_OK;
}
int sqlcipher_codec_ctx_set_fast_kdf_iter(codec_ctx *ctx, int fast_kdf_iter, int for_ctx) {
cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
int rc;
c_ctx->fast_kdf_iter = fast_kdf_iter;
c_ctx->derive_key = 1;
if(for_ctx == 2)
if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
return rc;
return SQLITE_OK;
}
int sqlcipher_codec_ctx_set_pass(codec_ctx *ctx, const void *zKey, int nKey, int for_ctx) {
cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
int rc;
if((rc = sqlcipher_cipher_ctx_set_pass(c_ctx, zKey, nKey)) != SQLITE_OK) return rc;
c_ctx->derive_key = 1;
if(for_ctx == 2)
if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
return rc;
return SQLITE_OK;
}
int sqlcipher_codec_ctx_set_cipher(codec_ctx *ctx, const char *cipher_name, int for_ctx) {
cipher_ctx *c_ctx = for_ctx ? ctx->write_ctx : ctx->read_ctx;
int rc;
c_ctx->provider->set_cipher(c_ctx->provider_ctx, cipher_name);
c_ctx->key_sz = c_ctx->provider->get_key_sz(c_ctx->provider_ctx);
c_ctx->iv_sz = c_ctx->provider->get_iv_sz(c_ctx->provider_ctx);
c_ctx->block_sz = c_ctx->provider->get_block_sz(c_ctx->provider_ctx);
c_ctx->hmac_sz = c_ctx->provider->get_hmac_sz(c_ctx->provider_ctx);
c_ctx->derive_key = 1;
if(for_ctx == 2)
if((rc = sqlcipher_cipher_ctx_copy( for_ctx ? ctx->read_ctx : ctx->write_ctx, c_ctx)) != SQLITE_OK)
return rc;
return SQLITE_OK;
}
int sqlcipher_codec_key_derive(codec_ctx *ctx) {
/* derive key on first use if necessary */
if(ctx->read_ctx->derive_key) {
if(sqlcipher_cipher_ctx_key_derive(ctx, ctx->read_ctx) != SQLITE_OK) return SQLITE_ERROR;
}
if(ctx->write_ctx->derive_key) {
if(sqlcipher_cipher_ctx_cmp(ctx->write_ctx, ctx->read_ctx) == 0) {
/* the relevant parameters are the same, just copy read key */
if(sqlcipher_cipher_ctx_copy(ctx->write_ctx, ctx->read_ctx) != SQLITE_OK) return SQLITE_ERROR;
} else {
if(sqlcipher_cipher_ctx_key_derive(ctx, ctx->write_ctx) != SQLITE_OK) return SQLITE_ERROR;
}
}
/* TODO: wipe and free passphrase after key derivation */
sqlcipher_cipher_ctx_set_pass(ctx->read_ctx, NULL, 0);
sqlcipher_cipher_ctx_set_pass(ctx->write_ctx, NULL, 0);
return SQLITE_OK;
}