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Generate a random salt when a page is encrypted before the salt is known #633

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Generate a random salt when a page is encrypted before the salt is known #633

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14 changes: 10 additions & 4 deletions src/sqlcipher.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1484,7 +1484,7 @@ static void sqlcipher_codec_ctx_set_error(codec_ctx *ctx, int error) {
ctx->error = error;
}

static int sqlcipher_codec_ctx_init_kdf_salt(codec_ctx *ctx) {
static int sqlcipher_codec_ctx_init_kdf_salt(codec_ctx *ctx, int read_header) {
sqlite3_file *fd = sqlite3PagerFile(sqlite3BtreePager(ctx->pBt));

if(SQLCIPHER_FLAG_GET(ctx->flags, CIPHER_FLAG_HAS_KDF_SALT)) {
Expand All @@ -1493,7 +1493,7 @@ static int sqlcipher_codec_ctx_init_kdf_salt(codec_ctx *ctx) {

/* read salt from header, if present, otherwise generate a new random salt */
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "sqlcipher_codec_ctx_init_kdf_salt: obtaining salt");
if(fd == NULL || fd->pMethods == 0 || sqlite3OsRead(fd, ctx->kdf_salt, ctx->kdf_salt_sz, 0) != SQLITE_OK) {
if(!read_header || fd == NULL || fd->pMethods == 0 || sqlite3OsRead(fd, ctx->kdf_salt, ctx->kdf_salt_sz, 0) != SQLITE_OK) {
sqlcipher_log(SQLCIPHER_LOG_DEBUG, SQLCIPHER_LOG_CORE, "sqlcipher_codec_ctx_init_kdf_salt: unable to read salt from file header, generating random");
if(ctx->provider->random(ctx->provider_ctx, ctx->kdf_salt, ctx->kdf_salt_sz) != SQLITE_OK) {
sqlcipher_log(SQLCIPHER_LOG_ERROR, SQLCIPHER_LOG_CORE, "sqlcipher_codec_ctx_init_kdf_salt: error retrieving random bytes from provider");
Expand All @@ -1519,7 +1519,7 @@ static int sqlcipher_codec_ctx_set_kdf_salt(codec_ctx *ctx, unsigned char *salt,
static int sqlcipher_codec_ctx_get_kdf_salt(codec_ctx *ctx, void** salt) {
int rc = SQLITE_OK;
if(!SQLCIPHER_FLAG_GET(ctx->flags, CIPHER_FLAG_HAS_KDF_SALT)) {
if((rc = sqlcipher_codec_ctx_init_kdf_salt(ctx)) != SQLITE_OK) {
if((rc = sqlcipher_codec_ctx_init_kdf_salt(ctx, 1)) != SQLITE_OK) {
sqlcipher_log(SQLCIPHER_LOG_ERROR, SQLCIPHER_LOG_CORE, "sqlcipher_codec_ctx_get_kdf_salt: error %d from sqlcipher_codec_ctx_init_kdf_salt", rc);
}
}
Expand Down Expand Up @@ -1867,7 +1867,7 @@ static int sqlcipher_cipher_ctx_key_derive(codec_ctx *ctx, cipher_ctx *c_ctx) {

/* if necessary, initialize the salt from the header or random source */
if(!SQLCIPHER_FLAG_GET(ctx->flags, CIPHER_FLAG_HAS_KDF_SALT)) {
if((rc = sqlcipher_codec_ctx_init_kdf_salt(ctx)) != SQLITE_OK) {
if((rc = sqlcipher_codec_ctx_init_kdf_salt(ctx, 1)) != SQLITE_OK) {
sqlcipher_log(SQLCIPHER_LOG_ERROR, SQLCIPHER_LOG_CORE, "%s: error %d from sqlcipher_codec_ctx_init_kdf_salt", __func__, rc);
goto error;
}
Expand Down Expand Up @@ -3523,6 +3523,12 @@ static void* sqlite3Codec(void *iCtx, void *data, Pgno pgno, int mode) {
goto cleanup;
}

/* encrypting before the salt is known means no page was read, so the file has no header yet */
if((mode == CODEC_WRITE_OP || mode == CODEC_JOURNAL_OP) && (rc = sqlcipher_codec_ctx_init_kdf_salt(ctx, 0)) != SQLITE_OK) {
sqlcipher_codec_ctx_set_error(ctx, rc);
goto cleanup;
}

/* call to derive keys if not present yet */
if((rc = sqlcipher_codec_key_derive(ctx)) != SQLITE_OK) {
sqlcipher_log(SQLCIPHER_LOG_ERROR, SQLCIPHER_LOG_CORE, "sqlite3Codec: error occurred during key derivation: %d", rc);
Expand Down
14 changes: 14 additions & 0 deletions test/sqlcipher-core.test
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,20 @@ do_test test-sqlcipher-header-overwrite {
} {0}
file delete -force test.db

# verify that a new database gets a random salt when the VFS preallocates on SQLITE_FCNTL_SIZE_HINT
do_test test-sqlcipher-salt-chunk-size {
sqlite_orig db test.db
execsql { PRAGMA key = 'test'; }
file_control_chunksize_test db main 65536
execsql { CREATE TABLE t1(a,b); INSERT INTO t1 VALUES (1, 2); }
db close
set rc [string equal [hexio_read test.db 0 16] [string repeat 0 32]]
sqlite_orig db test.db
lappend rc [execsql { PRAGMA key = 'test'; SELECT * FROM t1; }]
} {0 {ok 1 2}}
db close
file delete -force test.db

# open the database and try to read from it without
# providing a passphrase. verify that the
# an error is returned from the library
Expand Down