MDEV-26747 improve corruption check for encrypted tables on ALTER IMPORT

fil_space_decrypt(): change signature to return status via dberr_t only.
Also replace impossible condition with an assertion and prove it via
test cases.

mysql-test/suite/encryption/r/encryption_key_corruption.result

+call mtr.add_suppression("InnoDB: .*: Page 0 at offset 0 looks corrupted");
+call mtr.add_suppression("Index for table 'dst' is corrupt; try to repair it");
+call mtr.add_suppression("Page for tablespace .* is index page with id .* but that index is not found from configuration file");
+CREATE TABLE src (pk INT PRIMARY KEY, value INT) ENGINE=INNODB;
+INSERT INTO src VALUES (1, 1), (2, 2), (3, 3);
+FLUSH TABLES src FOR EXPORT;
+UNLOCK TABLES;
+DROP TABLE src;
+CREATE TABLE dst (pk INT PRIMARY KEY, value INT) ENGINE=INNODB;
+ALTER TABLE dst DISCARD TABLESPACE;
+ALTER TABLE dst IMPORT TABLESPACE;
+ERROR HY000: Internal error: Cannot reset LSNs in table `test`.`dst` : Data structure corruption
+DROP TABLE dst;

mysql-test/suite/encryption/t/encryption_key_corruption.combinations

+[crc32]
+innodb-checksum-algorithm=crc32
+[none]
+innodb-checksum-algorithm=none
+[innodb]
+innodb-checksum-algorithm=innodb

mysql-test/suite/encryption/t/encryption_key_corruption.opt

+--innodb-encrypt-tables=1

mysql-test/suite/encryption/t/encryption_key_corruption.test

+--source include/have_innodb.inc
+--source include/have_example_key_management_plugin.inc
+
+call mtr.add_suppression("InnoDB: .*: Page 0 at offset 0 looks corrupted");
+call mtr.add_suppression("Index for table 'dst' is corrupt; try to repair it");
+call mtr.add_suppression("Page for tablespace .* is index page with id .* but that index is not found from configuration file");
+
+let MYSQLD_DATADIR = `SELECT @@datadir`;
+
+
+CREATE TABLE src (pk INT PRIMARY KEY, value INT) ENGINE=INNODB;
+INSERT INTO src VALUES (1, 1), (2, 2), (3, 3);
+
+FLUSH TABLES src FOR EXPORT;
+
+--copy_file $MYSQLD_DATADIR/test/src.ibd $MYSQLD_DATADIR/test/tmp.ibd
+--copy_file $MYSQLD_DATADIR/test/src.cfg $MYSQLD_DATADIR/test/tmp.cfg
+
+perl;
+use strict;
+die unless open(FILE, "+<$ENV{MYSQLD_DATADIR}/test/tmp.ibd");
+binmode FILE;
+die unless seek(FILE, 3 * 16384 + 26, 0);
+print FILE pack("N", 0x00000000);
+close(FILE);
+EOF
+
+UNLOCK TABLES;
+
+DROP TABLE src;
+
+CREATE TABLE dst (pk INT PRIMARY KEY, value INT) ENGINE=INNODB;
+ALTER TABLE dst DISCARD TABLESPACE;
+
+--copy_file $MYSQLD_DATADIR/test/tmp.ibd $MYSQLD_DATADIR/test/dst.ibd
+--copy_file $MYSQLD_DATADIR/test/tmp.cfg $MYSQLD_DATADIR/test/dst.cfg
+
+--error ER_INTERNAL_ERROR
+ALTER TABLE dst IMPORT TABLESPACE;
+
+DROP TABLE dst;
+
+--remove_file $MYSQLD_DATADIR/test/tmp.ibd
+--remove_file $MYSQLD_DATADIR/test/tmp.cfg

storage/innobase/fil/fil0crypt.cc

@@ -668,16 +668,14 @@ fil_space_encrypt(
 @param[in]	tmp_frame		Temporary buffer
 @param[in]	page_size		Page size
 @param[in,out]	src_frame		Page to decrypt
-@param[out]	err			DB_SUCCESS or DB_DECRYPTION_FAILED
-@return true if page decrypted, false if not.*/
+@return DB_SUCCESS or error */
 UNIV_INTERN
-bool
+dberr_t
 fil_space_decrypt(
 	fil_space_crypt_t*	crypt_data,
 	byte*			tmp_frame,
 	const page_size_t&	page_size,
-	byte*			src_frame,
-	dberr_t*		err)
+	byte*			src_frame)
 {
 	ulint page_type = mach_read_from_2(src_frame+FIL_PAGE_TYPE);
 	uint key_version = mach_read_from_4(src_frame + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION);
@@ -686,12 +684,7 @@ fil_space_decrypt(
 	uint space = mach_read_from_4(src_frame + FIL_PAGE_ARCH_LOG_NO_OR_SPACE_ID);
 	ib_uint64_t lsn = mach_read_from_8(src_frame + FIL_PAGE_LSN);
 
-	*err = DB_SUCCESS;
-
-	if (key_version == ENCRYPTION_KEY_NOT_ENCRYPTED) {
-		return false;
-	}
-
+	ut_a(key_version != ENCRYPTION_KEY_NOT_ENCRYPTED);
 	ut_a(crypt_data != NULL && crypt_data->is_encrypted());
 
 	/* read space & lsn */
@@ -722,8 +715,7 @@ fil_space_decrypt(
 	if (! ((rc == MY_AES_OK) && ((ulint) dstlen == srclen))) {
 
 		if (rc == -1) {
-			*err = DB_DECRYPTION_FAILED;
-			return false;
+			return DB_DECRYPTION_FAILED;
 		}
 
 		ib::fatal() << "Unable to decrypt data-block "
@@ -748,7 +740,7 @@ fil_space_decrypt(
 
 	srv_stats.pages_decrypted.inc();
 
-	return true; /* page was decrypted */
+	return DB_SUCCESS; /* page was decrypted */
 }
 
 /**
@@ -765,27 +757,21 @@ fil_space_decrypt(
 	byte*		tmp_frame,
 	byte*		src_frame)
 {
-	dberr_t err = DB_SUCCESS;
-	byte* res = NULL;
 	const page_size_t page_size(space->flags);
 
 	ut_ad(space->crypt_data != NULL && space->crypt_data->is_encrypted());
 	ut_ad(space->n_pending_ios > 0);
 
-	bool encrypted = fil_space_decrypt(space->crypt_data, tmp_frame,
-					   page_size, src_frame, &err);
+	if (DB_SUCCESS != fil_space_decrypt(space->crypt_data, tmp_frame,
+					    page_size, src_frame)) {
+		return NULL;
+	}
 
-	if (err == DB_SUCCESS) {
-		if (encrypted) {
 	/* Copy the decrypted page back to page buffer, not
 	really any other options. */
 	memcpy(src_frame, tmp_frame, page_size.physical());
-		}
-
-		res = src_frame;
-	}
 
-	return res;
+	return src_frame;
 }
 
 /******************************************************************

storage/innobase/include/fil0crypt.h

@@ -359,16 +359,14 @@ Decrypt a page.
 @param[in]	tmp_frame		Temporary buffer
 @param[in]	page_size		Page size
 @param[in,out]	src_frame		Page to decrypt
-@param[out]	err			DB_SUCCESS or error
-@return true if page decrypted, false if not.*/
+@return DB_SUCCESS or error */
 UNIV_INTERN
-bool
+dberr_t
 fil_space_decrypt(
 	fil_space_crypt_t*	crypt_data,
 	byte*			tmp_frame,
 	const page_size_t&	page_size,
-	byte*			src_frame,
-	dberr_t*		err);
+	byte*			src_frame);
 
 /******************************************************************
 Decrypt a page

storage/innobase/row/row0import.cc

@@ -3502,9 +3502,12 @@ dberr_t FetchIndexRootPages::run(const fil_iterator_t& iter,
     if (!fil_space_verify_crypt_checksum(readptr, get_page_size()))
       goto page_corrupted;
 
-    if (!fil_space_decrypt(iter.crypt_data, readptr,
-                           get_page_size(), readptr, &err) ||
-        err != DB_SUCCESS)
+    if (ENCRYPTION_KEY_NOT_ENCRYPTED ==
+        mach_read_from_4(readptr + FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION))
+      goto page_corrupted;
+
+    if ((err = fil_space_decrypt(iter.crypt_data, readptr,
+				 get_page_size(), readptr)))
       goto func_exit;
   }
 
@@ -3647,7 +3650,6 @@ static dberr_t fil_iterate(
 			} else if (!mach_read_from_4(
 					   FIL_PAGE_FILE_FLUSH_LSN_OR_KEY_VERSION
 					   + src)) {
-not_encrypted:
 				if (block->page.id.page_no() == 0
 				    && block->page.zip.data) {
 					block->page.zip.data = src;
@@ -3666,18 +3668,13 @@ static dberr_t fil_iterate(
 					goto page_corrupted;
 				}
 
-				decrypted = fil_space_decrypt(
+				if ((err = fil_space_decrypt(
 					iter.crypt_data, dst,
-					callback.get_page_size(), src, &err);
-
-				if (err != DB_SUCCESS) {
+					callback.get_page_size(), src))) {
 					goto func_exit;
 				}
 
-				if (!decrypted) {
-					goto not_encrypted;
-				}
-
+				decrypted = true;
 				updated = true;
 			}