MDEV-11340 Allow multiple alternative authentication methods for the same user

introduce the syntax

... IDENTIFIED { WITH | VIA }
      plugin [ { USING | AS } auth ]
 [ OR plugin [ { USING | AS } auth ]
 [ OR ... ]]

Server will try auth plugins in the specified order until the first
success. No protocol changes, server uses the existing "switch plugin"
packet.

The auth chain is stored in json as

  "auth_or":[{"plugin":"xxx","authentication_string":"yyy"},
             {},
             {"plugin":"foo","authentication_string":"bar"},
            ...],
  "plugin":"aaa", "authentication_string":"bbb"

Note:
* "auth_or" implies that there might be "auth_and" someday;
* one entry in the array is an empty object, meaning to take plugin/auth
  from the main json object. This preserves compatibility with
  the existing mysql.global_priv table and with the mysql.user view.
  This entry is preferrably a mysql_native_password plugin for a
  non-empty mysql.user.password column.

SET PASSWORD is supported and changes the password for the *first*
plugin in the chain that has a notion of a "password"

1 files changed, 36 insertions, 0 deletions

diff --git a/plugin/auth_gssapi/mysql-test/auth_gssapi/multiauth.test b/plugin/auth_gssapi/mysql-test/auth_gssapi/multiauth.test
new file mode 100644
index 00000000000..10e1e80907e
--- /dev/null
+++ b/plugin/auth_gssapi/mysql-test/auth_gssapi/multiauth.test
@@ -0,0 +1,36 @@
+--replace_regex /name '[^']+'/name 'localhost'/
+INSTALL SONAME 'auth_gssapi';
+
+# gssapi,password
+CREATE USER 'nosuchuser' IDENTIFIED WITH gssapi OR mysql_native_password as password("good");
+replace_result $MASTER_MYSOCK MASTER_MYSOCK $MASTER_MYPORT MASTER_MYPORT;
+error ER_ACCESS_DENIED_ERROR;
+connect (con1,localhost,nosuchuser,,);
+connect (con1,localhost,nosuchuser,good,);
+SELECT USER(),CURRENT_USER();
+disconnect con1;
+connection default;
+DROP USER nosuchuser;
+
+# password,gssapi
+CREATE USER 'nosuchuser' IDENTIFIED WITH mysql_native_password as password("good") OR gssapi;
+replace_result $MASTER_MYSOCK MASTER_MYSOCK $MASTER_MYPORT MASTER_MYPORT $GSSAPI_SHORTNAME GSSAPI_SHORTNAME;
+error ER_ACCESS_DENIED_ERROR;
+connect (con1,localhost,nosuchuser,,);
+connect (con1,localhost,nosuchuser,good,);
+SELECT USER(),CURRENT_USER();
+disconnect con1;
+connection default;
+DROP USER nosuchuser;
+
+replace_result $GSSAPI_SHORTNAME GSSAPI_SHORTNAME;
+eval CREATE USER '$GSSAPI_SHORTNAME' IDENTIFIED WITH mysql_native_password as password("good") OR gssapi;
+connect (con1,localhost,$GSSAPI_SHORTNAME,,);
+replace_result $GSSAPI_SHORTNAME GSSAPI_SHORTNAME;
+SELECT USER(),CURRENT_USER();
+disconnect con1;
+connection default;
+replace_result $GSSAPI_SHORTNAME GSSAPI_SHORTNAME;
+eval DROP USER '$GSSAPI_SHORTNAME';
+
+UNINSTALL SONAME 'auth_gssapi';