sasl: fix sqlite3 plugin value inserts

[SyntevoAlex]

Consider the following configuration:

sqlite3 database sqlite.db:

CREATE TABLE data(username TEXT, realm TEXT, property TEXT, value TEXT)

saslpasswd.conf file

pwcheck_method: auxprop
mech_list: CRAM-MD5
auxprop_plugin: sql
sql_engine: sqlite3
sql_database: sqlite.db
sql_select: SELECT value FROM data WHERE username = '%u' AND realm = '%r' AND property = '%p'
sql_insert: INSERT INTO data (username, realm, property, value) VALUES ('%u', '%r', '%p', '%v')
sql_update: UPDATE data SET value='%v' WHERE username = '%u' AND realm = '%r' AND property = '%p'

Now, when using saslpasswd2 -u TestRealm -c TestUser it pretended to succeed, but in fact did nothing.
Worse yet, it's not just about saslpasswd2. In fact, sqlite3 auxprop couldn't insert any new data in the db.

Please refer to commit message for the explanation.

[SyntevoAlex]

Could be related: https://lists.andrew.cmu.edu/pipermail/cyrus-sasl/2020-July/003283.html

[hyc]

Getting more than one result should be a failure, certainly it is a security vulnerability to have ambiguous credentials. If an attacker can insert their own creds in front of the valid ones, etc...

[Neustradamus]

@SyntevoAlex: Have you seen the @hyc comment?

[SyntevoAlex]

Sorry, I will no longer work on this PR, because I no longer work with the employer. It can be closed now.