When using DOUBLE_QUOTED_STRING, passwords with '\"' may not work

[平林 哲]

Hi!

When using DOUBLE_QUOTED_STRING, passwords with '\"' may not work.

Register a user in ActiveDirectory with the password "pass\"word at 2022",
the following LDAP settings.

===
# cat /usr/local/etc/raddb/mods-enabled/ldap1
ldap {
         server = '192.168.1.6'
         identity = 
'cn=tkt10886-3,cn=users,dc=srv2022,dc=rdd-osaka,dc=soliton,dc=example,dc=jp'
         password = "pass\"word at 2022"

         base_dn = 'dc=srv2022,dc=rdd-osaka,dc=soliton,dc=example,dc=jp'
===


When attempting to start the RADIUS service in this state, a syntax 
error occurred.

=====
# /usr/local/sbin/radiusd -X
FreeRADIUS Version 3.2.3
Copyright (C) 1999-2022 The FreeRADIUS server project and contributors
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE
You may redistribute copies of FreeRADIUS under the terms of the
GNU General Public License
For more information about these matters, see the file named COPYRIGHT
Starting - reading configuration files ...
including dictionary file /usr/local/share/freeradius/dictionary
including dictionary file /usr/local/share/freeradius/dictionary.dhcp
including dictionary file /usr/local/share/freeradius/dictionary.vqp
including dictionary file /usr/local/etc/raddb/dictionary
including configuration file /usr/local/etc/raddb/radiusd.conf
including configuration file /usr/local/etc/raddb/proxy.conf
including configuration file /usr/local/etc/raddb/clients.conf
including files in directory /usr/local/etc/raddb/mods-enabled/
including configuration file 
/usr/local/etc/raddb/mods-enabled/dynamic_clients
including configuration file /usr/local/etc/raddb/mods-enabled/realm
including configuration file /usr/local/etc/raddb/mods-enabled/chap
including configuration file /usr/local/etc/raddb/mods-enabled/utf8
including configuration file /usr/local/etc/raddb/mods-enabled/date
including configuration file /usr/local/etc/raddb/mods-enabled/exec
including configuration file /usr/local/etc/raddb/mods-enabled/unix
including configuration file /usr/local/etc/raddb/mods-enabled/expr
including configuration file /usr/local/etc/raddb/mods-enabled/totp
including configuration file /usr/local/etc/raddb/mods-enabled/always
including configuration file /usr/local/etc/raddb/mods-enabled/preprocess
including configuration file /usr/local/etc/raddb/mods-enabled/ldap1
/usr/local/etc/raddb/mods-enabled/ldap1[4]: Syntax error: Expected comma 
after 'pass\\': word at 2022"
Errors reading or parsing /usr/local/etc/raddb/radiusd.conf
=====

We also tried several patterns and summarised the results.

    Password        |   Configration        | Result
-------------------|-----------------------|-------
pass"word at 2022     | "pass\"word at 2022"     |  OK
pass\"word at 2022    | "pass\\"word at 2022"    |  Syntax error
pass\\"word at 2022   | "pass\\\"word at 2022"   |  OK
pass\\\"word at 2022  | "pass\\\\"word at 2022"  |  Syntax error

As mentioned above, a Syntax Error occurs when '\' is an even number in 
the configuration.

After investigating the cause of this, it appears that there is a 
problem with the determination of '˶' in the following section.

===
			/*
			 *	Convert backslash-quote to quote, but
			 *	leave everything else alone.
			 */
			if (p[1] == quote) { /* convert '\'' --> ' */
				p++;
			} else {
				if (buflen < 2) {
					fr_strerror_printf("Truncated input");
					return T_INVALID;
				}

				*(s++) = *(p++);
			}
			*(s++) = *(p++);
		}
===

This problem was solved by changing the above section as follows.

===
                 } else {
                         /*
                          *      Convert backslash-quote to quote, but
                          *      leave everything else alone.
                          */
                         if (p[1] == quote) { /* convert '\'' --> ' */
                                 if (p[2] != '\0') {
                                         p++;
                                 }
                         }
                         *(s++) = *(p++);
                 }
===

Is this the right approach?
Any advice would be appreciated.