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From Lupe Christoph <l...@alanya.m.isar.de>
Subject mod_auth-any/2924: segfault due to collaboration of mod_dir, mod_auth, mod_perl, and AuthenDBI
Date Sat, 29 Aug 1998 12:19:11 GMT

>Number:         2924
>Category:       mod_auth-any
>Synopsis:       segfault due to collaboration of mod_dir, mod_auth, mod_perl, and AuthenDBI
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    apache
>State:          open
>Class:          sw-bug
>Submitter-Id:   apache
>Arrival-Date:   Sat Aug 29 05:20:00 PDT 1998
>Originator:     lupe@alanya.m.isar.de
>Release:        1.3.1
Solaris 2.6 x86 (105182-06),
gcc version egcs-2.90.29 980515 (egcs-1.0.3 release),
mod_perl 1.15, ApacheDBI 0.80
The docroot contains a directory auth-required that is protected by:
	AuthType Basic
	PerlAuthenHandler Apache::AuthenDBI
Because the docroot contains no index.html, mod_dir is used to provide
an index page. Doing so, it calls for authorisation on auth-required
even though that directory is not accessed, only listed (this might also
be a bug, dunno).

Unless AuthenDBI is used, this works OK. With AuthenDBI, the Apache process
segfaults like this:

Program received signal SIGSEGV, Segmentation fault.
0xdfeec75c in strcmp ()
(gdb) where
#0  0xdfeec75c in strcmp ()
#1  0x80a3eba in check_user_access (r=0x82f8038) at mod_auth.c:279
#2  0x80a99ac in run_method (r=0x82f8038, offset=8, run_all=0) at 
#3  0x80a9bac in ap_check_auth (r=0x82f8038) at http_config.c:414
#4  0x80bdd69 in ap_sub_req_lookup_file (new_file=0x821b856 "auth-required", 
r=0x82f4038) at http_request.c:840
#5  0x809b96d in make_autoindex_entry (name=0x821b856 "auth-required", 
autoindex_opts=7, d=0x81ed830, r=0x82f4038, keyid=78 'N', direction=65 'A')
    at mod_autoindex.c:754
#6  0x809c9a4 in index_directory (r=0x82f4038, autoindex_conf=0x81ed830) at 
#7  0x809cc06 in handle_autoindex (r=0x82f4038) at mod_autoindex.c:1223
#8  0x80a9f23 in ap_invoke_handler (r=0x82f4038) at http_config.c:505
#9  0x80be975 in process_request_internal (r=0x82f4038) at http_request.c:1174
#10 0x80be9cf in ap_process_request (r=0x82f4038) at http_request.c:1191
#11 0x80b5d9d in child_main (child_num_arg=0) at http_main.c:3665
#12 0x80b5f54 in make_child (s=0x81ec838, slot=0, now=904201492) at 
#13 0x80b60e3 in startup_children (number_to_start=1) at http_main.c:3812
#14 0x80b6760 in standalone_main (argc=4, argv=0x8046f14) at http_main.c:4090
#15 0x80b6f8b in main (argc=4, argv=0x8046f14) at http_main.c:4367
(gdb) up
#1  0x80a3eba in check_user_access (r=0x82f8038) at mod_auth.c:279
279                     if (!strcmp(user, w))
(gdb) p user
$1 = 0x0
(gdb) p w
$2 = 0x82f89d0 "lupe"

This is because AuthenDBI does not do authorisation for auth-required
and returns like this:
	    return OK unless $r->is_initial_req; # only the first internal request

mod_auth gets handed a NULL pointer, and crashes.

More details available on request.
Install mod_perl 1.15 and ApacheDBI 0.80, plus some database, plus DBI, plus DBD::<whatever>.
This is the config fragment:
	<Directory /sw/www-turkey/auth-required>
		order deny,allow
		deny from all
		allow from alanya.m.isar.de
		allow from
		allow from localhost
		AddHandler cgi-script .cgi
		AddHandler cgi-script .pl
		Options Indexes FollowSymLinks ExecCGI
		AllowOverride AuthConfig
		<Limit GET POST>
			AuthType Basic
			AuthName Turkey
			PerlAuthenHandler Apache::AuthenDBI
			PerlSetVar Auth_DBI_data_source DBI:mysql:www
			PerlSetVar Auth_DBI_username auth
			PerlSetVar Auth_DBI_password auth
			PerlSetVar Auth_DBI_pwd_table auth
			PerlSetVar Auth_DBI_uid_field name
			PerlSetVar Auth_DBI_pwd_field pw
			require user lupe

I have asked Doug McEachern and the mod_perl list first. This is
what Doug said:

ouch, something should be fixed in mod_auth.c

Either mod_dir should not try to authenticate (even with mod_auth, the
user is not required to authenticate; it just returns somehow), or mod_auth
should check for NULL pointers.
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