** Description changed:
- Impact
- ------
+ [Impact]
Users willing to use the slapd rwm overlay will face a slapd
segmentation fault when trying to rewrite some rules. Backporting this
fix will allow users using stable releases to take advantage of this
feature without crashing slapd. This issue was fixed by upstream not
freeing the rwm overlay filter memory without prior checking.
- Test Case
- ---------
+ [Test Case]
In this test case, the rwm overlay will be used and a rule will be
created to deny any search request for uid=root, then the 'ldapsearch'
will be invoked to trigger the failure. It is important to mention that
the 'ldapsearch' command should fail regardless the presence of the bug
in the package, the target here is the slapd crash. To reproduce this
bug one can follow the procedure below in Ubuntu xenial, bionic or
disco:
$ sudo apt-get update
-
Use debconf to pre-seed slapd questions before install it:
$ debconf-set-selections << EOF
slapd slapd/no_configuration boolean false
slapd slapd/domain string example.com
slapd shared/organization string example.com
slapd slapd/password1 password test
slapd slapd/password2 password test
slapd slapd/backend select MDB
slapd slapd/move_old_database boolean false
EOF
$ sudo apt-get install slapd ldap-utils -y
-
Create a file called 'add-rwm.ldif' with the following content:
$ cat add-rwm.ldif
dn: cn=module{0},cn=config
changetype: modify
add: olcModuleLoad
olcModuleLoad: rwm
dn: olcOverlay=rwm,olcDatabase={1}mdb,cn=config
changetype: add
objectClass: olcOverlayConfig
objectClass: olcRwmConfig
olcOverlay: rwm
olcRwmRewrite: {0} rwm-rewriteEngine "on"
olcRwmRewrite: {1} rwm-rewriteContext "searchFilter"
olcRwmRewrite: {2} rwm-rewriteRule "(.*)(uid=root)(.*)" "$1$2$3" "#"
With this file in place, run:
$ sudo ldapadd -Q -Y EXTERNAL -H ldapi:/// -f add-rwm.ldif
Now, to trigger the crash:
$ ldapsearch -x -h localhost -b dc=example,dc=com -LLL uid=root
Server is unwilling to perform (53)
Additional information: searchFilter/searchFilterAttrDN massage error
-
- slapd process will die, and /var/crash will have a crash file for slapd. You
can run the following command to confirm the error:
+ slapd process will die, and /var/crash will have a crash file for slapd.
+ You can run the following command to confirm the error:
$ cat /var/log/syslog | grep filter_free
Aug 9 19:51:05 popular-gorilla slapd[1479]: filter_free: unknown filter
type=28530
-> Expected behavior
In this test case, as mentioned before, the 'ldapsearch' command should
fail but the 'slapd' process should not die. As result, we don't expect
a slapd crash report in /var/crash directory.
-
- Regression Potential
- --------------------
+ [Regression Potential]
Since the fix is a patch provided by upstream (reviewed by maintainers
and us) simple mistakes like typos are not expected. The patch impacts
only the rwm module which is not loaded by default. So any regression
would affect only the users that make use of this overlay. If an user is
not using rwm overlay and is facing any issue, it should be related to
other problems related to LDAP directory services.
-
[Original message]
Hello!
We have faced slapd crash, seems an attacker was trying to brute force one
of our services and uid parsing failures caused slapd crash:
Jul 26 18:59:47 slapd[1252]: conn=1466 op=13 SRCH
base="ou=test,dc=test,dc=com" scope=2 deref=0
filter="(&(uid=aistar123<>!n)(objectClass=posixAccount)(uid=*)(&(uidNumber=*)(!(uidNumber=0))))"
Jul 26 18:59:47 slapd[1252]: conn=1466 op=13 SRCH attr=objectClass uid
userPassword uidNumber gidNumber gecos homeDirectory loginShell
krbPrincipalName cn memberOf modifyTimestamp modifyTimestamp
shadowLastChange shadowMin shadow
Max shadowWarning shadowInactive shadowExpire shadowFlag krbLastPwdChange
krbPasswordExpiration pwdAttribute authorizedService accountExpires
userAccountControl nsAccountLock host loginDisabled loginExpirationTime
loginAllowedTimeMap sshPublic
Key
Jul 26 18:59:47 slapd[1252]: conn=1466 op=13 SEARCH RESULT tag=101 err=0
nentries=0 text=massaged filter parse error
Jul 26 18:59:47 kernel: [ 9441.554161] slapd[2367]: segfault at 18 ip
00007fc8d18ec512 sp 00007fc8889e2810 error 4 in libc-2.23.so
[7fc8d1868000+1c0000]
Another faulty filter example:
filter="(&(uid=sql<>?)(objectClass=posixAccount)(&(uidNumber=*)(!(uidNumber=0))))"
filter="(&(uid=fugeone<>?123)(objectClass=posixAccount)(uid=*)(&(uidNumber=*)(!(uidNumber=0))))"
$ lsb_release -rd
Description: Ubuntu 16.04.5 LTS
Release: 16.04
$ slapd -VVV
@(#) $OpenLDAP: slapd (Ubuntu) (May 22 2018 13:54:12) $
buildd@lcy01-amd64-019
:/build/openldap-t_Ta0O/openldap-2.4.42+dfsg/debian/build/servers/slapd
Included static backends:
config
ldif
$ apt-cache policy slapd
slapd:
Installed: 2.4.42+dfsg-2ubuntu3.3
Candidate: 2.4.42+dfsg-2ubuntu3.5
Version table:
2.4.42+dfsg-2ubuntu3.5 500
500 http://nl.archive.ubuntu.com/ubuntu xenial-updates/main amd64
Packages
*** 2.4.42+dfsg-2ubuntu3.3 100
100 /var/lib/dpkg/status
2.4.42+dfsg-2ubuntu3.2 500
500 http://security.ubuntu.com/ubuntu xenial-security/main amd64
Packages
2.4.42+dfsg-2ubuntu3 500
500 http://nl.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
affects ubuntu/openldap
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https://bugs.launchpad.net/bugs/1838370
Title:
slapd segfault on filter parse error
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