Nick Tait <ntait () redhat com> wrote: [1] Heap Buffer Overflow in Rsync due to Improper Checksum Length Handling

CVE ID: CVE-2024-12084

CVSS 3.1: 9.8 - AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Description: A heap-based buffer overflow flaw was found in the rsync daemon. This issue is due to improper handling of attacker-controlled checksum lengths (s2length) in the code. When MAXDIGESTLEN exceeds the fixed SUMLENGTH (16 bytes), an attacker can write out of bounds in the sum2 buffer. Does anybody know if this issue is also present in the code executing when you use SSH instead of rsyncd?

I'd expect the "rsync --server --sender" functionality to possibly (likely?) share code here, but the current description might lead folks to not consider this scenario and only look for cases where they offer rsyncd (e.g., port 873).

-Jan

Hi Douglas,

On Tue, Jun 25, 2024 at 11:49:40AM +1200, Douglas Bagnall wrote: So Samba was very susceptible to this bug. The good news is ldbqsort() is not used in very many places, and some of those places already used transitive comparison functions. The other good news is that now it is patched with the "tmpptr > baseptr &&" fix. And the third good news is that the comparison functions are fixed. That's in 4.19.7 and 4.20.2. This is really interesting, thank you very much for your work on all this and for taking the time to write this detailed analysis! We are extremely happy that our advisory has been useful.

With best regards,

-- the Qualys Security Advisory team

This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Samba. Authentication is not required to exploit this vulnerability.

This vulnerability allows remote attackers to create a denial-of-service condition on affected installations of Samba. Authentication is not required to exploit this vulnerability.

This vulnerability allows remote attackers to disclose sensitive information on affected installations of Samba. Authentication is not required to exploit this vulnerability.

This vulnerability allows remote attackers to disclose sensitive information on affected installations of Samba. Authentication is not required to exploit this vulnerability.

This vulnerability allows remote attackers to disclose sensitive information on affected installations of Samba. Authentication is required to exploit this vulnerability, and SMB1 must be enabled on the target.

This vulnerability allows remote attackers to disclose sensitive information on affected installations of Samba. Authentication is required to exploit this vulnerability, and SMB1 must be enabled on the target.

The Samba AD DC administration tool, when operating against a remote LDAP server, will by default send new or reset passwords over a signed-only connection.

A flaw was found in Samba. An incomplete access check on dnsHostName allows authenticated but otherwise unprivileged users to delete this attribute from any object in the directory.

The fix in 4.6.16, 4.7.9, 4.8.4 and 4.9.7 for CVE-2018-10919 Confidential attribute disclosure vi LDAP filters was insufficient and an attacker may be able to obtain confidential BitLocker recovery keys from a Samba AD DC.

All versions of Samba prior to 4.13.16 are vulnerable to a malicious client using an SMB1 or NFS race to allow a directory to be created in an area of the server file system not exported under the share definition. Note that SMB1 has to be enabled, or the share also available via NFS in order for this attack to succeed.

As per upstream report:

In order to avoid issues like CVE-2020-25717 AD Kerberos accepting services need access to unique, and ideally long-term stable identifiers of a user to perform authorization.

The AD PAC provides this, but the most useful information is kept in a buffer which is NDR encoded, which means that so far in Free Software only Samba and applications which use Samba components under the hood like FreeIPA and SSSD decode PAC.

Recognising that the issues seen in Samba are not unique, Samba now provides an extension to UPNDNSINFO, a component of the AD PAC, in a way that can be parsed using basic pointer handling.

From this, future non-Samba based Kerberised applications can easily obtain the user's SID, in the same packing as objectSID in LDAP, confident that the ticket represents a specific user, not matter subsequent renames.

This will allow such non-Samba applications to avoid confusing one Kerberos user for another, even if they have the same string name (due to the gap between time of ticket printing by the KDC and time of ticket acceptance).

As per upstream report:

In DCE/RPC it is possible to share the handles (cookies for resource state) between multiple connections via a mechanism called 'association groups'. These handles can reference connections to our sam.ldb database. However while the database was correctly shared, the user credentials state was only pointed at, and when one connection within that association group ended, the database would be left pointing at an invalid 'struct sessioninfo'.

The most likely outcome here is a crash, but it is possible that the use-after-free could instead allow different user state to be pointed at and this might allow more privileged access.

As per upstream advisory:

Samba as an Active Directory Domain Controller has to take care to protect a number of sensitive attributes, and to follow a security model from Active Directory that relies totally on the intersection of NT security descriptors and the underlying X.500 Directory Access Protocol (as then expressed in LDAP) schema constraints for security.

Some attributes in Samba AD are sensitive, they apply to one object but protect others.

Users who can set msDS-AllowedToDelegateTo can become any user in the domain on the server pointed at by this list. Likewise in a domain mixed with Microsoft Windows, Samba's lack of protection of sidHistory would be a similar issue.

This would be limited to users with the right to create users or modify them (typically those who created them), however, due to other flaws, all users are able to create new user objects.

A flaw was found in the way samba, as an Active Directory Domain Controller, is able to support an RODC (read-only domain controller). This would allow an RODC to print administrator tickets.

A flaw was found in Samba's libldb. Multiple, consecutive leading spaces in an LDAP attribute can lead to an out-of-bounds memory write, leading to a crash of the LDAP server process handling the request. The highest threat from this vulnerability is to system availability.

A flaw was found in samba. Spaces used in a string around a domain name (DN), while supposed to be ignored, can cause invalid DN strings with spaces to instead write a zero-byte into out-of-bounds memory, resulting in a crash. The highest threat from this vulnerability is to system availability.

A flaw was found in samba. A race condition in the password lockout code may lead to the risk of brute force attacks being sucessful if special conditions are met.

References:

https://bugzilla.samba.org/showbug.cgi?id=14611

A flaw was found in samba. A race condition in the password lockout code may lead to the risk of brute force attacks being successful if special conditions are met.

A flaw was found in samba's DNS server. An authenticated user could use this flaw to the RPC server to crash. This RPC server, which also serves protocols other than dnsserver, will be restarted after a short delay, but it is easy for an authenticated non administrative attacker to crash it again as soon as it returns. The Samba DNS server itself will continue to operate, but many RPC services will not.

A flaw was found in the AD DC NBT server in all Samba versions before 4.10.17, before 4.11.11 and before 4.12.4. A samba user could send an empty UDP packet to cause the samba server to crash.

A flaw was found when using samba as an Active Directory Domain Controller. Due to the way samba handles certain requests as an Active Directory Domain Controller LDAP server, an unauthorized user can cause a stack overflow leading to a denial of service. The highest threat from this vulnerability is to system availability. This issue affects all samba versions before 4.10.15, before 4.11.8 and before 4.12.2.

A use-after-free flaw was found in the way samba AD DC LDAP servers, handled 'Paged Results' control is combined with the 'ASQ' control. A malicious user in a samba AD could use this flaw to cause denial of service. This issue affects all samba versions before 4.10.15, before 4.11.8 and before 4.12.2.

A flaw was found in samba 4.0.0 before samba 4.9.15 and samba 4.10.x before 4.10.10. An attacker can crash AD DC LDAP server via dirsync resulting in denial of service. Privilege escalation is not possible with this issue.

A flaw was found in Samba, all versions starting samba 4.5.0 before samba 4.9.15, samba 4.10.10, samba 4.11.2, in the way it handles a user password change or a new password for a samba user. The Samba Active Directory Domain Controller can be configured to use a custom script to check for password complexity. This configuration can fail to verify password complexity when non-ASCII characters are used in the password, which could lead to weak passwords being set for samba users, making it vulnerable to dictionary attacks.

A flaw was found in the samba client, all samba versions before samba 4.11.2, 4.10.10 and 4.9.15, where a malicious server can supply a pathname to the client with separators. This could allow the client to access files and folders outside of the SMB network pathnames. An attacker could use this vulnerability to create files outside of the current working directory using the privileges of the client user.

A flaw was found in samba's Heimdal KDC implementation, versions 4.8.x up to, excluding 4.8.12, 4.9.x up to, excluding 4.9.8 and 4.10.x up to, excluding 4.10.3, when used in AD DC mode. A man in the middle attacker could use this flaw to intercept the request to the KDC and replace the user name (principal) in the request with any desired user name (principal) that exists in the KDC effectively obtaining a ticket for that principal.

A flaw was found in the way samba implemented an RPC endpoint emulating the Windows registry service API. An unprivileged attacker could use this flaw to create a new registry hive file anywhere they have unix permissions which could lead to creation of a new file in the Samba share. Versions before 4.8.11, 4.9.6 and 4.10.2 are vulnerable.

Samba from version 4.9.0 and before version 4.9.3 that have AD DC configurations watching for bad passwords (to restrict brute forcing of passwords) in a window of more than 3 minutes may not watch for bad passwords at all. The primary risk from this issue is with regards to domains that have been upgraded from Samba 4.8 and earlier. In these cases the manual testing done to confirm an organisation's password policies apply as expected may not have been re-done after the upgrade.