I reviewed adsys 0.8 as checked into jammy. This shouldn't be
considered a full audit but rather a quick gauge of maintainability. As
usual with golang code, there's vastly more code in the package than we've
authored, and it's not feasible to review the entirety.
adsys allows network administrators to include Ubuntu systems in Windows
Group Policy ecosystem. There's easy support for a lot of individual
tunable elements, as well as generic support for running both machine and
user scripts on login, logout, etc.
- CVE History:
none :)
- Build-Depends?
Build-Depends: debhelper-compat (= 13),
dh-apport,
dh-golang,
golang-go (>= 2:1.16~),
libsmbclient-dev,
libdbus-1-dev,
python3,
python3-samba,
samba-dsdb-modules,
libpam0g-dev,
samba,
dbus,
- pre/post inst/rm scripts?
mostly added automatically by dh_ helpers; registers and unregisters pam
module, enables systemd units, purges and unmasks systemd units, etc.
- init scripts?
none
- systemd units?
sets up socket activation, sets up timers, refreshes policies, runs
machine scripts in machine units, runs user scripts in user units
- dbus services?
none
- setuid binaries?
none
- binaries in PATH?
adsysd, adsysctl
- sudo fragments?
/etc/sudoers.d/99-adsys-privilege-enforcement is under control of the
application:
"%admin ALL=(ALL) !ALL\n"
"%sudo ALL=(ALL:ALL) !ALL\n"
contentSudo += fmt.Sprintf("\"%s\" ALL=(ALL:ALL) ALL\n", e)
these are very powerful; I'd appreciate a second set of eyes here :)
- polkit files?
yes, seems reasonable
- udev rules?
none
- unit tests / autopkgtests?
yes, many tests, run during the build
- cron jobs?
none, systemd timer units used instead
- Build logs:
the shell completion files are dumped during build, it's a bit noisy,
but otherwise looks clean
- Processes spawned?
Yes -- pam module, copied from pam_exec.c
Yes -- adsys spawned from the user manager will run scripts, seems okay
- Memory management?
Most is golang, safe enough
pam module has some memory leaks; when reported to upstream pam_exec.c
folks, they appear to be leaning towards leaking even more memory :) so
probably fine.
- File IO?
Some issues, raised elsewhere.
- Logging?
pam module looked fine
- Environment variable usage?
NO_COLOR and KRB5CCNAME, seemed safe
- Use of privileged functions?
chown
- Use of cryptography / random number sources etc?
none
- Use of temp files?
none
- Use of networking?
grpc; to the extent I looked at it, it felt safe enough
- Use of WebKit?
none
- Use of PolicyKit?
yes, internal/authorizer/authorizer.go
looks up process start time by searching *backwards* through
/proc/pid/stat file for a ), then looking forward 19 fields. I didn't
double-check the math but it sure sounds promising.
- Any significant cppcheck results?
memory leaks in pam_adsys.c, upstream for inspiration pam_exec didn't seem
bothered
- Any significant Coverity results?
none
- Any significant shellcheck results?
none
- Any significant bandit results?
none
adsys is carefully written, well-documented, and didrocks and jibel were
very responsive to comments and feedback.
Security team ACK for promoting adsys to main.
I filed a few bugs along the way:
https://github.com/grpc/grpc-go/issues/5137
https://github.com/olekukonko/tablewriter/issues/199
And some miscellaneous notes I took:
Are there any conditions that can be added to adsys-boot.service to make
it less likely to spam the journal every five seconds for ten hours when on an
airplane?
https://bugs.launchpad.net/ubuntu/+source/adsys/+bug/1961459
pam_adsys.c update_policy() arggv leak in fork() failure
pam_adsys.c update_machine_policy() arggv leak in fork() failure
pam_adsys.c update_machine_policy() -- status != 0 looks like it ought to
work but I don't think that's how that API is supposed to be used
pam_adsys.c pam_sm_open_session() -- gethostname() indentation is funny
https://bugs.launchpad.net/ubuntu/+source/adsys/+bug/1961458
[redacted]
./internal/policies/scripts/scripts.go -- typo %qto
./conf.example/adsys.yaml
./doc/5.-The-adsys-daemon.md
Both these use /tmp/adsysd/ .. paths in configuration files -- is this
the recommended way to use adsys? It'd be nice if the configs were "real",
production-ready, defaults, etc.
** Bug watch added: github.com/grpc/grpc-go/issues #5137
https://github.com/grpc/grpc-go/issues/5137
** Bug watch added: github.com/olekukonko/tablewriter/issues #199
https://github.com/olekukonko/tablewriter/issues/199
** Changed in: adsys (Ubuntu)
Status: New => In Progress
** Changed in: adsys (Ubuntu)
Assignee: Ubuntu Security Team (ubuntu-security) => (unassigned)
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https://bugs.launchpad.net/bugs/1936907
Title:
[MIR] ADSys
Status in adsys package in Ubuntu:
In Progress
Bug description:
[Availability]
Available on all archs, available starting hirsute. It will be
backported to Focal once an FFe has been accepted.
[Rationale]
We are supporting GPO Active Directory support on ubuntu starting
hirsute. This features allows for an administrator to configure their
Active Directory server to deploy per-machine and per-user
configurations, enforce rules and other domain policies.
Right now, dconf keys, sudo administration rights and computer and
user scripts are supported.
This feature is built and use the krb5 tickets which are provided by SSSD.
Basically:
- SSSD is dealing with user and machine registration/authentification and
enforce password policies
- ADSys is handling GPO enforcement and support. The Ubuntu specific policies
needs to be installed on the Active Directory server (they are contained in the
daemon).
[Security]
The daemon is started is running as a root user to be able to enforce
machine policies, like rebuilding dconf databases, setting profiles.
User only interacts with the client side (both sides communicates over
GRPC), which can be ran as any user.
Polkit is used to restrain access to some part of the API.
There is a PAM module to build on demand per-user policy once
authenticated with SSSD. They are rejected if the authentication or
not all affected policies could be downloaded.
[Quality assurance]
Joining a domain in the ubiquity desktop installer makes the machine
joining the AD domain and install adsys functionality. The package
will be seeded directly on the desktop ISO.
An extensive testsuite (more than 1k) is included and available as
autopkgtests for rdepends. The whole stack is tested (even the
client/daemon interaction) and coverage is measured (including in the
small python script). However, tests with a real Active Directory
server can only be done manually as there is no setup available in the
autopkgtests infrastructure.
[Dependencies]
Main dependencies are libsmbclient, python3 (an embeeded script
allows, via samba, connecting to AD LDAP) and SSSD/KRB5.
This is a Go package, and all dependencies are vendored, and versions
are controlled via go.mod. We are using dependabot (from Github) to
automatically get notified of any dependencies updates (and security
issues), which opens a PR, rebuild and run all tests to report it
there. We are thus able to quickly merge them.
[Standards compliance]
Standard debhelper packaging, including a systemd service.
[Maintenance]
The desktop team will maintain it.
* we commit to test no-change-rebuilds triggered by a dependent
library/compiler and to fix any issues found for the lifetime of the release
(including ESM when included)
* we will provide timely testing of no-change-rebuilds from the security
team, fixing the rebuilt package as necessary
* we commit to provide updates to the security team for any affected
vendored code for the lifetime of the release (including ESM when included)
* we will provide timely, high quality updates for the security team to
sponsor to fix issues in the affected vendored code
[Background information]
ADSys is composed of:
- a daemon, named adsysd, running as root. This one will shutdown after a
period of inactivity without any active request. It is socket activated.
- a client, named adsysctl (which is a symlink to adsysd and only differ
behavior from its executable name), which is running as the user (or root on
boot for machine update). This ones optionally wakes up adsysd, connect through
an Unix socket with SO_PEERCRED to communicate current user running the
process. We are using grpc to communicate between the client and service.
Each client request is validated through polkit, matching user name
and permissions. The daemon will reject any unauthorized client
connections. Note that all actions are always performed from executing
the client, even the scheduled one by a cron.
The daemon contains a python embedded script that uses samba utilities
to connect with GSSAPI to the AD LDAP server and list available GPOs.
GPOs are then downloaded in a cache directory which isn’t accessible
to users.
The daemon also contains all GPOs policies to install on the Active
Directory side to reflect them in the UI. This could be accessed
online or dumped directly via the command line tool. Finally, those
are automatically refreshed for any supported LTSes and intermediate
versions. The availability of features can be different cross-release
and is supported in the daemon.
Many utilities for debugging, following daemon or per transaction
logs, streamed via our GRPC protocol are available.
We have different sync point with the system:
- at boot, the system will refresh the machine GPOs and build rules
enforcements
- on login via the PAM module, which will:
a. download the machine GPOs if we couldn‘t before (due to no network
available on boot/issues with NTP sync) and build rules enforcements
b. download the user-speciifc GPOs and build rules enforcements
- refresh every 30 minutes (same timing than windows client) the machine and
all connected AD users GPOs, and rebuild rules enforcements if needed.
An offline mode (similar to SSSD) is available, so that you can carry
your machine away of the network. The last successfully applied rules
will still be enforced. Connection will be denied if you hadn’t
connected once.
Documentation is available online
(https://github.com/ubuntu/adsys/wiki) and also on the command line
tool (offline). Note that updating the online documentation will
update the command line tool one as an automated PR and updating the
command line documentation will automatically update the wiki.
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/adsys/+bug/1936907/+subscriptions
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