busybox does not verify TLS connections with CONFIG_FEATURE_WGET_OPENSSL=y and CONFIG_FEATURE_WGET_HTTPS unset, and doesn't warn either about it

[Dimitri John Ledkov]

[Impact]

 * CONFIG_FEATURE_WGET_OPENSSL=y enables https support in wget busybox applet using openssl

 * CONFIG_FEATURE_WGET_HTTPS=y enables https support in wget busybox applet using internal TLS code

 * CVE-2018-1000500 ensured that when CONFIG_FEATURE_WGET_HTTPS=y is used, a message is printed to notify the users that TLS verification is not perfomed.

 * However, when one configures with CONFIG_FEATURE_WGET_OPENSSL=y and CONFIG_FEATURE_WGET_HTTPS unset - no such message is printed.

 * Also TLS verification is not performed under OPENSSL case.

 * When performing https requests, it works openssl s_client and communicates with it to perform https download
 * Whilst doing so, it does not pass `-verify_return_error` option, meaning any verification errors are ignored

 * There is no warning that TLS verification was not performed

[Test Case]

 * Preparation: sudo apt install busybox; or build busybox with CONFIG_FEATURE_WGET_OPENSSL=y

 * Test case: /bin/busybox wget https://untrusted-root.badssl.com/

 * Expected: download failed, or download suceeds with warning printed that verification is disabled

 * Observed: download success without a warning that verification is disabled.

$ /bin/busybox wget https://untrusted-root.badssl.com/
Connecting to untrusted-root.badssl.com (104.154.89.105:443)
index.html 100% |*************************************************************************************| 600 0:00:00 ETA

$ cat index.html | grep certificate
  The certificate for this site is signed using an untrusted root.

[Regression Potential]

 * The fact that /bin/busybox wget https:// succeeds without TLS verification might be relied upon. If this issue is fixed, ensure that `--no-check-certificate` is honored.

[Other Info]

 * Proposed fix

   pass `-verify_return_error` to s_client, unless `--no-check-certificate` is specified

[Marc Deslauriers (mdeslaur)]

This is already known as CVE-2018-1000500

This is what upstream did:

https://git.busybox.net/busybox/commit/networking/wget.c?id=0972c7f7a570c38edb68e1c60a45614b7a7c7d55

[Marc Deslauriers (mdeslaur)]

Behaviour is documented here:

https://git.busybox.net/busybox/tree/networking/wget.c?id=8bc418f07eab79a9c8d26594629799f6157a9466#n49

[Marc Deslauriers (mdeslaur)]

More info here:

http://lists.busybox.net/pipermail/busybox/2018-May/086444.html

[Dimitri John Ledkov (xnox)]

By default the message that certificate verification is disabled is not printed.

It is trivial to implement verification for OPENSSL case.

I'm making a patch with that CVE reference then.

[Dimitri John Ledkov (xnox)]

I want all three in Focal and up.

At least just the warning, in the other series.

[Launchpad Janitor (janitor)]

This bug was fixed in the package busybox - 1:1.30.1-4ubuntu8

---------------
busybox (1:1.30.1-4ubuntu8) groovy; urgency=medium

  * Enable TLS verification with OpenSSL. LP: #1879533

busybox (1:1.30.1-4ubuntu7) groovy; urgency=medium

  * Enable TLS in initramfs flavour of wget applet, requires openssl. LP:
    #1879525

 -- Dimitri John Ledkov <email address hidden> Wed, 20 May 2020 14:44:54 +0100

[Łukasz Zemczak (sil2100)]

Seeing that this is a fix for a documented CVE, do we also want to upload this to -security? Should we build this first in a security enabled PPA?

[Łukasz Zemczak (sil2100)]

Ok, xnox cleared out the situation for me. This is not needed in -security.

[Łukasz Zemczak (sil2100)]

Hello Dimitri, or anyone else affected,

Accepted busybox into focal-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/busybox/1:1.30.1-4ubuntu6.1 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed. Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested, what testing has been performed on the package and change the tag from verification-needed-focal to verification-done-focal. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-focal. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance for helping!

N.B. The updated package will be released to -updates after the bug(s) fixed by this package have been verified and the package has been in -proposed for a minimum of 7 days.

[Ubuntu SRU Bot (ubuntu-sru-bot)]

All autopkgtests for the newly accepted busybox (1:1.30.1-4ubuntu6.1) for focal have finished running.
The following regressions have been reported in tests triggered by the package:

casper/1.445 (amd64)

Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-migration/focal/update_excuses.html#busybox

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

[Dimitri John Ledkov (xnox)]

Build focal subiquity image with proposed enabled and busybox version 1:1.30.1-4ubuntu6.1 at https://launchpad.net/~xnox/+livefs/ubuntu/focal/any/+build/221093

downloaded just the initrd & vmlinuz.

Waited for it to fail to boot, and sourced /scripts/functions and executed configure_networking.

Downloaded https://start.ubuntu.com successfully
Failed to download https://untrusted-root.badssl.com

Verification successful.

[Launchpad Janitor (janitor)]

This bug was fixed in the package busybox - 1:1.30.1-4ubuntu6.1

---------------
busybox (1:1.30.1-4ubuntu6.1) focal; urgency=medium

  * Enable TLS verification with OpenSSL. LP: #1879533
  * Enable TLS in initramfs flavour of wget applet, requires openssl. LP:
    #1879525

 -- Dimitri John Ledkov <email address hidden> Tue, 19 May 2020 16:16:23 +0100

[Brian Murray (brian-murray)]

The verification of the Stable Release Update for busybox has completed successfully and the package is now being released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.