[gentoo-user] net-libs/gnutls-3.7.2 fails to verify some certificates (duplicate server certificate?)

[Branko Grubić]

Hi,

I have few applications which use webkit-gtk and gnutls behind as far
as I know, recently I noticed that RSS feeds for some distrowatch.com
subscriptions I had started to fail, initially I did ignore them I
thought something is wrong on the server side and it was not critical.

But since it wasn't fixed I started to investigate a little bit more.

So, in the end it seems to be related to gnutls on Gentoo (I'm running
~amd64)

net-libs/gnutls-3.7.2 abi_x86_64 cxx idn nls openssl seccomp tls-
heartbeat tools

Important note, websites using Let's Encrypt certificates work fine,
except this one (only example known to me). Based on the output of
`gnutls-cli` it seems that server certificate is served twice compared
to other working ones (I could be wrong).

Example output:
$ gnutls-cli  distrowatch.com:443  
Processed 130 CA certificate(s).
Resolving 'distrowatch.com:443'...
Connecting to '82.103.129.71:443'...
- Certificate type: X.509
- Got a certificate list of 4 certificates.
- Certificate[0] info:
 - subject `CN=distrowatch.com', issuer `CN=R3,O=Let's Encrypt,C=US',
serial 0x0408fd5a5ae26286bed92e97da0c830f623c, RSA key 2048 bits,
signed using RSA-SHA256, activated `2021-09-15 03:49:15 UTC', expires
`2021-12-14 03:49:14 UTC', pin-
sha256="QoW1tiDGE8S3FLukw86yRL8IfevROPxnx0qwVuu/rUI="
	Public Key ID:
		sha1:fcd2b25ac6ffd73fce3ef65211defd25331dc151
		sha256:4285b5b620c613c4b714bba4c3ceb244bf087debd138fc6
7c74ab056ebbfad42
	Public Key PIN:
		pin-
sha256:QoW1tiDGE8S3FLukw86yRL8IfevROPxnx0qwVuu/rUI=

- Certificate[1] info:
 - subject `CN=distrowatch.com', issuer `CN=R3,O=Let's Encrypt,C=US',
serial 0x0408fd5a5ae26286bed92e97da0c830f623c, RSA key 2048 bits,
signed using RSA-SHA256, activated `2021-09-15 03:49:15 UTC', expires
`2021-12-14 03:49:14 UTC', pin-
sha256="QoW1tiDGE8S3FLukw86yRL8IfevROPxnx0qwVuu/rUI="
- Certificate[2] info:
 - subject `CN=R3,O=Let's Encrypt,C=US', issuer `CN=ISRG Root
X1,O=Internet Security Research Group,C=US', serial
0x00912b084acf0c18a753f6d62e25a75f5a, RSA key 2048 bits, signed using
RSA-SHA256, activated `2020-09-04 00:00:00 UTC', expires `2025-09-15
16:00:00 UTC', pin-
sha256="jQJTbIh0grw0/1TkHSumWb+Fs0Ggogr621gT3PvPKG0="
- Certificate[3] info:
 - subject `CN=ISRG Root X1,O=Internet Security Research Group,C=US',
issuer `CN=DST Root CA X3,O=Digital Signature Trust Co.', serial
0x4001772137d4e942b8ee76aa3c640ab7, RSA key 4096 bits, signed using
RSA-SHA256, activated `2021-01-20 19:14:03 UTC', expires `2024-09-30
18:14:03 UTC', pin-
sha256="C5+lpZ7tcVwmwQIMcRtPbsQtWLABXhQzejna0wHFr8M="
- Status: The certificate is NOT trusted. The certificate issuer is
unknown. 
*** PKI verification of server certificate failed...
*** Fatal error: Error in the certificate.


Firefox and Chrome open website just fine, no complains. Also openssl
client doesn't complain if I read the output right.


I have tested this on Fedora 35 as well using gnutls-cli, it comes with
same gnutls release, and has no issues connecting to problematic host.
So I suspect it's something to do with my system, Gentoo ebuild, or
combination of libraries used for gnutls on my Gentoo system.

I have found an interesting (similar) bug[1] which was fixed in the
current release (fix is included in 3.7.2 based on the NEWS/Release
notes) where gnutls would fail if Root CA certificate is present twice
in the chain.

Can anyone confirm it happening on their system as well, I was not sure
should I open a Gentoo bug.

Regards,
Branko


[1] https://gitlab.com/gnutls/gnutls/-/issues/1131