Re: GnuTLS | Behavioral PKCS#1 v1.5 decryption oracle (Ok/Err bit) (#1901)

Read-only notification of GnuTLS library development activities <[email protected]> Thu, 11 Jun 2026 05:03:01 +0000
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Mark Esler commented: https://gitlab.com/gnutls/gnutls/-/work_items/1901#=
note_3444450399


Cheers for the triage @dueno and @tomato42 =F0=9F=99=8F

And nice fix on the timing channel in #1050. (Alicja, I'd filed this befo=
re we spoke and hadn't seen 1050 at the time, overlap's on me.)

Agree that it can be used safety. If an attacker has access to the behavi=
oral (Ok/Err) oracle, against a 4096-bit key it takes ~40k decrypt querie=
s to recover a plaintext and ~110k to forge a signature.

Enhancement + removal sounds good to me.

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<p style=3D"color: #777777;">
<a href=3D"https://gitlab.com/eslerm">Mark Esler</a>
<a href=3D"https://gitlab.com/gnutls/gnutls/-/work_items/1901#note_344445=
0399">commented</a>:
</p>
<div class=3D"md" style=3D"position: relative; z-index: 1; color: #3a383f=
; word-wrap: break-word;">
<p dir=3D"auto" style=3D"color: #3a383f; margin: 0px 0px 1rem;" align=3D"=
initial">Cheers for the triage <a href=3D"https://gitlab.com/dueno" title=
=3D"Daiki Ueno" class=3D"gfm gfm-project_member js-user-link" data-user=3D=
"470892" data-original=3D"@dueno" data-container=3D"body" data-placement=3D=
"top" data-reference-type=3D"user" style=3D"color: #284779; background-co=
lor: #cbe2f9; border-radius: .25rem; margin-top: 0px; padding: 0 2px;">@d=
ueno</a> and <a href=3D"https://gitlab.com/tomato42" title=3D"Alicja Kari=
o (@mention me if you need reply)" class=3D"gfm gfm-project_member js-use=
r-link" data-user=3D"258094" data-original=3D"@tomato42" data-container=3D=
"body" data-placement=3D"top" data-reference-type=3D"user" style=3D"color=
: #284779; background-color: #cbe2f9; border-radius: .25rem; padding: 0 2=
px;">@tomato42</a> <gl-emoji title=3D"folded hands" data-name=3D"pray" da=
ta-unicode-version=3D"6.0">=F0=9F=99=8F</gl-emoji></p>
<p dir=3D"auto" style=3D"color: #3a383f; margin: 0px 0px 1rem;" align=3D"=
initial">And nice fix on the timing channel in <a href=3D"https://gitlab.=
com/gnutls/gnutls/-/work_items/1050" title=3D"Timing sidechannel in RSA d=
ecryption" class=3D"gfm gfm-issue" data-original=3D"#1050" data-link=3D"f=
alse" data-link-reference=3D"false" data-issue=3D"57399389" data-project=3D=
"179611" data-iid=3D"1050" data-namespace-path=3D"gnutls/gnutls" data-pro=
ject-path=3D"gnutls/gnutls" data-issue-type=3D"issue" data-container=3D"b=
ody" data-placement=3D"top" data-reference-type=3D"issue" style=3D"margin=
-top: 0px;">#1050 (closed)</a>. (Alicja, I'd filed this before we spoke a=
nd hadn't seen 1050 at the time, overlap's on me.)</p>
<p dir=3D"auto" style=3D"color: #3a383f; margin: 0px 0px 1rem;" align=3D"=
initial">Agree that it can be used safety. If an attacker has access to t=
he behavioral (Ok/Err) oracle, against a 4096-bit key it takes ~40k decry=
pt queries to recover a plaintext and ~110k to forge a signature.</p>
<p dir=3D"auto" style=3D"color: #3a383f; margin: 0px;" align=3D"initial">=
Enhancement + removal sounds good to me.</p>
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