Bug 1826177 (CVE-2020-12399) - CVE-2020-12399 nss: Timing attack on DSA signature generation
Summary: CVE-2020-12399 nss: Timing attack on DSA signature generation
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: CVE-2020-12399
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1838376 1838377 1838378
Blocks: 1826178
TreeView+ depends on / blocked
 
Reported: 2020-04-21 07:47 UTC by Marian Rehak
Modified: 2023-09-25 07:01 UTC (History)
19 users (show)

Fixed In Version: nss 3.44.4, nss 3.52.1, thunderbird 68.9.0
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in the DSA signature generation function in nss. During the process of generating a DSA signature, the nonce value 'k' is not padded, exposing the bit length. Combined with other techniques, this can result in the recovery of the DSA private key. The highest threat from this vulnerability is to data confidentiality.
Clone Of:
Environment:
Last Closed: 2021-01-18 22:44:56 UTC
Embargoed:


Attachments (Terms of Use)

Description Marian Rehak 2020-04-21 07:47:53 UTC
During DSA signature generation in the function `dsa_SignDigest`, the nonce value `k` is not padded, exposing the bit length of `k`, i.e. the most significant bits (MSBs) of the nonce. Combined with other techniques this can result in DSA private keys recovery.

Comment 1 Mark Cooper 2020-04-22 05:51:32 UTC
OpenShift 4.x only packages nss-altfiles and has been confirmed to *not* share any of the vulnerable signature code:
    - nss-altfiles only reads information from files in the same format as /etc/passwd and /etc/group.

Comment 2 Huzaifa S. Sidhpurwala 2020-05-20 03:17:47 UTC
Upstream patch: https://hg.mozilla.org/projects/nss/rev/daa823a4a29bcef0fec33a379ec83857429aea2e
Upstream bug (still private): https://bugzilla.mozilla.org/show_bug.cgi?id=1631576

Comment 7 Huzaifa S. Sidhpurwala 2020-05-21 02:44:44 UTC
Acknowledgments:

Name: the Mozilla Project
Upstream: Cesar Pereida Garcia and the Network and Information Security Group (NISEC) (Tampere University)

Comment 9 Huzaifa S. Sidhpurwala 2020-05-21 02:49:09 UTC
Created nss tracking bugs for this issue:

Affects: fedora-all [bug 1838376]

Comment 12 Huzaifa S. Sidhpurwala 2020-05-21 04:26:20 UTC
Mitigation:

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Comment 13 Mark Denihan 2020-05-28 15:46:10 UTC
@Huzaifa Can you clarify the mitigation statement? Is the mitigation not available or is it available and doesn't meet the Red Hat Product Security criteria. Is there any indication of when a mitigation would be available?

Comment 15 Doran Moppert 2020-06-15 03:25:55 UTC
Statement:

A timing attack was found in the way NSS generated DSA signatures. A man-in-the-middle attacker could use this attack during DSA signature generation to recover the private key. This attack is only feasible when the attacker is local to the machine or in certain cross-VM scenarios where the signature is being generated. Attacks over the network or via the internet are not feasible.

Firefox and Thunderbird on Red Hat Enterprise Linux are built against the system nss library.


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