Bug 1942533 (CVE-2021-20305) - CVE-2021-20305 nettle: Out of bounds memory access in signature verification
Summary: CVE-2021-20305 nettle: Out of bounds memory access in signature verification
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2021-20305
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 1942535 1942918 1942919 1942921 1942922 1942923 1942924 1942925 1942926 1942927 1942928 1942929 1942930 1942931 1943156 1946910 1946960 1948707 1950937 1950938 1950939 1950940 1950942 1950943 1950944 1950945 1962738 1962739 1966261 1976077
Blocks: 1939224 1945330
TreeView+ depends on / blocked
 
Reported: 2021-03-24 14:12 UTC by Cedric Buissart
Modified: 2022-04-17 21:15 UTC (History)
32 users (show)

Fixed In Version: nettle 3.7.2
Doc Type: If docs needed, set a value
Doc Text:
A flaw was found in Nettle, where several Nettle signature verification functions (GOST DSA, EDDSA & ECDSA) result in the Elliptic Curve Cryptography point (ECC) multiply function being called with out-of-range scalers, possibly resulting in incorrect results. This flaw allows an attacker to force an invalid signature, causing an assertion failure or possible validation. The highest threat to this vulnerability is to confidentiality, integrity, as well as system availability.
Clone Of:
Environment:
Last Closed: 2021-04-08 23:35:19 UTC
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2021:2495 0 None None None 2021-06-21 06:44:27 UTC
Red Hat Product Errata RHSA-2021:2280 0 None None None 2021-06-07 22:29:50 UTC
Red Hat Product Errata RHSA-2021:2356 0 None None None 2021-06-09 09:28:08 UTC
Red Hat Product Errata RHSA-2021:2758 0 None None None 2021-07-15 19:01:40 UTC
Red Hat Product Errata RHSA-2021:2760 0 None None None 2021-07-19 07:53:20 UTC

Description Cedric Buissart 2021-03-24 14:12:36 UTC 
Certain signatures result in the ecc point multiply function being called with out-of-range scalars, which may give incorrect results, or crash in an assertion failure. It's an old bug, probably since Nettle's initial implementation of ECDSA.

Even when it's not possible to trigger an assertion failure, it's easy to produce valid-looking input "signatures" that hit out-of range intermediate scalar values where point multiplication may misbehave. This applies to all the NIST secp* curves as well as the GOST curves.

Reference:
https://lists.lysator.liu.se/pipermail/nettle-bugs/2021/009457.html
Comment 1 Cedric Buissart 2021-03-24 14:13:07 UTC 
Created gnutls tracking bugs for this issue:

Affects: fedora-all [bug 1942535]
Comment 2 Cedric Buissart 2021-03-24 14:41:52 UTC 
List of upstream fixes:

- New functions ecc_mod_mul_canonical and ecc_mod_sqr_canonical.
https://git.lysator.liu.se/nettle/nettle/-/commit/a63893791280d441c713293491da97c79c0950fe
- Use ecc_mod_mul_canonical for point comparison.
https://git.lysator.liu.se/nettle/nettle/-/commit/971bed6ab4b27014eb23085e8176917e1a096fd5
- Fix bug in ecc_ecdsa_verify.
https://git.lysator.liu.se/nettle/nettle/-/commit/74ee0e82b6891e090f20723750faeb19064e31b2
- Ensure ecdsa_sign output is canonically reduced.
https://git.lysator.liu.se/nettle/nettle/-/commit/51f643eee00e2caa65c8a2f5857f49acdf3ef1ce
- Analogous fix to ecc_gostdsa_verify.
https://git.lysator.liu.se/nettle/nettle/-/commit/401c8d53d8a8cf1e79980e62bda3f946f8e07c14
- Similar fix for eddsa.
https://git.lysator.liu.se/nettle/nettle/-/commit/ae3801a0e5cce276c270973214385c86048d5f7b
- Fix canonical reduction in gostdsa_vko. 
https://git.lysator.liu.se/nettle/nettle/-/commit/63f222c60b03470c0005aa9bc4296fbf585f68b9
Comment 4 Cedric Buissart 2021-03-25 10:52:47 UTC 
Created nettle tracking bugs for this issue:

Affects: fedora-all [bug 1942921]
Comment 13 errata-xmlrpc 2021-04-08 21:44:23 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2021:1145 https://access.redhat.com/errata/RHSA-2021:1145
Comment 14 Product Security DevOps Team 2021-04-08 23:35:19 UTC 
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):

https://access.redhat.com/security/cve/cve-2021-20305
Comment 15 Pedro Sampaio 2021-04-12 19:02:15 UTC 
Created mingw-nettle tracking bugs for this issue:

Affects: fedora-all [bug 1948707]
Comment 16 errata-xmlrpc 2021-04-14 20:30:33 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2021:1206 https://access.redhat.com/errata/RHSA-2021:1206
Comment 18 errata-xmlrpc 2021-04-19 11:47:34 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.1 Extended Update Support

Via RHSA-2021:1245 https://access.redhat.com/errata/RHSA-2021:1245
Comment 19 errata-xmlrpc 2021-04-19 11:54:06 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.2 Extended Update Support

Via RHSA-2021:1246 https://access.redhat.com/errata/RHSA-2021:1246
Comment 20 Cedric Buissart 2021-04-19 15:03:11 UTC 
Acknowledgments:

Name: Niels Möller
Comment 21 Cedric Buissart 2021-04-20 15:08:33 UTC 
External References:

https://lists.lysator.liu.se/pipermail/nettle-bugs/2021/009457.html
Comment 25 Cedric Buissart 2021-05-05 06:37:07 UTC 
Statement:

* Although Red Hat OpenStack's dibbler package bundles nettle, it does not include the flawed functionality and is therefore unaffected.
Comment 31 errata-xmlrpc 2021-06-07 22:29:47 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.7 Extended Update Support

Via RHSA-2021:2280 https://access.redhat.com/errata/RHSA-2021:2280
Comment 32 errata-xmlrpc 2021-06-09 09:28:02 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.6 Advanced Update Support
  Red Hat Enterprise Linux 7.6 Telco Extended Update Support
  Red Hat Enterprise Linux 7.6 Update Services for SAP Solutions

Via RHSA-2021:2356 https://access.redhat.com/errata/RHSA-2021:2356
Comment 36 errata-xmlrpc 2021-07-15 19:01:39 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.4 Advanced Update Support
  Red Hat Enterprise Linux 7.4 Update Services for SAP Solutions
  Red Hat Enterprise Linux 7.4 Telco Extended Update Support

Via RHSA-2021:2758 https://access.redhat.com/errata/RHSA-2021:2758
Comment 37 errata-xmlrpc 2021-07-19 07:53:21 UTC 
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.3 Advanced Update Support

Via RHSA-2021:2760 https://access.redhat.com/errata/RHSA-2021:2760
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