PT-2020-20368 · Google · Go-Tpm

Chris Fenner + 1 · Published 2020-08-11 · Updated 2022-02-11 · CVE-2020-8918

Positive Technologies (AI Summary)

CVSS v3.1

7.1

High

Base vector

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Name of the Vulnerable Software and Affected Versions go-tpm versions prior to 0.3.0

Description The issue arises from an improperly initialized 'migrationAuth' value in the go-tpm library, allowing an eavesdropping attacker to discover the auth value for a key created with CreateWrapKey. This is due to the repeated usage of a XOR key, enabling the attacker to calculate usageAuth for keys created using CreateWrapKey, despite it being encrypted. The attacker can collect both encUsageAuth and encMigrationAuth, and then calculate usageAuth ^ encMigrationAuth as the migrationAuth can be guessed for all keys created with CreateWrapKey. TPM 2.0 users are unaffected by this issue.

Recommendations For go-tpm versions prior to 0.3.0, update the library to 0.3.0 or later. As a temporary workaround, consider calling CreateWrapKey with a random 20-byte value for migrationAuth, even though that value is not used again, and do not store or log this value.

Exploit

Fix

Improper Initialization

Weakness Enumeration

CWE-665

Related Identifiers

CVE-2020-8918

GHSA-5X29-3HR9-6WPW

GO-2021-0095

Affected Products

Go-Tpm

References · 9

• 🔥 https://github.com/google/go-tpm/security/advisories/GHSA-5x29-3hr9-6wpw · Exploit
• https://osv.dev/vulnerability/GHSA-5x29-3hr9-6wpw · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2020-8918 · Vendor Advisory
• https://osv.dev/vulnerability/GO-2021-0095 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2020-8918 · Security Note
• https://github.com/google/go-tpm/commit/d7806cce857a1a020190c03348e5361725d8f141 · Note
• https://github.com/google/go-tpm/pull/195 · Note
• https://github.com/google/go-tpm · Note
• https://pkg.go.dev/vuln/GO-2021-0095 · Note