[tdf-discuss] security related information, CVE-2021-25636

tl:dr upgrade to LibreOffice 7-2 to 7.2.5
(or libreoffice 7.3.0)

LibreOffice supports digital signatures of ODF documents and macros
within documents, presenting visual aids that no alteration of the
document occurred since the last signing and that the signature is
valid.

The Network and Data Security group at Ruhr University Bochum
reported a flaw with the implementation of this.

CVE-2021-25636 Incorrect trust validation of signature with ambiguous
KeyInfo children

An Improper Certificate Validation vulnerability in LibreOffice allowed
an attacker to create a digitally signed ODF document, by manipulating
the documentsignatures.xml or macrosignatures.xml stream within the
document to contain both "X509Data" and "KeyValue" children of the
"KeyInfo" tag[1], which when opened caused LibreOffice to verify using
the "KeyValue" but to report verification with the unrelated "X509Data"
value.

In versions >= 7.2.5 (and >= 7.3.0) certificate validation is now
configured to only consider X509Data children to limit validation to
X509 certificates only.

[1] https://www.w3.org/TR/xmldsig-core1/#sec-KeyInfo


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