Headline
CVE-2019-11841
A message-forgery issue was discovered in crypto/openpgp/clearsign/clearsign.go in supplementary Go cryptography libraries 2019-03-25. According to the OpenPGP Message Format specification in RFC 4880 chapter 7, a cleartext signed message can contain one or more optional “Hash” Armor Headers. The “Hash” Armor Header specifies the message digest algorithm(s) used for the signature. However, the Go clearsign package ignores the value of this header, which allows an attacker to spoof it. Consequently, an attacker can lead a victim to believe the signature was generated using a different message digest algorithm than what was actually used. Moreover, since the library skips Armor Header parsing in general, an attacker can not only embed arbitrary Armor Headers, but also prepend arbitrary text to cleartext messages without invalidating the signatures.
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OpenPGP.js is a JavaScript implementation of the OpenPGP protocol. In affected versions OpenPGP Cleartext Signed Messages are cryptographically signed messages where the signed text is readable without special tools. These messages typically contain a "Hash: ..." header declaring the hash algorithm used to compute the signature digest. OpenPGP.js up to v5.9.0 ignored any data preceding the "Hash: ..." texts when verifying the signature. As a result, malicious parties could add arbitrary text to a third-party Cleartext Signed Message, to lead the victim to believe that the arbitrary text was signed. A user or application is vulnerable to said attack vector if it verifies the CleartextMessage by only checking the returned `verified` property, discarding the associated `data` information, and instead _visually trusting_ the contents of the original message. Since `verificationResult.data` would always contain the actual signed data, users and apps that check this information are not vulne...