CVE-2019-11841

NameCVE-2019-11841
DescriptionA 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-1920-1
NVD severitymedium (attack range: remote)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
golang-go.crypto (PTS)jessie0.0~hg190-1vulnerable
jessie (security)0.0~hg190-1+deb8u2fixed
stretch1:0.0~git20170407.0.55a552f+REALLY.0.0~git20161012.0.5f31782-1vulnerable
buster1:0.0~git20181203.505ab14-1vulnerable
bullseye, sid1:0.0~git20190701.4def268-2vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
golang-go.cryptosource(unstable)(unfixed)medium
golang-go.cryptosourcejessie0.0~hg190-1+deb8u2mediumDLA-1920-1

Notes

https://go.googlesource.com/crypto/+/c05e17bb3b2dca130fc919668a96b4bec9eb9442
Patch fixes the second part of the CVE ("prepend arbitrary text")
but not the first ("ignores the value of [the Hash] header"), as hinted at reporter's 2019-05-09 note:
https://packetstormsecurity.com/files/152840/Go-Cryptography-Libraries-Cleartext-Message-Spoofing.html

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