CVE-2019-11840

An issue was discovered in supplementary Go cryptography libraries, aka golang-googlecode-go-crypto, before 2019-03-20. A flaw was found in the amd64 implementation of golang.org/x/crypto/salsa20 and golang.org/x/crypto/salsa20/salsa. If more than 256 GiB of keystream is generated, or if the counter otherwise grows greater than 32 bits, the amd64 implementation will first generate incorrect output, and then cycle back to previously generated keystream. Repeated keystream bytes can lead to loss of confidentiality in encryption applications, or to predictability in CSPRNG applications.

Weakness

The product uses insufficiently random numbers or values in a security context that depends on unpredictable numbers.

Affected Software

Potential Mitigations

• Use a well-vetted algorithm that is currently considered to be strong by experts in the field, and select well-tested implementations with adequate length seeds.
• In general, if a pseudo-random number generator is not advertised as being cryptographically secure, then it is probably a statistical PRNG and should not be used in security-sensitive contexts.
• Pseudo-random number generators can produce predictable numbers if the generator is known and the seed can be guessed. A 256-bit seed is a good starting point for producing a “random enough” number.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/112.html
• https://cwe.mitre.org/data/definitions/485.html
• https://cwe.mitre.org/data/definitions/59.html

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1691529
• https://github.com/golang/go/issues/30965
• https://go.googlesource.com/crypto/+/b7391e95e576cacdcdd422573063bc057239113d
• https://groups.google.com/forum/#%21msg/golang-announce/tjyNcJxb2vQ/n0NRBziSCAAJ
• https://lists.debian.org/debian-lts-announce/2019/06/msg00029.html
• https://lists.debian.org/debian-lts-announce/2020/10/msg00014.html
• https://lists.debian.org/debian-lts-announce/2020/11/msg00016.html
• https://lists.debian.org/debian-lts-announce/2020/11/msg00030.html
• https://lists.debian.org/debian-lts-announce/2021/01/msg00015.html
• https://lists.debian.org/debian-lts-announce/2023/06/msg00017.html