An issue has been found in OpenSSL <= 1.1.1b, where an application using ChaCha20-Poly1305 could set a non-default nonce length to be longer than 12 bytes and then mistakenly reuse a nonce. ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for every encryption operation. RFC 7539 specifies that the nonce value (IV) should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and front pads the nonce with 0 bytes if it is less than 12 bytes. However it also incorrectly allows a nonce to be set of up to 16 bytes. In this case only the last 12 bytes are significant and any additional leading bytes are ignored.
An issue has been found in OpenSSL <= 1.1.1b, where an application using ChaCha20-Poly1305 could set a non-default nonce length to be longer than 12 bytes and then mistakenly reuse a nonce. ChaCha20-Poly1305 is an AEAD cipher, and requires a unique nonce input for every encryption operation. RFC 7539 specifies that the nonce value (IV) should be 96 bits (12 bytes). OpenSSL allows a variable nonce length and front pads the nonce with 0 bytes if it is less than 12 bytes. However it also incorrectly allows a nonce to be set of up to 16 bytes. In this case only the last 12 bytes are significant and any additional leading bytes are ignored.
https://www.openssl.org/news/secadv/20190306.txt https://github.com/openssl/openssl/commit/f426625b6a
Vulmon