From 7c8ae5f664ee9d36cc42527208362c9bfe5b25ab Mon Sep 17 00:00:00 2001 From: Steven Fackler Date: Wed, 9 Nov 2016 18:54:29 +0000 Subject: [PATCH] Better docs for AEAD tag --- openssl/src/symm.rs | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/openssl/src/symm.rs b/openssl/src/symm.rs index 07235e244..6e9c5796c 100644 --- a/openssl/src/symm.rs +++ b/openssl/src/symm.rs @@ -287,6 +287,10 @@ impl Crypter { /// as AES GCM. /// /// When encrypting data with an AEAD cipher, this must be called after `finalize`. + /// + /// The size of the buffer indicates the required size of the tag. While some ciphers support a + /// range of tag sizes, it is recommended to pick the maximum size. For AES GCM, this is 16 + /// bytes, for example. pub fn get_tag(&self, tag: &mut [u8]) -> Result<(), ErrorStack> { unsafe { assert!(tag.len() <= c_int::max_value() as usize); @@ -370,6 +374,10 @@ pub fn encrypt_aead(t: Cipher, /// /// Additional Authenticated Data can be provided in the `aad` field, and the authentication tag /// should be provided in the `tag` field. +/// +/// The size of the `tag` buffer indicates the required size of the tag. While some ciphers support +/// a range of tag sizes, it is recommended to pick the maximum size. For AES GCM, this is 16 bytes, +/// for example. pub fn decrypt_aead(t: Cipher, key: &[u8], iv: Option<&[u8]>, @@ -650,6 +658,8 @@ mod tests { f4fc97416ee52abe"; let tag = "e20b6655"; + // this tag is smaller than you'd normally want, but I pulled this test from the part of + // the NIST test vectors that cover 4 byte tags. let mut actual_tag = [0; 4]; let out = encrypt_aead(Cipher::aes_128_gcm(), &key.from_hex().unwrap(), -- GitLab