From: "drbrain (Eric Hodel)" <drbrain@...7.net>
Date: 2013-07-23T08:03:57+09:00
Subject: [ruby-core:56112] [ruby-trunk - Bug #8667][Assigned]  Unable to set OpenSSL GCM iv_length in Ruby


Issue #8667 has been updated by drbrain (Eric Hodel).

Category set to ext/openssl
Status changed from Open to Assigned
Assignee set to MartinBosslet (Martin Bosslet)
ruby -v set to -


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Bug #8667:  Unable to set OpenSSL GCM iv_length in Ruby
https://bugs.ruby-lang.org/issues/8667#change-40611

Author: Anonymous
Status: Assigned
Priority: Normal
Assignee: MartinBosslet (Martin Bosslet)
Category: ext/openssl
Target version: 
ruby -v: -
Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN


 Hello,
 
 In OpenSSL you are allowed to change the iv_length on an AES-BCM cipher. (
 http://www.openssl.org/docs/crypto/EVP_EncryptInit.html#GCM_Mode) However
 this was not implemented in the ruby-wrapper. Since I am a novice in C and
 OpenSSL I think by no means my supplied patch is complete, it is a start
 however. Maybe this missing function can be added to Ruby 2.0?
 
 You can now set the iv_length using:
 
 cipher = OpenSSL::Cipher.new('aes-128-gcm').encrypt
 cipher.iv_len = 16
 
 An issue I already spotted is that OpenSSL sets the ivlen on the
 cipher_data (snippet from OpenSSL crypto/evp/e_aes.c):
 EVP_AES_GCM_CTX *gctx = c->cipher_data;
 gctx->ivlen = arg;
 
 and not the c->cipher->iv_len. So querying for the iv_len in ruby by using
 cipher.iv_len will still report the default which is 12. Encryption however
 is done correctly using the new iv-length. I tested it by comparing it to
 results from other programming languages (Java and C#).
 
 Regards Andres


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