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AWS 提供 OpenVPN-based VPN 服務

不知道為什麼在 feed reader 裡面沒注意到這則,後來是在 Facebook 上看到的。

AWS 推出了 OpenVPN-based 的 VPN 服務 AWS VPN:「Introducing AWS Client VPN to Securely Access AWS and On-Premises Resources」。

看起來是這個價錢:

AWS Client VPN pricing
$0.05 per AWS Client VPN connection hour
$0.10 per AWS Client VPN endpoint association hour

所以服務本身的費用要 $72/month 左右,另外 client 接上去的費用另外算?

目前支援的區域有限,暫時只有歐美的大區:

AWS Client VPN is available in US East (Virginia), US East (Ohio), US West (Oregon) and EU (Ireland) AWS Regions. Support for other AWS Regions is coming soon.

最近 OpenVPN 的安全性漏洞...

看到「The OpenVPN post-audit bug bonanza」這個只有苦笑啊...

作者在 OpenVPN 經過一連串的安全加強後 (包括 harden 計畫與兩個外部單位的程式碼稽核找到不少問題),決定出手挖看看:

After a hardening of the OpenVPN code (as commissioned by the Dutch intelligence service AIVD) and two recent audits 1 2, I thought it was now time for some real action ;).

然後就挖出不少問題了...

可以看到作者透過 fuzzing 打出一卡車,包含了不少 crash XDDD:(然後有一個是 stack buffer corruption,不知道有沒有機會變成 RCE)

  • Remote server crashes/double-free/memory leaks in certificate processing (CVE-2017-7521)
  • Remote (including MITM) client crash, data leak (CVE-2017-7520)
  • Remote (including MITM) client stack buffer corruption
  • Remote server crash (forced assertion failure) (CVE-2017-7508)
  • Crash mbed TLS/PolarSSL-based server (CVE-2017-7522)
  • Stack buffer overflow if long –tls-cipher is given

SWEET32:攻 Blowfish 與 3DES

最新的攻擊算是實戰類的攻擊,理論基礎以前都已經知道了,只是沒有人實際「完成」。算是近期少數直接對演算法的攻擊,而這些演算法剛好還是被用在 TLSOpenVPN 上,所以嚴重性比較高:「SWEET32: Birthday attacks on 64-bit block ciphers in TLS and OpenVPN」。

攻擊的條件是 block cipher 的 block size,而非 key length,所以就算是 256 bits 的 Blowfish 也一樣也受到影響。

這次順利打下 Blowfish3DES。這兩個 cipher 的 block size 都是 64 bits,所以對於 birthday attack 來說只要 232 就可以搞定:

This problem is well-known by cryptographers, who always require keys to be changed well before 2n/2 blocks. However it is often minimized by practitioners because the attacks require known plaintext, and reveal only little information. Indeed, standard bodies only recommend to change the key just before 2n/2 blocks, and many implementations don't enforce any limit on the use of a key.

在 OpenVPN 打 Blowfish 的部份 (Blowfish 是 OpenVPN 預設的 cipher):

In our demo, it took 18.6 hours and 705 GB, and we successfully recovered the 16-byte authentication token.

以及 HTTPS 打 3DES 的部份 (為了相容性問題):

Experimentally, we have recovered a two-block cookie from an HTTPS trace of only 610 GB, captured in 30.5 hours.

都是有可能的等級。也該來拔掉對 IE8 的支援了... orz

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