Home » 2017 » February

在 Kindle 上讓 PDF 變得更容易看的工具

在這邊看到 K2pdfopt 這個工具:

之後把一些 PDF 轉進 Kindle Paperwhite 看看效果,不然看 PDF 看得好痛苦 XD

Nokia 3310 的復出...

這消息傳遍了整個科技界:「HMD Global will launch the Nokia 3, 5, and 6 at MWC, plus a 3310 homage」,不過一個最大的問題是只支援 2.5G:(出自「Nokia 3310 (2017)」)

The phone only runs on 2.5G at the time of launch, which has subjected the phone to criticism, and means that it will not initially be released in many countries, including Australia, which is switching its 2G mobile network off.

這種賣感情的東西,連任天堂都知道復刻時要加上 HDMI 了 (參考 NES Classic Edition),Nokia 你在想什麼...

出自「iPhone 7 Nokia 3310 Hammer Test! Will it Survive?

結果 AWS Console 對 EC2 的 IAM Role 被拔掉了...

在 console 上發現不見了,跑去 forum 上看看是不是有其他人遇到同樣的問題,結果發現被拔掉了:「Attach IAM Role to existing EC2 instance in console not available」。

On Friday, Feb 24th, we were made aware that under certain conditions, the feature was not working for customers using the EC2 console. As a result, we have temporarily removed this capability from the EC2 console, but we will enable this feature when this issue has been resolved.

Ouch... 只好先用 CLI 了...

Cloudbleed:Cloudflare 這次的安全問題

Cloudflare 把完整的時間軸與影響範圍都列出來了:「Incident report on memory leak caused by Cloudflare parser bug」。

出自於 2/18 時 GoogleTavis Ormandy 直接在 Twitter 上找 Cloudflare 的人:

Google 的 Project Zero 上的資料:「cloudflare: Cloudflare Reverse Proxies are Dumping Uninitialized Memory」。

起因在於 bug 造成有時候會送出不應該送的東西,可能包含了敏感資料:

It turned out that in some unusual circumstances, which I’ll detail below, our edge servers were running past the end of a buffer and returning memory that contained private information such as HTTP cookies, authentication tokens, HTTP POST bodies, and other sensitive data.

不過這邊不包括 SSL 的 key,主要是因為隔離開了:

For the avoidance of doubt, Cloudflare customer SSL private keys were not leaked. Cloudflare has always terminated SSL connections through an isolated instance of NGINX that was not affected by this bug.

不過由於這些敏感資料甚至還被 Google 收進 search engine,算是相當的嚴重,所以不只是 Cloudflare 得修好這個問題,還得跟眾多的 search engine 合作將這些資料移除:

Because of the seriousness of such a bug, a cross-functional team from software engineering, infosec and operations formed in San Francisco and London to fully understand the underlying cause, to understand the effect of the memory leakage, and to work with Google and other search engines to remove any cached HTTP responses.

bug 影響的時間從 2016/09/22 開始:

2016-09-22 Automatic HTTP Rewrites enabled
2017-01-30 Server-Side Excludes migrated to new parser
2017-02-13 Email Obfuscation partially migrated to new parser
2017-02-18 Google reports problem to Cloudflare and leak is stopped

而以 2/13 到 2/18 的流量反推估算,大約是 0.00003% 的 request 會可能產生這樣的問題:

The greatest period of impact was from February 13 and February 18 with around 1 in every 3,300,000 HTTP requests through Cloudflare potentially resulting in memory leakage (that’s about 0.00003% of requests).

不過不得不說 Tavis Ormandy 真的很硬,在沒有 source code 以及 Cloudflare 幫助的情況下直接打出可重製的步驟:

I worked with cloudflare over the weekend to help clean up where I could. I've verified that the original reproduction steps I sent cloudflare no longer work.


2017-02-18 0011 Tweet from Tavis Ormandy asking for Cloudflare contact information
2017-02-18 0032 Cloudflare receives details of bug from Google
2017-02-18 0040 Cross functional team assembles in San Francisco
2017-02-18 0119 Email Obfuscation disabled worldwide
2017-02-18 0122 London team joins
2017-02-18 0424 Automatic HTTPS Rewrites disabled worldwide
2017-02-18 0722 Patch implementing kill switch for cf-html parser deployed worldwide
2017-02-20 2159 SAFE_CHAR fix deployed globally
2017-02-21 1803 Automatic HTTPS Rewrites, Server-Side Excludes and Email Obfuscation re-enabled worldwide

另外在「List of Sites possibly affected by Cloudflare's #Cloudbleed HTTPS Traffic Leak」這邊有人整理出受影響的大站台有哪些 (小站台就沒列上去了)。

Firefox 下一個版本 (52) 將預設關閉 SHA-1 支援

順著 SHA-1 正式被打穿,Mozilla 也正式宣佈從下一個版本的 Firefox 將完全關閉 SHA-1 支援 (看敘述應該還是可以透過 about:config 開):「The end of SHA-1 on the Public Web」。

As announced last fall, we’ve been disabling SHA-1 for increasing numbers of Firefox users since the release of Firefox 51 using a gradual phase-in technique. Tomorrow, this deprecation policy will reach all Firefox users. It is enabled by default in Firefox 52.


Amazon EC2 推出 I3 系列機器

Amazon EC2 推出使用 NVMe SSD 的機器,I3 系列:「Now Available – I3 Instances for Demanding, I/O Intensive Applications」。

以東京區的價錢來看,r4.16xlarge 與 i3.16xlarge 都是 64 vCPU 與 488GB RAM。不一樣的地方只有兩個:

  • 第一個是 r4 只有 195 vCPU,而 i3 有 200 vCPU,快了一些。
  • 第二個是 i3 多了 8 個 1900 NVMe SSD。

但價錢卻只差一些 ($5.12/hr 與 $5.856/hr),如果速度可以善用 SSD 的話,跟 r4.* 比起來其實頗超值的...

對 SHA-3 的攻擊

隔壁棚剛順利打趴 SHA-1 (Google 與 CWI Amsterdam 合作,找到 SHA-1 第一個 collision),還是有人在針對比較新的演算法在攻擊:「SymSum: Symmetric-Sum Distinguishers Against Round Reduced SHA3」。

完整的 SHA-3 是 24 rounds,這次打的是 9 rounds 版本,雖然有段距離,但這等於是大進展:

Based on this we propose a new distinguisher called SymSum for the SHA3 family which penetrates up to 9 rounds and outperforms the ZeroSum distinguisher by a factor of four.

不過 SHA-3 用的人不算多,該不會在還沒成為主流就被打趴...


在「AES-GCM-SIV: Specification and Analysis」這邊看到 AES-GCM-SIV 的作者自己投稿上去的資料,是個已經被放進 BoringSSL 並且在 QUIC 上使用的演算法:

We remark that AES-GCM-SIV is already integrated into Google's BoringSSL library \cite{BoringSSL}, and its deployment for ticket encryption in QUIC \cite{QUIC} is underway.

在 RFC 上的說明解釋了這個演算法的目的是希望當 nonce 沒有被正確實作時仍然可以有比 AES-GCM 強的保護:

This memo specifies two authenticated encryption algorithms that are nonce misuse-resistant - that is that they do not fail catastrophically if a nonce is repeated.

在 128 bits 的情況下,加密的速度大約是 AES-GCM 的 2/3 (在都有硬體加速的情況下),但解密的速度則與 AES-GCM 相當:

For encryption, it is slower than AES-GCM, because achieving nonce-misuse resistance requires, by definition, two (serialized) passes over the data. Nevertheless, optimized implementations run GCM-SIV (for 128-bit keys) at less than one cycle per byte on modern processors (roughly 2/3 of the speed of nonce-respecting AES-GCM). On the other hand, GCM-SIV decryption runs at almost the same speed as AES-GCM.

不過這就是 trade-off 了,如果 nonce 有正確被實作的話,其實不需要這個...