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Cloudflare 提供的 DNS Resolver 服務拓展到 Tor 上

Cloudflare 宣佈 DNS Resolver 提供 Tor 的版本,讓使用者可以在不暴露自己的 IP address 的情況下,使用 Cloudflare 提供的 DNS Resolver 服務:「Introducing DNS Resolver for Tor」。

不過沒看懂,如果使用者想要透過 Tor 保護自己的話,本來就可以透過 Tor 存取 1.1.1.11.0.0.1 甚至是其他家有提供 DNS-over-TLS 或是 DNS-over-HTTPS 的服務了?(像是 Google8.8.8.8)

好像找不到什麼使用的理由...

義大利政府的反貪組織用 Tor 的 Onion (Hidden Service) 接受檢舉

在「Italian Anti-Corruption Authority (ANAC) Adopts Onion Services」這邊看到,義大利政府因為法令要求必須保護告密者,而不只是在需要提供身份的階段才保護:

Many national laws (such as Italian Dlgs. 231/2001) require companies to adopt corporate governance structures and risk prevention systems, which can include allowing whistleblowing submissions. However, most whistleblowing laws only protect whistleblowers when their identity is disclosed, which can put the person reporting corruption at risk.

In 2016, the International Standards Organization (ISO) released a new model for organizations setting up and operating anti-bribery management systems, ISO 37001:2016. To meet ISO standards, organizations or companies implementing anti-corruption procedures must allow anonymous reporting, as explicitly indicated in point 8.9 of section C of ISO 37001:2016.

Furthermore, national laws (such as recent Italian 179/2017) require the adoption of IT systems for whistleblowing, leading to the practical integration and use of Tor for its technological anonymity features.

而義大利政府的系統選擇用 Tor 的 Onion (Hidden Service) 提供服務接受檢舉:

To comply with these standards, the Italian Anti-Corruption Authority (ANAC), an administrative watchdog, just launched their national online whistleblowing platform using onion services, giving whistleblowers who come forward a secure way to report illegal activity while protecting their identities.

這使用了 hidden service 的特性,讓伺服器端完全無法得知 client 的位置,對於使用有足夠保護的 browser 來說 (像是 Tor Browser),這可以完全讓 server 端無法得知身份,即使政府的伺服器都入侵也沒辦法知道告密者是誰。

這點頗先進的...

Tor 0.3.2.9 釋出,支援下一代的 Hidden Service

Tor 放出了新的 stable 版本:「Tor 0.3.2.9 is released: We have a new stable series!」。

這個版本支援新一代的 hidden service,也就是之前在「下一代的 Tor Hidden Service」這邊提到的東西,將原來 hostname 的部份從 16 chars 變成 56 chars,也就是像 7fa6xlti5joarlmkuhjaifa47ukgcwz6tfndgax45ocyn4rixm632jid.onion 這樣的網址。

這對 hidden service 很重要,因為這代表了淘汰掉舊的演算法,尤其裡面有兩個 (SHA1 與 RSA1024) 都已經確定有問題了:

a) Better crypto (replaced SHA1/DH/RSA1024 with SHA3/ed25519/curve25519)

Elsevier 讓德國的研究機構在還沒有續約的情況下繼續使用

德國的研究機構在 2017 年年底前,也就是與 Elsevier 的合約到期前,還是沒有續約,但 Elsevier 決定還是先繼續提供服務,暫時性的為期一年,繼續談判:

The Dutch publishing giant Elsevier has granted uninterrupted access to its paywalled journals for researchers at around 200 German universities and research institutes that had refused to renew their individual subscriptions at the end of 2017.

The institutions had formed a consortium to negotiate a nationwide licence with the publisher. They sought a collective deal that would give most scientists in Germany full online access to about 2,500 journals at about half the price that individual libraries have paid in the past. But talks broke down and, by the end of 2017, no deal had been agreed. Elsevier now says that it will allow the country’s scientists to access its paywalled journals without a contract until a national agreement is hammered out.

Elsevier 會這樣做主要是要避免讓德國的學術機構發現「沒有 Elsevier 其實也活的很好」。而不少研究人員已經知道這件事情,在大多數的情況下都有 Elsevier 的替代方案,不需要浪費錢簽那麼貴的費用:

Günter Ziegler, a mathematician at the Free University of Berlin and a member of the consortium's negotiating team, says that German researchers have the upper hand in the negotiations. “Most papers are now freely available somewhere on the Internet, or else you might choose to work with preprint versions,” he says. “Clearly our negotiating position is strong. It is not clear that we want or need a paid extension of the old contracts.”

替代方案有幾個方面,像是自由開放下載的 arXiv 愈來愈受到重視,很多研究者都會把投稿的論文在上面放一份 pre-print 版本 (甚至會更新),而且近年來有些知名的證明只放在上面 (像是 Poincaré conjecture)。而且放在人家家裡比放在自己網站來的簡單 (不需要自己維護),這都使得 arXiv 變成學術界新的標準平台。

除了 arXiv 外,其他領域也有自己習慣的平台。像是密碼學這邊的「Cryptology ePrint Archive」也運作很久了。

除了找平台外,放在自家網站上的論文 (通常是學校或是學術機構的個人空間),也因為搜尋引擎的發達,使得大家更容易找到對應檔案可以下載。

而且更直接的攻擊性網站是 Sci-Hub,讓大家從 paywall 下載後丟上去公開讓人搜尋。雖然因為常常被封鎖的原因而常常在換網址,不過透過 Tor Browser (或是自己設定 Tor Proxy) 存取他們的 Hidden Service 就應該沒這個問題。

希望德國可以撐下去,證明其實已經不需要 Elsevier...

下一代的 Tor Hidden Service

Tor 公佈了下一代的 Hidden Service (Onion Service):「Tor's Fall Harvest: the Next Generation of Onion Services」。

三年前 Facebook 自己暴力算出 facebookcorewwwi.onion 這個很特別的名字 (參考「Facebook 證明 Tor 的 Hidden Service 不安全」),這陣子連紐約時報也能暴力算出 nytimes3xbfgragh.onion 這個好名字 (參考「紐約時報網站上 Tor 的 Hidden Service (i.e. Tor Onion Service)」,這讓只有 16 chars 的 hostname 的 hashed-space 不夠大的問題愈來愈明顯 (只有 80 bits 的空間)。

如果你也想要找出一個有趣的 hostname 的話,可以用 lachesis/scallion 這樣的工具,這程式用 CPU 產生出 RSA key 後,再用 GPU 算 SHA-1

The inital RSA key generation is done the CPU. An ivybridge i7 can generate 51 keys per second using a single core. Each key can provide 1 gigahash worth of exponents to mine and a decent CPU can keep up with several GPUs as it is currently implemented.

也因為如此,Facebook 與紐約時報在上線時並不是直接在 Hidden Service 上裸奔,而是上了 HTTPS 作為 workaround,以避免資料外洩。

但這畢竟是 workaround,Tor 的人還是希望協定本身就可以提供一個夠安全的架構,而花了四年多發展出下一代的 Hidden Service,也就是這次提到的成果了。

最大的改變就是 hostname 變長很多了,從本來的 16 chars 變成 56 chars:

And finally from the casuals user's PoV, the only thing that changes is that new onions are bigger, tastier and they now look like this: 7fa6xlti5joarlmkuhjaifa47ukgcwz6tfndgax45ocyn4rixm632jid.onion.

hostname 變長主要是因為把整個 256 bits public key 放進去,可以從 spec 看到:

6. Encoding onion addresses [ONIONADDRESS]

   The onion address of a hidden service includes its identity public key, a
   version field and a basic checksum. All this information is then base32
   encoded as shown below:

     onion_address = base32(PUBKEY | CHECKSUM | VERSION) + ".onion"
     CHECKSUM = H(".onion checksum" | PUBKEY | VERSION)[:2]

     where:
       - PUBKEY is the 32 bytes ed25519 master pubkey of the hidden service.
       - VERSION is an one byte version field (default value '\x03')
       - ".onion checksum" is a constant string
       - CHECKSUM is truncated to two bytes before inserting it in onion_address

  Here are a few example addresses:

       pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd.onion
       sp3k262uwy4r2k3ycr5awluarykdpag6a7y33jxop4cs2lu5uz5sseqd.onion
       xa4r2iadxm55fbnqgwwi5mymqdcofiu3w6rpbtqn7b2dyn7mgwj64jyd.onion

   For more information about this encoding, please see our discussion thread
   at [ONIONADDRESS-REFS].

這是因為在 ECC 的安全性被廣泛認可後,ECC 的優點就被拿出來用在這次設計上了:

  • 256 bits 的 ECC key 強度大約是 3072 bits RSA key (以現在最好的攻擊演算法來估算)。
  • 直接放 public key 不需要經過 hash function 計算,可以避免掉 hash function 被找到 collision 時的風險。

於是因為 hostname 放的下,就硬塞進去了 XDDD

不過如果要玩的人需要裝 alpha 版本,目前的 stable 版本還沒有這個功能:

Tor as of version 0.3.2.1-alpha supports the next-gen onion services protocol for clients and services! As part of this release, ​the core of proposal 224 has been implemented and is available for experimentation and testing by our users.

Firefox 計劃性的將 Tor Browser 提供的隱私保護移植回 Firefox 瀏覽器上

Tor Browser 是個基於 Firefox 改出來的瀏覽器,將 Tor 包進去,讓使用者可以很方便的直接透過 Tor 上網,不需要另外再安裝其他程式。

Twitter 上看到 The Tor Project 的這則 tweet,提到 Tor Browser 阻擋 Canvas Fingerprinting 的功能將被移植回 Firefox:

將會在 Firefox 58 (現在是 56) 可以用到這個功能:「Prompt (w/ Site Permission) before allowing content to extract canvas data (Tor 6253)」。借用 Tor Browser 阻擋的範例,之後可能會長這樣:

另外也提到了這其實是 Tor Uplift 計畫中的一個項目:

Firefox 直接支援後,Tor Browser 也可以少維護一段程式碼...

紐約時報網站上 Tor 的 Hidden Service (i.e. Tor Onion Service)

紐約時報官方把整個站台放到 TorHidden Service 上了:「The New York Times is Now Available as a Tor Onion Service」。

而且也買了 SSL certficiate:

The address for our Onion Service is:
https://www.nytimes3xbfgragh.onion/

讓所有人想看到的人都有辦法看到是紐約時報的目標,所以就推出了許多不一樣的方式讓使用者可以看到內容...

The Times is dedicated to delivering quality, independent journalism, and our engineering team is committed to making sure that readers can access our journalism securely. This is why we are exploring ways to improve the experience of readers who use Tor to access our website.

OnionShare:透過 Tor 的 Hidden Service 分享檔案

OnionShare 官網上的說明是這樣寫:

OnionShare is an open source tool that lets you securely and anonymously share a file of any size.

Wiki 的說明比較清楚,實際上是在本機開一個 Hidden Service,而使用者必須透過 Tor Browser 這類的服務下載,這樣可以達成提供者與下載者都彼此匿名:

OnionShare lets you securely and anonymously share files of any size. It works by starting a web server, making it accessible as a Tor onion service, and generating an unguessable URL to access and download the files. It doesn't require setting up a server on the internet somewhere or using a third party filesharing service. You host the file on your own computer and use a Tor onion service to make it temporarily accessible over the internet. The other user just needs to use Tor Browser to download the file from you.

用法的部份就更清楚了:

Open OnionShare, drag and drop files and folders you wish to share into it, and click Start Sharing. After a moment, it will show you a .onion URL such as http://asxmi4q6i7pajg2b.onion/egg-cain. This is the secret URL that can be used to download the file you're sharing.

如果下載者不是那麼在意匿名性的話,Tor2web 這類的服務應該也可以用...

感覺以現在提供的功能來看還是不夠便利,實驗性質居多 XD

Tails 3.0 出了,然後又開始提供 BitTorrent 下載了...

Tails 是個 Tor 的獨立環境,可以直接用 USB 開機或是透過虛擬機上線,避免受到其他干擾而洩漏資訊。

剛剛看到了 Tails 發佈 3.0 版的消息:「Tails 3.0 is out」,比較特別的是在下載頁面發現 BitTorrent 的下載方式又被放回去了。

前陣子本來在「BitTorrent 對 SHA-1 的改善計畫?」這邊有提到 Tails 的團隊因應 SHA-1 的問題,在討論是否要繼續提供 BitTorrent 的問題 (因為 BitTorrent 裡使用 SHA-1 做很多事情),當時的決議其實是暫時使用 BitTorrent 發佈:「Biterrant attack」。

不過後續的更新這樣寫,所以看起來暫時會先恢復 BitTorrent 下載的方式:

After reading this discussion, my current conclusion is that we've totally misunderstood the impact of the attack, and that the security of our bittorrent downloads is still good enough. So I propose we revert to what we did before the 2.12 release, i.e. ship Torrents, for the foreseeable future when 2nd pre-image attacks are not realistic yet.

回到 Tails 3.0 本身,其中比較大的改變是放棄了 32bits 的支援:

Tails 3.0 works on 64-bit computers only and not on 32-bit computers anymore.

然後以前要在開機進到進階選單才有的語言設定,現在變成預設就會提醒了:

也許該再來測試看看注音輸入法好不好用的問題了 XD

Tor 在考慮使用 Rust 改寫

不過也不確定是不是愚人節消息就是了:「[tor-dev] Tor in a safer language: Network team update from Amsterdam」。

Tor 考慮使用 Rust 改寫,目前已經完成的部份,以及接下來的規劃:

What has already been done:
- Rust in Tor build
- Putting together environment setup instructions and a (very small) initial draft for coding standards
- Initial work to identify good candidates for migration (not tightly interdependent)

What we think are next steps:
- Define conventions for the API boundary between Rust and C
- Add a non-trivial Rust API and deploy with a flag to optionally use (to test support with a safe fallback)
- Learn from similar projects
- Add automated tooling for Rust, such as linting and testing

目前看到後續的討論只有「[tor-dev] Tor in a safer language: Network team update from Amsterdam」這篇,也許等全世界的 4/1 都過了之後再回來確認吧...

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