tor-webwml.git

1) ## translation metadata

2) # Revision: $Revision$

3) # Translation-Priority: 2-medium
4) 
5) #include "head.wmi" TITLE="Tor Project: Verifying Signatures" CHARSET="UTF-8"
6) <div id="content" class="clearfix">
7)   <div id="breadcrumbs">

8)     <a href="<page index>">Home &raquo; </a>

9)     <a href="<page docs/verifying-signatures>">Verifying Signatures</a>
10)   </div>

11)   <div id="maincol">

12) 

13) <section class="accordion">
14) <!--
15)   This section uses a CSS accordion to hide and show topics.
16)   Styles are defined at the bottom of layout.css.
17) -->
18)  <div>
19)    <input id="ac-0" name="accordion-0" type="checkbox" checked />
20)    <label for="ac-0">
21)     <h1><a name="TOC">How to verify signatures for packages</a></h1>

22)     <hr>

23)    </label>
24)    <article class="ac-small">
25) <!-- TOC -->
26)     <div class="nav img-shadow">
27)     <div class="sidenav-sub">
28)     <ul>
29)       <li><a href="#Why-verify-signature">Always verify downloads</a></li>
30)       <li><a href="#Keys">Trust in keys</a></li>
31)       <li><a href="#Windows">Windows</a></li>
32)       <li><a href="#MacosLinux">Mac OS X and Linux</a></li>
33)       <li><a href="#BuildVerification">Verify files</a></li>
34)       <li><a href="#MARVerification">MAR files</a></li>
35)       <li><a href="#Scripts">Scripts</a></li>
36)     </ul>
37)     </div>
38)     </div>

39) 

40) <!-- Intro -->

41)     <p>Digital signature is a process ensuring that a certain package was
42)     generated by its developers and has not been tampered with. Below we explain
43)     why it is important and how to verify that the Tor program you download is
44)     the one we have created and has not been modified by some attacker.</p>
45) 

46)     <p>If you want to learn more about how it works see<br/>

47)     <a href="https://en.wikipedia.org/wiki/Digital_signature">
48)     https://en.wikipedia.org/wiki/Digital_signature</a>.</p>
49) 

50)     <p class="hint">(Click on each headline to show or hide it.)</p>
51)   </article>
52)  </div>

53) 

54) <!-- Motivation -->
55)  <div>
56)    <input id="ac-1" name="accordion-1" type="checkbox" />
57)    <label for="ac-1">
58)     <a class="nav" title="link here" href="#Why-verify-signature">&#9668;</a>
59)     <h3><a name="Why-verify-signature">Always verify the signature of downloaded files</a></h3>

60)     <hr>

61)     <p>
62)     How do you know that the Tor program you have is really the one we made?

63)     Digital signatures ensure that the package you are downloading was created by

64)     our developers. It uses a cryptographic mechanism to ensure that the software package

65)     that you have just downloaded is authentic. <span class="hint">(click to toggle)</span></p>
66)    </label>
67)    <article class="ac-small">
68) 

69) 

70)     <p>
71)     For many Tor users it is important to verify that the Tor software is authentic

72)     as they have very real adversaries who might try to give them a fake version

73)     of Tor.
74)     </p>

75) 

76)     <p>
77)     If the Tor package has been modified by some attacker it is not safe to use.
78)     It doesn't matter how secure and anonymous Tor is if you're not running the real Tor.
79)     </p>

80) 

81)     <p>
82)     Before you go ahead and download something, there are a few extra steps you
83)     should take to make sure you have downloaded an authentic version of Tor.
84)     </p>

85) 
86)     <h4>Always download Tor from torproject.org</h4>
87) 

88)     <p>
89)     There are a variety of attacks that can be used to make you download a fake

90)     version of Tor. For example, an attacker could trick you into thinking some other

91)     website is a great place to download Tor. You should

92)     always download Tor from <a href="https://www.torproject.org"><b>https</b>://www.torproject.org/</a>.
93)     </p>

94) 

95)     <h4>Always make sure you are browsing over https</h4>
96) 

97)     <p>
98)     <a href="https://www.torproject.org">https://www.torproject.org/</a> uses https.

99)     Https is the secure version of the http protocol which uses encryption and authentication between your
100)     browser and the website. This makes it much harder for the attacker

101)     to modify your download. But it's not perfect. Some places in the

102)     world block the Tor website, making users to download Tor
103)     <a href="<page docs/faq>#GetTor">somewhere else</a>.

104)     </p>

105) 

106)     <p>
107)     Large companies sometimes force employees to use a modified browser,

108)     so the company can listen in on all their browsing. We've even <a
109)     href="https://blog.torproject.org/blog/diginotar-debacle-and-what-you-should-do-about-it">seen</a>
110)     attackers who have the ability to trick your browser into thinking

111)     you're talking to the Tor website with https when you're not.
112)     </p>

113) 

114)     <h4>Always verify signatures of packages you have downloaded</h4>
115) 

116)     <p>
117)     Some software sites list
118)     <a href="https://en.wikipedia.org/wiki/Cryptographic_hash_function">sha1

119)     hashes</a> alongside the software on their website, so users can
120)     verify that they downloaded the file without any errors. These
121)     "checksums" help you answer the question "Did I download this file
122)     correctly from whoever sent it to me?" They do a good job at making
123)     sure you didn't have any random errors in your download, but they
124)     don't help you figure out whether you were downloading it from the
125)     attacker. The better question to answer is: "Is this file that I

126)     just downloaded the file that Tor intended me to get?"
127)     </p>

128)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
129)   </article>
130)  </div>
131) 
132) <!-- Location of keys -->
133)  <div>
134)   <input id="ac-2" name="accordion-2" type="checkbox" checked />
135)   <label for="ac-2">
136)     <a class="nav" title="link here" href="#Keys">&#9668;</a>
137)     <h3><a name="Keys">Where do I get the signatures and the keys that made them?</a></h3>

138)     <hr>

139)     <p>
140)     Each file on <a href="<page download/download>">our download

141)     page</a> is accompanied by a file with the same name as the
142)     package and the extension ".asc". These .asc files are GPG
143)     signatures. They allow you to verify the file you've downloaded
144)     is exactly the one that we intended you to get. For example,

145)     torbrowser-install-<version-torbrowserbundle>_en-US.exe is accompanied by
146)     torbrowser-install-<version-torbrowserbundle>_en-US.exe.asc. For a list

147)     of which developer signs which package, see our
148)     <a href="<page docs/signing-keys>">signing keys</a> page.
149)     </p>

150)   </label>
151)   <article class="ac-medium">

152)     <p>

153)     In the following section We now show how you can verify the downloaded file's digital signature on

154)     different operating systems. Please notice that a signature is dated the
155)     moment the package has been signed. Therefore every time a new file is
156)     uploaded a new signature is generated with a different date. As long as you
157)     have verified the signature you should not worry that the reported date may
158)     vary.

159)     </p>

160)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
161)   </article>
162)  </div>
163) 
164) <!-- Windows -->
165)  <div>
166)   <input id="ac-3" name="accordion-3" type="checkbox" />
167)    <label for="ac-3">
168)     <a class="nav" title="link here" href="#Windows">&#9668;</a>
169)     <h3><a name="Windows">Windows</a></h3>

170)     <hr>

171)    </label>
172)    <article class="ac-small">

173)     <p>
174)     First of all you need to have GnuPG installed before you can verify
175)     signatures.
176)     <br/>
177)     Download it from
178)     <a href="https://gpg4win.org/download.html">https://gpg4win.org/download.html</a>.
179)     </p>
180)     <p>
181)     Once it's installed, use GnuPG to import the key that signed your

182)     package. In order to verify the signature you will need to type a few commands
183)     in windows command-line, <i>cmd.exe</i>.

184)     </p>
185)     <p>
186)     The Tor Browser team signs Tor Browser releases. Import its key
187)     (0x4E2C6E8793298290) by starting <i>cmd.exe</i> and typing:
188)     </p>

189)     <pre>gpg.exe --keyserver pool.sks-keyservers.net --recv-keys 0x4E2C6E8793298290</pre>

190)     <p>
191)     After importing the key, you can verify that the fingerprint
192)     is correct:
193)     </p>

194)     <pre>gpg.exe --fingerprint 0x4E2C6E8793298290</pre>

195)     <p>You should see:</p>
196)     <pre>

197) pub   rsa4096/0x4E2C6E8793298290 2014-12-15 [C] [expires: 2020-08-24]
198)       Key fingerprint = EF6E 286D DA85 EA2A 4BA7  DE68 4E2C 6E87 9329 8290

199) uid                   [ unknown] Tor Browser Developers (signing key) <torbrowser@torproject.org>

200) sub   rsa4096/0xD1483FA6C3C07136 2016-08-24 [S] [expires: 2018-08-24]
201)       Key fingerprint = A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136
202) sub   rsa4096/0xEB774491D9FF06E2 2018-05-26 [S] [expires: 2020-09-12]
203)       Key fingerprint = 1107 75B5 D101 FB36 BC6C  911B EB77 4491 D9FF 06E2

204)     </pre>
205)     <p>
206)     To verify the signature of the package you downloaded, you will need

207)     to download the ".asc" file as well. Assuming you downloaded the

208)     package and its signature to your Desktop, run:
209)     </p>

210)     <pre>gpg.exe --verify C:\Users\Alice\Desktop\torbrowser-install-<version-torbrowserbundle>_en-US.exe.asc</pre>

211)     <p>Please substitute "Alice" with your own username.</p>

212)     <p>The output should say "Good signature":</p>

213)     <pre>

214) gpg: assuming signed data in 'torbrowser-install-<version-torbrowserbundle>_en-US.exe'
215) gpg: Signature made Wed 15 Nov 2017 05:52:38 PM CET
216) gpg:                using RSA key 0xD1483FA6C3C07136

217) gpg: Good signature from "Tor Browser Developers (signing key) <torbrowser@torproject.org>" [unknown]

218) gpg: WARNING: This key is not certified with a trusted signature!
219) gpg:          There is no indication that the signature belongs to the owner.
220) Primary key fingerprint: EF6E 286D DA85 EA2A 4BA7  DE68 4E2C 6E87 9329 8290
221)      Subkey fingerprint: A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136

222)     </pre>
223)     <p>Currently valid subkey fingerprints are:</p>

224)     <pre>
225)     5242 013F 02AF C851 B1C7  36B8 7017 ADCE F65C 2036

226)     BA1E E421 BBB4 5263 180E  1FC7 2E1A C68E D408 14E0

227)     A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136
228)     </pre>

229)     <p>
230)     Notice that there is a warning because you haven't assigned a trust
231)     index to this person. This means that GnuPG verified that the key made
232)     that signature, but it's up to you to decide if that key really belongs
233)     to the developer. The best method is to meet the developer in person and
234)     exchange key fingerprints.
235)     </p>

236)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
237)   </article>
238)  </div>
239) 
240) <!-- MacOS / Linux -->
241)  <div>
242)   <input id="ac-4" name="accordion-4" type="checkbox" />
243)    <label for="ac-4">
244)     <a class="nav" title="link here" href="#MacosLinux">&#9668;</a>
245)     <h3><a name="MacosLinux">Mac OS X and Linux</a></h3>

246)     <hr>

247)    </label>
248)    <article class="ac-small">

249)     <p>You need to have GnuPG installed before you can verify

250)     signatures. If you are using Mac OS X, you can install it from <a

251)     href="https://www.gpgtools.org/">https://www.gpgtools.org/</a>. If you

252)     are using Linux, then it's probably you already have GnuPG in your
253)     system, as most Linux distributions come with it preinstalled.

254)     </p>

255) 

256)     <p>The next step is to use GnuPG to import the key that signed

257)     your package. The Tor Browser team signs Tor Browser releases. Import its

258)     key (0x4E2C6E8793298290) by starting the terminal (under "Applications"

259)     in Mac OS X) and typing:</p>

260)     <pre>gpg --keyserver pool.sks-keyservers.net --recv-keys 0x4E2C6E8793298290</pre>

261)     <p>
262)     After importing the key, you can verify that the fingerprint
263)     is correct:
264)     </p>

265)     <pre>gpg --fingerprint 0x4E2C6E8793298290</pre>

266)     <p>You should see:</p>
267)     <pre>

268) pub   rsa4096/0x4E2C6E8793298290 2014-12-15 [C] [expires: 2020-08-24]
269)       Key fingerprint = EF6E 286D DA85 EA2A 4BA7  DE68 4E2C 6E87 9329 8290

270) uid                   [ unknown] Tor Browser Developers (signing key) <torbrowser@torproject.org>

271) sub   rsa4096/0xD1483FA6C3C07136 2016-08-24 [S] [expires: 2018-08-24]
272)       Key fingerprint = A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136
273) sub   rsa4096/0xEB774491D9FF06E2 2018-05-26 [S] [expires: 2020-09-12]
274)       Key fingerprint = 1107 75B5 D101 FB36 BC6C  911B EB77 4491 D9FF 06E2
275)     </pre>

276)     <p>
277)     To verify the signature of the package you downloaded, you will need

278)     to download the ".asc" file as well. Assuming you downloaded the

279)     package and its signature to your Downloads folder, run:
280)     </p>

281) 

282)     <p><strong>For Mac OS X users</strong>:<br /></p>

283)     <pre>gpg --verify ~/Downloads/TorBrowser-<version-torbrowserbundleosx64>-osx64_en-US.dmg{.asc*,}</pre>
284) 

285)     <p><strong>For Linux users</strong> (change 64 to 32 if you have the 32-bit package):</p>
286) 

287)     <pre>gpg --verify tor-browser-linux64-<version-torbrowserbundlelinux64>_en-US.tar.xz.asc</pre>

288) 

289)     <p>The output should say "Good signature":</p>

290) 

291)     <pre>

292) gpg: assuming signed data in 'tor-browser-linux64-<version-torbrowserbundlelinux64>_en-US.tar.xz'
293) gpg: Signature made Wed 15 Nov 2017 05:52:38 PM CET
294) gpg:                using RSA key 0xD1483FA6C3C07136

295) gpg: Good signature from "Tor Browser Developers (signing key) <torbrowser@torproject.org>" [unknown]

296) gpg: WARNING: This key is not certified with a trusted signature!
297) gpg:          There is no indication that the signature belongs to the owner.
298) Primary key fingerprint: EF6E 286D DA85 EA2A 4BA7  DE68 4E2C 6E87 9329 8290
299)      Subkey fingerprint: A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136
300)     </pre>

301)     <p>
302)     Currently valid subkey fingerprints are:
303)     </p>

304)     <pre>
305)     5242 013F 02AF C851 B1C7  36B8 7017 ADCE F65C 2036

306)     BA1E E421 BBB4 5263 180E  1FC7 2E1A C68E D408 14E0

307)     A430 0A6B C93C 0877 A445  1486 D148 3FA6 C3C0 7136
308)     </pre>

309)     <p>
310)     Notice that there is a warning because you haven't assigned a trust
311)     index to this person. This means that GnuPG verified that the key made
312)     that signature, but it's up to you to decide if that key really belongs
313)     to the developer. The best method is to meet the developer in person and
314)     exchange key fingerprints.
315)     </p>

316) 

317)     <p>
318)     If you're a Linux user and you're using the <b>Debian</b> Tor (not Tor
319)     Browser) packages, you should read the instructions on <a
320)     href="<page docs/debian>#packages">importing these keys to apt</a>.
321)     If you're using the <b>RPMs</b> (for Tor, not Tor Browser), you can
322)     manually verify the signatures on the RPM packages by
323)     <pre>rpm -K filename.rpm</pre>
324)     </p>

325) 
326)     <p>See <a

327)     href="https://www.gnupg.org/documentation/">https://www.gnupg.org/documentation/</a>

328)     to learn more about GnuPG.</p>

329)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
330)   </article>
331)  </div>
332) 
333) <!-- Build verification -->
334)  <div>
335)   <input id="ac-5" name="accordion-5" type="checkbox" />
336)    <label for="ac-5">
337)     <a class="nav" title="link here" href="#BuildVerification">&#9668;</a>
338)     <h3><a id="BuildVerification">Verifying sha256sums (advanced)</a></h3>

339)     <hr>

340)    </label>
341)    <article class="ac-small">

342)     <p>Build reproducibility is a <a
343)        href="https://blog.torproject.org/blog/deterministic-builds-part-one-cyberwar-and-global-compromise">security

344)        property</a> of Tor Browser 3.0 and later. Anyone can build
345)        Tor Browser on their own machine and produce a binary that is
346)        bit-for-bit identical to the binary we offer on the download page.

347)        Fortunately, it is not necessary for everyone to build Tor Browser

348)        locally to get this security. Verifying and comparing the signed list
349)        of <a href="https://en.wikipedia.org/wiki/Cryptographic_hash">hashes</a>
350)        will confirm that multiple people have built Tor Browsers

351)        identical to the download.</p>
352) 
353)       <p>The steps below walk through this process:</p>
354) 
355)     <ul>

356)       <li>Download the Tor Browser package, the <tt>sha256sums-unsigned-build.txt</tt>
357)       file, and the <tt>sha256sums-unsigned-build.txt.asc</tt> signature file.
358)       They can all be found in the same directory under
359)       <a href="https://www.torproject.org/dist/torbrowser/">

360)       https://www.torproject.org/dist/torbrowser/</a>, for example in '<version-torbrowserbundlelinux64>'
361)       for Tor Browser <version-torbrowserbundlelinux64>.</li>

362) 

363)       <li>In case your operating system is adding the .txt extension
364)       automatically to the SHA256 sums signature file strip it again by running
365)       <pre>mv sha256sums-unsigned-build.txt.asc.txt sha256sums-unsigned-build.txt.asc</pre>

366) 

367)       <li>Retrieve the signers' GPG keys. This can be done from the command
368)       line by entering something like

369)       <pre>gpg --keyserver keys.mozilla.org --recv-keys 0x4E2C6E8793298290</pre>
370)       (This will bring you the public part of the Tor Browser developers'

371)        signing key. Other developers' key IDs can be found on

372)       <a href="<page docs/signing-keys>">this

373)       page</a>.)</li>

374) 
375)       <li>
376)       Verify the sha256sums-unsigned-build.txt file by executing this command:
377)       <pre>
378)       gpg --verify sha256sums-unsigned-build.txt.asc sha256sums-unsigned-build.txt
379)       </pre>
380)       </li>
381) 
382)       <li>
383)       You should see a message like "Good signature from &lt;DEVELOPER
384)       NAME&gt;". If you don't, there is a problem. Try these steps again.
385)       </li>
386) 

387)       <li>If you want to verify a Windows Tor Browser package you need to first

388)       strip off the authenticode signature of it. Tools that can be used for

389)       this purpose are
390)       <a href="http://osslsigncode.sourceforge.net">osslsigncode</a> and

391)       <a href="http://forum.xda-developers.com/showthread.php?t=416175">delcert.exe</a>.
392)       Assuming you have built e.g. <tt>osslsigncode</tt> on a Linux computer you can enter

393)       <pre>/path/to/your/osslsigncode remove-signature &#92;

394)         /path/to/your/<TOR BROWSER FILE NAME>.exe <TOR BROWSER FILE NAME>.exe
395)       </pre>
396)       </li>
397) 

398)       <li>Now you can take the sha256sum of the Tor Browser package. On

399)       Windows you can use the <a href="http://md5deep.sourceforge.net/">
400)       hashdeep utility</a> and run

401)       <pre>
402)       C:\location\where\you\saved\hashdeep -c sha256sum &lt;TOR BROWSER FILE NAME&gt;.exe
403)       </pre>

404)       <p>On Linux you can run</p>
405)       <pre>sha256sum &lt;TOR BROWSER FILE NAME&gt;.tar.gz</pre>
406)       without having to download a utility. Note: this does not work for OS X
407)       yet due to Apple's codesigning requirement.</li>

408) 

409)       <li>You will see a string of letters and numbers.</li>

410) 

411)       <li>Open <tt>sha256sums-unsigned-build.txt</tt> in a text editor.</li>

412) 

413)       <li>Locate the name of the Tor Browser file you downloaded.</li>

414) 

415)       <li>Compare the string of letters and numbers to the left of your

416)       filename with the string of letters and numbers that appeared
417)       on your command line. If they match, you've successfully verified the
418)       build.</li>

419)     </ul>

420)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
421)   </article>
422)  </div>
423) 
424) <!-- MAR verification -->
425)  <div>
426)   <input id="ac-6" name="accordion-6" type="checkbox" />
427)    <label for="ac-6">
428)     <a class="nav" title="link here" href="#MARVerification">&#9668;</a>
429)     <h3><a id="MARVerification">Verifying MAR files we ship (advanced)</a></h3>

430)     <hr>

431)    </label>
432)    <article class="ac-small">

433)     <p>Starting with Tor Browser 4.5a4 we sign our MAR files which helps
434)     securing our update process. The downside of this is the need for additional
435)     instructions to verify that the MAR files we ship are indeed the ones we

436)     produced with our rbm setup.</p>

437) 
438)     <p>Assuming the verification happens on a Linux computer one first needs the
439)     <tt>mar-tools-linux*.zip</tt> out of the <tt>gitian-builder/inputs</tt>
440)     directory to remove the embedded signature(s). The steps to get the unsigned
441)     MAR file on a 64 bit Linux are</p>
442)     <pre>
443)     cd /path/to/MAR/file
444)     unzip /path/to/gitian-builder/inputs/mar-tools-linux64.zip

445)     export LD_LIBRARY_PATH=/path/to/MAR/file/mar-tools

446)     mar-tools/signmar -r your-signed-mar-file.mar your-unsigned-mar-file.mar</pre>
447)     <p>Now you can compare the SHA256 sum of <tt>your-unsigned-mar-file.mar</tt>

448)     with the one provided in the <tt>sha265sums-unsigned-build.txt</tt> or
449)     <tt>sha256sums-unsigned-build.incremental.txt</tt> as outlined in
450)     <a href="#BuildVerification">Verifying sha256sums (advancded)</a> above.</p>

451)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
452)   </article>
453)  </div>
454) 
455) <!-- Scripts -->
456)  <div>
457)   <input id="ac-7" name="accordion-7" type="checkbox" checked />
458)    <label for="ac-7">
459)     <a class="nav" title="link here" href="#Scripts">&#9668;</a>
460)     <h3><a id="Scripts">Automate the process with a script</a></h3>
461)     <hr>
462)    </label>
463)    <article class="ac-small">
464)     <p><a href="https://github.com/isislovecruft/scripts/blob/master/verify-gitian-builder-signatures">Scripts</a>
465)     to <a href="https://tor.stackexchange.com/questions/648/how-to-verify-tor-browser-bundle-tbb-3-x">automate</a>
466)     these steps have been written, but to use them you will need to modify
467)     them yourself with the latest Tor Browser filename.</p>
468)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
469)   </article>
470)  </div>
471) </section>

472) 

473)   </div>
474)   <!-- END MAINCOL -->
475)   <div id = "sidecol">
476) #include "side.wmi"
477) #include "info.wmi"
478)   </div>
479)   <!-- END SIDECOL -->
480) </div>
481) <!-- END CONTENT -->