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 the section.)</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
60)         downloaded files</a></h3>

61)     <hr>

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

64)     Digital signatures ensure that the package you are downloading was created
65)     by our <a href="<>page about/corepeople>">developers</a>. It uses a
66)     cryptographic mechanism to ensure that the software package that you have
67)     just downloaded is authentic.
68)     <span class="hint">(click to toggle)</span></p>

69)    </label>
70)    <article class="ac-small">
71) 

72) 

73)     <p>

74)     For many Tor users it is important to verify that the Tor software is
75)     authentic as they have very real adversaries who might try to give them a
76)     fake version of Tor.

77)     </p>

78) 

79)     <p>

80)     If the Tor package has been modified by some attacker it is not safe to use
81)     it. It doesn't matter how secure and anonymous Tor is if you're not running
82)     the real Tor.

83)     </p>

84) 

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

89) 
90)     <h4>Always download Tor from torproject.org</h4>
91) 

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

94)     version of Tor. For example, an attacker could trick you into thinking some
95)     other website is a great place to download Tor. You should always download
96)     Tor from
97)     <a href="https://www.torproject.org"><b>https</b>://www.torproject.org/</a>.

98)     </p>

99) 

100)     <h4>Always make sure you are browsing over https</h4>
101) 

102)     <p>

103)     <a href="https://www.torproject.org">https://www.torproject.org/</a> uses
104)     https. Https is the secure version of the http protocol which uses
105)     encryption and authentication between your browser and the website.
106)     This makes it much harder for the attacker to modify your download. But
107)     it's not perfect. Some places in the world block the Tor website, making
108)     users to download Tor <a href="<page docs/faq>#GetTor">somewhere else</a>.

109)     </p>

110) 

111)     <p>
112)     Large companies sometimes force employees to use a modified browser,

113)     so the company can listen in on all their browsing. We've even
114)     <a href="https://blog.torproject.org/blog/diginotar-debacle-and-what-you-should-do-about-it">seen</a>

115)     attackers who have the ability to trick your browser into thinking

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

118) 

119)     <h4>Always verify signatures of packages you have downloaded</h4>
120) 

121)     <p>
122)     Some software sites list
123)     <a href="https://en.wikipedia.org/wiki/Cryptographic_hash_function">sha1

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

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

133)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
134)   </article>
135)  </div>
136) 
137) <!-- Location of keys -->
138)  <div>
139)   <input id="ac-2" name="accordion-2" type="checkbox" checked />
140)   <label for="ac-2">
141)     <a class="nav" title="link here" href="#Keys">&#9668;</a>

142)     <h3><a name="Keys">Where do I get the signatures and the keys that made
143)         them?</a></h3>

144)     <hr>

145)     <p>
146)     Each file on <a href="<page download/download>">our download

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

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

153)     of which developer signs which package, see our
154)     <a href="<page docs/signing-keys>">signing keys</a> page.
155)     </p>

156)   </label>
157)   <article class="ac-medium">

158)     <p>

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

160)     different operating systems. Please notice that a signature is dated the
161)     moment the package has been signed. Therefore every time a new file is
162)     uploaded a new signature is generated with a different date. As long as you
163)     have verified the signature you should not worry that the reported date may
164)     vary.

165)     </p>

166)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
167)   </article>
168)  </div>
169) 

170)   <input id="ac-3" name="accordion-3" type="checkbox" checked />
171)   <label for="ac-3">
172)     <a class="nav" title="link here" href="#Keys">&#9668;</a>
173)     <h3><a name="Keys">How to verify files with OpenPGP signatures</a></h3>
174)     <hr>
175)     <p>
176)     In the following section We now show how you can verify the downloaded file's digital signature on
177)     different operating systems. Please notice that a signature is dated the
178)     moment the package has been signed. Therefore every time a new file is
179)     uploaded a new signature is generated with a different date. As long as you
180)     have verified the signature you should not worry that the reported date may
181)     vary.
182)     </p>
183)   </label>
184)   <article class="ac-medium">
185) 

186) <!-- Windows -->
187)  <div>

188)   <input id="ac-3-1" name="accordion-3-1" type="checkbox" />
189)    <label for="ac-3-1">

190)     <a class="nav" title="link here" href="#Windows">&#9668;</a>

191)     <h4><a name="Windows">Windows</a></h4>

192)     <hr>

193)    </label>
194)    <article class="ac-small">

195)     <p>
196)     First of all you need to have GnuPG installed before you can verify
197)     signatures.
198)     <br/>
199)     Download it from
200)     <a href="https://gpg4win.org/download.html">https://gpg4win.org/download.html</a>.
201)     </p>
202)     <p>
203)     Once it's installed, use GnuPG to import the key that signed your

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

206)     </p>
207)     <p>
208)     The Tor Browser team signs Tor Browser releases. Import its key
209)     (0x4E2C6E8793298290) by starting <i>cmd.exe</i> and typing:
210)     </p>

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

212)     <p>
213)     After importing the key, you can verify that the fingerprint
214)     is correct:
215)     </p>

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

217)     <p>You should see:</p>
218)     <pre>

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

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

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

226)     </pre>
227)     <p>
228)     To verify the signature of the package you downloaded, you will need

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

230)     package and its signature to your Desktop, run:
231)     </p>

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

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

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

235)     <pre>

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

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

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

244)     </pre>
245)     <p>Currently valid subkey fingerprints are:</p>

246)     <pre>
247)     5242 013F 02AF C851 B1C7  36B8 7017 ADCE F65C 2036

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

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

251)     <p>
252)     Notice that there is a warning because you haven't assigned a trust
253)     index to this person. This means that GnuPG verified that the key made
254)     that signature, but it's up to you to decide if that key really belongs
255)     to the developer. The best method is to meet the developer in person and
256)     exchange key fingerprints.
257)     </p>

258)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
259)   </article>
260)  </div>
261) 
262) <!-- MacOS / Linux -->
263)  <div>

264)   <input id="ac-4-1" name="accordion-4-1" type="checkbox" />
265)    <label for="ac-4-1">

266)     <a class="nav" title="link here" href="#MacosLinux">&#9668;</a>

267)     <h4><a name="MacosLinux">Mac OS X and Linux</a></h4>

268)     <hr>

269)    </label>
270)    <article class="ac-small">

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

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

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

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

276)     </p>

277) 

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

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

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

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

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

283)     <p>
284)     After importing the key, you can verify that the fingerprint
285)     is correct:
286)     </p>

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

288)     <p>You should see:</p>
289)     <pre>

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

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

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

298)     <p>
299)     To verify the signature of the package you downloaded, you will need

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

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

303) 

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

305)     <pre>gpg --verify ~/Downloads/TorBrowser-<version-torbrowserbundleosx64>-osx64_en-US.dmg{.asc*,}</pre>
306) 

307)     <p><strong>For Linux users</strong> (change 64 to 32 if you have the 32-bit package):</p>
308) 

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

310) 

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

312) 

313)     <pre>

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

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

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

323)     <p>
324)     Currently valid subkey fingerprints are:
325)     </p>

326)     <pre>
327)     5242 013F 02AF C851 B1C7  36B8 7017 ADCE F65C 2036

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

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

331)     <p>
332)     Notice that there is a warning because you haven't assigned a trust
333)     index to this person. This means that GnuPG verified that the key made
334)     that signature, but it's up to you to decide if that key really belongs
335)     to the developer. The best method is to meet the developer in person and
336)     exchange key fingerprints.
337)     </p>

338) 

339)     <p>
340)     If you're a Linux user and you're using the <b>Debian</b> Tor (not Tor
341)     Browser) packages, you should read the instructions on <a
342)     href="<page docs/debian>#packages">importing these keys to apt</a>.
343)     If you're using the <b>RPMs</b> (for Tor, not Tor Browser), you can
344)     manually verify the signatures on the RPM packages by
345)     <pre>rpm -K filename.rpm</pre>
346)     </p>

347) 
348)     <p>See <a

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

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

351)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
352)   </article>
353)  </div>
354) 

355)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
356)   </article>
357)  </div>
358) 

359) <!-- Build verification -->
360)  <div>
361)   <input id="ac-5" name="accordion-5" type="checkbox" />
362)    <label for="ac-5">
363)     <a class="nav" title="link here" href="#BuildVerification">&#9668;</a>
364)     <h3><a id="BuildVerification">Verifying sha256sums (advanced)</a></h3>

365)     <hr>

366)    </label>
367)    <article class="ac-small">

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

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

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

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

377)        identical to the download.</p>
378) 
379)       <p>The steps below walk through this process:</p>
380) 
381)     <ul>

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

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

388) 

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

392) 

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

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

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

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

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

400) 
401)       <li>
402)       Verify the sha256sums-unsigned-build.txt file by executing this command:
403)       <pre>
404)       gpg --verify sha256sums-unsigned-build.txt.asc sha256sums-unsigned-build.txt
405)       </pre>
406)       </li>
407) 
408)       <li>
409)       You should see a message like "Good signature from &lt;DEVELOPER
410)       NAME&gt;". If you don't, there is a problem. Try these steps again.
411)       </li>
412) 

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

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

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

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

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

420)         /path/to/your/<TOR BROWSER FILE NAME>.exe <TOR BROWSER FILE NAME>.exe
421)       </pre>
422)       </li>
423) 

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

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

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

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

434) 

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

436) 

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

438) 

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

440) 

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

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

445)     </ul>

446)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
447)   </article>
448)  </div>
449) 
450) <!-- MAR verification -->
451)  <div>
452)   <input id="ac-6" name="accordion-6" type="checkbox" />
453)    <label for="ac-6">
454)     <a class="nav" title="link here" href="#MARVerification">&#9668;</a>
455)     <h3><a id="MARVerification">Verifying MAR files we ship (advanced)</a></h3>

456)     <hr>

457)    </label>
458)    <article class="ac-small">

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

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

463) 
464)     <p>Assuming the verification happens on a Linux computer one first needs the
465)     <tt>mar-tools-linux*.zip</tt> out of the <tt>gitian-builder/inputs</tt>
466)     directory to remove the embedded signature(s). The steps to get the unsigned
467)     MAR file on a 64 bit Linux are</p>
468)     <pre>
469)     cd /path/to/MAR/file
470)     unzip /path/to/gitian-builder/inputs/mar-tools-linux64.zip

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

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

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

477)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
478)   </article>
479)  </div>
480) 
481) <!-- Scripts -->
482)  <div>
483)   <input id="ac-7" name="accordion-7" type="checkbox" checked />
484)    <label for="ac-7">
485)     <a class="nav" title="link here" href="#Scripts">&#9668;</a>
486)     <h3><a id="Scripts">Automate the process with a script</a></h3>
487)     <hr>
488)    </label>
489)    <article class="ac-small">
490)     <p><a href="https://github.com/isislovecruft/scripts/blob/master/verify-gitian-builder-signatures">Scripts</a>
491)     to <a href="https://tor.stackexchange.com/questions/648/how-to-verify-tor-browser-bundle-tbb-3-x">automate</a>
492)     these steps have been written, but to use them you will need to modify
493)     them yourself with the latest Tor Browser filename.</p>
494)     <a class="nav" href="#TOC" title="go up">&uarr;</a>
495)   </article>
496)  </div>
497) </section>

498) 

499)   </div>
500)   <!-- END MAINCOL -->
501)   <div id = "sidecol">
502) #include "side.wmi"
503) #include "info.wmi"
504)   </div>
505)   <!-- END SIDECOL -->
506) </div>
507) <!-- END CONTENT -->