code.delx.au - refind/blob - docs/refind/secureboot.html

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  12   <h1>The rEFInd Boot Manager:<br />Managing Secure Boot</h1>
  13
  14   <p class="subhead">by Roderick W. Smith, <a
  15 href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.com</a></p>
  16
  17 <p>Originally written: 11/13/2012; last Web page update:
  18 6/18/2013, referencing rEFInd 0.6.12</p>
  19
  20
  21 <p>I'm a technical writer and consultant specializing in Linux technologies. This Web page is provided free of charge and with no annoying outside ads; however, I did take time to prepare it, and Web hosting does cost money. If you find this Web page useful, please consider making a small donation to help keep this site up and running. Thanks!</p>
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 125 <hr />
 126
 127 <p>This page is part of the documentation for the rEFInd boot manager. If a Web search has brought you here, you may want to start at the <a href="index.html">main page.</a></p>
 128
 129 <hr />
 130
 131 <p class="sidebar"><b>Note:</b> My <a href="http://www.rodsbooks.com/efi-bootloaders/">Managing EFI Boot Loaders for Linux</a> Web page includes a much more detailed description of Secure Boot in its <a href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html">Dealing with Secure Boot</a> sub-page. You should consult this page if you want to disable Secure Boot, generate your own keys, or perform other such tasks.</p>
 132
 133 <div class="navbar">
 134
 135 <h4 class="tight">Contents</h4>
 136
 137 <ul>
 138
 139 <li class="tight"><a href="#basic">Basic Issues</li>
 140
 141 <li class="tight"><a href="#shim">Using rEFInd with Shim</a></li>
 142     <ul>
 143     <li class="tight"><a href="#installation">Installing Shim and rEFInd</a></li>
 144     <li class="tight"><a href="#mok">Managing Your MOKs</a></li>
 145     </ul>
 146
 147 <li class="tight"><a href="#prebootloader">Using rEFInd with PreBootloader</a></li>
 148
 149 <li class="tight"><a href="#caveats">Secure Boot Caveats</a></li>
 150
 151 </ul>
 152
 153 </div>
 154
 155 <p>If you're using a computer that supports Secure Boot, you may run into extra complications. This feature is intended to make it difficult for malware to insert itself early into the computer's boot process. Unfortunately, it also complicates multi-boot configurations such as those that rEFInd is intended to manage. This page describes some <a href="#basic">secure boot basics</a> and two specific ways of using rEFInd with Secure Boot: <a href="#shim">Using the shim program</a> and <a href="#prebootloader">using the PreBootloader program.</a> It concludes with a look at <a href="#caveats">known bugs and limitations</a> in rEFInd's Secure Boot features.</p>
 156
 157 <a name="basic">
 158 <h2>Basic Issues</h2>
 159 </a>
 160
 161 <p class="sidebar"><b>Note:</b> You don't <i>have to</i> use Secure Boot.
 162 If you don't want it, you can <a
 163 href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html#disable">disable
 164 it,</a> at least on <i>x</i>86-64 PCs. If an ARM-based computer ships with
 165 Windows 8, this isn't an option for it. Unfortunately, the shim and PreBootloader programs described on this page currently support only <i>x</i>86-64, not <i>x</i>86 or ARM.</p>
 166
 167 <p>Through 2012, it became obvious that Secure Boot would be a feature that was controlled, to a large extent, by Microsoft. This is because Microsoft requires that non-server computers that display Windows 8 logos ship with Secure Boot enabled. As a practical matter, this also means that such computers ship with Microsoft's keys in their firmware. In the absence of an industry-standard body to manage the signing of Secure Boot keys, this means that Microsoft's key is the only one that's more-or-less guaranteed to be installed on the computer, thus blocking the ability to boot any OS that lacks a boot path through Microsoft's signing key.</p>
 168
 169 <p>Fortunately, Microsoft will sign third-party binaries with their key&mdash;or more precisely, with a key that Microsoft uses to sign third-party binaries. (Microsoft uses another key to sign its own binaries, and some devices, such as the Microsoft Surface tablet, lack the third-party Microsoft key.) A payment of $99 to Verisign enables a software distributor to sign as many binaries as desired. Red Hat (Fedora), Novell (SUSE), and Canonical (Ubuntu) are all using this system to enable their boot loaders to run. Unfortunately, using a third-party signing service is an awkward solution for open source software. In fact, for this very reason two separate programs exist that shift the Secure Boot "train" from Microsoft's proprietary "track" to one that's more friendly to open source authors. Both of these programs (shim and PreBootloader) are available in binary form signed by Microsoft's key. Shim enables the computer to launch binaries that are signed by a key that's built into it or that the user adds to a list known as the Machine Owner Key (MOK) list. PreBootloader enables the computer to launch binaries that the user has explicitly identified as being OK. Distributions beginning with Ubuntu 12.10 (and 12.04.2), Fedora 18, and OpenSUSE 12.3 use shim, although Ubuntu ships with an early version of shim that's useless for launching rEFInd, at least through Ubuntu 13.04. To the best of my knowledge, no major distribution uses PreBootloader, but it may see use on live CDs and is easier to set up if you're not using a distribution that supports shim.</p>
 170
 171 <p>There are three ways to sign a binary that will get it launched on a computer that uses shim:</p>
 172
 173 <ul>
 174
 175 <li><b>Secure Boot keys</b>&mdash;These keys are managed by the EFI
 176     firmware. In a default configuration, Microsoft is the only party
 177     that's more-or-less guaranteed to be able to sign boot loaders with
 178     these keys; however, it's possible to <a
 179     href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html#add_keys">replace
 180     Microsoft's keys with your own,</a> in order to take full control of
 181     Secure Boot on your computer. The trouble is that this process is
 182     tedious and varies in details from one computer to another.</li>
 183
 184 <li><b>Shim's built-in keys</b>&mdash;It's possible, but not necessary, to
 185     compile shim with a built-in public key. Its private counterpart can
 186     then be used to sign binaries. In practice, this key type is limited in
 187     utility; it's likely to be used by distribution maintainers to sign
 188     their own version of GRUB and the Linux kernels that it launches,
 189     nothing more. On the plus side, shim's keys require little or no
 190     maintenance by users. One potential complication is that if you swap
 191     out one shim binary for another, its built-in key may change, which
 192     means that the replacement shim might no longer launch its follow-on
 193     boot loader.</li>
 194
 195 <li><b>MOKs</b>&mdash;Versions 0.2 and later of shim support MOKs, which
 196     give you the ability to add your own keys to the computer. If you want
 197     to install multiple Linux distributions in Secure Boot mode, MOKs are
 198     likely to be helpful. They're vital if you want to launch kernels you
 199     compile yourself or use boot managers or boot loaders other than those
 200     provided by your distribution.</li>
 201
 202 </ul>
 203
 204 <p>All three key types are the same in form&mdash;shim's built-in keys and MOKs are both generated using the same tools used to generate Secure Boot keys. The keys can be generated with the common <tt>openssl</tt> program, but signing EFI binaries requires a rarer program called <tt>sbsign</tt> or <tt>pesign</tt>. If you use shim with a distribution that doesn't support this tool, you'll need to either sign the kernels yourself, which can be a hassle, or launch the kernels by way of a boot loader that doesn't check for signatures, such as ELILO.</p>
 205
 206 <p class="sidebar">Shim's author is working on merging it and PreBootloader. Thus, future versions of shim may provide the advantages of both programs.</p>
 207
 208 <p>PreBootloader is easier to set up on a distribution that doesn't support shim because PreBootloader doesn't rely on keys; instead, you tell it which binaries you trust and it will let you launch them. This works well on a system with boot managers, boot loaders, and kernels that seldom change. It's not a good solution for distribution maintainers, though, because it requires that users manually add binaries to PreBootloader's list of approved binaries when the OS is installed and every time those binaries change. Also, PreBootloader relies on a helper program, HashTool, to enroll hashes. (This is Geek for "tell the computer that a binary is OK.") Unfortunately, HashTool can enroll hashes only from the partition from which it was launched, so if you want to use rEFInd to launch Linux kernels directly, it's easiest if you mount your ESP at <tt>/boot</tt> in Linux or copy your kernels to the ESP. Another approach is to copy <tt>HashTool.efi</tt> to the partition that holds your kernel and rename it to almost anything else. rEFInd will then treat it like an OS boot loader and create a menu entry for it, enabling you to launch it as needed.</p>
 209
 210 <p>Beginning with version 0.5.0, rEFInd can communicate with the shim system to authenticate boot loaders. If a boot loader has been signed by a valid UEFI Secure Boot key, a valid shim key, or a valid MOK key, rEFInd will launch it. rEFInd will also launch unsigned boot loaders or those with invalid signatures <i>if</i> Secure Boot is disabled in or unsupported by the firmware. (If that's your situation, you needn't bother reading this page.) PreBootloader is designed in such a way that it requires no explicit support in rEFInd to work.</p>
 211
 212 <p>Version 0.5.0 ships signed with my own keys, and I provide the public version of this key with the rEFInd package. This can help simplify setup, since you needn't generate your own keys to get rEFInd working; however, if you lack public keys for the boot loaders that rEFInd launches, you'll need to generate your own keys and sign your boot loaders, as described in the <a href="#mok">Managing Your MOKs</a> section.</p>
 213
 214 <a name="shim">
 215 <h2>Using rEFInd with Shim</h2>
 216 </a>
 217
 218 <p>Because several major distributions support shim, I describe it first. You may need to adjust the rEFInd installation process to get it working with shim, especially if you're not using a distribution that uses this software. In addition to installing shim, you should know how to manage your MOKs, so I describe this topic, too. If you don't want to use shim, you can skip ahead to <a href="#prebootloader">the section on PreBootloader.</a></p>
 219
 220 <a name="installation">
 221 <h3>Installing Shim and rEFInd</h3>
 222 </a>
 223
 224 <p>A working Secure Boot installation of rEFInd involves at least three programs, and probably four or more, each of which must be installed in a specific way:</p>
 225
 226 <ul>
 227
 228 <li><b>shim</b>&mdash;You can download a version of shim signed with Microsoft's Secure Boot key <a href="http://www.codon.org.uk/~mjg59/shim-signed/">here.</a> This version (created by shim's developer, former Red Hat employee Matthew J. Garrett) includes a shim key that's used by nothing but the <tt>MokManager.efi</tt> program that also ships with the program. Thus, to use this version of shim, you must use MOKs. Fedora 18's and OpenSUSE 12.3's versions of shim include their own keys and can also use MOKs; but to use these packages with rEFInd, you must still enroll rEFInd's MOK. Ubuntu 12.10 and 13.04 ship with an earlier version of shim that version doesn't support MOKs. Ubuntu's shim is useless for launching rEFInd. Future distributions will probably come with their own variants of shim, most of which will no doubt support their own shim keys as well as MOKs. You should install shim just as you would install other EFI boot loaders, as described <a href="http://www.rodsbooks.com/efi-bootloaders/installation.html">here.</a> For use in launching rEFInd, it makes sense to install <tt>shim.efi</tt> in <tt>EFI/refind</tt> on your ESP, although of course this detail is up to you.</li>
 229
 230 <li><b>MokManager</b>&mdash;This program is included with shim 0.2 and later (including the versions of shim that ship with Fedora 18 and OpenSUSE 12.3). It presents a crude user interface for managing MOKs, and it's launched by shim if shim can't find its default boot loader (generally <tt>grubx64.efi</tt>) or if that program isn't properly signed. In principle, this program could be signed with a Secure Boot key or a MOK, but the binary in Garrett's shim 0.2 is signed with a shim key, and I expect that versions distributed with most Linux distributions will also be signed by their respective shim keys. This program should reside in the same directory as <tt>shim.efi</tt>, under the name <tt>MokManager.efi</tt>. Although you could theoretically do without MokManager, in practice you'll need it at least temporarily to install the MOK with which rEFInd is signed.</li>
 231
 232 <li><b>rEFInd</b>&mdash;Naturally, you need rEFInd. Because shim is hard-coded to launch a program called <tt>grubx64.efi</tt>, you must install rEFInd using that name and to the same directory in which <tt>shim.efi</tt> resides. In theory, rEFInd could be signed with a Secure Boot key, a shim key, or a MOK; however, because Microsoft won't sign binaries distributed under the GPLv3, I can't distribute a version of rEFInd signed with Microsoft's Secure Boot key; and as I don't have access to the private shim keys used by any distribution, I can't distribute a rEFInd binary signed by them. (If distributions begin including rEFInd in their package sets, though, such distribution-provided binaries could be signed with the distributions' shim keys.) Thus, rEFInd will normally be signed by a MOK. Beginning with version 0.5.0, rEFInd binaries that I provide are signed by me. Beginning with version 0.5.1, the installation script provides an option to sign the rEFInd binary with your own key, provided the necessary support software is installed.</li>
 233
 234 <li><b>Your boot loaders and kernels</b>&mdash;Your OS boot loaders, and perhaps your Linux kernels, must be signed. They can be signed with any of the three key types. Indeed, your system may have a mix of all three types&mdash;a Windows 8 boot loader will most likely be signed with Microsoft's Secure Boot key, GRUB and kernels provided by most distributions will be signed with their own shim keys, and if you use your own locally-compiled kernel or a boot loader from an unusual source you may need to sign it with a MOK. Aside from signing, these files can be installed in exactly the same way as if your computer were not using Secure Boot.</li>
 235
 236 </ul>
 237
 238 <p>If you've installed Fedora 18 or OpenSUSE 12.3 and can boot it with Secure Boot active, and if you then install rEFInd using the RPM file that I provide or by running <tt>install.sh</tt>, chances are you'll end up with a working rEFInd that will start up the first time, with one caveat: You'll have to use MokManager to add rEFInd's MOK to your MOK list, as described shortly. If you don't already have a working copy of shim on your ESP, your task is more complex. Broadly speaking, the procedure should be something like this:</p>
 239
 240 <ol>
 241
 242 <li>Boot the computer. This can be a challenge in and of itself. You may
 243     need to use a Secure Boot&ndash;enabled Linux emergency disc,
 244     temporarily disable Secure Boot, or do the work from Windows.</li>
 245
 246 <li><a href="getting.html">Download rEFInd</a> in binary form (the binary
 247     zip or CD-R image file). If you download the binary zip file, unzip it;
 248     if you get the CD-R image file, burn it to a CD-R and mount it.</li>
 249
 250 <li>Download shim from <a
 251     href="http://www.codon.org.uk/~mjg59/shim-signed/">Matthew J. Garrett's
 252     download site</a> or from your distribution. (Don't use Ubuntu's
 253     version, though; as noted earlier, it's inadequate for use with
 254     rEFInd.)</li>
 255
 256 <p class="sidebar"><b>Tip:</b> If you're running Linux, you can save some effort by using the <tt>install.sh</tt> script with its <tt>--shim <tt class="variable">/path/to/shim.efi</tt></tt> option rather than installing manually, as in steps 4&ndash;6 of this procedure. If you've installed <tt>openssl</tt> and <tt>sbsign</tt>, using <tt>--localkeys</tt> will generate local signing keys and re-sign the rEFInd binaries with your own key, too. You can then use <tt>sbsign</tt> and the keys in <tt>/etc/refind.d/keys</tt> to sign your kernels or boot loaders.</p>
 257
 258 <li>Copy the <tt>shim.efi</tt> and <tt>MokManager.efi</tt> binaries to the
 259     directory you intend to use for rEFInd&mdash;for instance,
 260     <tt>EFI/refind</tt> on the ESP.</li>
 261
 262 <li>Follow the installation instructions for rEFInd on the <a
 263     href="installing.html">Installing rEFInd</a> page; however, give rEFInd
 264     the filename <tt>grubx64.efi</tt> and register <tt>shim.efi</tt> with
 265     the EFI by using <tt>efibootmgr</tt> in Linux or <tt>bcdedit</tt> in
 266     Windows. Be sure that rEFInd (as <tt>grubx64.efi</tt>),
 267     <tt>shim.efi</tt>, and <tt>MokManager.efi</tt> all reside in the same
 268     directory.</li>
 269
 270 <li>Copy the <tt>refind.cer</tt> file from the rEFInd package to your ESP,
 271     ideally to a location with few other files. (The rEFInd installation
 272     directory should work fine.)</li>
 273
 274 <li>Reboot. With any luck, you'll see a simple text-mode user interface
 275     with a label of <tt>Shim UEFI key management</tt>. This is the
 276     MokManager program, which shim launched when rEFInd failed verification
 277     because its key is not yet enrolled.</li>
 278
 279 <li>Press your down arrow key and press Enter to select <tt>Enroll key from
 280     disk</tt>. The screen will clear and prompt you to select a key, as
 281     shown here:</li>
 282
 283     <br /><img src="MokManager1.png" align="CENTER" width="676"
 284     height="186" alt="MokManager's user interface is crude but effective."
 285     border=2> <br />
 286
 287 <li>Each of the lines with a long awkward string represents a disk
 288     partition. Select one and you'll see a list of files. Continue
 289     selecting subdirectories until you find the <tt>refind.cer</tt> file
 290     you copied to the ESP earlier. (Note that the long lines can wrap
 291     and hide valid entries on the next line, so you may need to select
 292     a disk whose entry is masked by another one!)</li>
 293
 294 <li>Select <tt>refind.cer</tt>. You can type <tt class="userinput">1</tt>
 295     to view the certificate's details if you like, or skip that and type
 296     <tt class="userinput">0</tt> to enroll the key.</li>
 297
 298 <li>Back out of any directories you entered and return to the MokManager
 299     main menu.</li>
 300
 301 <li>Select <tt>Continue boot</tt> at the main menu.</li>
 302
 303 </ol>
 304
 305 <p>At this point the computer may boot into its default OS, reboot, or perhaps even hang. When you reboot it, though, rEFInd should start up in Secure Boot mode. (You can verify this by selecting the <i>About rEFInd</i> tool in the main menu. Check the <i>Platform</i> item in the resulting screen; it should verify that Secure Boot is active.) You should now be able to launch any boot loader signed with a key recognized by the firmware or by shim (including any MOKs you've enrolled). If you want to manage keys in the future, rEFInd displays a new icon in the second (tools) row you can use to launch MokManager. (This icon appears by default if MokManager is installed, but if you edit <tt>showtools</tt> in <tt>refind.conf</tt>, you must be sure to include <tt>mok_tool</tt> as an option in order to gain access to it.)</p>
 306
 307 <p>If you're using Ubuntu, you can't use its version of shim, but you can replace it with Garrett's shim. If you do so, though, you'll have to add Ubuntu's public key as a MOK, at least if you intend to launch Ubuntu's version of GRUB or launch Ubuntu-provided signed kernels. Ubuntu's public key is available in the <a href="http://archive.ubuntu.com/ubuntu/pool/main/s/shim/shim_0~20120906.bcd0a4e8-0ubuntu4.debian.tar.gz">shim_0~20120906.bcd0a4e8-0ubuntu4.debian.tar.gz</a> tarball, as <tt>canonical-uefi-ca.der</tt>. (The filename extensions <tt>.cer</tt> and <tt>.der</tt> are interchangeable for most purposes.) I've also included this key with rEFInd, in the <tt>refind/keys</tt> subdirectory of its package file. To use this key, copy it to your ESP and enroll it with MokManager. See <a href="http://falstaff.agner.ch/2012/12/12/secure-boot-implementation-of-ubuntu-12-10-quantal-quetzal/">this blog post</a> for further details on Ubuntu 12.10's handling of Secure Boot. In principle, you should be able to use shim 0.2 or later from future distributions that include it; but you must be sure that whatever you use supports MokManager.</p>
 308
 309 <a name="mok">
 310 <h3>Managing Your MOKs</h3>
 311 </a>
 312
 313 <p>The preceding instructions provided the basics of getting rEFInd up and running, including using MokManager to enroll a MOK on your computer. If you need to sign binaries, though, you'll have to use additional tools. The OpenSSL package provides the cryptographic tools necessary, but actually signing EFI binaries requires additional software. Two packages for this are available: <tt>sbsigntool</tt> and <tt>pesign</tt>. Both are available in binary form from <a href="https://build.opensuse.org/project/show?project=home%3Ajejb1%3AUEFI">this OpenSUSE Build Service (OBS)</a> repository. The following procedure uses <tt>sbsigntool</tt>. To sign your own binaries, follow these steps (you can skip the first five steps if you've used <tt>install.sh</tt>'s <tt>--localkeys</tt> option):</p>
 314
 315 <ol>
 316
 317 <li>If it's not already installed, install OpenSSL on your computer. (It
 318     normally comes in a package called <tt>openssl</tt>.)</li>
 319
 320 <li>If you did <i>not</i> re-sign your rEFInd binaries with
 321     <tt>install.sh</tt>'s <tt>--localkeys</tt> option, type the following
 322     two commands to generate your public and private keys:
 323
 324 <pre class="listing">
 325 $ <tt class="userinput">openssl req -new -x509 -newkey rsa:2048 -keyout refind_local.key \
 326   -out refind_local.crt -nodes -days 3650 -subj "/CN=Your Name/"</tt>
 327 $ <tt class="userinput">openssl x509 -in refind_local.crt -out refind_local.cer -outform DER</tt>
 328 </pre>
 329
 330     Change <tt>Your Name</tt> to your own name or other identifying
 331     characteristics, and adjust the certificate's time span (set via
 332     <tt>-days</tt>) as you see fit. If you omit the <tt>-nodes</tt> option,
 333     the program will prompt you for a passphrase for added security.
 334     Remember this, since you'll need it to sign your binaries. The result
 335     is a private key file (<tt>refind_local.key</tt>), which is highly
 336     sensitive since it's required to sign binaries, and two public keys
 337     (<tt>refind_local.crt</tt> and <tt>refind_local.cer</tt>), which can be
 338     used to verify signed binaries' authenticity. The two public key files
 339     are equivalent, but are used by different
 340     tools&mdash;<tt>sbsigntool</tt> uses <tt>refind_local.crt</tt> to sign
 341     binaries, but MokManager uses <tt>refind_local.cer</tt> to enroll the
 342     key. If you used <tt>install.sh</tt>'s <tt>--localkeys</tt> option,
 343     this step is unnecessary, since these keys have already been created
 344     and are stored in <tt>/etc/refind.d/keys</tt>.</li>
 345
 346 <li>Copy the three key files to a secure location and adjust permissions
 347     such that only you can read <tt>refind_local.key</tt>. You'll need
 348     these keys to sign future binaries, so don't discard them.</li>
 349
 350 <li>Copy the <tt>refind_local.cer</tt> file to your ESP, ideally to a
 351     location with few other files. (MokManager's user interface becomes
 352     unreliable when browsing directories with lots of files.)</li>
 353
 354 <li>Download and install the <tt>sbsigntool</tt> package. Binary links for
 355     various distributions are available from the <a
 356     href="https://build.opensuse.org/package/show?package=sbsigntools&project=home%3Ajejb1%3AUEFI">OpenSUSE
 357     Build Service</a>, or you can obtain the source code by typing <tt
 358     class="userinput">git clone
 359     git://kernel.ubuntu.com/jk/sbsigntool</tt>.</li>
 360
 361 <li>Sign your binary by typing <tt class="userinput">sbsign --key
 362     refind_local.key --cert refind_local.crt --output <tt
 363     class="variable">binary-signed.efi binary.efi</tt></tt>, adjusting the
 364     paths to the keys and the binary names.</li>
 365
 366 <li>Copy your signed binary to a suitable location on the ESP for rEFInd to
 367     locate it. Be sure to include any support files that it needs,
 368     too.</li>
 369
 370 <li>Check your <tt>refind.conf</tt> file to ensure that the
 371     <tt>showtools</tt> option is either commented out or includes
 372     <tt>mok_tool</tt> among its options.</li>
 373
 374 <li>Reboot. You can try launching the boot loader you just installed, but
 375     chances are it will generate an <tt>Access Denied</tt> message. For it
 376     to work, you must launch MokManager using the tool that rEFInd presents
 377     on its second row. You can then enroll your <tt>refind_local.cer</tt>
 378     key just as you enrolled the <tt>refind.cer</tt> key.</li>
 379
 380 </ol>
 381
 382 <p>At this point you should be able to launch the binaries you've signed. Unfortunately, there can still be problems at this point....</p>
 383
 384 <a name="prebootloader">
 385 <h2>Using rEFInd with PreBootloader</h2>
 386 </a>
 387
 388 <p>If you want to use Secure Boot with a distribution that doesn't come with shim but the preceding description exhausts you, take heart: PreBootloader is easier to set up and use for your situation! Unfortunately, it's still not as easy to use as not using Secure Boot at all, and it's got some drawbacks, but it may represent an acceptable middle ground. To get started, proceed as follows:</p>
 389
 390 <ol>
 391
 392 <li>Boot the computer. As with shim, this can be a challenge; you may need
 393     to boot with Secure Boot disabled, use a Secure Boot&ndash;enabled live
 394     CD, or do the installation from Windows.</li>
 395
 396 <li><a href="getting.html">Download rEFInd</a> in binary form (the binary
 397     zip or CD-R image file). If you download the binary zip file, unzip it;
 398     if you get the CD-R image file, burn it to a CD-R and mount it.</li>
 399
 400 <li>Download PreBootloader from <a
 401     href="http://blog.hansenpartnership.com/linux-foundation-secure-boot-system-released/">its
 402     release page</a> or by clicking the following links. Be sure to get
 403     both the <tt><a
 404     href="http://blog.hansenpartnership.com/wp-uploads/2013/PreLoader.efi">PreLoader.efi</a></tt>
 405     and <tt><a
 406     href="http://blog.hansenpartnership.com/wp-uploads/2013/HashTool.efi">HashTool.efi</a></tt>
 407     files.</li>
 408
 409 <li>Copy the <tt>PreLoader.efi</tt> and <tt>HashTool.efi</tt> binaries to
 410     the directory you intend to use for rEFInd&mdash;for instance,
 411     <tt>EFI/refind</tt> on the ESP.</li>
 412
 413 <li>Follow the installation instructions for rEFInd on the <a
 414     href="installing.html">Installing rEFInd</a> page; however, give rEFInd
 415     the filename <tt>loader.efi</tt> and register <tt>PreLoader.efi</tt>
 416     with the EFI by using <tt>efibootmgr</tt> in Linux or <tt>bcdedit</tt>
 417     in Windows. Be sure that rEFInd (as <tt>loader.efi</tt>),
 418     <tt>PreLoader.efi</tt>, and <tt>HashTool.efi</tt> all reside in the
 419     same directory.</li>
 420
 421 <li>Reboot. With any luck, you'll see HashTool appear with a warning
 422     message stating that it was unable to launch <tt>loader.efi</tt> and
 423     declaring that it will launch <tt>HashTool.efi</tt>. Press the Enter
 424     key to continue.</li>
 425
 426 <li>HashTool should now appear. It should give you three or four options,
 427     including <tt>Enroll Hash</tt>, as shown here. Select this option</li>
 428
 429     <br /><img src="HashTool1.png" align="CENTER" width="641" height="459"
 430     alt="HashTool provide a somewhat nicer user interface than
 431     MokManager's." border=2> <br />
 432
 433 <li>You can now select the binary you want to authorize. You should first
 434     select <tt>loader.efi</tt>, since that's rEFInd. The program presents
 435     the hash (a very long number) and asks for confirmation. Be sure to
 436     select <tt>Yes</tt>.</li>
 437
 438     <br /><img src="HashTool2.png" align="CENTER" width="638" height="455"
 439     alt="Be sure to select the right binary when you enroll its hash."
 440     border=2> <br />
 441
 442 <p class="sidebar"><b>Note:</b> Unfortunately, HashTool's file selector can't change filesystems. Thus, if you want to boot a Linux kernel using rEFInd and PreBootloader, you'll need to copy the kernel to the ESP, at least temporarily. Alternatively, as noted earlier, you can copy <tt>HashTool.efi</tt> to the directory that holds the kernels or to another directory on that partition that rEFInd scans&mdash;but be sure to rename <tt>HashTool.efi</tt> or rEFInd will ignore it. You'll then see a boot loader entry for HashTool.</p>
 443
 444 <li>Repeat the preceding two steps for any additional binaries you might
 445     want to enroll. These include any EFI filesystem drivers you're using,
 446     any boot loaders you're launching from rEFInd (other than those that
 447     are already signed, such as Microsoft's boot loader), and possibly your
 448     Linux kernel.</li>
 449
 450 <li>At the HashTool main menu, select <tt>Exit</tt>. rEFInd should
 451     launch.</li>
 452
 453 </ol>
 454
 455 <p>If you did everything right, rEFInd should now launch follow-on boot loaders and kernels, including both programs signed with the platform's Secure Boot keys and binaries that you've authorized with HashTool. If you need to authorize additional programs, you can do so from rEFInd by using the MOK utility tool icon that launches <tt>HashTool.efi</tt> from the second row of icons. (This icon should appear by default, but if you uncomment the <tt>showtools</tt> token in <tt>refind.conf</tt>, be sure that <tt>mok_tool</tt> is present among the options.)</p>
 456
 457 <a name="caveats">
 458 <h2>Secure Boot Caveats</h2>
 459 </a>
 460
 461 <p>rEFInd's Secure Boot support is brand-new with version 0.5.0 of the program, and was revamped for version 0.6.2. I believe rEFInd 0.6.2's Secure Boot support to be significantly superior to that of previous versions, but you might still run into problems. Some issues you might encounter include the following:</p>
 462
 463 <ul>
 464
 465 <li>Under certain circumstances, the time required to launch a boot loader
 466     can increase. This is unlikely to be noticeable for the average small
 467     boot loader, but could be significant for larger boot loaders on slow
 468     filesystems, such as Linux kernels on ext2fs, ext3fs, or ReiserFS
 469     partitions.</li>
 470
 471 <li>As of version 0.6.2, rEFInd's own Secure Boot support is theoretically
 472     able to work on non-<i>x</i>86-64 platforms; however, shim 0.2 and
 473     PreBootloader both work only on <i>x</i>86-64, and rEFInd is dependent
 474     upon these tools. Thus, you'll have to wait for future developments if
 475     you want to use Secure Boot on <i>x</i>86 or ARM computers.</li>
 476
 477 <li>In theory, signing Microsoft's boot loader with a MOK should work. This
 478     might be handy if you want to replace your computer's built-in keys
 479     with your own but still boot Windows&mdash;but be aware that if Windows
 480     replaces its boot loader, it will then stop working.</li>
 481
 482 </ul>
 483
 484 <p>If you launch a boot loader or other program from rEFInd that relies on the EFI's standard program-launching code, that program should take advantage of shim and its MOKs. For instance, if you launch <a href="http://freedesktop.org/wiki/Software/gummiboot">gummiboot</a> from rEFInd (and rEFInd from shim), gummiboot should be able to launch shim/MOK-signed Linux kernels. This is not currently true if you launch gummiboot directly from shim. (You can launch gummiboot from PreBootloader and it should work, though, because of technical differences between how shim and PreBootloader work.)</p>
 485
 486 <p>My focus in testing rEFInd's Secure Boot capabilities has been on getting Linux kernels with EFI stub loaders to launch correctly. I've done some minimal testing with GRUB 2, though. I've also tested some self-signed binaries, such as an EFI shell and MokManager. (The EFI shell launches, but will not itself launch anything that's not been signed with a UEFI Secure Boot key, even with rEFInd 0.6.2. This of course limits its utility.)</p>
 487
 488 <p>At the moment, I consider rEFInd's shim/MOK support to be of late alpha quality. I'm releasing it in this state in the hope of getting feedback from adventurous early adopters. Some of the usability improvements are dependent upon MOK-capable versions of shim being released with major distributions; such versions of shim, with kernels signed with the key that matches the one built into shim, will greatly reduce the need for users to sign boot loaders.</p>
 489
 490 <hr />
 491
 492 <p>copyright &copy; 2012&ndash;2013 by Roderick W. Smith</p>
 493
 494 <p>This document is licensed under the terms of the <a href="FDL-1.3.txt">GNU Free Documentation License (FDL), version 1.3.</a></p>
 495
 496 <p>If you have problems with or comments about this Web page, please e-mail me at <a href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.com.</a> Thanks.</p>
 497
 498 <p><a href="index.html">Go to the main rEFInd page</a></p>
 499
 500 <p><a href="revisions.html">Learn about rEFInd's history</a></p>
 501
 502
 503   <p><a href="http://www.rodsbooks.com/">Return</a> to my main Web page.</p>
 504 </body>
 505 </html>