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

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  14   <h1>The rEFInd Boot Manager:<br />Managing Secure Boot</h1>
  15
  16   <p class="subhead">by Roderick W. Smith, <a
  17 href="mailto:rodsmith@rodsbooks.com">rodsmith@rodsbooks.com</a></p>
  18
  19 <p>Originally written: 11/13/2012; last Web page update:
  20 11/8/2015, referencing rEFInd 0.10.0</p>
  21
  22
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 127 <hr />
 128
 129 <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>
 130
 131 <hr />
 132
 133 <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 two of its subpages. Consult <a href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html">Dealing with Secure Boot</a> for more information on disabling Secure Boot, using Shim, and using PreLoader; and read <a href="http://www.rodsbooks.com/efi-bootloaders/controlling-sb.html">Controlling Secure Boot</a> for more information on using your own keys instead of or in addition to those that came with your computer.</p>
 134
 135 <div class="navbar">
 136
 137 <h4 class="tight">Contents</h4>
 138
 139 <ul>
 140
 141 <li class="tight"><a href="#basic">Basic Issues</li>
 142
 143 <li class="tight"><a href="#shim">Using rEFInd with Shim</a></li>
 144     <ul>
 145     <li class="tight"><a href="#installation">Installing Shim and rEFInd</a></li>
 146     <li class="tight"><a href="#mok">Managing Your MOKs</a></li>
 147     </ul>
 148
 149 <li class="tight"><a href="#preloader">Using rEFInd with PreLoader</a></li>
 150
 151 <li class="tight"><a href="#caveats">Secure Boot Caveats</a></li>
 152
 153 </ul>
 154
 155 </div>
 156
 157 <p class="sidebar"><b>Note:</b> Macs don't (yet?) support Secure Boot, but
 158 as of version 10.11 ("El Capitan"), OS X uses its own new security feature,
 159 <i>System Integrity Protection (SIP),</i> which creates its own set of
 160 hoops through which rEFInd users must jump. See the <a
 161 href="sip.html">rEFInd and System Integrity Protection</a> page for
 162 details.</p>
 163
 164 <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="#preloader">using the PreLoader program.</a> (My separate <a href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html">EFI Boot Loaders for Linux page on Secure Boot</a> covers the additional topics of disabling Secure Boot and adding keys to the firmware's own set of keys.) This page concludes with a look at <a href="#caveats">known bugs and limitations</a> in rEFInd's Secure Boot features.</p>
 165
 166 <a name="basic">
 167 <h2>Basic Issues</h2>
 168 </a>
 169
 170 <p class="sidebar"><b>Note:</b> You don't <i>have to</i> use Secure Boot.
 171 If you don't want it, you can <a
 172 href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html#disable">disable
 173 it,</a> at least on <i>x</i>86-64 PCs. If an ARM-based computer ships with
 174 Windows 8, this isn't an option for it. Unfortunately, the Shim and PreLoader programs described on this page currently support only <i>x</i>86-64, not <i>x</i>86 or ARM.</p>
 175
 176 <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>
 177
 178 <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 PreLoader) 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. PreLoader 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 the Ubuntu initially shipped with an early version of Shim that's useless for launching rEFInd. (Current versions of Ubuntu ship with more flexible versions of Shim.) PreLoader is used by some smaller and more specialized distributions, such as Arch Linux. You can switch from one to the other if you like, no matter what your distribution uses by default.</p>
 179
 180 <p>There are three ways to sign a binary that will get it launched on a computer that uses Shim:</p>
 181
 182 <ul>
 183
 184 <li><b>Secure Boot keys</b>&mdash;These keys are managed by the EFI
 185     firmware. In a default configuration, Microsoft is the only party
 186     that's more-or-less guaranteed to be able to sign boot loaders with
 187     these keys; however, it's possible to <a
 188     href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html#add_keys">replace
 189     Microsoft's keys with your own,</a> in order to take full control of
 190     Secure Boot on your computer. The trouble is that this process is
 191     tedious and varies in details from one computer to another. It's worth
 192     noting that many, but not all, computers ship with Canonical's key,
 193     which can help slightly when booting Ubuntu; if your computer is so
 194     equipped, you can use any Shim you like and not worry about adding
 195     Canonical's key to your MOK list, although you must still add a MOK key
 196     for rEFInd itself.</li>
 197
 198 <li><b>Shim's built-in keys</b>&mdash;It's possible, but not necessary, to
 199     compile Shim with a built-in public key. Its private counterpart can
 200     then be used to sign binaries. In practice, this key type is limited in
 201     utility; it's likely to be used by distribution maintainers to sign
 202     their own version of GRUB and the Linux kernels that it launches,
 203     nothing more. On the plus side, Shim's keys require little or no
 204     maintenance by users. One potential complication is that if you swap
 205     out one Shim binary for another, its built-in key may change, which
 206     means that the replacement Shim might no longer launch its follow-on
 207     boot loader or kernels linked to the first Shim.</li>
 208
 209 <li><b>MOKs</b>&mdash;Versions 0.2 and later of Shim support MOKs, which
 210     give you the ability to add your own keys to the computer. If you want
 211     to install multiple Linux distributions in Secure Boot mode, MOKs are
 212     likely to be helpful. They're vital if you want to launch kernels you
 213     compile yourself or use boot managers or boot loaders other than those
 214     provided by your distribution.</li>
 215
 216 </ul>
 217
 218 <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 either of two rarer programs: <tt>sbsign</tt> or <tt>pesign</tt>. If you use Shim with a distribution that doesn't support Secure Boot, 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>
 219
 220 <p class="sidebar">Shim's author is working on merging it and PreLoader. Thus, future versions of Shim may provide the advantages of both programs.</p>
 221
 222 <p>PreLoader is easier to set up on a distribution that doesn't support Shim because PreLoader 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 PreLoader's list of approved binaries when the OS is installed and every time those binaries change. Also, PreLoader relies on a helper program, HashTool, to enroll hashes. (This is Geek for "tell the computer that a binary is OK.") Unfortunately, the initial (and, as far as I know, only signed) 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 EFI System Partition (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>
 223
 224 <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, 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.) PreLoader is designed in such a way that it requires no explicit support in rEFInd to work.</p>
 225
 226 <p>My binary builds of rEFInd version 0.5.0 and later ship 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. The rEFInd PPA for Ubuntu ships unsigned binaries, but the installation script that runs automatically when the package is installed signs the binaries with a local key as it installs them. In either case, if you lack public keys for the boot loaders that rEFInd launches, you'll need to sign your boot loaders, as described in the <a href="#mok">Managing Your MOKs</a> section.</p>
 227
 228 <a name="shim">
 229 <h2>Using rEFInd with Shim</h2>
 230 </a>
 231
 232 <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="#preloader">the section on PreLoader.</a></p>
 233
 234 <a name="installation">
 235 <h3>Installing Shim and rEFInd</h3>
 236 </a>
 237
 238 <p class="sidebar"><b>Note:</b> rEFInd's <tt>refind-install</tt> script attempts to identify whether your computer was booted with Secure Boot active and, if it was, to locate existing Shim binaries and make use of whatever it finds. Thus, you may not need to explicitly set up Shim after you install rEFInd, although you will probably have to enroll rEFInd's key in your MOK list, as described shortly.</p>
 239
 240 <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>
 241
 242 <ul>
 243
 244 <li><b>Shim</b>&mdash;You can use any version of Shim you like. In many cases, one will already be installed on your computer from your distribution, called <tt>shim.efi</tt> or <tt>shimx64.efi</tt> in the distribution's directory on the ESP. If so, it's probably best to use that version, since its built-in key will handle your distribution's kernels. If you don't currently have a Shim installed, you can copy one from another computer, copy the file from a distribution installation disc, or download a version of Shim 0.2 (old, but still usable) 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. No matter what version of Shim you use, you must enroll rEFInd's MOK. Ubuntu 12.10 and 13.04 ship with an earlier version of Shim (0.1) that doesn't support MOKs; avoid Shim 0.1 for use with rEFInd. 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>
 245
 246 <li><b>MokManager</b>&mdash;This program is included with Shim 0.2 and later. It presents a 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 such binaries are usually signed by 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>
 247
 248 <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>
 249
 250 <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>
 251
 252 </ul>
 253
 254 <p>If you've installed a distribution that provides Shim 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>refind-install</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>
 255
 256 <ol>
 257
 258 <li>Boot the computer. This can be a challenge in and of itself. You may
 259     need to use a Secure Boot&ndash;enabled Linux emergency disc,
 260     temporarily disable Secure Boot, or do the work from Windows.</li>
 261
 262 <li><a href="getting.html">Download rEFInd</a> in binary form (the binary
 263     zip or CD-R image file). If you download the binary zip file, unzip it;
 264     if you get the CD-R image file, burn it to a CD-R and mount it.</li>
 265
 266 <li>Download Shim from <a
 267     href="http://www.codon.org.uk/~mjg59/shim-signed/">Matthew J. Garrett's
 268     download site</a> or from your distribution. (Don't use an early 0.1
 269     version, though; as noted earlier, it's inadequate for use with
 270     rEFInd.)</li>
 271
 272 <p class="sidebar"><b>Tip:</b> If you're running Linux, you can save some effort by using the <tt>refind-install</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>
 273
 274 <li>Copy the <tt>shim.efi</tt> and <tt>MokManager.efi</tt> binaries to the
 275     directory you intend to use for rEFInd&mdash;for instance,
 276     <tt>EFI/refind</tt> on the ESP.</li>
 277
 278 <li>Follow the installation instructions for rEFInd on the <a
 279     href="installing.html">Installing rEFInd</a> page; however, you should
 280     normally give rEFInd the filename <tt>grubx64.efi</tt> and register
 281     <tt>shim.efi</tt> with the EFI by using <tt>efibootmgr</tt> in Linux or
 282     <tt>bcdedit</tt> in Windows. Be sure that rEFInd (as
 283     <tt>grubx64.efi</tt>), <tt>shim.efi</tt>, and <tt>MokManager.efi</tt>
 284     all reside in the same directory. If you're using Shim 0.7 or later and
 285     installing it under Linux, you may optionally keep rEFInd's
 286     <tt>refind_x64.efi</tt> name; but you must then tell Shim to use rEFInd
 287     by passing an additional <tt>-u "shim.efi refind_x64.efi"</tt> option
 288     to <tt>efibootmgr</tt>. Change the filenames to the actual filenames
 289     used by Shim and rEFInd, respectively.</li>
 290
 291 <li>Copy the <tt>refind.cer</tt> file from the rEFInd package to your ESP,
 292     ideally to a location with few other files. (The rEFInd installation
 293     directory should work fine.)</li>
 294
 295 <li>Reboot. With any luck, you'll see a simple text-mode user interface
 296     with a label of <tt>Shim UEFI key management</tt>. This is the
 297     MokManager program, which Shim launched when rEFInd failed verification
 298     because its key is not yet enrolled.</li>
 299
 300 <li>Press your down arrow key and press Enter to select <tt>Enroll key from
 301     disk</tt>. The screen will clear and prompt you to select a key, as
 302     shown here:
 303
 304     <br /><img src="MokManager1.png" align="CENTER" width="676"
 305     height="186" alt="MokManager's user interface is crude but effective."
 306     border=2> <br />
 307
 308     This user interface was used in early versions of MokManager, but
 309     somewhere between versions 0.4 and 0.7, the user interface received an
 310     upgrade. If you've got a more recent version, it will look more like
 311     this:
 312
 313     <br /><img src="MokManager2.png" align="CENTER" width="800"
 314     height="345" alt="Recent versions of MokManager provide a somewhat more
 315     user-friendly user interface." border=2> <br /> </li>
 316
 317 <li>Each of the lines with a long awkward string represents a disk
 318     partition. Select one and you'll see a list of files. Continue
 319     selecting subdirectories until you find the <tt>refind.cer</tt> file
 320     you copied to the ESP earlier. (Note that in the early user interface
 321     the long lines can wrap and hide valid entries on the next line, so you
 322     may need to select a disk whose entry is masked by another one!)</li>
 323
 324 <li>Select <tt>refind.cer</tt>. You can type <tt class="userinput">1</tt>
 325     to view the certificate's details if you like, or skip that and type
 326     <tt class="userinput">0</tt> to enroll the key.</li>
 327
 328 <li>Back out of any directories you entered and return to the MokManager
 329     main menu.</li>
 330
 331 <li>Select <tt>Continue boot</tt> at the main menu.</li>
 332
 333 </ol>
 334
 335 <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>
 336
 337 <p>If you're using rEFInd to boot multiple Linux versions, chances are you'll need to add the keys for the distributions whose Shim you're not using as MOKs. rEFInd ships with a selection of such keys and copies them to the <tt>keys</tt> subdirectory of the rEFInd installation directory on the ESP as a convenience. Note that you must enroll keys with <tt>.cer</tt> or <tt>.der</tt> filename extensions. Although <tt>.crt</tt> files contain the same information, their format is different and they cannot be used by MokManager.</p>
 338
 339 <a name="mok">
 340 <h3>Managing Your MOKs</h3>
 341 </a>
 342
 343 <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, and many distributions ship with at least one of them. 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 successfully used <tt>refind-install</tt>'s <tt>--localkeys</tt> option):</p>
 344
 345 <ol>
 346
 347 <li>If it's not already installed, install OpenSSL on your computer. (It
 348     normally comes in a package called <tt>openssl</tt>.)</li>
 349
 350 <li>If you did <i>not</i> re-sign your rEFInd binaries with
 351     <tt>refind-install</tt>'s <tt>--localkeys</tt> option, type the
 352     following two commands to generate your public and private keys:
 353
 354 <pre class="listing">
 355 $ <tt class="userinput">openssl req -new -x509 -newkey rsa:2048 -keyout refind_local.key \
 356   -out refind_local.crt -nodes -days 3650 -subj "/CN=Your Name/"</tt>
 357 $ <tt class="userinput">openssl x509 -in refind_local.crt -out refind_local.cer -outform DER</tt>
 358 </pre>
 359
 360     Change <tt>Your Name</tt> to your own name or other identifying
 361     characteristics, and adjust the certificate's time span (set via
 362     <tt>-days</tt>) as you see fit. If you omit the <tt>-nodes</tt> option,
 363     the program will prompt you for a passphrase for added security.
 364     Remember this, since you'll need it to sign your binaries. The result
 365     is a private key file (<tt>refind_local.key</tt>), which is highly
 366     sensitive since it's required to sign binaries, and two public keys
 367     (<tt>refind_local.crt</tt> and <tt>refind_local.cer</tt>), which can be
 368     used to verify signed binaries' authenticity. The two public key files
 369     are equivalent, but are used by different
 370     tools&mdash;<tt>sbsigntool</tt> uses <tt>refind_local.crt</tt> to sign
 371     binaries, but MokManager uses <tt>refind_local.cer</tt> to enroll the
 372     key. If you used <tt>refind-install</tt>'s <tt>--localkeys</tt> option,
 373     this step is unnecessary, since these keys have already been created
 374     and are stored in <tt>/etc/refind.d/keys/</tt>.</li>
 375
 376 <li>Copy the three key files to a secure location and adjust permissions
 377     such that only you can read <tt>refind_local.key</tt>. You'll need
 378     these keys to sign future binaries, so don't discard them.</li>
 379
 380 <li>Copy the <tt>refind_local.cer</tt> file to your ESP, ideally to a
 381     location with few other files. (MokManager's user interface becomes
 382     unreliable when browsing directories with lots of files.)</li>
 383
 384 <li>Download and install the <tt>sbsigntool</tt> package. Binary links for
 385     various distributions are available from the <a
 386     href="https://build.opensuse.org/package/show?package=sbsigntools&project=home%3Ajejb1%3AUEFI">OpenSUSE
 387     Build Service</a>, or you can obtain the source code by typing <tt
 388     class="userinput">git clone
 389     git://kernel.ubuntu.com/jk/sbsigntool</tt>.</li>
 390
 391 <li>Sign your binary by typing <tt class="userinput">sbsign --key
 392     refind_local.key --cert refind_local.crt --output <tt
 393     class="variable">binary-signed.efi binary.efi</tt></tt>, adjusting the
 394     paths to the keys and the binary names.</li>
 395
 396 <li>Copy your signed binary to a suitable location on the ESP for rEFInd to
 397     locate it. Be sure to include any support files that it needs,
 398     too.</li>
 399
 400 <li>Check your <tt>refind.conf</tt> file to ensure that the
 401     <tt>showtools</tt> option is either commented out or includes
 402     <tt>mok_tool</tt> among its options.</li>
 403
 404 <li>Reboot. You can try launching the boot loader you just installed, but
 405     chances are it will generate an <tt>Access Denied</tt> message. For it
 406     to work, you must launch MokManager using the tool that rEFInd presents
 407     on its second row. You can then enroll your <tt>refind_local.cer</tt>
 408     key just as you enrolled the <tt>refind.cer</tt> key.</li>
 409
 410 </ol>
 411
 412 <p>At this point you should be able to launch the binaries you've signed. Unfortunately, there can still be problems; see the upcoming section, <a href="#caveats">Secure Boot Caveats,</a> for information on them. Alternatively, you can try using PreLoader rather than Shim.</p>
 413
 414 <a name="preloader">
 415 <h2>Using rEFInd with PreLoader</h2>
 416 </a>
 417
 418 <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: PreLoader 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>
 419
 420 <ol>
 421
 422 <li>Boot the computer. As with Shim, this can be a challenge; you may need
 423     to boot with Secure Boot disabled, use a Secure Boot&ndash;enabled live
 424     CD, or do the installation from Windows.</li>
 425
 426 <li><a href="getting.html">Download rEFInd</a> in binary form (the binary
 427     zip or CD-R image file). If you download the binary zip file, unzip it;
 428     if you get the CD-R image file, burn it to a CD-R and mount it.</li>
 429
 430 <li>Download PreLoader from <a
 431     href="http://blog.hansenpartnership.com/linux-foundation-secure-boot-system-released/">its
 432     release page</a> or by clicking the following links. Be sure to get
 433     both the <tt><a
 434     href="http://blog.hansenpartnership.com/wp-uploads/2013/PreLoader.efi">PreLoader.efi</a></tt>
 435     and <tt><a
 436     href="http://blog.hansenpartnership.com/wp-uploads/2013/HashTool.efi">HashTool.efi</a></tt>
 437     files.</li>
 438
 439 <li>Copy the <tt>PreLoader.efi</tt> and <tt>HashTool.efi</tt> binaries to
 440     the directory you intend to use for rEFInd&mdash;for instance,
 441     <tt>EFI/refind</tt> on the ESP.</li>
 442
 443 <li>Follow the installation instructions for rEFInd on the <a
 444     href="installing.html">Installing rEFInd</a> page; however, give rEFInd
 445     the filename <tt>loader.efi</tt> and register <tt>PreLoader.efi</tt>
 446     with the EFI by using <tt>efibootmgr</tt> in Linux or <tt>bcdedit</tt>
 447     in Windows. Be sure that rEFInd (as <tt>loader.efi</tt>),
 448     <tt>PreLoader.efi</tt>, and <tt>HashTool.efi</tt> all reside in the
 449     same directory.</li>
 450
 451 <li>Reboot. With any luck, you'll see HashTool appear with a warning
 452     message stating that it was unable to launch <tt>loader.efi</tt> and
 453     declaring that it will launch <tt>HashTool.efi</tt>. Press the Enter
 454     key to continue.</li>
 455
 456 <li>HashTool should now appear. It should give you three or four options,
 457     including <tt>Enroll Hash</tt>, as shown here. Select this option</li>
 458
 459     <br /><img src="HashTool1.png" align="CENTER" width="641" height="459"
 460     alt="HashTool provide a somewhat nicer user interface than
 461     MokManager's." border=2> <br />
 462
 463 <li>You can now select the binary you want to authorize. You should first
 464     select <tt>loader.efi</tt>, since that's rEFInd. The program presents
 465     the hash (a very long number) and asks for confirmation. Be sure to
 466     select <tt>Yes</tt>.</li>
 467
 468     <br /><img src="HashTool2.png" align="CENTER" width="638" height="455"
 469     alt="Be sure to select the right binary when you enroll its hash."
 470     border=2> <br />
 471
 472 <p class="sidebar"><b>Note:</b> Unfortunately, the initial version of HashTool's file selector can't change filesystems. Thus, if you want to boot a Linux kernel using rEFInd and PreLoader, 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. More recent versions of HashTool can access multiple partitions, but I have yet to find a pre-signed version, so if you want to use it, you'll need to compile it yourself and then register its hash with an earlier version (or with Secure Boot temporarily disabled).</p>
 473
 474 <li>Repeat the preceding two steps for any additional binaries you might
 475     want to enroll. These include any EFI filesystem drivers you're using,
 476     any boot loaders you're launching from rEFInd (other than those that
 477     are already signed, such as Microsoft's boot loader), and possibly your
 478     Linux kernel.</li>
 479
 480 <li>At the HashTool main menu, select <tt>Exit</tt>. rEFInd should
 481     launch.</li>
 482
 483 </ol>
 484
 485 <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>
 486
 487 <p>Although PreLoader is easier to set up than Shim, particularly if you need to launch programs or kernels that aren't already signed, it suffers from the problem that you must register every new program you install, including Linux kernels if you launch them directly from rEFInd. This need can be a hassle if you update your kernels frequently, and every new registration chews up a little space in your NVRAM. Nonetheless, PreLoader can be a good Secure Boot solution for many users or if you want to build a portable Linux installation that you can use on any computer with minimal fuss.</p>
 488
 489 <a name="caveats">
 490 <h2>Secure Boot Caveats</h2>
 491 </a>
 492
 493 <p>rEFInd's Secure Boot originated with version 0.5.0 of the program, and was revamped for version 0.6.2, both released in late 2012. It's worked well for myself and several others with whom I've corresponded; but you might still run into problems. Some issues you might encounter include the following:</p>
 494
 495 <ul>
 496
 497 <li>rEFInd uses the same EFI "hooks" as PreLoader. This method, however, is
 498     part of an optional EFI subsystem, so in theory some EFIs might not
 499     support it. For months, I knew of no such implementation, but <a
 500     href="http://superuser.com/questions/615142/uefi-failed-to-install-override-security-policy">this
 501     SuperUser question</a> indicates that at least one such implementation
 502     exists. Subsequent discussions on the site imply that the computer
 503     doesn't support Secure Boot at all. The bottom line: If you encounter
 504     the error message <tt>Failed to install override security policy,</tt>
 505     try removing PreLoader from your boot path.</li>
 506
 507 <li>Under certain circumstances, the time required to launch a boot loader
 508     can increase. This is unlikely to be noticeable for the average small
 509     boot loader, but could be significant for larger boot loaders on slow
 510     filesystems, such as Linux kernels on ext2fs, ext3fs, or ReiserFS
 511     partitions.</li>
 512
 513 <li>rEFInd's own Secure Boot support is theoretically able to work on
 514     non-<i>x</i>86-64 platforms; however, to the best of my knowledge, Shim
 515     and PreLoader both work only on <i>x</i>86-64, and rEFInd is dependent
 516     upon these tools. In principle, you should be able to <a
 517     href="http://www.rodsbooks.com/efi-bootloaders/secureboot.html#add_keys">replace
 518     your computer's standard Secure Boot keys</a> to use Secure Boot on
 519     these platforms with rEFInd, but this approach will require either
 520     built-in key-modification tools in the computer's setup utility or a
 521     build of <tt>LockDown.efi</tt> for your platform. I've not tested this
 522     approach on <i>x</i>86 or ARM, so I can't say whether it would actually
 523     work.</li>
 524
 525 <li>In theory, signing Microsoft's boot loader with a MOK should work. This
 526     might be handy if you want to replace your computer's built-in keys
 527     with your own but still boot Windows&mdash;but be aware that if Windows
 528     replaces its boot loader, it will then stop working.</li>
 529
 530 </ul>
 531
 532 <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 PreLoader and it should work, though, because of technical differences between how Shim and PreLoader work.)</p>
 533
 534 <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. This of course limits its utility.)</p>
 535
 536 <p>Some of the awkwardness of using rEFInd with Secure Boot is due to the need to manage MOKs (either keys with Shim or hashes with PreLoader). Such problems would evaporate if you could get a copy of rEFInd signed with your distribution's Secure Boot key. Thus, if you're annoyed by such problems, try filing a feature request with your distribution maintainer to have them include rEFInd (and sign it!) with their official package set.</p>
 537
 538 <hr />
 539
 540 <p>copyright &copy; 2012&ndash;2015 by Roderick W. Smith</p>
 541
 542 <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>
 543
 544 <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>
 545
 546 <p><a href="index.html">Go to the main rEFInd page</a></p>
 547
 548 <p><a href="revisions.html">Learn about rEFInd's history</a></p>
 549
 550
 551   <p><a href="http://www.rodsbooks.com/">Return</a> to my main Web page.</p>
 552 </body>
 553 </html>