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150 lines
7.4 KiB
150 lines
7.4 KiB
8 months ago
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From 0e471978c582a614467d20d041f65c935c407abf Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Fri, 14 Oct 2022 15:54:09 +0200
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Subject: [PATCH] gpt-auto-generator: automatically measure root/var volume
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keys into PCR 15
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let's enable PCR 15 measurements automatically if gpt-auto discovery is
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used and systemd-stub is also used.
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(cherry picked from commit ff386f985bb51a48a11f74f6370dedf1bbfb4658)
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Related: RHEL-16182
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---
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man/systemd-gpt-auto-generator.xml | 8 +++++
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src/gpt-auto-generator/gpt-auto-generator.c | 36 ++++++++++++++++++---
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2 files changed, 39 insertions(+), 5 deletions(-)
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diff --git a/man/systemd-gpt-auto-generator.xml b/man/systemd-gpt-auto-generator.xml
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index 8ad249ec5d..f26bda511c 100644
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--- a/man/systemd-gpt-auto-generator.xml
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+++ b/man/systemd-gpt-auto-generator.xml
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@@ -221,6 +221,13 @@
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systems, make sure to set the correct default subvolumes on them,
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using <command>btrfs subvolume set-default</command>.</para>
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+ <para>If the system was booted via
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+ <citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> and the
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+ stub reported to userspace that the kernel image was measured to a TPM2 PCR, then any discovered root and
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+ <filename>/var/</filename> volume identifiers (and volume encryption key in case it is encrypted) will be
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+ automatically measured into PCR 15 on activation, via
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+ <citerefentry><refentrytitle>systemd-pcrfs@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
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+
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<para><filename>systemd-gpt-auto-generator</filename> implements
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
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</refsect1>
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@@ -272,6 +279,7 @@
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<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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+ <citerefentry><refentrytitle>systemd-pcrfs@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
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<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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diff --git a/src/gpt-auto-generator/gpt-auto-generator.c b/src/gpt-auto-generator/gpt-auto-generator.c
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index 0bab43e69a..2134185f04 100644
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--- a/src/gpt-auto-generator/gpt-auto-generator.c
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+++ b/src/gpt-auto-generator/gpt-auto-generator.c
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@@ -47,10 +47,11 @@ static int add_cryptsetup(
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const char *what,
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bool rw,
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bool require,
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+ bool measure,
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char **ret_device) {
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#if HAVE_LIBCRYPTSETUP
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- _cleanup_free_ char *e = NULL, *n = NULL, *d = NULL;
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+ _cleanup_free_ char *e = NULL, *n = NULL, *d = NULL, *options = NULL;
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_cleanup_fclose_ FILE *f = NULL;
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int r;
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@@ -84,7 +85,28 @@ static int add_cryptsetup(
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"After=%s\n",
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d, d);
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- r = generator_write_cryptsetup_service_section(f, id, what, NULL, rw ? NULL : "read-only");
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+ if (!rw) {
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+ options = strdup("read-only");
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+ if (!options)
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+ return log_oom();
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+ }
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+
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+ if (measure) {
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+ /* We only measure the root volume key into PCR 15 if we are booted with sd-stub (i.e. in a
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+ * UKI), and sd-stub measured the UKI. We do this in order not to step into people's own PCR
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+ * assignment, under the assumption that people who are fine to use sd-stub with its PCR
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+ * assignments are also OK with our PCR 15 use here. */
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+
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+ r = efi_get_variable(EFI_LOADER_VARIABLE(StubPcrKernelImage), NULL, NULL, NULL); /* we don't actually care which PCR the UKI used for itself */
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+ if (r == -ENOENT)
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+ log_debug_errno(r, "Will not measure volume key of volume '%s', because not booted via systemd-stub with measurements enabled.", id);
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+ else if (r < 0)
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+ log_debug_errno(r, "Failed to determine whether booted via systemd-stub with measurements enabled, ignoring: %m");
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+ else if (!strextend_with_separator(&options, ",", "tpm2-measure-pcr=yes"))
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+ return log_oom();
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+ }
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+
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+ r = generator_write_cryptsetup_service_section(f, id, what, NULL, options);
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if (r < 0)
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return r;
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@@ -139,6 +161,7 @@ static int add_mount(
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const char *fstype,
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bool rw,
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bool growfs,
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+ bool measure,
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const char *options,
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const char *description,
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const char *post) {
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@@ -159,7 +182,7 @@ static int add_mount(
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log_debug("Adding %s: %s fstype=%s", where, what, fstype ?: "(any)");
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if (streq_ptr(fstype, "crypto_LUKS")) {
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- r = add_cryptsetup(id, what, rw, true, &crypto_what);
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+ r = add_cryptsetup(id, what, rw, /* require= */ true, measure, &crypto_what);
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if (r < 0)
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return r;
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@@ -277,6 +300,7 @@ static int add_partition_mount(
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p->fstype,
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p->rw,
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p->growfs,
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+ /* measure= */ STR_IN_SET(id, "root", "var"), /* by default measure rootfs and /var, since they contain the "identity" of the system */
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NULL,
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description,
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SPECIAL_LOCAL_FS_TARGET);
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@@ -301,7 +325,7 @@ static int add_partition_swap(DissectedPartition *p) {
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}
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if (streq_ptr(p->fstype, "crypto_LUKS")) {
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- r = add_cryptsetup("swap", p->node, true, true, &crypto_what);
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+ r = add_cryptsetup("swap", p->node, /* rw= */ true, /* require= */ true, /* measure= */ false, &crypto_what);
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if (r < 0)
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return r;
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what = crypto_what;
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@@ -374,6 +398,7 @@ static int add_automount(
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fstype,
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rw,
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growfs,
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+ /* measure= */ false,
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opt,
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description,
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NULL);
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@@ -582,7 +607,7 @@ static int add_root_cryptsetup(void) {
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/* If a device /dev/gpt-auto-root-luks appears, then make it pull in systemd-cryptsetup-root.service, which
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* sets it up, and causes /dev/gpt-auto-root to appear which is all we are looking for. */
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- return add_cryptsetup("root", "/dev/gpt-auto-root-luks", true, false, NULL);
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+ return add_cryptsetup("root", "/dev/gpt-auto-root-luks", /* rw= */ true, /* require= */ false, /* measure= */ true, NULL);
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#else
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return 0;
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#endif
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@@ -629,6 +654,7 @@ static int add_root_mount(void) {
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NULL,
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/* rw= */ arg_root_rw > 0,
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/* growfs= */ false,
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+ /* measure= */ true,
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NULL,
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"Root Partition",
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in_initrd() ? SPECIAL_INITRD_ROOT_FS_TARGET : SPECIAL_LOCAL_FS_TARGET);
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