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Message-Id: <1634151995-16266-15-git-send-email-deven.desai@linux.microsoft.com>
Date: Wed, 13 Oct 2021 12:06:33 -0700
From: deven.desai@...ux.microsoft.com
To: corbet@....net, axboe@...nel.dk, agk@...hat.com,
snitzer@...hat.com, ebiggers@...nel.org, tytso@....edu,
paul@...l-moore.com, eparis@...hat.com, jmorris@...ei.org,
serge@...lyn.com
Cc: jannh@...gle.com, dm-devel@...hat.com, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-block@...r.kernel.org,
linux-fscrypt@...r.kernel.org, linux-audit@...hat.com,
linux-security-module@...r.kernel.org
Subject: [RFC PATCH v7 14/16] scripts: add boot policy generation program
From: Deven Bowers <deven.desai@...ux.microsoft.com>
Enables an IPE policy to be enforced from kernel start, enabling access
control based on trust from kernel startup. This is accomplished by
transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a
c-string literal that is parsed at kernel startup as an unsigned policy.
Signed-off-by: Deven Bowers <deven.desai@...ux.microsoft.com>
---
Relevant changes since v6:
* Move patch 01/12 to [14/16] of the series
---
MAINTAINERS | 1 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 1 +
scripts/ipe/polgen/Makefile | 6 ++
scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
security/ipe/.gitignore | 1 +
security/ipe/Kconfig | 10 +++
security/ipe/Makefile | 13 +++
security/ipe/ctx.c | 18 +++++
10 files changed, 198 insertions(+)
create mode 100644 scripts/ipe/Makefile
create mode 100644 scripts/ipe/polgen/.gitignore
create mode 100644 scripts/ipe/polgen/Makefile
create mode 100644 scripts/ipe/polgen/polgen.c
create mode 100644 security/ipe/.gitignore
diff --git a/MAINTAINERS b/MAINTAINERS
index f1e76f791d47..a84ca781199b 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9283,6 +9283,7 @@ INTEGRITY POLICY ENFORCEMENT (IPE)
M: Deven Bowers <deven.desai@...ux.microsoft.com>
M: Fan Wu <wufan@...ux.microsoft.com>
S: Supported
+F: scripts/ipe/
F: security/ipe/
INTEL 810/815 FRAMEBUFFER DRIVER
diff --git a/scripts/Makefile b/scripts/Makefile
index 9adb6d247818..a31da6d57a36 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -41,6 +41,7 @@ targets += module.lds
subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
subdir-$(CONFIG_MODVERSIONS) += genksyms
subdir-$(CONFIG_SECURITY_SELINUX) += selinux
+subdir-$(CONFIG_SECURITY_IPE) += ipe
# Let clean descend into subdirs
subdir- += basic dtc gdb kconfig mod
diff --git a/scripts/ipe/Makefile b/scripts/ipe/Makefile
new file mode 100644
index 000000000000..e87553fbb8d6
--- /dev/null
+++ b/scripts/ipe/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+subdir-y := polgen
diff --git a/scripts/ipe/polgen/.gitignore b/scripts/ipe/polgen/.gitignore
new file mode 100644
index 000000000000..80f32f25d200
--- /dev/null
+++ b/scripts/ipe/polgen/.gitignore
@@ -0,0 +1 @@
+polgen
diff --git a/scripts/ipe/polgen/Makefile b/scripts/ipe/polgen/Makefile
new file mode 100644
index 000000000000..066060c22b4a
--- /dev/null
+++ b/scripts/ipe/polgen/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+hostprogs-always-y := polgen
+HOST_EXTRACFLAGS += \
+ -I$(srctree)/include \
+ -I$(srctree)/include/uapi \
+
diff --git a/scripts/ipe/polgen/polgen.c b/scripts/ipe/polgen/polgen.c
new file mode 100644
index 000000000000..73cf13e743f7
--- /dev/null
+++ b/scripts/ipe/polgen/polgen.c
@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation. All rights reserved.
+ */
+
+#include <stdlib.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <errno.h>
+
+static void usage(const char *const name)
+{
+ printf("Usage: %s OutputFile (PolicyFile)\n", name);
+ exit(EINVAL);
+}
+
+static int policy_to_buffer(const char *pathname, char **buffer, size_t *size)
+{
+ int rc = 0;
+ FILE *fd;
+ char *lbuf;
+ size_t fsize;
+ size_t read;
+
+ fd = fopen(pathname, "r");
+ if (!fd) {
+ rc = errno;
+ goto out;
+ }
+
+ fseek(fd, 0, SEEK_END);
+ fsize = ftell(fd);
+ rewind(fd);
+
+ lbuf = malloc(fsize);
+ if (!lbuf) {
+ rc = ENOMEM;
+ goto out_close;
+ }
+
+ read = fread((void *)lbuf, sizeof(*lbuf), fsize, fd);
+ if (read != fsize) {
+ rc = -1;
+ goto out_free;
+ }
+
+ *buffer = lbuf;
+ *size = fsize;
+ fclose(fd);
+
+ return rc;
+
+out_free:
+ free(lbuf);
+out_close:
+ fclose(fd);
+out:
+ return rc;
+}
+
+static int write_boot_policy(const char *pathname, const char *buf, size_t size)
+{
+ int rc = 0;
+ FILE *fd;
+ size_t i;
+
+ fd = fopen(pathname, "w");
+ if (!fd) {
+ rc = errno;
+ goto err;
+ }
+
+ fprintf(fd, "/* This file is automatically generated.");
+ fprintf(fd, " Do not edit. */\n");
+ fprintf(fd, "#include <stddef.h>\n");
+ fprintf(fd, "\nextern const char *const ipe_boot_policy;\n\n");
+ fprintf(fd, "const char *const ipe_boot_policy =\n");
+
+ if (!buf || size == 0) {
+ fprintf(fd, "\tNULL;\n");
+ fclose(fd);
+ return 0;
+ }
+
+ fprintf(fd, "\t\"");
+
+ for (i = 0; i < size; ++i) {
+ switch (buf[i]) {
+ case '"':
+ fprintf(fd, "\\\"");
+ break;
+ case '\'':
+ fprintf(fd, "'");
+ break;
+ case '\n':
+ fprintf(fd, "\\n\"\n\t\"");
+ break;
+ case '\\':
+ fprintf(fd, "\\\\");
+ break;
+ case '\t':
+ fprintf(fd, "\\t");
+ break;
+ case '\?':
+ fprintf(fd, "\\?");
+ break;
+ default:
+ fprintf(fd, "%c", buf[i]);
+ }
+ }
+ fprintf(fd, "\";\n");
+ fclose(fd);
+
+ return 0;
+
+err:
+ if (fd)
+ fclose(fd);
+ return rc;
+}
+
+int main(int argc, const char *const argv[])
+{
+ int rc = 0;
+ size_t len = 0;
+ char *policy = NULL;
+
+ if (argc < 2)
+ usage(argv[0]);
+
+ if (argc > 2) {
+ rc = policy_to_buffer(argv[2], &policy, &len);
+ if (rc != 0)
+ goto cleanup;
+ }
+
+ rc = write_boot_policy(argv[1], policy, len);
+cleanup:
+ if (policy)
+ free(policy);
+ if (rc != 0)
+ perror("An error occurred during policy conversion: ");
+ return rc;
+}
diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore
new file mode 100644
index 000000000000..eca22ad5ed22
--- /dev/null
+++ b/security/ipe/.gitignore
@@ -0,0 +1 @@
+boot-policy.c
\ No newline at end of file
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index fcf82a8152ec..39df680b67a2 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -20,6 +20,16 @@ menuconfig SECURITY_IPE
if SECURITY_IPE
+config IPE_BOOT_POLICY
+ string "Integrity policy to apply on system startup"
+ help
+ This option specifies a filepath to a IPE policy that is compiled
+ into the kernel. This policy will be enforced until a policy update
+ is deployed via the $securityfs/ipe/policies/$policy_name/active
+ interface.
+
+ If unsure, leave blank.
+
choice
prompt "Hash algorithm used in auditing policies"
default IPE_AUDIT_HASH_SHA1
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 1e7b2d7fcd9e..89fec670f954 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -7,7 +7,18 @@
ccflags-y := -I$(srctree)/security/ipe/modules
+quiet_cmd_polgen = IPE_POL $(2)
+ cmd_polgen = scripts/ipe/polgen/polgen security/ipe/boot-policy.c $(2)
+
+$(eval $(call config_filename,IPE_BOOT_POLICY))
+
+targets += boot-policy.c
+
+$(obj)/boot-policy.c: scripts/ipe/polgen/polgen $(IPE_BOOT_POLICY_FILENAME) FORCE
+ $(call if_changed,polgen,$(IPE_BOOT_POLICY_FILENAME))
+
obj-$(CONFIG_SECURITY_IPE) += \
+ boot-policy.o \
ctx.o \
eval.o \
fs.o \
@@ -21,3 +32,5 @@ obj-$(CONFIG_SECURITY_IPE) += \
policyfs.o \
obj-$(CONFIG_AUDIT) += audit.o
+
+clean-files := boot-policy.c \
diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c
index fc9b8e467bc9..879acf4ceac5 100644
--- a/security/ipe/ctx.c
+++ b/security/ipe/ctx.c
@@ -15,6 +15,7 @@
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
+extern const char *const ipe_boot_policy;
static bool success_audit;
static bool enforce = true;
@@ -329,6 +330,7 @@ void ipe_put_ctx(struct ipe_context *ctx)
int __init ipe_init_ctx(void)
{
int rc = 0;
+ struct ipe_policy *p = NULL;
struct ipe_context *lns = NULL;
lns = create_ctx();
@@ -342,10 +344,26 @@ int __init ipe_init_ctx(void)
WRITE_ONCE(lns->enforce, enforce);
spin_unlock(&lns->lock);
+ if (ipe_boot_policy) {
+ p = ipe_new_policy(ipe_boot_policy, strlen(ipe_boot_policy),
+ NULL, 0);
+ if (IS_ERR(p)) {
+ rc = PTR_ERR(lns);
+ goto err;
+ }
+
+ ipe_add_policy(lns, p);
+ rc = ipe_set_active_pol(p);
+ if (!rc)
+ goto err;
+ }
+
rcu_assign_pointer(*ipe_tsk_ctx(current), lns);
+ ipe_put_policy(p);
return 0;
err:
+ ipe_put_policy(p);
ipe_put_ctx(lns);
return rc;
}
--
2.33.0
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