[RFC PATCH v13 18/20] scripts: add boot policy generation program

Fan Wu
2024-02-29T00:55:25Z

From: Deven Bowers <deven.desai@linux.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@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>

---
v2:
+ No Changes

v3:
+ No Changes

v4:
+ No Changes

v5:
+ No Changes

v6:
+ No Changes

v7:
+ Move from 01/11 to 14/16
+ Don't return errno directly.
+ Make output of script more user-friendly
+ Add escaping for tab and '?'
+ Mark argv pointer const
+ Invert return code check in the boot policy parsing code path.

v8:
+ No significant changes.

v9:
+ No changes

v10:
+ Update the init part code for rcu changes in the eval loop patch

v11:
+ Fix code style issues

v12:
+ No changes

v13:
+ No changes
---
MAINTAINERS | 1 +
scripts/Makefile | 1 +
scripts/ipe/Makefile | 2 +
scripts/ipe/polgen/.gitignore | 2 +
scripts/ipe/polgen/Makefile | 5 ++
scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++
security/ipe/.gitignore | 2 +
security/ipe/Kconfig | 10 +++
security/ipe/Makefile | 11 +++
security/ipe/fs.c | 8 ++
security/ipe/ipe.c | 12 +++
11 files changed, 199 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 834601f158c9..b2db91a215c6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10654,6 +10654,7 @@ M: Fan Wu <wufan@linux.microsoft.com>
L: linux-security-module@vger.kernel.org
S: Supported
T: git https://github.com/microsoft/ipe.git
+F: scripts/ipe/
F: security/ipe/

INTEL 810/815 FRAMEBUFFER DRIVER
diff --git a/scripts/Makefile b/scripts/Makefile
index 576cf64be667..1dbaf3a49aef 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -50,6 +50,7 @@ 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..b6f05cf3dc0e
--- /dev/null
+++ b/scripts/ipe/polgen/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+polgen
diff --git a/scripts/ipe/polgen/Makefile b/scripts/ipe/polgen/Makefile
new file mode 100644
index 000000000000..c20456a2f2e9
--- /dev/null
+++ b/scripts/ipe/polgen/Makefile
@@ -0,0 +1,5 @@
+# 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..40b6fe07f47b
--- /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 <linux/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..07313d3fd74a
--- /dev/null
+++ b/security/ipe/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+boot-policy.c
diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig
index 9dd5c4769d79..a6c5d48dd0a3 100644
--- a/security/ipe/Kconfig
+++ b/security/ipe/Kconfig
@@ -18,6 +18,16 @@ menuconfig SECURITY_IPE
If unsure, answer N.

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.
+
menu "IPE Trust Providers"

config IPE_PROP_DM_VERITY
diff --git a/security/ipe/Makefile b/security/ipe/Makefile
index 66de53687d11..ce23101b66ba 100644
--- a/security/ipe/Makefile
+++ b/security/ipe/Makefile
@@ -5,7 +5,16 @@
# Makefile for building the IPE module as part of the kernel tree.
#

+quiet_cmd_polgen = IPE_POL $(2)
+ cmd_polgen = scripts/ipe/polgen/polgen security/ipe/boot-policy.c $(2)
+
+targets += boot-policy.c
+
+$(obj)/boot-policy.c: scripts/ipe/polgen/polgen $(CONFIG_IPE_BOOT_POLICY) FORCE
+ $(call if_changed,polgen,$(CONFIG_IPE_BOOT_POLICY))
+
obj-$(CONFIG_SECURITY_IPE) += \
+ boot-policy.o \
digest.o \
eval.o \
hooks.o \
@@ -15,3 +24,5 @@ obj-$(CONFIG_SECURITY_IPE) += \
policy_fs.o \
policy_parser.o \
audit.o \
+
+clean-files := boot-policy.c \
diff --git a/security/ipe/fs.c b/security/ipe/fs.c
index b16d87443a3b..8af6e39f9914 100644
--- a/security/ipe/fs.c
+++ b/security/ipe/fs.c
@@ -190,6 +190,7 @@ static const struct file_operations enforce_fops = {
static int __init ipe_init_securityfs(void)
{
int rc = 0;
+ struct ipe_policy *ap;

if (!ipe_enabled)
return -EOPNOTSUPP;
@@ -220,6 +221,13 @@ static int __init ipe_init_securityfs(void)
goto err;
}

+ ap = rcu_access_pointer(ipe_active_policy);
+ if (ap) {
+ rc = ipe_new_policyfs_node(ap);
+ if (rc)
+ goto err;
+ }
+
np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops);
if (IS_ERR(np)) {
rc = PTR_ERR(np);
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 598333d3ef14..c7dc6fe5002d 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -9,6 +9,7 @@
#include "hooks.h"
#include "eval.h"

+extern const char *const ipe_boot_policy;
bool ipe_enabled;

static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
@@ -73,9 +74,20 @@ static struct security_hook_list ipe_hooks[] __ro_after_init = {
*/
static int __init ipe_init(void)
{
+ struct ipe_policy *p = NULL;
+
security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), &ipe_lsmid);
ipe_enabled = true;

+ if (ipe_boot_policy) {
+ p = ipe_new_policy(ipe_boot_policy, strlen(ipe_boot_policy),
+ NULL, 0);
+ if (IS_ERR(p))
+ return PTR_ERR(p);
+
+ rcu_assign_pointer(ipe_active_policy, p);
+ }
+
return 0;
}

--
2.43.1