[PATCH v8 0/8] powerpc: Enabling IMA arch specific secure boot policies

[PATCH v8 0/8] powerpc: Enabling IMA arch specific secure boot policies

[Nayna Jain]

This patchset extends the previous version[1] by adding support for
checking against a blacklist of binary hashes.

The IMA subsystem supports custom, built-in, arch-specific policies to
define the files to be measured and appraised. These policies are honored
based on priority, where arch-specific policy is the highest and custom
is the lowest.

PowerNV system uses a Linux-based bootloader to kexec the OS. The
bootloader kernel relies on IMA for signature verification of the OS
kernel before doing the kexec. This patchset adds support for powerpc
arch-specific IMA policies that are conditionally defined based on a
system's secure boot and trusted boot states. The OS secure boot and
trusted boot states are determined via device-tree properties.

The verification needs to be performed only for binaries that are not
blacklisted. The kernel currently only checks against the blacklist of
keys. However, doing so results in blacklisting all the binaries that
are signed by the same key. In order to prevent just one particular
binary from being loaded, it must be checked against a blacklist of
binary hashes. This patchset also adds support to IMA for checking
against a hash blacklist for files. signed by appended signature.

[1] http://patchwork.ozlabs.org/cover/1149262/ 

Changelog:
v8:
* Updates the Patch Description as per Michael's and Mimi's feedback
* Includes feedbacks from Michael for the device tree and policies
  * removes the arch-policy hack by defining three arrays.
  * fixes related to device-tree calls 
  * other code specific feedbacks
* Includes feedbacks from Mimi on the blacklist
  * generic blacklist function is modified than previous version
  * other coding fixes

v7:
* Removes patch related to dt-bindings as per input from Rob Herring. 
* fixes Patch 1/8 to use new device-tree updates as per Oliver
  feedback to device-tree documentation in skiboot mailing list.
(https://lists.ozlabs.org/pipermail/skiboot/2019-September/015329.html)
* Includes feedbacks from Mimi, Thiago
  * moves function get_powerpc_fw_sb_node() from Patch 1 to Patch 3 
  * fixes Patch 2/8 to use CONFIG_MODULE_SIG_FORCE.
  * updates Patch description in Patch 5/8
  * adds a new patch to add wrapper is_binary_blacklisted()
  * removes the patch that deprecated permit_directio

v6:
* includes feedbacks from Michael Ellerman on the patchset v5
  * removed email ids from comments
  * add the doc for the device-tree
  * renames the secboot.c to secure_boot.c and secboot.h to secure_boot.h
  * other code specific fixes
* split the patches to differentiate between secureboot and trustedboot
state of the system
* adds the patches to support the blacklisting of the binary hash.

v5:
* secureboot state is now read via device tree entry rather than OPAL
secure variables
* ima arch policies are updated to use policy based template for
measurement rules

v4:
* Fixed the build issue as reported by Satheesh Rajendran.

v3:
* OPAL APIs in Patch 1 are updated to provide generic interface based on
key/keylen. This patchset updates kernel OPAL APIs to be compatible with
generic interface.
* Patch 2 is cleaned up to use new OPAL APIs.
* Since OPAL can support different types of backend which can vary in the
variable interpretation, the Patch 2 is updated to add a check for the
backend version
* OPAL API now expects consumer to first check the supported backend version
before calling other secvar OPAL APIs. This check is now added in patch 2.
* IMA policies in Patch 3 is updated to specify appended signature and
per policy template.
* The patches now are free of any EFIisms.

v2:

* Removed Patch 1: powerpc/include: Override unneeded early ioremap
functions
* Updated Subject line and patch description of the Patch 1 of this series
* Removed dependency of OPAL_SECVAR on EFI, CPU_BIG_ENDIAN and UCS2_STRING
* Changed OPAL APIs from static to non-static. Added opal-secvar.h for the
same
* Removed EFI hooks from opal_secvar.c
* Removed opal_secvar_get_next(), opal_secvar_enqueue() and
opal_query_variable_info() function
* get_powerpc_sb_mode() in secboot.c now directly calls OPAL Runtime API
rather than via EFI hooks.
* Fixed log messages in get_powerpc_sb_mode() function.
* Added dependency for PPC_SECURE_BOOT on configs PPC64 and OPAL_SECVAR
* Replaced obj-$(CONFIG_IMA) with obj-$(CONFIG_PPC_SECURE_BOOT) in
arch/powerpc/kernel/Makefile

Nayna Jain (8):
  powerpc: detect the secure boot mode of the system
  powerpc/ima: add support to initialize ima policy rules
  powerpc: detect the trusted boot state of the system
  powerpc/ima: add measurement rules to ima arch specific policy
  ima: make process_buffer_measurement() generic
  certs: add wrapper function to check blacklisted binary hash
  ima: check against blacklisted hashes for files with modsig
  powerpc/ima: update ima arch policy to check for blacklist

 Documentation/ABI/testing/ima_policy   |  1 +
 arch/powerpc/Kconfig                   | 11 ++++
 arch/powerpc/include/asm/secure_boot.h | 29 +++++++++++
 arch/powerpc/kernel/Makefile           |  2 +
 arch/powerpc/kernel/ima_arch.c         | 71 ++++++++++++++++++++++++++
 arch/powerpc/kernel/secure_boot.c      | 54 ++++++++++++++++++++
 certs/blacklist.c                      |  9 ++++
 include/keys/system_keyring.h          |  6 +++
 include/linux/ima.h                    |  3 +-
 security/integrity/ima/ima.h           | 11 ++++
 security/integrity/ima/ima_appraise.c  | 31 +++++++++++
 security/integrity/ima/ima_main.c      | 63 +++++++++++++++--------
 security/integrity/ima/ima_policy.c    | 10 +++-
 security/integrity/integrity.h         |  1 +
 14 files changed, 277 insertions(+), 25 deletions(-)
 create mode 100644 arch/powerpc/include/asm/secure_boot.h
 create mode 100644 arch/powerpc/kernel/ima_arch.c
 create mode 100644 arch/powerpc/kernel/secure_boot.c

-- 
2.20.1

[PATCH v8 1/8] powerpc: detect the secure boot mode of the system

[Nayna Jain]

This patch defines a function to detect the secure boot state of a
PowerNV system.

The PPC_SECURE_BOOT config represents the base enablement of secure boot
for powerpc.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 arch/powerpc/Kconfig                   | 10 +++++++++
 arch/powerpc/include/asm/secure_boot.h | 23 ++++++++++++++++++++
 arch/powerpc/kernel/Makefile           |  2 ++
 arch/powerpc/kernel/secure_boot.c      | 30 ++++++++++++++++++++++++++
 4 files changed, 65 insertions(+)
 create mode 100644 arch/powerpc/include/asm/secure_boot.h
 create mode 100644 arch/powerpc/kernel/secure_boot.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 3e56c9c2f16e..56ea0019b616 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -934,6 +934,16 @@ config PPC_MEM_KEYS
 
 	  If unsure, say y.
 
+config PPC_SECURE_BOOT
+	prompt "Enable secure boot support"
+	bool
+	depends on PPC_POWERNV
+	help
+	  Systems with firmware secure boot enabled need to define security
+	  policies to extend secure boot to the OS. This config allows a user
+	  to enable OS secure boot on systems that have firmware support for
+	  it. If in doubt say N.
+
 endmenu
 
 config ISA_DMA_API
diff --git a/arch/powerpc/include/asm/secure_boot.h b/arch/powerpc/include/asm/secure_boot.h
new file mode 100644
index 000000000000..07d0fe0ca81f
--- /dev/null
+++ b/arch/powerpc/include/asm/secure_boot.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Secure boot definitions
+ *
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+#ifndef _ASM_POWER_SECURE_BOOT_H
+#define _ASM_POWER_SECURE_BOOT_H
+
+#ifdef CONFIG_PPC_SECURE_BOOT
+
+bool is_ppc_secureboot_enabled(void);
+
+#else
+
+static inline bool is_ppc_secureboot_enabled(void)
+{
+	return false;
+}
+
+#endif
+#endif
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index a7ca8fe62368..e2a54fa240ac 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -161,6 +161,8 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
 obj-y				+= ucall.o
 endif
 
+obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o
+
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
 KCOV_INSTRUMENT_prom_init.o := n
diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
new file mode 100644
index 000000000000..99bba7915629
--- /dev/null
+++ b/arch/powerpc/kernel/secure_boot.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+#include <linux/types.h>
+#include <linux/of.h>
+#include <asm/secure_boot.h>
+
+bool is_ppc_secureboot_enabled(void)
+{
+	struct device_node *node;
+	bool enabled = false;
+
+	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-v1");
+	if (!of_device_is_available(node)) {
+		pr_err("Cannot find secure variable node in device tree; failing to secure state\n");
+		goto out;
+	}
+
+	/*
+	 * secureboot is enabled if os-secure-enforcing property exists,
+	 * else disabled.
+	 */
+	enabled = of_property_read_bool(node, "os-secure-enforcing");
+
+out:
+	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
+	return enabled;
+}
-- 
2.20.1

[PATCH v8 2/8] powerpc/ima: add support to initialize ima policy rules

[Nayna Jain]

PowerNV system use a Linux-based bootloader, which relies on the IMA
subsystem to enforce different secure boot modes. Since the verification
policy may differ based on the secure boot mode of the system, the
policies must be defined at runtime.

This patch implements arch-specific support to define IMA policy
rules based on the runtime secure boot mode of the system.

This patch provides arch-specific IMA policies if PPC_SECURE_BOOT
config is enabled.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 arch/powerpc/Kconfig           |  1 +
 arch/powerpc/kernel/Makefile   |  2 +-
 arch/powerpc/kernel/ima_arch.c | 39 ++++++++++++++++++++++++++++++++++
 include/linux/ima.h            |  3 ++-
 4 files changed, 43 insertions(+), 2 deletions(-)
 create mode 100644 arch/powerpc/kernel/ima_arch.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 56ea0019b616..c795039bdc73 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -938,6 +938,7 @@ config PPC_SECURE_BOOT
 	prompt "Enable secure boot support"
 	bool
 	depends on PPC_POWERNV
+	depends on IMA_ARCH_POLICY
 	help
 	  Systems with firmware secure boot enabled need to define security
 	  policies to extend secure boot to the OS. This config allows a user
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index e2a54fa240ac..e8eb2955b7d5 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -161,7 +161,7 @@ ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
 obj-y				+= ucall.o
 endif
 
-obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o
+obj-$(CONFIG_PPC_SECURE_BOOT)	+= secure_boot.o ima_arch.o
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
new file mode 100644
index 000000000000..65d82ee74ea4
--- /dev/null
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+
+#include <linux/ima.h>
+#include <asm/secure_boot.h>
+
+bool arch_ima_get_secureboot(void)
+{
+	return is_ppc_secureboot_enabled();
+}
+
+/*
+ * The "secure_rules" are enabled only on "secureboot" enabled systems.
+ * These rules verify the file signatures against known good values.
+ * The "appraise_type=imasig|modsig" option allows the known good signature
+ * to be stored as an xattr or as an appended signature.
+ */
+static const char *const secure_rules[] = {
+	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+#ifndef CONFIG_MODULE_SIG_FORCE
+	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+#endif
+	NULL
+};
+
+/*
+ * Returns the relevant IMA arch-specific policies based on the system secure
+ * boot state.
+ */
+const char *const *arch_get_ima_policy(void)
+{
+	if (is_ppc_secureboot_enabled())
+		return secure_rules;
+
+	return NULL;
+}
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 1c37f17f7203..6d904754d858 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -29,7 +29,8 @@ extern void ima_kexec_cmdline(const void *buf, int size);
 extern void ima_add_kexec_buffer(struct kimage *image);
 #endif
 
-#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390)
+#if (defined(CONFIG_X86) && defined(CONFIG_EFI)) || defined(CONFIG_S390) \
+	|| defined(CONFIG_PPC_SECURE_BOOT)
 extern bool arch_ima_get_secureboot(void);
 extern const char * const *arch_get_ima_policy(void);
 #else
-- 
2.20.1

[PATCH v8 3/8] powerpc: detect the trusted boot state of the system

[Nayna Jain]

While secure boot permits only properly verified signed kernels to be
booted, trusted boot takes a measurement of the kernel image prior to
boot that can be subsequently compared against good known values via
attestation services.

This patch reads the trusted boot state of a PowerNV system. The state
is used to conditionally enable additional measurement rules in the IMA
arch-specific policies.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 arch/powerpc/include/asm/secure_boot.h |  6 ++++++
 arch/powerpc/kernel/secure_boot.c      | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/powerpc/include/asm/secure_boot.h b/arch/powerpc/include/asm/secure_boot.h
index 07d0fe0ca81f..a2ff556916c6 100644
--- a/arch/powerpc/include/asm/secure_boot.h
+++ b/arch/powerpc/include/asm/secure_boot.h
@@ -11,6 +11,7 @@
 #ifdef CONFIG_PPC_SECURE_BOOT
 
 bool is_ppc_secureboot_enabled(void);
+bool is_ppc_trustedboot_enabled(void);
 
 #else
 
@@ -19,5 +20,10 @@ static inline bool is_ppc_secureboot_enabled(void)
 	return false;
 }
 
+static inline bool is_ppc_trustedboot_enabled(void)
+{
+	return false;
+}
+
 #endif
 #endif
diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
index 99bba7915629..9753470ab08a 100644
--- a/arch/powerpc/kernel/secure_boot.c
+++ b/arch/powerpc/kernel/secure_boot.c
@@ -7,6 +7,17 @@
 #include <linux/of.h>
 #include <asm/secure_boot.h>
 
+static struct device_node *get_ppc_fw_sb_node(void)
+{
+	static const struct of_device_id ids[] = {
+		{ .compatible = "ibm,secureboot-v1", },
+		{ .compatible = "ibm,secureboot-v2", },
+		{},
+	};
+
+	return of_find_matching_node(NULL, ids);
+}
+
 bool is_ppc_secureboot_enabled(void)
 {
 	struct device_node *node;
@@ -28,3 +39,16 @@ bool is_ppc_secureboot_enabled(void)
 	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
 	return enabled;
 }
+
+bool is_ppc_trustedboot_enabled(void)
+{
+	struct device_node *node;
+	bool enabled = false;
+
+	node = get_ppc_fw_sb_node();
+	enabled = of_property_read_bool(node, "trusted-enabled");
+
+	pr_info("Trusted boot mode %s\n", enabled ? "enabled" : "disabled");
+
+	return enabled;
+}
-- 
2.20.1

[PATCH v8 4/8] powerpc/ima: add measurement rules to ima arch specific policy

[Nayna Jain]

This patch adds the measurement rules to the arch specific policies on
trusted boot enabled systems.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 arch/powerpc/kernel/ima_arch.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
index 65d82ee74ea4..710872ea8f35 100644
--- a/arch/powerpc/kernel/ima_arch.c
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -26,6 +26,32 @@ static const char *const secure_rules[] = {
 	NULL
 };
 
+/*
+ * The "measure_rules" are enabled only on "trustedboot" enabled systems.
+ * These rules add the kexec kernel image and kernel modules file hashes to
+ * the IMA measurement list.
+ */
+static const char *const trusted_rules[] = {
+	"measure func=KEXEC_KERNEL_CHECK",
+	"measure func=MODULE_CHECK",
+	NULL
+};
+
+/*
+ * The "secure_and_trusted_rules" contains rules for both the secure boot and
+ * trusted boot. The "template=ima-modsig" option includes the appended
+ * signature, when available, in the IMA measurement list.
+ */
+static const char *const secure_and_trusted_rules[] = {
+	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
+	"measure func=MODULE_CHECK template=ima-modsig",
+	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+#ifndef CONFIG_MODULE_SIG_FORCE
+	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+#endif
+	NULL
+};
+
 /*
  * Returns the relevant IMA arch-specific policies based on the system secure
  * boot state.
@@ -33,7 +59,13 @@ static const char *const secure_rules[] = {
 const char *const *arch_get_ima_policy(void)
 {
 	if (is_ppc_secureboot_enabled())
-		return secure_rules;
+		if (is_ppc_trustedboot_enabled())
+			return secure_and_trusted_rules;
+		else
+			return secure_rules;
+	else
+		if (is_ppc_trustedboot_enabled())
+			return trusted_rules;
 
 	return NULL;
 }
-- 
2.20.1

[PATCH v8 5/8] ima: make process_buffer_measurement() generic

[Nayna Jain]

process_buffer_measurement() is limited to measuring the kexec boot
command line. This patch makes process_buffer_measurement() more
generic, allowing it to measure other types of buffer data (e.g.
blacklisted binary hashes or key hashes).

This patch modifies the function to conditionally retrieve the policy
defined pcr and template based on the func.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 security/integrity/ima/ima.h      |  3 ++
 security/integrity/ima/ima_main.c | 51 ++++++++++++++++++++-----------
 2 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 3689081aaf38..a65772ffa427 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -217,6 +217,9 @@ void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
 			   struct evm_ima_xattr_data *xattr_value,
 			   int xattr_len, const struct modsig *modsig, int pcr,
 			   struct ima_template_desc *template_desc);
+void process_buffer_measurement(const void *buf, int size,
+				const char *eventname, enum ima_hooks func,
+				int pcr);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
 			   const unsigned char *filename);
 int ima_alloc_init_template(struct ima_event_data *event_data,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 60027c643ecd..fe0b704ffdeb 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -626,14 +626,14 @@ int ima_load_data(enum kernel_load_data_id id)
  * @buf: pointer to the buffer that needs to be added to the log.
  * @size: size of buffer(in bytes).
  * @eventname: event name to be used for the buffer entry.
- * @cred: a pointer to a credentials structure for user validation.
- * @secid: the secid of the task to be validated.
+ * @func: IMA hook
+ * @pcr: pcr to extend the measurement
  *
  * Based on policy, the buffer is measured into the ima log.
  */
-static void process_buffer_measurement(const void *buf, int size,
-				       const char *eventname,
-				       const struct cred *cred, u32 secid)
+void process_buffer_measurement(const void *buf, int size,
+				const char *eventname, enum ima_hooks func,
+				int pcr)
 {
 	int ret = 0;
 	struct ima_template_entry *entry = NULL;
@@ -642,19 +642,38 @@ static void process_buffer_measurement(const void *buf, int size,
 					    .filename = eventname,
 					    .buf = buf,
 					    .buf_len = size};
-	struct ima_template_desc *template_desc = NULL;
+	struct ima_template_desc *template = NULL;
 	struct {
 		struct ima_digest_data hdr;
 		char digest[IMA_MAX_DIGEST_SIZE];
 	} hash = {};
 	int violation = 0;
-	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 	int action = 0;
+	u32 secid;
 
-	action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
-				&template_desc);
-	if (!(action & IMA_MEASURE))
-		return;
+	if (func) {
+		security_task_getsecid(current, &secid);
+		action = ima_get_action(NULL, current_cred(), secid, 0, func,
+					&pcr, &template);
+		if (!(action & IMA_MEASURE))
+			return;
+	}
+
+	if (!pcr)
+		pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+
+	if (!template) {
+		template = lookup_template_desc("ima-buf");
+		ret = template_desc_init_fields(template->fmt,
+						&(template->fields),
+						&(template->num_fields));
+		if (ret < 0) {
+			pr_err("template %s init failed, result: %d\n",
+			       (strlen(template->name) ?
+				template->name : template->fmt), ret);
+			return;
+		}
+	}
 
 	iint.ima_hash = &hash.hdr;
 	iint.ima_hash->algo = ima_hash_algo;
@@ -664,7 +683,7 @@ static void process_buffer_measurement(const void *buf, int size,
 	if (ret < 0)
 		goto out;
 
-	ret = ima_alloc_init_template(&event_data, &entry, template_desc);
+	ret = ima_alloc_init_template(&event_data, &entry, template);
 	if (ret < 0)
 		goto out;
 
@@ -686,13 +705,9 @@ static void process_buffer_measurement(const void *buf, int size,
  */
 void ima_kexec_cmdline(const void *buf, int size)
 {
-	u32 secid;
-
-	if (buf && size != 0) {
-		security_task_getsecid(current, &secid);
+	if (buf && size != 0)
 		process_buffer_measurement(buf, size, "kexec-cmdline",
-					   current_cred(), secid);
-	}
+					   KEXEC_CMDLINE, 0);
 }
 
 static int __init init_ima(void)
-- 
2.20.1

[PATCH v8 6/8] certs: add wrapper function to check blacklisted binary hash

[Nayna Jain]

The -EKEYREJECTED error returned by existing is_hash_blacklisted() is
misleading when called for checking against blacklisted hash of a
binary.

This patch adds a wrapper function is_binary_blacklisted() to return
-EPERM error if binary is blacklisted.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 certs/blacklist.c             | 9 +++++++++
 include/keys/system_keyring.h | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/certs/blacklist.c b/certs/blacklist.c
index ec00bf337eb6..6514f9ebc943 100644
--- a/certs/blacklist.c
+++ b/certs/blacklist.c
@@ -135,6 +135,15 @@ int is_hash_blacklisted(const u8 *hash, size_t hash_len, const char *type)
 }
 EXPORT_SYMBOL_GPL(is_hash_blacklisted);
 
+int is_binary_blacklisted(const u8 *hash, size_t hash_len)
+{
+	if (is_hash_blacklisted(hash, hash_len, "bin") == -EKEYREJECTED)
+		return -EPERM;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(is_binary_blacklisted);
+
 /*
  * Initialise the blacklist
  */
diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
index c1a96fdf598b..fb8b07daa9d1 100644
--- a/include/keys/system_keyring.h
+++ b/include/keys/system_keyring.h
@@ -35,12 +35,18 @@ extern int restrict_link_by_builtin_and_secondary_trusted(
 extern int mark_hash_blacklisted(const char *hash);
 extern int is_hash_blacklisted(const u8 *hash, size_t hash_len,
 			       const char *type);
+extern int is_binary_blacklisted(const u8 *hash, size_t hash_len);
 #else
 static inline int is_hash_blacklisted(const u8 *hash, size_t hash_len,
 				      const char *type)
 {
 	return 0;
 }
+
+static inline int is_binary_blacklisted(const u8 *hash, size_t hash_len)
+{
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_IMA_BLACKLIST_KEYRING
-- 
2.20.1

[PATCH v8 7/8] ima: check against blacklisted hashes for files with modsig

[Nayna Jain]

Asymmetric private keys are used to sign multiple files. The kernel
currently support checking against blacklisted keys. However, if the
public key is blacklisted, any file signed by the blacklisted key will
automatically fail signature verification. We might not want to blacklist
all the files signed by a particular key, but just a single file.
Blacklisting the public key is not fine enough granularity.

This patch adds support for checking against the blacklisted hash of the
file based on the IMA policy. The blacklisted hash is the file hash
without the appended signature. Defined is a new policy option
"appraise_flag=check_blacklist".

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
 Documentation/ABI/testing/ima_policy  |  1 +
 security/integrity/ima/ima.h          |  8 +++++++
 security/integrity/ima/ima_appraise.c | 31 +++++++++++++++++++++++++++
 security/integrity/ima/ima_main.c     | 12 +++++++----
 security/integrity/ima/ima_policy.c   | 10 +++++++--
 security/integrity/integrity.h        |  1 +
 6 files changed, 57 insertions(+), 6 deletions(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index 29ebe9afdac4..4c97afcc0f3c 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -25,6 +25,7 @@ Description:
 			lsm:	[[subj_user=] [subj_role=] [subj_type=]
 				 [obj_user=] [obj_role=] [obj_type=]]
 			option:	[[appraise_type=]] [template=] [permit_directio]
+				[appraise_flag=[check_blacklist]]
 		base: 	func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
 				[FIRMWARE_CHECK]
 				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index a65772ffa427..df4ca482fb53 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -256,6 +256,8 @@ int ima_policy_show(struct seq_file *m, void *v);
 #define IMA_APPRAISE_KEXEC	0x40
 
 #ifdef CONFIG_IMA_APPRAISE
+int ima_check_blacklist(struct integrity_iint_cache *iint,
+			const struct modsig *modsig, int pcr);
 int ima_appraise_measurement(enum ima_hooks func,
 			     struct integrity_iint_cache *iint,
 			     struct file *file, const unsigned char *filename,
@@ -271,6 +273,12 @@ int ima_read_xattr(struct dentry *dentry,
 		   struct evm_ima_xattr_data **xattr_value);
 
 #else
+static inline int ima_check_blacklist(struct integrity_iint_cache *iint,
+				      const struct modsig *modsig, int pcr)
+{
+	return 0;
+}
+
 static inline int ima_appraise_measurement(enum ima_hooks func,
 					   struct integrity_iint_cache *iint,
 					   struct file *file,
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 136ae4e0ee92..7a002b08dde8 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -12,6 +12,7 @@
 #include <linux/magic.h>
 #include <linux/ima.h>
 #include <linux/evm.h>
+#include <keys/system_keyring.h>
 
 #include "ima.h"
 
@@ -303,6 +304,36 @@ static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
 	return rc;
 }
 
+/*
+ * ima_blacklist_measurement - Checks whether the binary is blacklisted. If
+ * yes, then adds the hash of the blacklisted binary to the measurement list.
+ *
+ * Returns -EPERM if the hash is blacklisted.
+ */
+int ima_check_blacklist(struct integrity_iint_cache *iint,
+			const struct modsig *modsig, int pcr)
+{
+	enum hash_algo hash_algo;
+	const u8 *digest = NULL;
+	u32 digestsize = 0;
+	int rc = 0;
+
+	if (!(iint->flags & IMA_CHECK_BLACKLIST))
+		return 0;
+
+	if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
+		ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
+
+		rc = is_binary_blacklisted(digest, digestsize);
+		if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
+			process_buffer_measurement(digest, digestsize,
+						   "blacklisted-hash", NONE,
+						   pcr);
+	}
+
+	return rc;
+}
+
 /*
  * ima_appraise_measurement - appraise file measurement
  *
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index fe0b704ffdeb..13a0d64580ef 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -335,10 +335,14 @@ static int process_measurement(struct file *file, const struct cred *cred,
 				      xattr_value, xattr_len, modsig, pcr,
 				      template_desc);
 	if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
-		inode_lock(inode);
-		rc = ima_appraise_measurement(func, iint, file, pathname,
-					      xattr_value, xattr_len, modsig);
-		inode_unlock(inode);
+		rc = ima_check_blacklist(iint, modsig, pcr);
+		if (rc != -EPERM) {
+			inode_lock(inode);
+			rc = ima_appraise_measurement(func, iint, file,
+						      pathname, xattr_value,
+						      xattr_len, modsig);
+			inode_unlock(inode);
+		}
 		if (!rc)
 			rc = mmap_violation_check(func, file, &pathbuf,
 						  &pathname, filename);
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 5380aca2b351..bfaae7a8443a 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -765,8 +765,8 @@ enum {
 	Opt_fsuuid, Opt_uid_eq, Opt_euid_eq, Opt_fowner_eq,
 	Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt,
 	Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt,
-	Opt_appraise_type, Opt_permit_directio,
-	Opt_pcr, Opt_template, Opt_err
+	Opt_appraise_type, Opt_appraise_flag,
+	Opt_permit_directio, Opt_pcr, Opt_template, Opt_err
 };
 
 static const match_table_t policy_tokens = {
@@ -798,6 +798,7 @@ static const match_table_t policy_tokens = {
 	{Opt_euid_lt, "euid<%s"},
 	{Opt_fowner_lt, "fowner<%s"},
 	{Opt_appraise_type, "appraise_type=%s"},
+	{Opt_appraise_flag, "appraise_flag=%s"},
 	{Opt_permit_directio, "permit_directio"},
 	{Opt_pcr, "pcr=%s"},
 	{Opt_template, "template=%s"},
@@ -1172,6 +1173,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 			else
 				result = -EINVAL;
 			break;
+		case Opt_appraise_flag:
+			ima_log_string(ab, "appraise_flag", args[0].from);
+			if (strstr(args[0].from, "blacklist"))
+				entry->flags |= IMA_CHECK_BLACKLIST;
+			break;
 		case Opt_permit_directio:
 			entry->flags |= IMA_PERMIT_DIRECTIO;
 			break;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index d9323d31a3a8..73fc286834d7 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -32,6 +32,7 @@
 #define EVM_IMMUTABLE_DIGSIG	0x08000000
 #define IMA_FAIL_UNVERIFIABLE_SIGS	0x10000000
 #define IMA_MODSIG_ALLOWED	0x20000000
+#define IMA_CHECK_BLACKLIST	0x40000000
 
 #define IMA_DO_MASK		(IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
 				 IMA_HASH | IMA_APPRAISE_SUBMASK)
-- 
2.20.1

[PATCH v8 8/8] powerpc/ima: update ima arch policy to check for blacklist

[Nayna Jain]

This patch updates the arch-specific policies for PowerNV system to make
sure that the binary hash is not blacklisted.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 arch/powerpc/kernel/ima_arch.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
index 710872ea8f35..98f3f8d9f9e4 100644
--- a/arch/powerpc/kernel/ima_arch.c
+++ b/arch/powerpc/kernel/ima_arch.c
@@ -19,9 +19,9 @@ bool arch_ima_get_secureboot(void)
  * to be stored as an xattr or as an appended signature.
  */
 static const char *const secure_rules[] = {
-	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+	"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
 #ifndef CONFIG_MODULE_SIG_FORCE
-	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+	"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
 #endif
 	NULL
 };
@@ -45,9 +45,9 @@ static const char *const trusted_rules[] = {
 static const char *const secure_and_trusted_rules[] = {
 	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
 	"measure func=MODULE_CHECK template=ima-modsig",
-	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
+	"appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
 #ifndef CONFIG_MODULE_SIG_FORCE
-	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
+	"appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig",
 #endif
 	NULL
 };
-- 
2.20.1

Re: [PATCH v8 4/8] powerpc/ima: add measurement rules to ima arch specific policy

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:
> This patch adds the measurement rules to the arch specific policies on
> trusted boot enabled systems.

This version does not add rules to the existing arch specific policy,
but defines an arch specific trusted boot only policy and a combined
secure and trusted boot policy.

> 
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> ---
>  arch/powerpc/kernel/ima_arch.c | 34 +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c
> index 65d82ee74ea4..710872ea8f35 100644
> --- a/arch/powerpc/kernel/ima_arch.c
> +++ b/arch/powerpc/kernel/ima_arch.c
> @@ -26,6 +26,32 @@ static const char *const secure_rules[] = {
>  	NULL
>  };
>  
> +/*
> + * The "measure_rules" are enabled only on "trustedboot" enabled systems.

Please update the policy name to reflect the new "trusted_rules" name.

> + * These rules add the kexec kernel image and kernel modules file hashes to
> + * the IMA measurement list.
> + */
> +static const char *const trusted_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK",
> +	"measure func=MODULE_CHECK",
> +	NULL
> +};
> +
> +/*
> + * The "secure_and_trusted_rules" contains rules for both the secure boot and
> + * trusted boot. The "template=ima-modsig" option includes the appended
> + * signature, when available, in the IMA measurement list.
> + */
> +static const char *const secure_and_trusted_rules[] = {
> +	"measure func=KEXEC_KERNEL_CHECK template=ima-modsig",
> +	"measure func=MODULE_CHECK template=ima-modsig",
> +	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
> +#ifndef CONFIG_MODULE_SIG_FORCE
> +	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
> +#endif
> +	NULL
> +};
> +
>  /*
>   * Returns the relevant IMA arch-specific policies based on the system secure
>   * boot state.
> @@ -33,7 +59,13 @@ static const char *const secure_rules[] = {
>  const char *const *arch_get_ima_policy(void)
>  {
>  	if (is_ppc_secureboot_enabled())
> -		return secure_rules;
> +		if (is_ppc_trustedboot_enabled())
> +			return secure_and_trusted_rules;
> +		else
> +			return secure_rules;
> +	else
> +		if (is_ppc_trustedboot_enabled())

No need for the "if" statement to be on a separate line.  Please
combine the "else" and "if" statements.

Mimi

> +			return trusted_rules;
>  
>  	return NULL;
>  }

Re: [PATCH v8 2/8] powerpc/ima: add support to initialize ima policy rules

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:

> index 000000000000..65d82ee74ea4
> --- /dev/null
> +++ b/arch/powerpc/kernel/ima_arch.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +
> +#include <linux/ima.h>
> +#include <asm/secure_boot.h>
> +
> +bool arch_ima_get_secureboot(void)
> +{
> +	return is_ppc_secureboot_enabled();
> +}
> +
> +/*
> + * The "secure_rules" are enabled only on "secureboot" enabled systems.
> + * These rules verify the file signatures against known good values.
> + * The "appraise_type=imasig|modsig" option allows the known good signature
> + * to be stored as an xattr or as an appended signature.

Please add another sentence or two as a separate paragraph with an
explanation why the kernel module rule is conditional (eg. Only verify
the appended kernel module signatures once.)

> + */
> +static const char *const secure_rules[] = {
> +	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig",
> +#ifndef CONFIG_MODULE_SIG_FORCE
> +	"appraise func=MODULE_CHECK appraise_type=imasig|modsig",
> +#endif
> +	NULL
> +};
> +

Mimi

Re: [PATCH v8 7/8] ima: check against blacklisted hashes for files with modsig

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:

> diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
> index 29ebe9afdac4..4c97afcc0f3c 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -25,6 +25,7 @@ Description:
>  			lsm:	[[subj_user=] [subj_role=] [subj_type=]
>  				 [obj_user=] [obj_role=] [obj_type=]]
>  			option:	[[appraise_type=]] [template=] [permit_directio]
> +				[appraise_flag=[check_blacklist]]

Like the other options, only "[[appraise_flag=]]" should be defined
here.  The values should be defined in the "option:" section.

>  		base: 	func:= [BPRM_CHECK][MMAP_CHECK][CREDS_CHECK][FILE_CHECK][MODULE_CHECK]
>  				[FIRMWARE_CHECK]
> 

>  				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 136ae4e0ee92..7a002b08dde8 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c

> @@ -303,6 +304,36 @@ static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
>  	return rc;
>  }
>  
> +/*
> + * ima_blacklist_measurement - Checks whether the binary is blacklisted. If

Please update the function name to reflect the actual function name.

> + * yes, then adds the hash of the blacklisted binary to the measurement list.

Refer to Documentation/process/coding-style.rst section "8)
Commenting" on how to format function comments.  Don't start a
sentence with "If yes,".

> + *
> + * Returns -EPERM if the hash is blacklisted.
> + */
> +int ima_check_blacklist(struct integrity_iint_cache *iint,
> +			const struct modsig *modsig, int pcr)
> +{
> +	enum hash_algo hash_algo;

> diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
> index 5380aca2b351..bfaae7a8443a 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c

> @@ -1172,6 +1173,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
>  			else
>  				result = -EINVAL;
>  			break;
> +		case Opt_appraise_flag:
> +			ima_log_string(ab, "appraise_flag", args[0].from);
> +			if (strstr(args[0].from, "blacklist"))
> +				entry->flags |= IMA_CHECK_BLACKLIST;
> +			break;

When adding a new policy rule option, ima_policy_show() needs to be
updated as well.

Mimi

>  		case Opt_permit_directio:
>  			entry->flags |= IMA_PERMIT_DIRECTIO;
>  			break;
> 

Re: [PATCH v8 5/8] ima: make process_buffer_measurement() generic

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:
> process_buffer_measurement() is limited to measuring the kexec boot
> command line. This patch makes process_buffer_measurement() more
> generic, allowing it to measure other types of buffer data (e.g.
> blacklisted binary hashes or key hashes).

based on "func".
> 
> This patch modifies the function to conditionally retrieve the policy
> defined pcr and template based on the func.

This would be done in a subsequent patch, not here.

> @@ -642,19 +642,38 @@ static void process_buffer_measurement(const void *buf, int size,
>  					    .filename = eventname,
>  					    .buf = buf,
>  					    .buf_len = size};
> -	struct ima_template_desc *template_desc = NULL;
> +	struct ima_template_desc *template = NULL;
>  	struct {
>  		struct ima_digest_data hdr;
>  		char digest[IMA_MAX_DIGEST_SIZE];
>  	} hash = {};
>  	int violation = 0;
> -	int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
>  	int action = 0;
> +	u32 secid;
>  
> -	action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr,
> -				&template_desc);
> -	if (!(action & IMA_MEASURE))
> -		return;
> +	if (func) {
> +		security_task_getsecid(current, &secid);
> +		action = ima_get_action(NULL, current_cred(), secid, 0, func,
> +					&pcr, &template);
> +		if (!(action & IMA_MEASURE))
> +			return;
> +	}
> +

Initially there is no need to test "func".  A specific "func" test
would be added as needed. 

Mimi

Re: [PATCH v8 3/8] powerpc: detect the trusted boot state of the system

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:
> While secure boot permits only properly verified signed kernels to be
> booted, trusted boot takes a measurement of the kernel image prior to
> boot that can be subsequently compared against good known values via
> attestation services.
> 

Instead of "takes a measurement", either "stores a measurement" or
"calculates the file hash of the kernel image and stores the
measurement prior to boot, that".

> This patch reads the trusted boot state of a PowerNV system. The state
> is used to conditionally enable additional measurement rules in the IMA
> arch-specific policies.
> 
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/secure_boot.h |  6 ++++++
>  arch/powerpc/kernel/secure_boot.c      | 24 ++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/secure_boot.h b/arch/powerpc/include/asm/secure_boot.h
> index 07d0fe0ca81f..a2ff556916c6 100644
> --- a/arch/powerpc/include/asm/secure_boot.h
> +++ b/arch/powerpc/include/asm/secure_boot.h
> 
> diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
> index 99bba7915629..9753470ab08a 100644
> --- a/arch/powerpc/kernel/secure_boot.c
> +++ b/arch/powerpc/kernel/secure_boot.c
> @@ -7,6 +7,17 @@
>  #include <linux/of.h>
>  #include <asm/secure_boot.h>
>  
> +static struct device_node *get_ppc_fw_sb_node(void)
> +{
> +	static const struct of_device_id ids[] = {
> +		{ .compatible = "ibm,secureboot-v1", },
> +		{ .compatible = "ibm,secureboot-v2", },
> +		{},
> +	};
> +

scripts/checkpatch.pl is complaining that secureboot-v1, secureboot-v2 
are not documented in the device tree bindings.

Mimi

Re: [PATCH v8 7/8] ima: check against blacklisted hashes for files with modsig

[Mimi Zohar]

On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:
> Asymmetric private keys are used to sign multiple files. The kernel
> currently support checking against blacklisted keys. However, if the
> public key is blacklisted, any file signed by the blacklisted key will
> automatically fail signature verification. We might not want to blacklist
> all the files signed by a particular key, but just a single file.
> Blacklisting the public key is not fine enough granularity.
> 
> This patch adds support for checking against the blacklisted hash of the
> file based on the IMA policy. The blacklisted hash is the file hash
> without the appended signature. Defined is a new policy option
> "appraise_flag=check_blacklist".

Please add an example of how to blacklist a file with an appended
signature.  The simplest example that works on x86 as well as Power
would be blacklisting a kernel module.  The example should include
calculating the kernel module hash without the appended signature,
enabling the Kconfig option (CONFIG_SYSTEM_BLACKLIST_HASH_LIST), and
the blacklist hash format (eg. "bin:<file hash>").

thanks, 

Mimi

Re: [PATCH v8 7/8] ima: check against blacklisted hashes for files with modsig

[Mimi Zohar]

On Sun, 2019-10-20 at 12:06 -0400, Mimi Zohar wrote:
> On Sat, 2019-10-19 at 14:06 -0400, Nayna Jain wrote:
> > Asymmetric private keys are used to sign multiple files. The kernel
> > currently support checking against blacklisted keys. However, if the
> > public key is blacklisted, any file signed by the blacklisted key will
> > automatically fail signature verification. We might not want to blacklist
> > all the files signed by a particular key, but just a single file.
> > Blacklisting the public key is not fine enough granularity.
> > 
> > This patch adds support for checking against the blacklisted hash of the
> > file based on the IMA policy. The blacklisted hash is the file hash
> > without the appended signature. Defined is a new policy option
> > "appraise_flag=check_blacklist".
> 
> Please add an example of how to blacklist a file with an appended
> signature.  The simplest example that works on x86 as well as Power
> would be blacklisting a kernel module.  The example should include
> calculating the kernel module hash without the appended signature,
> enabling the Kconfig option (CONFIG_SYSTEM_BLACKLIST_HASH_LIST), and
> the blacklist hash format (eg. "bin:<file hash>").

And of course, the IMA appraise kernel module policy rule containing
"appraise_flag=check_blacklist".

thanks,

Mimi

Re: [PATCH v8 1/8] powerpc: detect the secure boot mode of the system

[Michael Ellerman]

Nayna Jain <nayna@linux.ibm.com> writes:
> diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
> new file mode 100644
> index 000000000000..99bba7915629
> --- /dev/null
> +++ b/arch/powerpc/kernel/secure_boot.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2019 IBM Corporation
> + * Author: Nayna Jain
> + */
> +#include <linux/types.h>
> +#include <linux/of.h>
> +#include <asm/secure_boot.h>
> +
> +bool is_ppc_secureboot_enabled(void)
> +{
> +	struct device_node *node;
> +	bool enabled = false;
> +
> +	node = of_find_compatible_node(NULL, NULL, "ibm,secvar-v1");

If this found a node then you have a node with an elevated refcount
which you need to drop on the way out.

> +	if (!of_device_is_available(node)) {
> +		pr_err("Cannot find secure variable node in device tree; failing to secure state\n");
> +		goto out;
> +	}
> +
> +	/*
> +	 * secureboot is enabled if os-secure-enforcing property exists,
> +	 * else disabled.
> +	 */
> +	enabled = of_property_read_bool(node, "os-secure-enforcing");
> +
> +out:

So here you need:

	of_node_put(node);


> +	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
> +	return enabled;
> +}

cheers

Re: [PATCH v8 3/8] powerpc: detect the trusted boot state of the system

[Michael Ellerman]

Nayna Jain <nayna@linux.ibm.com> writes:
> diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
> index 99bba7915629..9753470ab08a 100644
> --- a/arch/powerpc/kernel/secure_boot.c
> +++ b/arch/powerpc/kernel/secure_boot.c
> @@ -28,3 +39,16 @@ bool is_ppc_secureboot_enabled(void)
>  	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
>  	return enabled;
>  }
> +
> +bool is_ppc_trustedboot_enabled(void)
> +{
> +	struct device_node *node;
> +	bool enabled = false;
> +
> +	node = get_ppc_fw_sb_node();
> +	enabled = of_property_read_bool(node, "trusted-enabled");

Also here you need:

	of_node_put(node);

> +
> +	pr_info("Trusted boot mode %s\n", enabled ? "enabled" : "disabled");
> +
> +	return enabled;
> +}

cheers