Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull security subsystem updates from James Morris:

 - kstrdup() return value fix from Eric Biggers

 - Add new security_load_data hook to differentiate security checking of
   kernel-loaded binaries in the case of there being no associated file
   descriptor, from Mimi Zohar.

 - Add ability to IMA to specify a policy at build-time, rather than
   just via command line params or by loading a custom policy, from
   Mimi.

 - Allow IMA and LSMs to prevent sysfs firmware load fallback (e.g. if
   using signed firmware), from Mimi.

 - Allow IMA to deny loading of kexec kernel images, as they cannot be
   measured by IMA, from Mimi.

* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security: check for kstrdup() failure in lsm_append()
  security: export security_kernel_load_data function
  ima: based on policy warn about loading firmware (pre-allocated buffer)
  module: replace the existing LSM hook in init_module
  ima: add build time policy
  ima: based on policy require signed firmware (sysfs fallback)
  firmware: add call to LSM hook before firmware sysfs fallback
  ima: based on policy require signed kexec kernel images
  kexec: add call to LSM hook in original kexec_load syscall
  security: define new LSM hook named security_kernel_load_data
  MAINTAINERS: remove the outdated "LINUX SECURITY MODULE (LSM) FRAMEWORK" entry

4 files changed, 158 insertions, 17 deletions

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 6a8f67714c83..004919d9bf09 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -156,6 +156,64 @@ config IMA_APPRAISE
 	  <http://linux-ima.sourceforge.net>
 	  If unsure, say N.
 
+config IMA_APPRAISE_BUILD_POLICY
+	bool "IMA build time configured policy rules"
+	depends on IMA_APPRAISE && INTEGRITY_ASYMMETRIC_KEYS
+	default n
+	help
+	  This option defines an IMA appraisal policy at build time, which
+	  is enforced at run time without having to specify a builtin
+	  policy name on the boot command line.  The build time appraisal
+	  policy rules persist after loading a custom policy.
+
+	  Depending on the rules configured, this policy may require kernel
+	  modules, firmware, the kexec kernel image, and/or the IMA policy
+	  to be signed.  Unsigned files might prevent the system from
+	  booting or applications from working properly.
+
+config IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
+	bool "Appraise firmware signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  This option defines a policy requiring all firmware to be signed,
+	  including the regulatory.db.  If both this option and
+	  CFG80211_REQUIRE_SIGNED_REGDB are enabled, then both signature
+	  verification methods are necessary.
+
+config IMA_APPRAISE_REQUIRE_KEXEC_SIGS
+	bool "Appraise kexec kernel image signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require all kexec'ed kernel images to
+	  be signed and verified by a public key on the trusted IMA
+	  keyring.
+
+	  Kernel image signatures can not be verified by the original
+	  kexec_load syscall.  Enabling this rule will prevent its
+	  usage.
+
+config IMA_APPRAISE_REQUIRE_MODULE_SIGS
+	bool "Appraise kernel modules signatures"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require all kernel modules to be signed
+	  and verified by a public key on the trusted IMA keyring.
+
+	  Kernel module signatures can only be verified by IMA-appraisal,
+	  via the finit_module syscall. Enabling this rule will prevent
+	  the usage of the init_module syscall.
+
+config IMA_APPRAISE_REQUIRE_POLICY_SIGS
+	bool "Appraise IMA policy signature"
+	depends on IMA_APPRAISE_BUILD_POLICY
+	default n
+	help
+	  Enabling this rule will require the IMA policy to be signed and
+	  and verified by a key on the trusted IMA keyring.
+
 config IMA_APPRAISE_BOOTPARAM
 	bool "ima_appraise boot parameter"
 	depends on IMA_APPRAISE
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index e4c1a236976c..a597b2795d2d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -232,6 +232,7 @@ int ima_policy_show(struct seq_file *m, void *v);
 #define IMA_APPRAISE_MODULES	0x08
 #define IMA_APPRAISE_FIRMWARE	0x10
 #define IMA_APPRAISE_POLICY	0x20
+#define IMA_APPRAISE_KEXEC	0x40
 
 #ifdef CONFIG_IMA_APPRAISE
 int ima_appraise_measurement(enum ima_hooks func,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index b286f37712d5..2d31921fbda4 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -429,16 +429,14 @@ void ima_post_path_mknod(struct dentry *dentry)
  */
 int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
 {
-	bool sig_enforce = is_module_sig_enforced();
-
-	if (!file && read_id == READING_MODULE) {
-		if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES) &&
-		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
-			pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
-			return -EACCES;	/* INTEGRITY_UNKNOWN */
-		}
-		return 0;	/* We rely on module signature checking */
-	}
+	/*
+	 * READING_FIRMWARE_PREALLOC_BUFFER
+	 *
+	 * Do devices using pre-allocated memory run the risk of the
+	 * firmware being accessible to the device prior to the completion
+	 * of IMA's signature verification any more than when using two
+	 * buffers?
+	 */
 	return 0;
 }
 
@@ -472,14 +470,13 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
 
 	if (!file && read_id == READING_FIRMWARE) {
 		if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
-		    (ima_appraise & IMA_APPRAISE_ENFORCE))
+		    (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+			pr_err("Prevent firmware loading_store.\n");
 			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
 		return 0;
 	}
 
-	if (!file && read_id == READING_MODULE) /* MODULE_SIG_FORCE enabled */
-		return 0;
-
 	/* permit signed certs */
 	if (!file && read_id == READING_X509_CERTIFICATE)
 		return 0;
@@ -496,6 +493,49 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
 				   MAY_READ, func);
 }
 
+/**
+ * ima_load_data - appraise decision based on policy
+ * @id: kernel load data caller identifier
+ *
+ * Callers of this LSM hook can not measure, appraise, or audit the
+ * data provided by userspace.  Enforce policy rules requring a file
+ * signature (eg. kexec'ed kernel image).
+ *
+ * For permission return 0, otherwise return -EACCES.
+ */
+int ima_load_data(enum kernel_load_data_id id)
+{
+	bool sig_enforce;
+
+	if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE)
+		return 0;
+
+	switch (id) {
+	case LOADING_KEXEC_IMAGE:
+		if (ima_appraise & IMA_APPRAISE_KEXEC) {
+			pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
+			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
+		break;
+	case LOADING_FIRMWARE:
+		if (ima_appraise & IMA_APPRAISE_FIRMWARE) {
+			pr_err("Prevent firmware sysfs fallback loading.\n");
+			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
+		break;
+	case LOADING_MODULE:
+		sig_enforce = is_module_sig_enforced();
+
+		if (!sig_enforce && (ima_appraise & IMA_APPRAISE_MODULES)) {
+			pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
+			return -EACCES;	/* INTEGRITY_UNKNOWN */
+		}
+	default:
+		break;
+	}
+	return 0;
+}
+
 static int __init init_ima(void)
 {
 	int error;
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index cdcc9a7b4e24..1659abb344f9 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -49,6 +49,7 @@
 
 int ima_policy_flag;
 static int temp_ima_appraise;
+static int build_ima_appraise __ro_after_init;
 
 #define MAX_LSM_RULES 6
 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE,
@@ -162,6 +163,25 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
 #endif
 };
 
+static struct ima_rule_entry build_appraise_rules[] __ro_after_init = {
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_MODULE_SIGS
+	{.action = APPRAISE, .func = MODULE_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_FIRMWARE_SIGS
+	{.action = APPRAISE, .func = FIRMWARE_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_KEXEC_SIGS
+	{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+#ifdef CONFIG_IMA_APPRAISE_REQUIRE_POLICY_SIGS
+	{.action = APPRAISE, .func = POLICY_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+#endif
+};
+
 static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
 	{.action = APPRAISE, .func = MODULE_CHECK,
 	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
@@ -435,7 +455,7 @@ void ima_update_policy_flag(void)
 			ima_policy_flag |= entry->action;
 	}
 
-	ima_appraise |= temp_ima_appraise;
+	ima_appraise |= (build_ima_appraise | temp_ima_appraise);
 	if (!ima_appraise)
 		ima_policy_flag &= ~IMA_APPRAISE;
 }
@@ -448,6 +468,8 @@ static int ima_appraise_flag(enum ima_hooks func)
 		return IMA_APPRAISE_FIRMWARE;
 	else if (func == POLICY_CHECK)
 		return IMA_APPRAISE_POLICY;
+	else if (func == KEXEC_KERNEL_CHECK)
+		return IMA_APPRAISE_KEXEC;
 	return 0;
 }
 
@@ -486,8 +508,8 @@ void __init ima_init_policy(void)
 	}
 
 	/*
-	 * Insert the appraise rules requiring file signatures, prior to
-	 * any other appraise rules.
+	 * Insert the builtin "secure_boot" policy rules requiring file
+	 * signatures, prior to any other appraise rules.
 	 */
 	for (i = 0; i < secure_boot_entries; i++) {
 		list_add_tail(&secure_boot_rules[i].list, &ima_default_rules);
@@ -495,6 +517,26 @@ void __init ima_init_policy(void)
 		    ima_appraise_flag(secure_boot_rules[i].func);
 	}
 
+	/*
+	 * Insert the build time appraise rules requiring file signatures
+	 * for both the initial and custom policies, prior to other appraise
+	 * rules.
+	 */
+	for (i = 0; i < ARRAY_SIZE(build_appraise_rules); i++) {
+		struct ima_rule_entry *entry;
+
+		if (!secure_boot_entries)
+			list_add_tail(&build_appraise_rules[i].list,
+				      &ima_default_rules);
+
+		entry = kmemdup(&build_appraise_rules[i], sizeof(*entry),
+				GFP_KERNEL);
+		if (entry)
+			list_add_tail(&entry->list, &ima_policy_rules);
+		build_ima_appraise |=
+			ima_appraise_flag(build_appraise_rules[i].func);
+	}
+
 	for (i = 0; i < appraise_entries; i++) {
 		list_add_tail(&default_appraise_rules[i].list,
 			      &ima_default_rules);