[PATCH 0/4] ima: builtin policy requiring file signatures

[PATCH 0/4] ima: builtin policy requiring file signatures

[Mimi Zohar]

The builtin "ima_appraise_tcb" policy should require file signatures
for at least a few of the hooks (eg. kernel modules, firmware, kexec
kernel image, and the IMA policy), but changing it would break the
existing userspace/kernel ABI.

This patch set extends the "ima_policy=" boot command line option to
support specifying multiple builtin policies, introduces a new builtin
policy named "secure_boot" to require file signatures, defines a new
Kconfig option to permit specifying "log" and "fix" modes as options on
the "ima_appraise=" boot command line, and defines is_ima_appraise_enabled().

These changes provide some of the missing functionality needed for the
"locked-down" patch set to detect whether file signatures are being
validated.

Mimi

Mimi Zohar (4):
  ima: extend the "ima_policy" boot command line to support multiple
    policies
  ima: define a set of appraisal rules requiring file signatures
  ima: define Kconfig IMA_APPRAISE_BOOTPARAM option
  ima: define is_ima_appraise_enabled()

 Documentation/admin-guide/kernel-parameters.txt | 21 +++++++++----
 include/linux/ima.h                             |  6 ++++
 security/integrity/ima/Kconfig                  |  8 +++++
 security/integrity/ima/ima_appraise.c           | 12 ++++++++
 security/integrity/ima/ima_policy.c             | 41 +++++++++++++++++++++----
 5 files changed, 76 insertions(+), 12 deletions(-)

-- 
2.7.4

[PATCH 1/4] ima: extend the "ima_policy" boot command line to support multiple policies

[Mimi Zohar]

Add support for providing multiple builtin policies on the "ima_policy="
boot command line.  Use "|" as the delimitor separating the policy names.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++------
 security/integrity/ima/ima_policy.c             | 15 ++++++++++-----
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2ba45caabada..06b95e28e5e2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1477,12 +1477,17 @@
 			in crypto/hash_info.h.
 
 	ima_policy=	[IMA]
-			The builtin measurement policy to load during IMA
-			setup.  Specyfing "tcb" as the value, measures all
-			programs exec'd, files mmap'd for exec, and all files
-			opened with the read mode bit set by either the
-			effective uid (euid=0) or uid=0.
-			Format: "tcb"
+			The builtin policies to load during IMA setup.
+			Format: "tcb | appraise_tcb"
+
+			The "tcb" policy measures all programs exec'd, files
+			mmap'd for exec, and all files opened with the read
+			mode bit set by either the effective uid (euid=0) or
+			uid=0.
+
+			The "appraise_tcb" policy appraises the integrity of
+			all files owned by root. (This is the equivalent
+			of ima_appraise_tcb.)
 
 	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
 			Load a policy which meets the needs of the Trusted
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 3ab1067db624..0ddc41389a9c 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -170,19 +170,24 @@ static int __init default_measure_policy_setup(char *str)
 }
 __setup("ima_tcb", default_measure_policy_setup);
 
+static bool ima_use_appraise_tcb __initdata;
 static int __init policy_setup(char *str)
 {
-	if (ima_policy)
-		return 1;
+	char *p;
 
-	if (strcmp(str, "tcb") == 0)
-		ima_policy = DEFAULT_TCB;
+	while ((p = strsep(&str, " |\n")) != NULL) {
+		if (*p == ' ')
+			continue;
+		if ((strcmp(p, "tcb") == 0) && !ima_policy)
+			ima_policy = DEFAULT_TCB;
+		else if (strcmp(p, "appraise_tcb") == 0)
+			ima_use_appraise_tcb = 1;
+	}
 
 	return 1;
 }
 __setup("ima_policy=", policy_setup);
 
-static bool ima_use_appraise_tcb __initdata;
 static int __init default_appraise_policy_setup(char *str)
 {
 	ima_use_appraise_tcb = 1;
-- 
2.7.4

[PATCH 2/4] ima: define a set of appraisal rules requiring file signatures

[Mimi Zohar]

The builtin "ima_appraise_tcb" policy should require file signatures for
at least a few of the hooks (eg. kernel modules, firmware, and the kexec
kernel image), but changing it would break the existing userspace/kernel
ABI.

This patch defines a new builtin policy named "secure_boot", which
can be specified on the "ima_policy=" boot command line, independently
or in conjunction with the "ima_appraise_tcb" policy, by specifing
ima_policy="appraise_tcb | secure_boot".  The new appraisal rules
requiring file signatures will be added prior to the "ima_appraise_tcb"
rules.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Changelog:
- Reference secure boot in the new builtin policy name. (Thiago Bauermann)
---
 Documentation/admin-guide/kernel-parameters.txt |  6 +++++-
 security/integrity/ima/ima_policy.c             | 26 ++++++++++++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 06b95e28e5e2..4e15b6a67d2c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1478,7 +1478,7 @@
 
 	ima_policy=	[IMA]
 			The builtin policies to load during IMA setup.
-			Format: "tcb | appraise_tcb"
+			Format: "tcb | appraise_tcb | secure_boot"
 
 			The "tcb" policy measures all programs exec'd, files
 			mmap'd for exec, and all files opened with the read
@@ -1489,6 +1489,10 @@
 			all files owned by root. (This is the equivalent
 			of ima_appraise_tcb.)
 
+			The "secure_boot" policy appraises the integrity
+			of files (eg. kexec kernel image, kernel modules,
+			firmware, policy, etc) based on file signatures.
+
 	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
 			Load a policy which meets the needs of the Trusted
 			Computing Base.  This means IMA will measure all
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 0ddc41389a9c..3653c86c70df 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -153,6 +153,17 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
 #endif
 };
 
+static struct ima_rule_entry secure_boot_rules[] __ro_after_init = {
+	{.action = APPRAISE, .func = MODULE_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+	{.action = APPRAISE, .func = FIRMWARE_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+	{.action = APPRAISE, .func = KEXEC_KERNEL_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+	{.action = APPRAISE, .func = POLICY_CHECK,
+	 .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
+};
+
 static LIST_HEAD(ima_default_rules);
 static LIST_HEAD(ima_policy_rules);
 static LIST_HEAD(ima_temp_rules);
@@ -171,6 +182,7 @@ static int __init default_measure_policy_setup(char *str)
 __setup("ima_tcb", default_measure_policy_setup);
 
 static bool ima_use_appraise_tcb __initdata;
+static bool ima_use_secure_boot __initdata;
 static int __init policy_setup(char *str)
 {
 	char *p;
@@ -182,6 +194,8 @@ static int __init policy_setup(char *str)
 			ima_policy = DEFAULT_TCB;
 		else if (strcmp(p, "appraise_tcb") == 0)
 			ima_use_appraise_tcb = 1;
+		else if (strcmp(p, "secure_boot") == 0)
+			ima_use_secure_boot = 1;
 	}
 
 	return 1;
@@ -410,12 +424,14 @@ void ima_update_policy_flag(void)
  */
 void __init ima_init_policy(void)
 {
-	int i, measure_entries, appraise_entries;
+	int i, measure_entries, appraise_entries, secure_boot_entries;
 
 	/* if !ima_policy set entries = 0 so we load NO default rules */
 	measure_entries = ima_policy ? ARRAY_SIZE(dont_measure_rules) : 0;
 	appraise_entries = ima_use_appraise_tcb ?
 			 ARRAY_SIZE(default_appraise_rules) : 0;
+	secure_boot_entries = ima_use_secure_boot ?
+			ARRAY_SIZE(secure_boot_rules) : 0;
 
 	for (i = 0; i < measure_entries; i++)
 		list_add_tail(&dont_measure_rules[i].list, &ima_default_rules);
@@ -434,6 +450,14 @@ void __init ima_init_policy(void)
 		break;
 	}
 
+	/*
+	 * Insert the appraise 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);
+
 	for (i = 0; i < appraise_entries; i++) {
 		list_add_tail(&default_appraise_rules[i].list,
 			      &ima_default_rules);
-- 
2.7.4

[PATCH 3/4] ima: define Kconfig IMA_APPRAISE_BOOTPARAM option

[Mimi Zohar]

Permit enabling the different "ima_appraise=" modes (eg. log, fix)
from the boot command line.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
 security/integrity/ima/Kconfig        | 8 ++++++++
 security/integrity/ima/ima_appraise.c | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
index 370eb2f4dd37..8b688a26033d 100644
--- a/security/integrity/ima/Kconfig
+++ b/security/integrity/ima/Kconfig
@@ -155,6 +155,14 @@ config IMA_APPRAISE
 	  <http://linux-ima.sourceforge.net>
 	  If unsure, say N.
 
+config IMA_APPRAISE_BOOTPARAM
+	bool "ima_appraise boot parameter"
+	depends on IMA_APPRAISE
+	default y
+	help
+	  This option enables the different "ima_appraise=" modes
+	  (eg. fix, log) from the boot command line.
+
 config IMA_TRUSTED_KEYRING
 	bool "Require all keys on the .ima keyring be signed (deprecated)"
 	depends on IMA_APPRAISE && SYSTEM_TRUSTED_KEYRING
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 5d0785cfe063..ac546df73afc 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -20,12 +20,14 @@
 
 static int __init default_appraise_setup(char *str)
 {
+#ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
 	if (strncmp(str, "off", 3) == 0)
 		ima_appraise = 0;
 	else if (strncmp(str, "log", 3) == 0)
 		ima_appraise = IMA_APPRAISE_LOG;
 	else if (strncmp(str, "fix", 3) == 0)
 		ima_appraise = IMA_APPRAISE_FIX;
+#endif
 	return 1;
 }
 
-- 
2.7.4

[PATCH 4/4] ima: define is_ima_appraise_enabled()

[Mimi Zohar]

Only return enabled if in enforcing mode, not fix or log modes.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Changes:
- Define is_ima_appraise_enabled() as a bool (Thiago Bauermann)
---
 include/linux/ima.h                   |  6 ++++++
 security/integrity/ima/ima_appraise.c | 10 ++++++++++
 2 files changed, 16 insertions(+)

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 7f6952f8d6aa..0e4647e0eb60 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -75,11 +75,17 @@ static inline void ima_add_kexec_buffer(struct kimage *image)
 #endif
 
 #ifdef CONFIG_IMA_APPRAISE
+extern bool is_ima_appraise_enabled(void);
 extern void ima_inode_post_setattr(struct dentry *dentry);
 extern int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
 		       const void *xattr_value, size_t xattr_value_len);
 extern int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name);
 #else
+static inline bool is_ima_appraise_enabled(void)
+{
+	return 0;
+}
+
 static inline void ima_inode_post_setattr(struct dentry *dentry)
 {
 	return;
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index ac546df73afc..7fe0566142d8 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -34,6 +34,16 @@ static int __init default_appraise_setup(char *str)
 __setup("ima_appraise=", default_appraise_setup);
 
 /*
+ * is_ima_appraise_enabled - return appraise status
+ *
+ * Only return enabled, if not in ima_appraise="fix" or "log" modes.
+ */
+bool is_ima_appraise_enabled(void)
+{
+	return (ima_appraise & IMA_APPRAISE_ENFORCE) ? 1 : 0;
+}
+
+/*
  * ima_must_appraise - set appraise flag
  *
  * Return 1 to appraise
-- 
2.7.4