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From: Nayna Jain <nayna@linux.ibm.com>
To: linuxppc-dev@ozlabs.org, linux-efi@vger.kernel.org,
	linux-integrity@vger.kernel.org, devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Michael Ellerman <mpe@ellerman.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Jeremy Kerr <jk@ozlabs.org>,
	Matthew Garret <matthew.garret@nebula.com>,
	Mimi Zohar <zohar@linux.ibm.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Claudio Carvalho <cclaudio@linux.ibm.com>,
	George Wilson <gcwilson@linux.ibm.com>,
	Elaine Palmer <erpalmer@us.ibm.com>,
	Eric Ricther <erichte@linux.ibm.com>,
	"Oliver O'Halloran" <oohall@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Nayna Jain <nayna@linux.ibm.com>
Subject: [PATCH v6 7/9] ima: check against blacklisted hashes for files with modsig
Date: Fri, 27 Sep 2019 10:25:58 -0400	[thread overview]
Message-ID: <1569594360-7141-8-git-send-email-nayna@linux.ibm.com> (raw)
In-Reply-To: <1569594360-7141-1-git-send-email-nayna@linux.ibm.com>

Asymmetric private keys are used to sign multiple files. The kernel
currently support checking against the 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 blacklisting binaries with appended signatures,
based on the IMA policy.  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          | 12 +++++++++
 security/integrity/ima/ima_appraise.c | 35 +++++++++++++++++++++++++++
 security/integrity/ima/ima_main.c     |  8 ++++--
 security/integrity/ima/ima_policy.c   | 10 ++++++--
 security/integrity/integrity.h        |  1 +
 6 files changed, 63 insertions(+), 4 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 9bf509217e8e..2c034728b239 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -254,6 +254,9 @@ int ima_policy_show(struct seq_file *m, void *v);
 #define IMA_APPRAISE_KEXEC	0x40
 
 #ifdef CONFIG_IMA_APPRAISE
+int ima_blacklist_measurement(struct integrity_iint_cache *iint,
+			      const struct modsig *modsig, int action,
+			      int pcr, struct ima_template_desc *template_desc);
 int ima_appraise_measurement(enum ima_hooks func,
 			     struct integrity_iint_cache *iint,
 			     struct file *file, const unsigned char *filename,
@@ -269,6 +272,15 @@ int ima_read_xattr(struct dentry *dentry,
 		   struct evm_ima_xattr_data **xattr_value);
 
 #else
+static inline int ima_blacklist_measurement(struct integrity_iint_cache *iint,
+					    const struct modsig *modsig,
+					    int action, int pcr,
+					    struct ima_template_desc
+					    *template_desc)
+{
+	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..a5a82e870e24 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 +304,40 @@ static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
 	return rc;
 }
 
+/*
+ * ima_blacklist_measurement - checks if the file measurement is blacklisted
+ *
+ * Returns -EKEYREJECTED if the hash is blacklisted.
+ */
+int ima_blacklist_measurement(struct integrity_iint_cache *iint,
+			      const struct modsig *modsig, int action, int pcr,
+			      struct ima_template_desc *template_desc)
+{
+	enum hash_algo hash_algo;
+	const u8 *digest = NULL;
+	u32 digestsize = 0;
+	u32 secid;
+	int rc = 0;
+
+	if (!(iint->flags & IMA_CHECK_BLACKLIST))
+		return 0;
+
+	if (iint->flags & IMA_MODSIG_ALLOWED) {
+		security_task_getsecid(current, &secid);
+		ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
+
+		rc = is_hash_blacklisted(digest, digestsize, "bin");
+
+		/* Returns -EKEYREJECTED on blacklisted hash found */
+		if ((rc == -EKEYREJECTED) && (iint->flags & IMA_MEASURE))
+			process_buffer_measurement(digest, digestsize,
+						   "blacklisted-hash", pcr,
+						   template_desc);
+	}
+
+	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 ae0c1bdc4eaf..92c446045637 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -336,8 +336,12 @@ static int process_measurement(struct file *file, const struct cred *cred,
 				      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);
+		rc = ima_blacklist_measurement(iint, modsig, action, pcr,
+					       template_desc);
+		if (rc != -EKEYREJECTED)
+			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,
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 4badc4fcda98..ad3b3af69460 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


  parent reply	other threads:[~2019-09-27 14:27 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-27 14:25 [PATCH v6 0/9] powerpc: Enabling IMA arch specific secure boot policies Nayna Jain
2019-09-27 14:25 ` [PATCH v6 1/9] dt-bindings: ibm,secureboot: secure boot specific properties for PowerNV Nayna Jain
2019-10-01 13:33   ` Rob Herring
2019-10-01 16:29     ` Nayna
2019-09-27 14:25 ` [PATCH v6 2/9] powerpc: detect the secure boot mode of the system Nayna Jain
2019-09-27 14:25 ` [PATCH v6 3/9] powerpc: add support to initialize ima policy rules Nayna Jain
2019-10-01  1:04   ` Thiago Jung Bauermann
2019-10-01 16:07     ` Nayna
2019-10-02  0:23       ` Thiago Jung Bauermann
2019-10-02 21:49       ` Mimi Zohar
2019-10-08 13:12         ` Nayna
2019-09-27 14:25 ` [PATCH v6 4/9] powerpc: detect the trusted boot state of the system Nayna Jain
2019-09-27 14:25 ` [PATCH v6 5/9] powerpc/ima: add measurement rules to ima arch specific policy Nayna Jain
2019-09-29  4:20   ` Mimi Zohar
2019-09-27 14:25 ` [PATCH v6 6/9] ima: make process_buffer_measurement() non static Nayna Jain
2019-10-02 22:04   ` Mimi Zohar
2019-09-27 14:25 ` Nayna Jain [this message]
2019-10-02 20:44   ` [PATCH v6 7/9] ima: check against blacklisted hashes for files with modsig Mimi Zohar
2019-09-27 14:25 ` [PATCH v6 8/9] ima: deprecate permit_directio, instead use appraise_flag Nayna Jain
2019-10-02 21:00   ` Mimi Zohar
2019-09-27 14:26 ` [PATCH v6 9/9] powerpc/ima: update ima arch policy to check for blacklist Nayna Jain

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