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From: Roberto Sassu <roberto.sassu@huawei.com>
To: <zohar@linux.ibm.com>, <mjg59@google.com>
Cc: <linux-integrity@vger.kernel.org>,
	<linux-security-module@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	Roberto Sassu <roberto.sassu@huawei.com>
Subject: [PATCH v5 11/12] ima: Introduce template field evmsig and write to field sig as fallback
Date: Wed, 7 Apr 2021 12:52:51 +0200
Message-ID: <20210407105252.30721-12-roberto.sassu@huawei.com> (raw)
In-Reply-To: <20210407105252.30721-1-roberto.sassu@huawei.com>

With the patch to accept EVM portable signatures when the
appraise_type=imasig requirement is specified in the policy, appraisal can
be successfully done even if the file does not have an IMA signature.

However, remote attestation would not see that a different signature type
was used, as only IMA signatures can be included in the measurement list.
This patch solves the issue by introducing the new template field 'evmsig'
to show EVM portable signatures and by including its value in the existing
field 'sig' if the IMA signature is not found.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
---
 Documentation/security/IMA-templates.rst  |  4 ++-
 security/integrity/ima/ima_template.c     |  2 ++
 security/integrity/ima/ima_template_lib.c | 33 ++++++++++++++++++++++-
 security/integrity/ima/ima_template_lib.h |  2 ++
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index c5a8432972ef..9f3e86ab028a 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -70,9 +70,11 @@ descriptors by adding their identifier to the format string
    prefix is shown only if the hash algorithm is not SHA1 or MD5);
  - 'd-modsig': the digest of the event without the appended modsig;
  - 'n-ng': the name of the event, without size limitations;
- - 'sig': the file signature;
+ - 'sig': the file signature, or the EVM portable signature if the file
+   signature is not found;
  - 'modsig' the appended file signature;
  - 'buf': the buffer data that was used to generate the hash without size limitations;
+ - 'evmsig': the EVM portable signature;
 
 
 Below, there is the list of defined template descriptors:
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index e22e510ae92d..90e8a8282927 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -45,6 +45,8 @@ static const struct ima_template_field supported_fields[] = {
 	 .field_show = ima_show_template_digest_ng},
 	{.field_id = "modsig", .field_init = ima_eventmodsig_init,
 	 .field_show = ima_show_template_sig},
+	{.field_id = "evmsig", .field_init = ima_eventevmsig_init,
+	 .field_show = ima_show_template_sig},
 };
 
 /*
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index c022ee9e2a4e..4314d9a3514c 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -10,6 +10,7 @@
  */
 
 #include "ima_template_lib.h"
+#include <linux/xattr.h>
 
 static bool ima_template_hash_algo_allowed(u8 algo)
 {
@@ -438,7 +439,7 @@ int ima_eventsig_init(struct ima_event_data *event_data,
 	struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
 
 	if ((!xattr_value) || (xattr_value->type != EVM_IMA_XATTR_DIGSIG))
-		return 0;
+		return ima_eventevmsig_init(event_data, field_data);
 
 	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
 					     DATA_FMT_HEX, field_data);
@@ -484,3 +485,33 @@ int ima_eventmodsig_init(struct ima_event_data *event_data,
 	return ima_write_template_field_data(data, data_len, DATA_FMT_HEX,
 					     field_data);
 }
+
+/*
+ *  ima_eventevmsig_init - include the EVM portable signature as part of the
+ *  template data
+ */
+int ima_eventevmsig_init(struct ima_event_data *event_data,
+			 struct ima_field_data *field_data)
+{
+	struct evm_ima_xattr_data *xattr_data = NULL;
+	int rc = 0;
+
+	if (!event_data->file)
+		return 0;
+
+	rc = vfs_getxattr_alloc(&init_user_ns, file_dentry(event_data->file),
+				XATTR_NAME_EVM, (char **)&xattr_data, 0,
+				GFP_NOFS);
+	if (rc <= 0)
+		return 0;
+
+	if (xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG) {
+		kfree(xattr_data);
+		return 0;
+	}
+
+	rc = ima_write_template_field_data((char *)xattr_data, rc, DATA_FMT_HEX,
+					   field_data);
+	kfree(xattr_data);
+	return rc;
+}
diff --git a/security/integrity/ima/ima_template_lib.h b/security/integrity/ima/ima_template_lib.h
index 6b3b880637a0..f4b2a2056d1d 100644
--- a/security/integrity/ima/ima_template_lib.h
+++ b/security/integrity/ima/ima_template_lib.h
@@ -46,4 +46,6 @@ int ima_eventbuf_init(struct ima_event_data *event_data,
 		      struct ima_field_data *field_data);
 int ima_eventmodsig_init(struct ima_event_data *event_data,
 			 struct ima_field_data *field_data);
+int ima_eventevmsig_init(struct ima_event_data *event_data,
+			 struct ima_field_data *field_data);
 #endif /* __LINUX_IMA_TEMPLATE_LIB_H */
-- 
2.26.2


  parent reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-07 10:52 [PATCH v5 00/12] evm: Improve usability of portable signatures Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 01/12] evm: Execute evm_inode_init_security() only when an HMAC key is loaded Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 02/12] evm: Load EVM key in ima_load_x509() to avoid appraisal Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 03/12] evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded Roberto Sassu
2021-04-30 20:28   ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 04/12] ima: Move ima_reset_appraise_flags() call to post hooks Roberto Sassu
2021-04-07 16:17   ` Casey Schaufler
2021-04-07 16:31     ` Roberto Sassu
2021-04-26 19:49     ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 05/12] evm: Introduce evm_status_revalidate() Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 06/12] evm: Ignore INTEGRITY_NOLABEL/INTEGRITY_NOXATTRS if conditions are safe Roberto Sassu
2021-05-03  0:12   ` Mimi Zohar
2021-05-03  7:55     ` Roberto Sassu
2021-05-03 12:07       ` Mimi Zohar
2021-05-03 14:15       ` Roberto Sassu
2021-05-03 14:34         ` Mimi Zohar
2021-05-04 13:16           ` Roberto Sassu
2021-05-04 13:45             ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 07/12] evm: Allow xattr/attr operations for portable signatures Roberto Sassu
2021-05-03  0:12   ` Mimi Zohar
2021-05-04 14:28     ` Roberto Sassu
2021-05-04 14:49       ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 08/12] evm: Pass user namespace to set/remove xattr hooks Roberto Sassu
2021-04-07 12:06   ` Christian Brauner
2021-04-07 10:52 ` [PATCH v5 09/12] evm: Allow setxattr() and setattr() for unmodified metadata Roberto Sassu
2021-04-07 12:05   ` Christian Brauner
2021-04-07 15:23   ` kernel test robot
2021-04-07 18:14   ` kernel test robot
2021-04-07 19:28     ` [RESEND][PATCH " Roberto Sassu
2021-05-03 13:00   ` [PATCH " Mimi Zohar
2021-05-03 14:48     ` Roberto Sassu
2021-05-03 15:13       ` Mimi Zohar
2021-05-03 15:30         ` Roberto Sassu
2021-05-03 15:11     ` Roberto Sassu
2021-05-03 15:26       ` Mimi Zohar
2021-05-03 15:32         ` Roberto Sassu
2021-05-03 15:48           ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 10/12] ima: Allow imasig requirement to be satisfied by EVM portable signatures Roberto Sassu
2021-04-07 10:52 ` Roberto Sassu [this message]
2021-04-07 10:52 ` [PATCH v5 12/12] ima: Don't remove security.ima if file must not be appraised Roberto Sassu

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