[RFC][PATCH v2 06/12] diglim: Interfaces - digest_list_add, digest_list_del

[Roberto Sassu]

Introduce <securityfs>/integrity/diglim/digest_list_add, which can be used
to upload a digest list and add the digests to the hash table; passed data
are interpreted as file path if the first byte is / or as the digest list
itself otherwise. ima_measure_critical_data() is called to calculate the
digest of the digest list and eventually, if an appropriate rule is set in
the IMA policy, to measure it.

Also introduce <securityfs>/integrity/diglim/digest_list_del, which can be
used to upload a digest list and delete the digests from the hash table;
data are interpreted in the same way as described for digest_list_add.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
 .../security/diglim/implementation.rst        |   9 +
 MAINTAINERS                                   |   1 +
 include/linux/kernel_read_file.h              |   1 +
 security/integrity/diglim/Makefile            |   2 +-
 security/integrity/diglim/diglim.h            |   2 +
 security/integrity/diglim/fs.c                | 239 ++++++++++++++++++
 security/integrity/integrity.h                |   4 +
 7 files changed, 257 insertions(+), 1 deletion(-)
 create mode 100644 security/integrity/diglim/fs.c

diff --git a/Documentation/security/diglim/implementation.rst b/Documentation/security/diglim/implementation.rst
index 9d679567a037..fc0cd8810a80 100644
--- a/Documentation/security/diglim/implementation.rst
+++ b/Documentation/security/diglim/implementation.rst
@@ -244,3 +244,12 @@ back when one of the steps fails.
 
 #. digest_list_parse() deletes the struct digest_list_item on unsuccessful
    add or successful delete.
+
+
+Interfaces
+----------
+
+This section introduces the interfaces in
+``<securityfs>/integrity/diglim`` necessary to interact with DIGLIM.
+
+.. kernel-doc:: security/integrity/diglim/fs.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 77c3613c600a..0672128fae7f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5464,6 +5464,7 @@ F:	Documentation/security/diglim/introduction.rst
 F:	include/linux/diglim.h
 F:	include/uapi/linux/diglim.h
 F:	security/integrity/diglim/diglim.h
+F:	security/integrity/diglim/fs.c
 F:	security/integrity/diglim/methods.c
 F:	security/integrity/diglim/parser.c
 
diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
index 575ffa1031d3..636ecdfdc616 100644
--- a/include/linux/kernel_read_file.h
+++ b/include/linux/kernel_read_file.h
@@ -14,6 +14,7 @@
 	id(KEXEC_INITRAMFS, kexec-initramfs)	\
 	id(POLICY, security-policy)		\
 	id(X509_CERTIFICATE, x509-certificate)	\
+	id(DIGEST_LIST, digest-list)	\
 	id(MAX_ID, )
 
 #define __fid_enumify(ENUM, dummy) READING_ ## ENUM,
diff --git a/security/integrity/diglim/Makefile b/security/integrity/diglim/Makefile
index 34e4e154fff3..ac345afdf5dd 100644
--- a/security/integrity/diglim/Makefile
+++ b/security/integrity/diglim/Makefile
@@ -5,4 +5,4 @@
 
 obj-$(CONFIG_DIGLIM) += diglim.o
 
-diglim-y := methods.o parser.o
+diglim-y := methods.o parser.o fs.o
diff --git a/security/integrity/diglim/diglim.h b/security/integrity/diglim/diglim.h
index 3adc218a0325..819703175eda 100644
--- a/security/integrity/diglim/diglim.h
+++ b/security/integrity/diglim/diglim.h
@@ -22,6 +22,8 @@
 #include <linux/hash_info.h>
 #include <linux/diglim.h>
 
+#include "../integrity.h"
+
 #define MAX_DIGEST_SIZE 64
 #define HASH_BITS 10
 #define DIGLIM_HTABLE_SIZE (1 << HASH_BITS)
diff --git a/security/integrity/diglim/fs.c b/security/integrity/diglim/fs.c
new file mode 100644
index 000000000000..07a0d75a0e33
--- /dev/null
+++ b/security/integrity/diglim/fs.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2005,2006,2007,2008 IBM Corporation
+ * Copyright (C) 2017-2021 Huawei Technologies Duesseldorf GmbH
+ *
+ * Author: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
+ *
+ * Functions for the interfaces exposed in securityfs.
+ */
+
+#include <linux/fcntl.h>
+#include <linux/kernel_read_file.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/rculist.h>
+#include <linux/rcupdate.h>
+#include <linux/parser.h>
+#include <linux/vmalloc.h>
+#include <linux/namei.h>
+#include <linux/ima.h>
+
+#include "diglim.h"
+
+#define MAX_DIGEST_LIST_SIZE (64 * 1024 * 1024 - 1)
+
+static struct dentry *diglim_dir;
+/**
+ * DOC: digest_list_add
+ *
+ * digest_list_add can be used to upload a digest list and add the digests
+ * to the hash table; passed data are interpreted as file path if the first
+ * byte is ``/`` or as the digest list itself otherwise.
+ *
+ * ima_measure_critical_data() is called to calculate the digest of the
+ * digest list and eventually, if an appropriate rule is set in the IMA
+ * policy, to measure it.
+ */
+static struct dentry *digest_list_add_dentry;
+/**
+ * DOC: digest_list_del
+ *
+ * digest_list_del can be used to upload a digest list and delete the
+ * digests from the hash table; data are interpreted in the same way as
+ * described for digest_list_add.
+ */
+static struct dentry *digest_list_del_dentry;
+char digest_label[NAME_MAX + 1];
+
+/*
+ * digest_list_read: read and parse the digest list from the path
+ */
+static ssize_t digest_list_read(char *path, enum ops op)
+{
+	void *data = NULL;
+	char *datap;
+	size_t size;
+	u8 actions = 0;
+	struct file *file;
+	char event_name[NAME_MAX + 9 + 1];
+	u8 digest[IMA_MAX_DIGEST_SIZE] = { 0 };
+	enum hash_algo algo;
+	int rc, pathlen = strlen(path);
+
+	/* Remove \n. */
+	datap = path;
+	strsep(&datap, "\n");
+
+	file = filp_open(path, O_RDONLY, 0);
+	if (IS_ERR(file)) {
+		pr_err("unable to open file: %s (%ld)", path, PTR_ERR(file));
+		return PTR_ERR(file);
+	}
+
+	rc = kernel_read_file(file, 0, &data, INT_MAX, NULL,
+			      READING_DIGEST_LIST);
+	if (rc < 0) {
+		pr_err("unable to read file: %s (%d)", path, rc);
+		goto out;
+	}
+
+	size = rc;
+
+	snprintf(event_name, sizeof(event_name), "%s_file_%s",
+		 op == DIGEST_LIST_ADD ? "add" : "del",
+		 file_dentry(file)->d_name.name);
+
+	rc = ima_measure_critical_data("diglim", event_name, data, size, false,
+				       digest, sizeof(digest));
+	if (rc < 0 && rc != -EEXIST)
+		goto out_vfree;
+
+	algo = ima_get_current_hash_algo();
+
+	if (!rc || rc == -EEXIST)
+		actions |= (1 << COMPACT_ACTION_IMA_MEASURED);
+
+	rc = digest_list_parse(size, data, op, actions, digest, algo, "");
+	if (rc < 0)
+		pr_err("unable to upload digest list %s (%d)\n", path, rc);
+out_vfree:
+	vfree(data);
+out:
+	fput(file);
+
+	if (rc < 0)
+		return rc;
+
+	return pathlen;
+}
+
+/*
+ * digest_list_write: write the digest list path or the digest list itself
+ */
+static ssize_t digest_list_write(struct file *file, const char __user *buf,
+				 size_t datalen, loff_t *ppos)
+{
+	char *data;
+	ssize_t result;
+	enum ops op = DIGEST_LIST_ADD;
+	struct dentry *dentry = file_dentry(file);
+	u8 digest[IMA_MAX_DIGEST_SIZE];
+	char event_name[NAME_MAX + 11 + 1];
+	enum hash_algo algo;
+	u8 actions = 0;
+
+	/* No partial writes. */
+	result = -EINVAL;
+	if (*ppos != 0)
+		goto out;
+
+	result = -EFBIG;
+	if (datalen > MAX_DIGEST_LIST_SIZE)
+		goto out;
+
+	data = memdup_user_nul(buf, datalen);
+	if (IS_ERR(data)) {
+		result = PTR_ERR(data);
+		goto out;
+	}
+
+	if (dentry == digest_list_del_dentry)
+		op = DIGEST_LIST_DEL;
+
+	result = -EPERM;
+
+	if (data[0] == '/') {
+		result = digest_list_read(data, op);
+	} else {
+		snprintf(event_name, sizeof(event_name), "%s_buffer_%s",
+			 op == DIGEST_LIST_ADD ? "add" : "del", digest_label);
+
+		result = ima_measure_critical_data("diglim", event_name, data,
+						   datalen, false, digest,
+						   sizeof(digest));
+		if (result < 0 && result != -EEXIST) {
+			pr_err("failed to measure buffer digest (%ld)\n",
+			       result);
+			goto out_kfree;
+		}
+
+		algo = ima_get_current_hash_algo();
+
+		if (!result || result == -EEXIST)
+			actions |= (1 << COMPACT_ACTION_IMA_MEASURED);
+
+		result = digest_list_parse(datalen, data, op, actions, digest,
+					   algo, "");
+		if (result != datalen) {
+			pr_err("unable to upload generated digest list\n");
+			result = -EINVAL;
+		}
+	}
+out_kfree:
+	kfree(data);
+out:
+	return result;
+}
+
+static unsigned long flags;
+
+/*
+ * digest_list_open: sequentialize access to the add/del files
+ */
+static int digest_list_open(struct inode *inode, struct file *filp)
+{
+	if ((filp->f_flags & O_ACCMODE) != O_WRONLY)
+		return -EACCES;
+
+	if (test_and_set_bit(0, &flags))
+		return -EBUSY;
+
+	return 0;
+}
+
+/*
+ * digest_list_release - release the add/del files
+ */
+static int digest_list_release(struct inode *inode, struct file *file)
+{
+	clear_bit(0, &flags);
+	return 0;
+}
+
+static const struct file_operations digest_list_upload_ops = {
+	.open = digest_list_open,
+	.write = digest_list_write,
+	.read = seq_read,
+	.release = digest_list_release,
+	.llseek = generic_file_llseek,
+};
+
+static int __init diglim_fs_init(void)
+{
+	diglim_dir = securityfs_create_dir("diglim", integrity_dir);
+	if (IS_ERR(diglim_dir))
+		return -1;
+
+	digest_list_add_dentry = securityfs_create_file("digest_list_add", 0200,
+						diglim_dir, NULL,
+						&digest_list_upload_ops);
+	if (IS_ERR(digest_list_add_dentry))
+		goto out;
+
+	digest_list_del_dentry = securityfs_create_file("digest_list_del", 0200,
+						diglim_dir, NULL,
+						&digest_list_upload_ops);
+	if (IS_ERR(digest_list_del_dentry))
+		goto out;
+
+	return 0;
+out:
+	securityfs_remove(digest_list_del_dentry);
+	securityfs_remove(digest_list_add_dentry);
+	securityfs_remove(diglim_dir);
+	return -1;
+}
+
+late_initcall(diglim_fs_init);
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 547425c20e11..ac45e1599c2d 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -6,6 +6,9 @@
  * Mimi Zohar <zohar@xxxxxxxxxx>
  */
 
+#ifndef __INTEGRITY_H
+#define __INTEGRITY_H
+
 #ifdef pr_fmt
 #undef pr_fmt
 #endif
@@ -283,3 +286,4 @@ static inline void __init add_to_platform_keyring(const char *source,
 {
 }
 #endif
+#endif /*__INTEGRITY_H*/
-- 
2.25.1