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-rw-r--r--security/integrity/ima/ima_main.c240
1 files changed, 240 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
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+++ b/security/integrity/ima/ima_main.c
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+/*
+ * Copyright (C) 2005,2006,2007,2008 IBM Corporation
+ *
+ * Authors:
+ * Reiner Sailer <sailer@watson.ibm.com>
+ * Serge Hallyn <serue@us.ibm.com>
+ * Kylene Hall <kylene@us.ibm.com>
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ *
+ * File: ima_main.c
+ * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
+ * and ima_file_check.
+ */
+#include <linux/module.h>
+#include <linux/file.h>
+#include <linux/binfmts.h>
+#include <linux/mount.h>
+#include <linux/mman.h>
+#include <linux/slab.h>
+
+#include "ima.h"
+
+int ima_initialized;
+
+char *ima_hash = "sha1";
+static int __init hash_setup(char *str)
+{
+ if (strncmp(str, "md5", 3) == 0)
+ ima_hash = "md5";
+ return 1;
+}
+__setup("ima_hash=", hash_setup);
+
+/*
+ * ima_rdwr_violation_check
+ *
+ * Only invalidate the PCR for measured files:
+ * - Opening a file for write when already open for read,
+ * results in a time of measure, time of use (ToMToU) error.
+ * - Opening a file for read when already open for write,
+ * could result in a file measurement error.
+ *
+ */
+static void ima_rdwr_violation_check(struct file *file)
+{
+ struct dentry *dentry = file->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+ fmode_t mode = file->f_mode;
+ int rc;
+ bool send_tomtou = false, send_writers = false;
+
+ if (!S_ISREG(inode->i_mode) || !ima_initialized)
+ return;
+
+ mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */
+
+ if (mode & FMODE_WRITE) {
+ if (atomic_read(&inode->i_readcount) && IS_IMA(inode))
+ send_tomtou = true;
+ goto out;
+ }
+
+ rc = ima_must_measure(inode, MAY_READ, FILE_CHECK);
+ if (rc < 0)
+ goto out;
+
+ if (atomic_read(&inode->i_writecount) > 0)
+ send_writers = true;
+out:
+ mutex_unlock(&inode->i_mutex);
+
+ if (send_tomtou)
+ ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
+ "ToMToU");
+ if (send_writers)
+ ima_add_violation(inode, dentry->d_name.name, "invalid_pcr",
+ "open_writers");
+}
+
+static void ima_check_last_writer(struct ima_iint_cache *iint,
+ struct inode *inode,
+ struct file *file)
+{
+ mode_t mode = file->f_mode;
+
+ mutex_lock(&iint->mutex);
+ if (mode & FMODE_WRITE &&
+ atomic_read(&inode->i_writecount) == 1 &&
+ iint->version != inode->i_version)
+ iint->flags &= ~IMA_MEASURED;
+ mutex_unlock(&iint->mutex);
+}
+
+/**
+ * ima_file_free - called on __fput()
+ * @file: pointer to file structure being freed
+ *
+ * Flag files that changed, based on i_version
+ */
+void ima_file_free(struct file *file)
+{
+ struct inode *inode = file->f_dentry->d_inode;
+ struct ima_iint_cache *iint;
+
+ if (!iint_initialized || !S_ISREG(inode->i_mode))
+ return;
+
+ iint = ima_iint_find(inode);
+ if (!iint)
+ return;
+
+ ima_check_last_writer(iint, inode, file);
+}
+
+static int process_measurement(struct file *file, const unsigned char *filename,
+ int mask, int function)
+{
+ struct inode *inode = file->f_dentry->d_inode;
+ struct ima_iint_cache *iint;
+ int rc = 0;
+
+ if (!ima_initialized || !S_ISREG(inode->i_mode))
+ return 0;
+
+ rc = ima_must_measure(inode, mask, function);
+ if (rc != 0)
+ return rc;
+retry:
+ iint = ima_iint_find(inode);
+ if (!iint) {
+ rc = ima_inode_alloc(inode);
+ if (!rc || rc == -EEXIST)
+ goto retry;
+ return rc;
+ }
+
+ mutex_lock(&iint->mutex);
+
+ rc = iint->flags & IMA_MEASURED ? 1 : 0;
+ if (rc != 0)
+ goto out;
+
+ rc = ima_collect_measurement(iint, file);
+ if (!rc)
+ ima_store_measurement(iint, file, filename);
+out:
+ mutex_unlock(&iint->mutex);
+ return rc;
+}
+
+/**
+ * ima_file_mmap - based on policy, collect/store measurement.
+ * @file: pointer to the file to be measured (May be NULL)
+ * @prot: contains the protection that will be applied by the kernel.
+ *
+ * Measure files being mmapped executable based on the ima_must_measure()
+ * policy decision.
+ *
+ * Return 0 on success, an error code on failure.
+ * (Based on the results of appraise_measurement().)
+ */
+int ima_file_mmap(struct file *file, unsigned long prot)
+{
+ int rc;
+
+ if (!file)
+ return 0;
+ if (prot & PROT_EXEC)
+ rc = process_measurement(file, file->f_dentry->d_name.name,
+ MAY_EXEC, FILE_MMAP);
+ return 0;
+}
+
+/**
+ * ima_bprm_check - based on policy, collect/store measurement.
+ * @bprm: contains the linux_binprm structure
+ *
+ * The OS protects against an executable file, already open for write,
+ * from being executed in deny_write_access() and an executable file,
+ * already open for execute, from being modified in get_write_access().
+ * So we can be certain that what we verify and measure here is actually
+ * what is being executed.
+ *
+ * Return 0 on success, an error code on failure.
+ * (Based on the results of appraise_measurement().)
+ */
+int ima_bprm_check(struct linux_binprm *bprm)
+{
+ int rc;
+
+ rc = process_measurement(bprm->file, bprm->filename,
+ MAY_EXEC, BPRM_CHECK);
+ return 0;
+}
+
+/**
+ * ima_path_check - based on policy, collect/store measurement.
+ * @file: pointer to the file to be measured
+ * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE
+ *
+ * Measure files based on the ima_must_measure() policy decision.
+ *
+ * Always return 0 and audit dentry_open failures.
+ * (Return code will be based upon measurement appraisal.)
+ */
+int ima_file_check(struct file *file, int mask)
+{
+ int rc;
+
+ ima_rdwr_violation_check(file);
+ rc = process_measurement(file, file->f_dentry->d_name.name,
+ mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
+ FILE_CHECK);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(ima_file_check);
+
+static int __init init_ima(void)
+{
+ int error;
+
+ error = ima_init();
+ ima_initialized = 1;
+ return error;
+}
+
+static void __exit cleanup_ima(void)
+{
+ ima_cleanup();
+}
+
+late_initcall(init_ima); /* Start IMA after the TPM is available */
+
+MODULE_DESCRIPTION("Integrity Measurement Architecture");
+MODULE_LICENSE("GPL");