diff options
Diffstat (limited to 'security/integrity/ima/ima_main.c')
-rw-r--r-- | security/integrity/ima/ima_main.c | 240 |
1 files changed, 240 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c new file mode 100644 index 00000000..39d66dc2 --- /dev/null +++ b/security/integrity/ima/ima_main.c @@ -0,0 +1,240 @@ +/* + * 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"); |