1/* 2 * Copyright (C) 2008 IBM Corporation 3 * 4 * Author: Mimi Zohar <zohar@us.ibm.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation, version 2 of the 9 * License. 10 * 11 * File: ima_api.c 12 * Implements must_measure, collect_measurement, store_measurement, 13 * and store_template. 14 */ 15#include <linux/module.h> 16#include <linux/slab.h> 17 18#include "ima.h" 19static const char *IMA_TEMPLATE_NAME = "ima"; 20 21/* 22 * ima_store_template - store ima template measurements 23 * 24 * Calculate the hash of a template entry, add the template entry 25 * to an ordered list of measurement entries maintained inside the kernel, 26 * and also update the aggregate integrity value (maintained inside the 27 * configured TPM PCR) over the hashes of the current list of measurement 28 * entries. 29 * 30 * Applications retrieve the current kernel-held measurement list through 31 * the securityfs entries in /sys/kernel/security/ima. The signed aggregate 32 * TPM PCR (called quote) can be retrieved using a TPM user space library 33 * and is used to validate the measurement list. 34 * 35 * Returns 0 on success, error code otherwise 36 */ 37int ima_store_template(struct ima_template_entry *entry, 38 int violation, struct inode *inode) 39{ 40 const char *op = "add_template_measure"; 41 const char *audit_cause = "hashing_error"; 42 int result; 43 44 memset(entry->digest, 0, sizeof(entry->digest)); 45 entry->template_name = IMA_TEMPLATE_NAME; 46 entry->template_len = sizeof(entry->template); 47 48 if (!violation) { 49 result = ima_calc_template_hash(entry->template_len, 50 &entry->template, 51 entry->digest); 52 if (result < 0) { 53 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, 54 entry->template_name, op, 55 audit_cause, result, 0); 56 return result; 57 } 58 } 59 result = ima_add_template_entry(entry, violation, op, inode); 60 return result; 61} 62 63/* 64 * ima_add_violation - add violation to measurement list. 65 * 66 * Violations are flagged in the measurement list with zero hash values. 67 * By extending the PCR with 0xFF's instead of with zeroes, the PCR 68 * value is invalidated. 69 */ 70void ima_add_violation(struct inode *inode, const unsigned char *filename, 71 const char *op, const char *cause) 72{ 73 struct ima_template_entry *entry; 74 int violation = 1; 75 int result; 76 77 /* can overflow, only indicator */ 78 atomic_long_inc(&ima_htable.violations); 79 80 entry = kmalloc(sizeof(*entry), GFP_KERNEL); 81 if (!entry) { 82 result = -ENOMEM; 83 goto err_out; 84 } 85 memset(&entry->template, 0, sizeof(entry->template)); 86 strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX); 87 result = ima_store_template(entry, violation, inode); 88 if (result < 0) 89 kfree(entry); 90err_out: 91 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, 92 op, cause, result, 0); 93} 94 95/** 96 * ima_must_measure - measure decision based on policy. 97 * @inode: pointer to inode to measure 98 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE) 99 * @function: calling function (FILE_CHECK, BPRM_CHECK, FILE_MMAP) 100 * 101 * The policy is defined in terms of keypairs: 102 * subj=, obj=, type=, func=, mask=, fsmagic= 103 * subj,obj, and type: are LSM specific. 104 * func: FILE_CHECK | BPRM_CHECK | FILE_MMAP 105 * mask: contains the permission mask 106 * fsmagic: hex value 107 * 108 * Must be called with iint->mutex held. 109 * 110 * Return 0 to measure. Return 1 if already measured. 111 * For matching a DONT_MEASURE policy, no policy, or other 112 * error, return an error code. 113*/ 114int ima_must_measure(struct ima_iint_cache *iint, struct inode *inode, 115 int mask, int function) 116{ 117 int must_measure; 118 119 if (iint->flags & IMA_MEASURED) 120 return 1; 121 122 must_measure = ima_match_policy(inode, function, mask); 123 return must_measure ? 0 : -EACCES; 124} 125 126/* 127 * ima_collect_measurement - collect file measurement 128 * 129 * Calculate the file hash, if it doesn't already exist, 130 * storing the measurement and i_version in the iint. 131 * 132 * Must be called with iint->mutex held. 133 * 134 * Return 0 on success, error code otherwise 135 */ 136int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file) 137{ 138 int result = -EEXIST; 139 140 if (!(iint->flags & IMA_MEASURED)) { 141 u64 i_version = file->f_dentry->d_inode->i_version; 142 143 memset(iint->digest, 0, IMA_DIGEST_SIZE); 144 result = ima_calc_hash(file, iint->digest); 145 if (!result) 146 iint->version = i_version; 147 } 148 return result; 149} 150 151/* 152 * ima_store_measurement - store file measurement 153 * 154 * Create an "ima" template and then store the template by calling 155 * ima_store_template. 156 * 157 * We only get here if the inode has not already been measured, 158 * but the measurement could already exist: 159 * - multiple copies of the same file on either the same or 160 * different filesystems. 161 * - the inode was previously flushed as well as the iint info, 162 * containing the hashing info. 163 * 164 * Must be called with iint->mutex held. 165 */ 166void ima_store_measurement(struct ima_iint_cache *iint, struct file *file, 167 const unsigned char *filename) 168{ 169 const char *op = "add_template_measure"; 170 const char *audit_cause = "ENOMEM"; 171 int result = -ENOMEM; 172 struct inode *inode = file->f_dentry->d_inode; 173 struct ima_template_entry *entry; 174 int violation = 0; 175 176 entry = kmalloc(sizeof(*entry), GFP_KERNEL); 177 if (!entry) { 178 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, 179 op, audit_cause, result, 0); 180 return; 181 } 182 memset(&entry->template, 0, sizeof(entry->template)); 183 memcpy(entry->template.digest, iint->digest, IMA_DIGEST_SIZE); 184 strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX); 185 186 result = ima_store_template(entry, violation, inode); 187 if (!result) 188 iint->flags |= IMA_MEASURED; 189 else 190 kfree(entry); 191} 192