diff options
Diffstat (limited to 'security/integrity/ima/ima_policy.c')
| -rw-r--r-- | security/integrity/ima/ima_policy.c | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c new file mode 100644 index 000000000000..7c3d1ffb1472 --- /dev/null +++ b/security/integrity/ima/ima_policy.c @@ -0,0 +1,126 @@ +/* + * Copyright (C) 2008 IBM Corporation + * Author: 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. + * + * ima_policy.c + * - initialize default measure policy rules + * + */ +#include <linux/module.h> +#include <linux/list.h> +#include <linux/audit.h> +#include <linux/security.h> +#include <linux/magic.h> + +#include "ima.h" + +/* flags definitions */ +#define IMA_FUNC 0x0001 +#define IMA_MASK 0x0002 +#define IMA_FSMAGIC 0x0004 +#define IMA_UID 0x0008 + +enum ima_action { DONT_MEASURE, MEASURE }; + +struct ima_measure_rule_entry { + struct list_head list; + enum ima_action action; + unsigned int flags; + enum ima_hooks func; + int mask; + unsigned long fsmagic; + uid_t uid; +}; + +static struct ima_measure_rule_entry default_rules[] = { + {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC, + .flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC, + .flags = IMA_FSMAGIC}, + {.action = DONT_MEASURE,.fsmagic = 0xF97CFF8C,.flags = IMA_FSMAGIC}, + {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC, + .flags = IMA_FUNC | IMA_MASK}, + {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC, + .flags = IMA_FUNC | IMA_MASK}, + {.action = MEASURE,.func = PATH_CHECK,.mask = MAY_READ,.uid = 0, + .flags = IMA_FUNC | IMA_MASK | IMA_UID} +}; + +static LIST_HEAD(measure_default_rules); +static struct list_head *ima_measure; + +/** + * ima_match_rules - determine whether an inode matches the measure rule. + * @rule: a pointer to a rule + * @inode: a pointer to an inode + * @func: LIM hook identifier + * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) + * + * Returns true on rule match, false on failure. + */ +static bool ima_match_rules(struct ima_measure_rule_entry *rule, + struct inode *inode, enum ima_hooks func, int mask) +{ + struct task_struct *tsk = current; + + if ((rule->flags & IMA_FUNC) && rule->func != func) + return false; + if ((rule->flags & IMA_MASK) && rule->mask != mask) + return false; + if ((rule->flags & IMA_FSMAGIC) + && rule->fsmagic != inode->i_sb->s_magic) + return false; + if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid) + return false; + return true; +} + +/** + * ima_match_policy - decision based on LSM and other conditions + * @inode: pointer to an inode for which the policy decision is being made + * @func: IMA hook identifier + * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) + * + * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) + * conditions. + * + * (There is no need for locking when walking the policy list, + * as elements in the list are never deleted, nor does the list + * change.) + */ +int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask) +{ + struct ima_measure_rule_entry *entry; + + list_for_each_entry(entry, ima_measure, list) { + bool rc; + + rc = ima_match_rules(entry, inode, func, mask); + if (rc) + return entry->action; + } + return 0; +} + +/** + * ima_init_policy - initialize the default measure rules. + * + * (Could use the default_rules directly, but in policy patch + * ima_measure points to either the measure_default_rules or the + * the new measure_policy_rules.) + */ +void ima_init_policy(void) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(default_rules); i++) + list_add_tail(&default_rules[i].list, &measure_default_rules); + ima_measure = &measure_default_rules; +} |