diff options
Diffstat (limited to 'security/integrity/ima/ima_policy.c')
| -rw-r--r-- | security/integrity/ima/ima_policy.c | 314 |
1 files changed, 266 insertions, 48 deletions
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index e0cc323f948f..5380aca2b351 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -1,15 +1,14 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * 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 - * */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + #include <linux/init.h> #include <linux/list.h> #include <linux/fs.h> @@ -80,6 +79,7 @@ struct ima_rule_entry { int type; /* audit type */ } lsm[MAX_LSM_RULES]; char *fsname; + struct ima_template_desc *template; }; /* @@ -199,7 +199,7 @@ static struct ima_rule_entry secure_boot_rules[] __ro_after_init = { }; /* An array of architecture specific rules */ -struct ima_rule_entry *arch_policy_entry __ro_after_init; +static struct ima_rule_entry *arch_policy_entry __ro_after_init; static LIST_HEAD(ima_default_rules); static LIST_HEAD(ima_policy_rules); @@ -249,31 +249,113 @@ static int __init default_appraise_policy_setup(char *str) } __setup("ima_appraise_tcb", default_appraise_policy_setup); +static void ima_lsm_free_rule(struct ima_rule_entry *entry) +{ + int i; + + for (i = 0; i < MAX_LSM_RULES; i++) { + kfree(entry->lsm[i].rule); + kfree(entry->lsm[i].args_p); + } + kfree(entry); +} + +static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry) +{ + struct ima_rule_entry *nentry; + int i, result; + + nentry = kmalloc(sizeof(*nentry), GFP_KERNEL); + if (!nentry) + return NULL; + + /* + * Immutable elements are copied over as pointers and data; only + * lsm rules can change + */ + memcpy(nentry, entry, sizeof(*nentry)); + memset(nentry->lsm, 0, FIELD_SIZEOF(struct ima_rule_entry, lsm)); + + for (i = 0; i < MAX_LSM_RULES; i++) { + if (!entry->lsm[i].rule) + continue; + + nentry->lsm[i].type = entry->lsm[i].type; + nentry->lsm[i].args_p = kstrdup(entry->lsm[i].args_p, + GFP_KERNEL); + if (!nentry->lsm[i].args_p) + goto out_err; + + result = security_filter_rule_init(nentry->lsm[i].type, + Audit_equal, + nentry->lsm[i].args_p, + &nentry->lsm[i].rule); + if (result == -EINVAL) + pr_warn("ima: rule for LSM \'%d\' is undefined\n", + entry->lsm[i].type); + } + return nentry; + +out_err: + ima_lsm_free_rule(nentry); + return NULL; +} + +static int ima_lsm_update_rule(struct ima_rule_entry *entry) +{ + struct ima_rule_entry *nentry; + + nentry = ima_lsm_copy_rule(entry); + if (!nentry) + return -ENOMEM; + + list_replace_rcu(&entry->list, &nentry->list); + synchronize_rcu(); + ima_lsm_free_rule(entry); + + return 0; +} + /* * The LSM policy can be reloaded, leaving the IMA LSM based rules referring * to the old, stale LSM policy. Update the IMA LSM based rules to reflect - * the reloaded LSM policy. We assume the rules still exist; and BUG_ON() if - * they don't. + * the reloaded LSM policy. */ static void ima_lsm_update_rules(void) { - struct ima_rule_entry *entry; - int result; - int i; + struct ima_rule_entry *entry, *e; + int i, result, needs_update; - list_for_each_entry(entry, &ima_policy_rules, list) { + list_for_each_entry_safe(entry, e, &ima_policy_rules, list) { + needs_update = 0; for (i = 0; i < MAX_LSM_RULES; i++) { - if (!entry->lsm[i].rule) - continue; - result = security_filter_rule_init(entry->lsm[i].type, - Audit_equal, - entry->lsm[i].args_p, - &entry->lsm[i].rule); - BUG_ON(!entry->lsm[i].rule); + if (entry->lsm[i].rule) { + needs_update = 1; + break; + } + } + if (!needs_update) + continue; + + result = ima_lsm_update_rule(entry); + if (result) { + pr_err("ima: lsm rule update error %d\n", + result); + return; } } } +int ima_lsm_policy_change(struct notifier_block *nb, unsigned long event, + void *lsm_data) +{ + if (event != LSM_POLICY_CHANGE) + return NOTIFY_DONE; + + ima_lsm_update_rules(); + return NOTIFY_OK; +} + /** * ima_match_rules - determine whether an inode matches the measure rule. * @rule: a pointer to a rule @@ -291,6 +373,11 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, { int i; + if (func == KEXEC_CMDLINE) { + if ((rule->flags & IMA_FUNC) && (rule->func == func)) + return true; + return false; + } if ((rule->flags & IMA_FUNC) && (rule->func != func && func != POST_SETATTR)) return false; @@ -327,11 +414,10 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, for (i = 0; i < MAX_LSM_RULES; i++) { int rc = 0; u32 osid; - int retried = 0; if (!rule->lsm[i].rule) continue; -retry: + switch (i) { case LSM_OBJ_USER: case LSM_OBJ_ROLE: @@ -352,11 +438,6 @@ retry: default: break; } - if ((rc < 0) && (!retried)) { - retried = 1; - ima_lsm_update_rules(); - goto retry; - } if (!rc) return false; } @@ -397,6 +478,7 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func) * @func: IMA hook identifier * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) * @pcr: set the pcr to extend + * @template_desc: the template that should be used for this rule * * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) * conditions. @@ -406,11 +488,15 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func) * than writes so ima_match_policy() is classical RCU candidate. */ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, - enum ima_hooks func, int mask, int flags, int *pcr) + enum ima_hooks func, int mask, int flags, int *pcr, + struct ima_template_desc **template_desc) { struct ima_rule_entry *entry; int action = 0, actmask = flags | (flags << 1); + if (template_desc) + *template_desc = ima_template_desc_current(); + rcu_read_lock(); list_for_each_entry_rcu(entry, ima_rules, list) { @@ -430,6 +516,7 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, action |= IMA_FAIL_UNVERIFIABLE_SIGS; } + if (entry->action & IMA_DO_MASK) actmask &= ~(entry->action | entry->action << 1); else @@ -438,6 +525,9 @@ int ima_match_policy(struct inode *inode, const struct cred *cred, u32 secid, if ((pcr) && (entry->flags & IMA_PCR)) *pcr = entry->pcr; + if (template_desc && entry->template) + *template_desc = entry->template; + if (!actmask) break; } @@ -498,10 +588,11 @@ static void add_rules(struct ima_rule_entry *entries, int count, list_add_tail(&entry->list, &ima_policy_rules); } - if (entries[i].action == APPRAISE) + if (entries[i].action == APPRAISE) { temp_ima_appraise |= ima_appraise_flag(entries[i].func); - if (entries[i].func == POLICY_CHECK) - temp_ima_appraise |= IMA_APPRAISE_POLICY; + if (entries[i].func == POLICY_CHECK) + temp_ima_appraise |= IMA_APPRAISE_POLICY; + } } } @@ -675,7 +766,7 @@ enum { Opt_uid_gt, Opt_euid_gt, Opt_fowner_gt, Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt, Opt_appraise_type, Opt_permit_directio, - Opt_pcr, Opt_err + Opt_pcr, Opt_template, Opt_err }; static const match_table_t policy_tokens = { @@ -709,6 +800,7 @@ static const match_table_t policy_tokens = { {Opt_appraise_type, "appraise_type=%s"}, {Opt_permit_directio, "permit_directio"}, {Opt_pcr, "pcr=%s"}, + {Opt_template, "template=%s"}, {Opt_err, NULL} }; @@ -756,12 +848,45 @@ static void ima_log_string(struct audit_buffer *ab, char *key, char *value) ima_log_string_op(ab, key, value, NULL); } +/* + * Validating the appended signature included in the measurement list requires + * the file hash calculated without the appended signature (i.e., the 'd-modsig' + * field). Therefore, notify the user if they have the 'modsig' field but not + * the 'd-modsig' field in the template. + */ +static void check_template_modsig(const struct ima_template_desc *template) +{ +#define MSG "template with 'modsig' field also needs 'd-modsig' field\n" + bool has_modsig, has_dmodsig; + static bool checked; + int i; + + /* We only need to notify the user once. */ + if (checked) + return; + + has_modsig = has_dmodsig = false; + for (i = 0; i < template->num_fields; i++) { + if (!strcmp(template->fields[i]->field_id, "modsig")) + has_modsig = true; + else if (!strcmp(template->fields[i]->field_id, "d-modsig")) + has_dmodsig = true; + } + + if (has_modsig && !has_dmodsig) + pr_notice(MSG); + + checked = true; +#undef MSG +} + static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) { struct audit_buffer *ab; char *from; char *p; bool uid_token; + struct ima_template_desc *template_desc; int result = 0; ab = integrity_audit_log_start(audit_context(), GFP_KERNEL, @@ -869,6 +994,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) entry->func = KEXEC_INITRAMFS_CHECK; else if (strcmp(args[0].from, "POLICY_CHECK") == 0) entry->func = POLICY_CHECK; + else if (strcmp(args[0].from, "KEXEC_CMDLINE") == 0) + entry->func = KEXEC_CMDLINE; else result = -EINVAL; if (!result) @@ -1038,6 +1165,10 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) ima_log_string(ab, "appraise_type", args[0].from); if ((strcmp(args[0].from, "imasig")) == 0) entry->flags |= IMA_DIGSIG_REQUIRED; + else if (ima_hook_supports_modsig(entry->func) && + strcmp(args[0].from, "imasig|modsig") == 0) + entry->flags |= IMA_DIGSIG_REQUIRED | + IMA_MODSIG_ALLOWED; else result = -EINVAL; break; @@ -1058,6 +1189,28 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) entry->flags |= IMA_PCR; break; + case Opt_template: + ima_log_string(ab, "template", args[0].from); + if (entry->action != MEASURE) { + result = -EINVAL; + break; + } + template_desc = lookup_template_desc(args[0].from); + if (!template_desc || entry->template) { + result = -EINVAL; + break; + } + + /* + * template_desc_init_fields() does nothing if + * the template is already initialised, so + * it's safe to do this unconditionally + */ + template_desc_init_fields(template_desc->fmt, + &(template_desc->fields), + &(template_desc->num_fields)); + entry->template = template_desc; + break; case Opt_err: ima_log_string(ab, "UNKNOWN", p); result = -EINVAL; @@ -1069,6 +1222,12 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) else if (entry->action == APPRAISE) temp_ima_appraise |= ima_appraise_flag(entry->func); + if (!result && entry->flags & IMA_MODSIG_ALLOWED) { + template_desc = entry->template ? entry->template : + ima_template_desc_current(); + check_template_modsig(template_desc); + } + audit_log_format(ab, "res=%d", !result); audit_log_end(ab); return result; @@ -1140,22 +1299,22 @@ void ima_delete_rules(void) } } +#define __ima_hook_stringify(str) (#str), + +const char *const func_tokens[] = { + __ima_hooks(__ima_hook_stringify) +}; + #ifdef CONFIG_IMA_READ_POLICY enum { mask_exec = 0, mask_write, mask_read, mask_append }; static const char *const mask_tokens[] = { - "MAY_EXEC", - "MAY_WRITE", - "MAY_READ", - "MAY_APPEND" -}; - -#define __ima_hook_stringify(str) (#str), - -static const char *const func_tokens[] = { - __ima_hooks(__ima_hook_stringify) + "^MAY_EXEC", + "^MAY_WRITE", + "^MAY_READ", + "^MAY_APPEND" }; void *ima_policy_start(struct seq_file *m, loff_t *pos) @@ -1209,6 +1368,7 @@ int ima_policy_show(struct seq_file *m, void *v) struct ima_rule_entry *entry = v; int i; char tbuf[64] = {0,}; + int offset = 0; rcu_read_lock(); @@ -1232,15 +1392,17 @@ int ima_policy_show(struct seq_file *m, void *v) if (entry->flags & IMA_FUNC) policy_func_show(m, entry->func); - if (entry->flags & IMA_MASK) { + if ((entry->flags & IMA_MASK) || (entry->flags & IMA_INMASK)) { + if (entry->flags & IMA_MASK) + offset = 1; if (entry->mask & MAY_EXEC) - seq_printf(m, pt(Opt_mask), mt(mask_exec)); + seq_printf(m, pt(Opt_mask), mt(mask_exec) + offset); if (entry->mask & MAY_WRITE) - seq_printf(m, pt(Opt_mask), mt(mask_write)); + seq_printf(m, pt(Opt_mask), mt(mask_write) + offset); if (entry->mask & MAY_READ) - seq_printf(m, pt(Opt_mask), mt(mask_read)); + seq_printf(m, pt(Opt_mask), mt(mask_read) + offset); if (entry->mask & MAY_APPEND) - seq_printf(m, pt(Opt_mask), mt(mask_append)); + seq_printf(m, pt(Opt_mask), mt(mask_append) + offset); seq_puts(m, " "); } @@ -1330,8 +1492,14 @@ int ima_policy_show(struct seq_file *m, void *v) } } } - if (entry->flags & IMA_DIGSIG_REQUIRED) - seq_puts(m, "appraise_type=imasig "); + if (entry->template) + seq_printf(m, "template=%s ", entry->template->name); + if (entry->flags & IMA_DIGSIG_REQUIRED) { + if (entry->flags & IMA_MODSIG_ALLOWED) + seq_puts(m, "appraise_type=imasig|modsig "); + else + seq_puts(m, "appraise_type=imasig "); + } if (entry->flags & IMA_PERMIT_DIRECTIO) seq_puts(m, "permit_directio "); rcu_read_unlock(); @@ -1339,3 +1507,53 @@ int ima_policy_show(struct seq_file *m, void *v) return 0; } #endif /* CONFIG_IMA_READ_POLICY */ + +#if defined(CONFIG_IMA_APPRAISE) && defined(CONFIG_INTEGRITY_TRUSTED_KEYRING) +/* + * ima_appraise_signature: whether IMA will appraise a given function using + * an IMA digital signature. This is restricted to cases where the kernel + * has a set of built-in trusted keys in order to avoid an attacker simply + * loading additional keys. + */ +bool ima_appraise_signature(enum kernel_read_file_id id) +{ + struct ima_rule_entry *entry; + bool found = false; + enum ima_hooks func; + + if (id >= READING_MAX_ID) + return false; + + func = read_idmap[id] ?: FILE_CHECK; + + rcu_read_lock(); + list_for_each_entry_rcu(entry, ima_rules, list) { + if (entry->action != APPRAISE) + continue; + + /* + * A generic entry will match, but otherwise require that it + * match the func we're looking for + */ + if (entry->func && entry->func != func) + continue; + + /* + * We require this to be a digital signature, not a raw IMA + * hash. + */ + if (entry->flags & IMA_DIGSIG_REQUIRED) + found = true; + + /* + * We've found a rule that matches, so break now even if it + * didn't require a digital signature - a later rule that does + * won't override it, so would be a false positive. + */ + break; + } + + rcu_read_unlock(); + return found; +} +#endif /* CONFIG_IMA_APPRAISE && CONFIG_INTEGRITY_TRUSTED_KEYRING */ |