ima: provide ">" and "<" operators for fowner/uid/euid rules.

For now we have only "=" operator for fowner/uid/euid rules. This
patch provide two more operators - ">" and "<" in order to make
fowner/uid/euid rules more flexible.

Examples of usage.

 Appraise all files owned by special and system users (SYS_UID_MAX 999):
    appraise fowner<1000
 Don't appraise files owned by normal users (UID_MIN 1000):
    dont_appraise fowner>999
 Appraise all files owned by users with UID 1000-1010:
    dont_appraise fowner>1010
    appraise fowner>999

Changelog v3:
- Removed code duplication in ima_parse_rule().
- Fix ima_policy_show() - (Mimi)

Changelog v2:
- Fixed default policy rules.

Signed-off-by: Mikhail Kurinnoi <viewizard@viewizard.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
 security/integrity/ima/ima_policy.c | 115 +++++++++++++++++++++++++++---------
 1 file changed, 87 insertions(+), 28 deletions(-)

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index e8498a3f4887facd715bedcdea80a5a2ae854a17..3ab1067db624d860f9303a5e3ea8587ebbed699b 100644 (file)
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -64,6 +64,8 @@ struct ima_rule_entry {
        u8 fsuuid[16];
        kuid_t uid;
        kuid_t fowner;
+       bool (*uid_op)(kuid_t, kuid_t);    /* Handlers for operators       */
+       bool (*fowner_op)(kuid_t, kuid_t); /* uid_eq(), uid_gt(), uid_lt() */
        int pcr;
        struct {
                void *rule;     /* LSM file metadata specific */
@@ -103,7 +105,8 @@ static struct ima_rule_entry original_measurement_rules[] __ro_after_init = {
        {.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
         .flags = IMA_FUNC | IMA_MASK},
        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
-        .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_MASK | IMA_UID},
+        .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
+        .flags = IMA_FUNC | IMA_MASK | IMA_UID},
        {.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
        {.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
 };
@@ -114,9 +117,11 @@ static struct ima_rule_entry default_measurement_rules[] __ro_after_init = {
        {.action = MEASURE, .func = BPRM_CHECK, .mask = MAY_EXEC,
         .flags = IMA_FUNC | IMA_MASK},
        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
-        .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_INMASK | IMA_EUID},
+        .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
+        .flags = IMA_FUNC | IMA_INMASK | IMA_EUID},
        {.action = MEASURE, .func = FILE_CHECK, .mask = MAY_READ,
-        .uid = GLOBAL_ROOT_UID, .flags = IMA_FUNC | IMA_INMASK | IMA_UID},
+        .uid = GLOBAL_ROOT_UID, .uid_op = &uid_eq,
+        .flags = IMA_FUNC | IMA_INMASK | IMA_UID},
        {.action = MEASURE, .func = MODULE_CHECK, .flags = IMA_FUNC},
        {.action = MEASURE, .func = FIRMWARE_CHECK, .flags = IMA_FUNC},
        {.action = MEASURE, .func = POLICY_CHECK, .flags = IMA_FUNC},
@@ -139,10 +144,11 @@ static struct ima_rule_entry default_appraise_rules[] __ro_after_init = {
        .flags = IMA_FUNC | IMA_DIGSIG_REQUIRED},
 #endif
 #ifndef CONFIG_IMA_APPRAISE_SIGNED_INIT
-       {.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .flags = IMA_FOWNER},
+       {.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .fowner_op = &uid_eq,
+        .flags = IMA_FOWNER},
 #else
        /* force signature */
-       {.action = APPRAISE, .fowner = GLOBAL_ROOT_UID,
+       {.action = APPRAISE, .fowner = GLOBAL_ROOT_UID, .fowner_op = &uid_eq,
         .flags = IMA_FOWNER | IMA_DIGSIG_REQUIRED},
 #endif
 };
@@ -240,19 +246,20 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
        if ((rule->flags & IMA_FSUUID) &&
            memcmp(rule->fsuuid, inode->i_sb->s_uuid, sizeof(rule->fsuuid)))
                return false;
-       if ((rule->flags & IMA_UID) && !uid_eq(rule->uid, cred->uid))
+       if ((rule->flags & IMA_UID) && !rule->uid_op(cred->uid, rule->uid))
                return false;
        if (rule->flags & IMA_EUID) {
                if (has_capability_noaudit(current, CAP_SETUID)) {
-                       if (!uid_eq(rule->uid, cred->euid)
-                           && !uid_eq(rule->uid, cred->suid)
-                           && !uid_eq(rule->uid, cred->uid))
+                       if (!rule->uid_op(cred->euid, rule->uid)
+                           && !rule->uid_op(cred->suid, rule->uid)
+                           && !rule->uid_op(cred->uid, rule->uid))
                                return false;
-               } else if (!uid_eq(rule->uid, cred->euid))
+               } else if (!rule->uid_op(cred->euid, rule->uid))
                        return false;
        }
 
-       if ((rule->flags & IMA_FOWNER) && !uid_eq(rule->fowner, inode->i_uid))
+       if ((rule->flags & IMA_FOWNER) &&
+           !rule->fowner_op(inode->i_uid, rule->fowner))
                return false;
        for (i = 0; i < MAX_LSM_RULES; i++) {
                int rc = 0;
@@ -486,7 +493,9 @@ enum {
        Opt_obj_user, Opt_obj_role, Opt_obj_type,
        Opt_subj_user, Opt_subj_role, Opt_subj_type,
        Opt_func, Opt_mask, Opt_fsmagic,
-       Opt_fsuuid, Opt_uid, Opt_euid, Opt_fowner,
+       Opt_fsuuid, Opt_uid_eq, Opt_euid_eq, Opt_fowner_eq,
+       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
 };
@@ -507,9 +516,15 @@ static match_table_t policy_tokens = {
        {Opt_mask, "mask=%s"},
        {Opt_fsmagic, "fsmagic=%s"},
        {Opt_fsuuid, "fsuuid=%s"},
-       {Opt_uid, "uid=%s"},
-       {Opt_euid, "euid=%s"},
-       {Opt_fowner, "fowner=%s"},
+       {Opt_uid_eq, "uid=%s"},
+       {Opt_euid_eq, "euid=%s"},
+       {Opt_fowner_eq, "fowner=%s"},
+       {Opt_uid_gt, "uid>%s"},
+       {Opt_euid_gt, "euid>%s"},
+       {Opt_fowner_gt, "fowner>%s"},
+       {Opt_uid_lt, "uid<%s"},
+       {Opt_euid_lt, "euid<%s"},
+       {Opt_fowner_lt, "fowner<%s"},
        {Opt_appraise_type, "appraise_type=%s"},
        {Opt_permit_directio, "permit_directio"},
        {Opt_pcr, "pcr=%s"},
@@ -541,24 +556,37 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry,
        return result;
 }
 
-static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
+static void ima_log_string_op(struct audit_buffer *ab, char *key, char *value,
+                             bool (*rule_operator)(kuid_t, kuid_t))
 {
-       audit_log_format(ab, "%s=", key);
+       if (rule_operator == &uid_gt)
+               audit_log_format(ab, "%s>", key);
+       else if (rule_operator == &uid_lt)
+               audit_log_format(ab, "%s<", key);
+       else
+               audit_log_format(ab, "%s=", key);
        audit_log_untrustedstring(ab, value);
        audit_log_format(ab, " ");
 }
+static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
+{
+       ima_log_string_op(ab, key, value, NULL);
+}
 
 static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 {
        struct audit_buffer *ab;
        char *from;
        char *p;
+       bool uid_token;
        int result = 0;
 
        ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE);
 
        entry->uid = INVALID_UID;
        entry->fowner = INVALID_UID;
+       entry->uid_op = &uid_eq;
+       entry->fowner_op = &uid_eq;
        entry->action = UNKNOWN;
        while ((p = strsep(&rule, " \t")) != NULL) {
                substring_t args[MAX_OPT_ARGS];
@@ -694,11 +722,21 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
                        if (!result)
                                entry->flags |= IMA_FSUUID;
                        break;
-               case Opt_uid:
-                       ima_log_string(ab, "uid", args[0].from);
-               case Opt_euid:
-                       if (token == Opt_euid)
-                               ima_log_string(ab, "euid", args[0].from);
+               case Opt_uid_gt:
+               case Opt_euid_gt:
+                       entry->uid_op = &uid_gt;
+               case Opt_uid_lt:
+               case Opt_euid_lt:
+                       if ((token == Opt_uid_lt) || (token == Opt_euid_lt))
+                               entry->uid_op = &uid_lt;
+               case Opt_uid_eq:
+               case Opt_euid_eq:
+                       uid_token = (token == Opt_uid_eq) ||
+                                   (token == Opt_uid_gt) ||
+                                   (token == Opt_uid_lt);
+
+                       ima_log_string_op(ab, uid_token ? "uid" : "euid",
+                                         args[0].from, entry->uid_op);
 
                        if (uid_valid(entry->uid)) {
                                result = -EINVAL;
@@ -713,12 +751,18 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
                                    (uid_t)lnum != lnum)
                                        result = -EINVAL;
                                else
-                                       entry->flags |= (token == Opt_uid)
+                                       entry->flags |= uid_token
                                            ? IMA_UID : IMA_EUID;
                        }
                        break;
-               case Opt_fowner:
-                       ima_log_string(ab, "fowner", args[0].from);
+               case Opt_fowner_gt:
+                       entry->fowner_op = &uid_gt;
+               case Opt_fowner_lt:
+                       if (token == Opt_fowner_lt)
+                               entry->fowner_op = &uid_lt;
+               case Opt_fowner_eq:
+                       ima_log_string_op(ab, "fowner", args[0].from,
+                                         entry->fowner_op);
 
                        if (uid_valid(entry->fowner)) {
                                result = -EINVAL;
@@ -1049,19 +1093,34 @@ int ima_policy_show(struct seq_file *m, void *v)
 
        if (entry->flags & IMA_UID) {
                snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->uid));
-               seq_printf(m, pt(Opt_uid), tbuf);
+               if (entry->uid_op == &uid_gt)
+                       seq_printf(m, pt(Opt_uid_gt), tbuf);
+               else if (entry->uid_op == &uid_lt)
+                       seq_printf(m, pt(Opt_uid_lt), tbuf);
+               else
+                       seq_printf(m, pt(Opt_uid_eq), tbuf);
                seq_puts(m, " ");
        }
 
        if (entry->flags & IMA_EUID) {
                snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->uid));
-               seq_printf(m, pt(Opt_euid), tbuf);
+               if (entry->uid_op == &uid_gt)
+                       seq_printf(m, pt(Opt_euid_gt), tbuf);
+               else if (entry->uid_op == &uid_lt)
+                       seq_printf(m, pt(Opt_euid_lt), tbuf);
+               else
+                       seq_printf(m, pt(Opt_euid_eq), tbuf);
                seq_puts(m, " ");
        }
 
        if (entry->flags & IMA_FOWNER) {
                snprintf(tbuf, sizeof(tbuf), "%d", __kuid_val(entry->fowner));
-               seq_printf(m, pt(Opt_fowner), tbuf);
+               if (entry->fowner_op == &uid_gt)
+                       seq_printf(m, pt(Opt_fowner_gt), tbuf);
+               else if (entry->fowner_op == &uid_lt)
+                       seq_printf(m, pt(Opt_fowner_lt), tbuf);
+               else
+                       seq_printf(m, pt(Opt_fowner_eq), tbuf);
                seq_puts(m, " ");
        }