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ima: provide ">" and "<" operators for fowner/uid/euid rules.
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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(-)
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Mikhail Kurinnoi authored and Mimi Zohar committed Mar 13, 2017
1 parent 1ac202e commit 3dd0c8d
Showing 1 changed file with 87 additions and 28 deletions.
115 changes: 87 additions & 28 deletions security/integrity/ima/ima_policy.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 */
Expand Down Expand Up @@ -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},
};
Expand All @@ -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},
Expand All @@ -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
};
Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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
};
Expand All @@ -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"},
Expand Down Expand Up @@ -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];
Expand Down Expand Up @@ -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;
Expand All @@ -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;
Expand Down Expand Up @@ -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, " ");
}

Expand Down

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