[PATCH v7 7/7] ima: add policy support for the new file open MAY_OPENEXEC flag

Mickaël Salaün
2020-07-23T17:13:12Z

From: Mimi Zohar <zohar@linux.ibm.com>

The kernel has no way of differentiating between a file containing data
or code being opened by an interpreter. The proposed O_MAYEXEC
openat2(2) flag bridges this gap by defining and enabling the
MAY_OPENEXEC flag.

This patch adds IMA policy support for the new MAY_OPENEXEC flag.

Example:
measure func=FILE_CHECK mask=^MAY_OPENEXEC
appraise func=FILE_CHECK appraise_type=imasig mask=^MAY_OPENEXEC

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Link: https://lore.kernel.org/r/1588167523-7866-3-git-send-email-zohar@linux.ibm.com
---
Documentation/ABI/testing/ima_policy | 2 +-
security/integrity/ima/ima_main.c | 3 ++-
security/integrity/ima/ima_policy.c | 15 +++++++++++----
3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index cd572912c593..caca46125fe0 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -31,7 +31,7 @@ Description:
[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
[KEXEC_CMDLINE] [KEY_CHECK]
mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
- [[^]MAY_EXEC]
+ [[^]MAY_EXEC] [[^]MAY_OPENEXEC]
fsmagic:= hex value
fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
uid:= decimal value
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index c1583d98c5e5..59fd1658a203 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -490,7 +490,8 @@ int ima_file_check(struct file *file, int mask)

security_task_getsecid(current, &secid);
return process_measurement(file, current_cred(), secid, NULL, 0,
- mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
+ mask & (MAY_READ | MAY_WRITE |
+ MAY_EXEC | MAY_OPENEXEC |
MAY_APPEND), FILE_CHECK);
}
EXPORT_SYMBOL_GPL(ima_file_check);
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index e493063a3c34..6487f0b2afdd 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -406,7 +406,8 @@ static bool ima_match_keyring(struct ima_rule_entry *rule,
* @cred: a pointer to a credentials structure for user validation
* @secid: the secid of the task to be validated
* @func: LIM hook identifier
- * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
+ * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC |
+ * MAY_OPENEXEC)
* @keyring: keyring name to check in policy for KEY_CHECK func
*
* Returns true on rule match, false on failure.
@@ -527,7 +528,8 @@ static int get_subaction(struct ima_rule_entry *rule, enum ima_hooks func)
* being made
* @secid: LSM secid of the task to be validated
* @func: IMA hook identifier
- * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC)
+ * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC |
+ * MAY_OPENEXEC)
* @pcr: set the pcr to extend
* @template_desc: the template that should be used for this rule
* @keyring: the keyring name, if given, to be used to check in the policy.
@@ -1091,6 +1093,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
entry->mask = MAY_READ;
else if (strcmp(from, "MAY_APPEND") == 0)
entry->mask = MAY_APPEND;
+ else if (strcmp(from, "MAY_OPENEXEC") == 0)
+ entry->mask = MAY_OPENEXEC;
else
result = -EINVAL;
if (!result)
@@ -1422,14 +1426,15 @@ const char *const func_tokens[] = {

#ifdef CONFIG_IMA_READ_POLICY
enum {
- mask_exec = 0, mask_write, mask_read, mask_append
+ mask_exec = 0, mask_write, mask_read, mask_append, mask_openexec
};

static const char *const mask_tokens[] = {
"^MAY_EXEC",
"^MAY_WRITE",
"^MAY_READ",
- "^MAY_APPEND"
+ "^MAY_APPEND",
+ "^MAY_OPENEXEC"
};

void *ima_policy_start(struct seq_file *m, loff_t *pos)
@@ -1518,6 +1523,8 @@ int ima_policy_show(struct seq_file *m, void *v)
seq_printf(m, pt(Opt_mask), mt(mask_read) + offset);
if (entry->mask & MAY_APPEND)
seq_printf(m, pt(Opt_mask), mt(mask_append) + offset);
+ if (entry->mask & MAY_OPENEXEC)
+ seq_printf(m, pt(Opt_mask), mt(mask_openexec) + offset);
seq_puts(m, " ");
}

--
2.27.0