[PATCH 2/7] ima: Introduce template fields iuid and igid

Roberto Sassu
2021-05-20T08:57:26Z

This patch introduces the new template fields iuid and igid, which include
respectively the inode UID and GID. If the inode is part of an idmapped
mount, the UID and GID are the mapped ones and need to be translated with
the new fields mntuidmap and mntgidmap included in a subsequent patch, in
order to get the original UID and GID.

These fields can be used to verify the EVM portable signature, if it was
included with the template fields sig or evmsig.

Cc: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
Documentation/security/IMA-templates.rst | 2 +
security/integrity/ima/ima_template.c | 4 ++
security/integrity/ima/ima_template_lib.c | 58 +++++++++++++++++++++++
security/integrity/ima/ima_template_lib.h | 4 ++
4 files changed, 68 insertions(+)

diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
index 9f3e86ab028a..bf8ce4cf5878 100644
--- a/Documentation/security/IMA-templates.rst
+++ b/Documentation/security/IMA-templates.rst
@@ -75,6 +75,8 @@ descriptors by adding their identifier to the format string
- 'modsig' the appended file signature;
- 'buf': the buffer data that was used to generate the hash without size limitations;
- 'evmsig': the EVM portable signature;
+ - 'iuid': the inode UID;
+ - 'igid': the inode GID;

Below, there is the list of defined template descriptors:
diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
index 7a60848c04a5..a5ecd9e2581b 100644
--- a/security/integrity/ima/ima_template.c
+++ b/security/integrity/ima/ima_template.c
@@ -47,6 +47,10 @@ static const struct ima_template_field supported_fields[] = {
.field_show = ima_show_template_sig},
{.field_id = "evmsig", .field_init = ima_eventevmsig_init,
.field_show = ima_show_template_sig},
+ {.field_id = "iuid", .field_init = ima_eventinodeuid_init,
+ .field_show = ima_show_template_uint},
+ {.field_id = "igid", .field_init = ima_eventinodegid_init,
+ .field_show = ima_show_template_uint},
};

/*
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index f23296c33da1..a191b861548b 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -551,3 +551,61 @@ int ima_eventevmsig_init(struct ima_event_data *event_data,
kfree(xattr_data);
return rc;
}
+
+static int ima_eventinodedac_init_common(struct ima_event_data *event_data,
+ struct ima_field_data *field_data,
+ bool get_uid)
+{
+ struct user_namespace *mnt_userns;
+ uid_t uid;
+ gid_t gid;
+ char *data_ptr = (char *)&uid;
+
+ if (!event_data->file)
+ return 0;
+
+ mnt_userns = file_mnt_user_ns(event_data->file);
+ if (get_uid) {
+ uid = from_kuid(&init_user_ns,
+ i_uid_into_mnt(mnt_userns,
+ file_inode(event_data->file)));
+ } else {
+ gid = from_kgid(&init_user_ns,
+ i_gid_into_mnt(mnt_userns,
+ file_inode(event_data->file)));
+ data_ptr = (char *)&gid;
+ }
+
+ if (ima_canonical_fmt) {
+ if (sizeof(uid) == sizeof(u16)) {
+ uid = cpu_to_le16(uid);
+ gid = cpu_to_le16(gid);
+ } else {
+ uid = cpu_to_le32(uid);
+ gid = cpu_to_le32(gid);
+ }
+ }
+
+ return ima_write_template_field_data(data_ptr, sizeof(uid),
+ DATA_FMT_UINT, field_data);
+}
+
+/*
+ * ima_eventinodeuid_init - include the inode UID as part of the template
+ * data
+ */
+int ima_eventinodeuid_init(struct ima_event_data *event_data,
+ struct ima_field_data *field_data)
+{
+ return ima_eventinodedac_init_common(event_data, field_data, true);
+}
+
+/*
+ * ima_eventinodegid_init - include the inode GID as part of the template
+ * data
+ */
+int ima_eventinodegid_init(struct ima_event_data *event_data,
+ struct ima_field_data *field_data)
+{
+ return ima_eventinodedac_init_common(event_data, field_data, false);
+}
diff --git a/security/integrity/ima/ima_template_lib.h b/security/integrity/ima/ima_template_lib.h
index 54b67c80b315..b0aaf109f386 100644
--- a/security/integrity/ima/ima_template_lib.h
+++ b/security/integrity/ima/ima_template_lib.h
@@ -50,4 +50,8 @@ int ima_eventmodsig_init(struct ima_event_data *event_data,
struct ima_field_data *field_data);
int ima_eventevmsig_init(struct ima_event_data *event_data,
struct ima_field_data *field_data);
+int ima_eventinodeuid_init(struct ima_event_data *event_data,
+ struct ima_field_data *field_data);
+int ima_eventinodegid_init(struct ima_event_data *event_data,
+ struct ima_field_data *field_data);
#endif /* __LINUX_IMA_TEMPLATE_LIB_H */
--
2.25.1