[PATCH v9 09/11] AppArmor: Add selfattr hooks

Casey Schaufler
2023-04-21T17:48:53Z

Add hooks for setselfattr and getselfattr. These hooks are not very
different from their setprocattr and getprocattr equivalents, and
much of the code is shared.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: John Johansen <john.johansen@canonical.com>
---
security/apparmor/include/procattr.h | 2 +-
security/apparmor/lsm.c | 96 ++++++++++++++++++++++++++--
security/apparmor/procattr.c | 11 +++-
3 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/security/apparmor/include/procattr.h b/security/apparmor/include/procattr.h
index 31689437e0e1..03dbfdb2f2c0 100644
--- a/security/apparmor/include/procattr.h
+++ b/security/apparmor/include/procattr.h
@@ -11,7 +11,7 @@
#ifndef __AA_PROCATTR_H
#define __AA_PROCATTR_H

-int aa_getprocattr(struct aa_label *label, char **string);
+int aa_getprocattr(struct aa_label *label, char **string, bool newline);
int aa_setprocattr_changehat(char *args, size_t size, int flags);

#endif /* __AA_PROCATTR_H */
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index ce6ccb7e06ec..bdaa8bac0404 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -630,6 +630,45 @@ static int apparmor_sb_pivotroot(const struct path *old_path,
return error;
}

+static int apparmor_getselfattr(unsigned int __user attr,
+ struct lsm_ctx __user *lx, size_t *size,
+ u32 __user flags)
+{
+ int error = -ENOENT;
+ struct aa_task_ctx *ctx = task_ctx(current);
+ struct aa_label *label = NULL;
+ size_t total_len;
+ char *value;
+
+ if (attr == LSM_ATTR_CURRENT)
+ label = aa_get_newest_label(cred_label(current_cred()));
+ else if (attr == LSM_ATTR_PREV && ctx->previous)
+ label = aa_get_newest_label(ctx->previous);
+ else if (attr == LSM_ATTR_EXEC && ctx->onexec)
+ label = aa_get_newest_label(ctx->onexec);
+ else
+ error = -EOPNOTSUPP;
+
+ if (label) {
+ error = aa_getprocattr(label, &value, false);
+ if (error > 0) {
+ total_len = ALIGN(error + sizeof(*ctx), 8);
+ if (total_len > *size)
+ error = -E2BIG;
+ else
+ lsm_fill_user_ctx(lx, value, error,
+ LSM_ID_APPARMOR, 0);
+ }
+ }
+
+ aa_put_label(label);
+
+ *size = total_len;
+ if (error > 0)
+ return 1;
+ return error;
+}
+
static int apparmor_getprocattr(struct task_struct *task, const char *name,
char **value)
{
@@ -649,7 +688,7 @@ static int apparmor_getprocattr(struct task_struct *task, const char *name,
error = -EINVAL;

if (label)
- error = aa_getprocattr(label, value);
+ error = aa_getprocattr(label, value, true);

aa_put_label(label);
put_cred(cred);
@@ -657,8 +696,7 @@ static int apparmor_getprocattr(struct task_struct *task, const char *name,
return error;
}

-static int apparmor_setprocattr(const char *name, void *value,
- size_t size)
+static int do_setattr(u64 attr, void *value, size_t size)
{
char *command, *largs = NULL, *args = value;
size_t arg_size;
@@ -689,7 +727,7 @@ static int apparmor_setprocattr(const char *name, void *value,
goto out;

arg_size = size - (args - (largs ? largs : (char *) value));
- if (strcmp(name, "current") == 0) {
+ if (attr == LSM_ATTR_CURRENT) {
if (strcmp(command, "changehat") == 0) {
error = aa_setprocattr_changehat(args, arg_size,
AA_CHANGE_NOFLAGS);
@@ -704,7 +742,7 @@ static int apparmor_setprocattr(const char *name, void *value,
error = aa_change_profile(args, AA_CHANGE_STACK);
} else
goto fail;
- } else if (strcmp(name, "exec") == 0) {
+ } else if (attr == LSM_ATTR_EXEC) {
if (strcmp(command, "exec") == 0)
error = aa_change_profile(args, AA_CHANGE_ONEXEC);
else if (strcmp(command, "stack") == 0)
@@ -724,13 +762,57 @@ static int apparmor_setprocattr(const char *name, void *value,

fail:
aad(&sa)->label = begin_current_label_crit_section();
- aad(&sa)->info = name;
+ if (attr == LSM_ATTR_CURRENT)
+ aad(&sa)->info = "current";
+ else if (attr == LSM_ATTR_EXEC)
+ aad(&sa)->info = "exec";
+ else
+ aad(&sa)->info = "invalid";
aad(&sa)->error = error = -EINVAL;
aa_audit_msg(AUDIT_APPARMOR_DENIED, &sa, NULL);
end_current_label_crit_section(aad(&sa)->label);
goto out;
}

+static int apparmor_setselfattr(unsigned int __user attr,
+ struct lsm_ctx __user *ctx, size_t __user size,
+ u32 __user flags)
+{
+ struct lsm_ctx *lctx;
+ void *context;
+ int rc;
+
+ if (attr != LSM_ATTR_CURRENT && attr != LSM_ATTR_EXEC)
+ return -EOPNOTSUPP;
+
+ context = kmalloc(size, GFP_KERNEL);
+ if (context == NULL)
+ return -ENOMEM;
+
+ lctx = (struct lsm_ctx *)context;
+ if (copy_from_user(context, ctx, size))
+ rc = -EFAULT;
+ else if (lctx->ctx_len > size)
+ rc = -EINVAL;
+ else
+ rc = do_setattr(attr, lctx + 1, lctx->ctx_len);
+
+ kfree(context);
+ if (rc > 0)
+ return 0;
+ return rc;
+}
+
+static int apparmor_setprocattr(const char *name, void *value,
+ size_t size)
+{
+ int attr = lsm_name_to_attr(name);
+
+ if (attr)
+ return do_setattr(attr, value, size);
+ return -EINVAL;
+}
+
/**
* apparmor_bprm_committing_creds - do task cleanup on committing new creds
* @bprm: binprm for the exec (NOT NULL)
@@ -1253,6 +1335,8 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
LSM_HOOK_INIT(file_lock, apparmor_file_lock),
LSM_HOOK_INIT(file_truncate, apparmor_file_truncate),

+ LSM_HOOK_INIT(getselfattr, apparmor_getselfattr),
+ LSM_HOOK_INIT(setselfattr, apparmor_setselfattr),
LSM_HOOK_INIT(getprocattr, apparmor_getprocattr),
LSM_HOOK_INIT(setprocattr, apparmor_setprocattr),

diff --git a/security/apparmor/procattr.c b/security/apparmor/procattr.c
index 197d41f9c32b..196f319aa3b2 100644
--- a/security/apparmor/procattr.c
+++ b/security/apparmor/procattr.c
@@ -20,6 +20,7 @@
* aa_getprocattr - Return the label information for @label
* @label: the label to print label info about (NOT NULL)
* @string: Returns - string containing the label info (NOT NULL)
+ * @newline: indicates that a newline should be added
*
* Requires: label != NULL && string != NULL
*
@@ -27,7 +28,7 @@
*
* Returns: size of string placed in @string else error code on failure
*/
-int aa_getprocattr(struct aa_label *label, char **string)
+int aa_getprocattr(struct aa_label *label, char **string, bool newline)
{
struct aa_ns *ns = labels_ns(label);
struct aa_ns *current_ns = aa_get_current_ns();
@@ -57,10 +58,14 @@ int aa_getprocattr(struct aa_label *label, char **string)
return len;
}

- (*string)[len] = '\n';
- (*string)[len + 1] = 0;
+ if (newline)
+ (*string)[len++] = '\n';
+ (*string)[len] = 0;

aa_put_ns(current_ns);
+
+ if (newline)
+ return len;
return len + 1;
}

--
2.39.2