1 files changed, 283 insertions, 0 deletions
diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c
new file mode 100644
index 000000000..41e973500
--- /dev/null
+++ b/security/keys/request_key_auth.c
@@ -0,0 +1,283 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Request key authorisation token key definition.
+ *
+ * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * See Documentation/security/keys/request-key.rst
+ */
+
+#include <linux/sched.h>
+#include <linux/err.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include "internal.h"
+#include <keys/request_key_auth-type.h>
+
+static int request_key_auth_preparse(struct key_preparsed_payload *);
+static void request_key_auth_free_preparse(struct key_preparsed_payload *);
+static int request_key_auth_instantiate(struct key *,
+					struct key_preparsed_payload *);
+static void request_key_auth_describe(const struct key *, struct seq_file *);
+static void request_key_auth_revoke(struct key *);
+static void request_key_auth_destroy(struct key *);
+static long request_key_auth_read(const struct key *, char *, size_t);
+
+/*
+ * The request-key authorisation key type definition.
+ */
+struct key_type key_type_request_key_auth = {
+	.name		= ".request_key_auth",
+	.def_datalen	= sizeof(struct request_key_auth),
+	.preparse	= request_key_auth_preparse,
+	.free_preparse	= request_key_auth_free_preparse,
+	.instantiate	= request_key_auth_instantiate,
+	.describe	= request_key_auth_describe,
+	.revoke		= request_key_auth_revoke,
+	.destroy	= request_key_auth_destroy,
+	.read		= request_key_auth_read,
+};
+
+static int request_key_auth_preparse(struct key_preparsed_payload *prep)
+{
+	return 0;
+}
+
+static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
+{
+}
+
+/*
+ * Instantiate a request-key authorisation key.
+ */
+static int request_key_auth_instantiate(struct key *key,
+					struct key_preparsed_payload *prep)
+{
+	rcu_assign_keypointer(key, (struct request_key_auth *)prep->data);
+	return 0;
+}
+
+/*
+ * Describe an authorisation token.
+ */
+static void request_key_auth_describe(const struct key *key,
+				      struct seq_file *m)
+{
+	struct request_key_auth *rka = dereference_key_rcu(key);
+
+	if (!rka)
+		return;
+
+	seq_puts(m, "key:");
+	seq_puts(m, key->description);
+	if (key_is_positive(key))
+		seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
+}
+
+/*
+ * Read the callout_info data (retrieves the callout information).
+ * - the key's semaphore is read-locked
+ */
+static long request_key_auth_read(const struct key *key,
+				  char *buffer, size_t buflen)
+{
+	struct request_key_auth *rka = dereference_key_locked(key);
+	size_t datalen;
+	long ret;
+
+	if (!rka)
+		return -EKEYREVOKED;
+
+	datalen = rka->callout_len;
+	ret = datalen;
+
+	/* we can return the data as is */
+	if (buffer && buflen > 0) {
+		if (buflen > datalen)
+			buflen = datalen;
+
+		memcpy(buffer, rka->callout_info, buflen);
+	}
+
+	return ret;
+}
+
+static void free_request_key_auth(struct request_key_auth *rka)
+{
+	if (!rka)
+		return;
+	key_put(rka->target_key);
+	key_put(rka->dest_keyring);
+	if (rka->cred)
+		put_cred(rka->cred);
+	kfree(rka->callout_info);
+	kfree(rka);
+}
+
+/*
+ * Dispose of the request_key_auth record under RCU conditions
+ */
+static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
+{
+	struct request_key_auth *rka =
+		container_of(rcu, struct request_key_auth, rcu);
+
+	free_request_key_auth(rka);
+}
+
+/*
+ * Handle revocation of an authorisation token key.
+ *
+ * Called with the key sem write-locked.
+ */
+static void request_key_auth_revoke(struct key *key)
+{
+	struct request_key_auth *rka = dereference_key_locked(key);
+
+	kenter("{%d}", key->serial);
+	rcu_assign_keypointer(key, NULL);
+	call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
+}
+
+/*
+ * Destroy an instantiation authorisation token key.
+ */
+static void request_key_auth_destroy(struct key *key)
+{
+	struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
+
+	kenter("{%d}", key->serial);
+	if (rka) {
+		rcu_assign_keypointer(key, NULL);
+		call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
+	}
+}
+
+/*
+ * Create an authorisation token for /sbin/request-key or whoever to gain
+ * access to the caller's security data.
+ */
+struct key *request_key_auth_new(struct key *target, const char *op,
+				 const void *callout_info, size_t callout_len,
+				 struct key *dest_keyring)
+{
+	struct request_key_auth *rka, *irka;
+	const struct cred *cred = current_cred();
+	struct key *authkey = NULL;
+	char desc[20];
+	int ret = -ENOMEM;
+
+	kenter("%d,", target->serial);
+
+	/* allocate a auth record */
+	rka = kzalloc(sizeof(*rka), GFP_KERNEL);
+	if (!rka)
+		goto error;
+	rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
+	if (!rka->callout_info)
+		goto error_free_rka;
+	rka->callout_len = callout_len;
+	strlcpy(rka->op, op, sizeof(rka->op));
+
+	/* see if the calling process is already servicing the key request of
+	 * another process */
+	if (cred->request_key_auth) {
+		/* it is - use that instantiation context here too */
+		down_read(&cred->request_key_auth->sem);
+
+		/* if the auth key has been revoked, then the key we're
+		 * servicing is already instantiated */
+		if (test_bit(KEY_FLAG_REVOKED,
+			     &cred->request_key_auth->flags)) {
+			up_read(&cred->request_key_auth->sem);
+			ret = -EKEYREVOKED;
+			goto error_free_rka;
+		}
+
+		irka = cred->request_key_auth->payload.data[0];
+		rka->cred = get_cred(irka->cred);
+		rka->pid = irka->pid;
+
+		up_read(&cred->request_key_auth->sem);
+	}
+	else {
+		/* it isn't - use this process as the context */
+		rka->cred = get_cred(cred);
+		rka->pid = current->pid;
+	}
+
+	rka->target_key = key_get(target);
+	rka->dest_keyring = key_get(dest_keyring);
+
+	/* allocate the auth key */
+	sprintf(desc, "%x", target->serial);
+
+	authkey = key_alloc(&key_type_request_key_auth, desc,
+			    cred->fsuid, cred->fsgid, cred,
+			    KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
+			    KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
+	if (IS_ERR(authkey)) {
+		ret = PTR_ERR(authkey);
+		goto error_free_rka;
+	}
+
+	/* construct the auth key */
+	ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
+	if (ret < 0)
+		goto error_put_authkey;
+
+	kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
+	return authkey;
+
+error_put_authkey:
+	key_put(authkey);
+error_free_rka:
+	free_request_key_auth(rka);
+error:
+	kleave("= %d", ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * Search the current process's keyrings for the authorisation key for
+ * instantiation of a key.
+ */
+struct key *key_get_instantiation_authkey(key_serial_t target_id)
+{
+	char description[16];
+	struct keyring_search_context ctx = {
+		.index_key.type		= &key_type_request_key_auth,
+		.index_key.description	= description,
+		.cred			= current_cred(),
+		.match_data.cmp		= key_default_cmp,
+		.match_data.raw_data	= description,
+		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
+		.flags			= (KEYRING_SEARCH_DO_STATE_CHECK |
+					   KEYRING_SEARCH_RECURSE),
+	};
+	struct key *authkey;
+	key_ref_t authkey_ref;
+
+	ctx.index_key.desc_len = sprintf(description, "%x", target_id);
+
+	rcu_read_lock();
+	authkey_ref = search_process_keyrings_rcu(&ctx);
+	rcu_read_unlock();
+
+	if (IS_ERR(authkey_ref)) {
+		authkey = ERR_CAST(authkey_ref);
+		if (authkey == ERR_PTR(-EAGAIN))
+			authkey = ERR_PTR(-ENOKEY);
+		goto error;
+	}
+
+	authkey = key_ref_to_ptr(authkey_ref);
+	if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
+		key_put(authkey);
+		authkey = ERR_PTR(-EKEYREVOKED);
+	}
+
+error:
+	return authkey;
+}