text: // SPDX-License-Identifier: LGPL-2.1
  /*
   *   SPNEGO upcall management for CIFS
   *
   *   Copyright (c) 2007 Red Hat, Inc.
   *   Author(s): Jeff Layton (jlayton@redhat.com)
   *
   */
  
  #include <linux/list.h>
  #include <linux/slab.h>
  #include <linux/string.h>
  #include <keys/user-type.h>
  #include <linux/key-type.h>
  #include <linux/keyctl.h>
  #include <linux/inet.h>
  #include "cifsglob.h"
  #include "cifs_spnego.h"
  #include "cifs_debug.h"
  #include "cifsproto.h"
  static const struct cred *spnego_cred;
  
  /* create a new cifs key */
  static int
  cifs_spnego_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
  {
  	char *payload;
  	int ret;
  
  	ret = -ENOMEM;
  	payload = kmemdup(prep->data, prep->datalen, GFP_KERNEL);
  	if (!payload)
  		goto error;
  
  	/* attach the data */
  	key->payload.data[0] = payload;
  	ret = 0;
  
  error:
  	return ret;
  }
  
  static void
  cifs_spnego_key_destroy(struct key *key)
  {
  	kfree(key->payload.data[0]);
  }
  
  
  /*
   * keytype for CIFS spnego keys
   */
  struct key_type cifs_spnego_key_type = {
  	.name		= "cifs.spnego",
  	.instantiate	= cifs_spnego_key_instantiate,
  	.destroy	= cifs_spnego_key_destroy,
  	.describe	= user_describe,
  };
  
  /* length of longest version string e.g.  strlen("ver=0xFF") */
  #define MAX_VER_STR_LEN		8
  
  /* length of longest security mechanism name, eg in future could have
   * strlen(";sec=ntlmsspi") */
  #define MAX_MECH_STR_LEN	13
  
  /* strlen of "host=" */
  #define HOST_KEY_LEN		5
  
  /* strlen of ";ip4=" or ";ip6=" */
  #define IP_KEY_LEN		5
  
  /* strlen of ";uid=0x" */
  #define UID_KEY_LEN		7
  
  /* strlen of ";creduid=0x" */
  #define CREDUID_KEY_LEN		11
  
  /* strlen of ";user=" */
  #define USER_KEY_LEN		6
  
  /* strlen of ";pid=0x" */
  #define PID_KEY_LEN		7
  
  /* get a key struct with a SPNEGO security blob, suitable for session setup */
  struct key *
  cifs_get_spnego_key(struct cifs_ses *sesInfo)
  {
  	struct TCP_Server_Info *server = cifs_ses_server(sesInfo);
  	struct sockaddr_in *sa = (struct sockaddr_in *) &server->dstaddr;
  	struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *) &server->dstaddr;
  	char *description, *dp;
  	size_t desc_len;
  	struct key *spnego_key;
  	const char *hostname = server->hostname;
  	const struct cred *saved_cred;
  
  	/* length of fields (with semicolons): ver=0xyz ip4=ipaddress
  	   host=hostname sec=mechanism uid=0xFF user=username */
  	desc_len = MAX_VER_STR_LEN +
  		   HOST_KEY_LEN + strlen(hostname) +
  		   IP_KEY_LEN + INET6_ADDRSTRLEN +
  		   MAX_MECH_STR_LEN +
  		   UID_KEY_LEN + (sizeof(uid_t) * 2) +
  		   CREDUID_KEY_LEN + (sizeof(uid_t) * 2) +
  		   PID_KEY_LEN + (sizeof(pid_t) * 2) + 1;
  
  	if (sesInfo->user_name)
  		desc_len += USER_KEY_LEN + strlen(sesInfo->user_name);
  
  	spnego_key = ERR_PTR(-ENOMEM);
  	description = kzalloc(desc_len, GFP_KERNEL);
  	if (description == NULL)
  		goto out;
  
  	dp = description;
  	/* start with version and hostname portion of UNC string */
  	spnego_key = ERR_PTR(-EINVAL);
  	sprintf(dp, "ver=0x%x;host=%s;", CIFS_SPNEGO_UPCALL_VERSION,
  		hostname);
  	dp = description + strlen(description);
  
  	/* add the server address */
  	if (server->dstaddr.ss_family == AF_INET)
  		sprintf(dp, "ip4=%pI4", &sa->sin_addr);
  	else if (server->dstaddr.ss_family == AF_INET6)
  		sprintf(dp, "ip6=%pI6", &sa6->sin6_addr);
  	else
  		goto out;
  
  	dp = description + strlen(description);
  
  	/* for now, only sec=krb5 and sec=mskrb5 are valid */
  	if (server->sec_kerberos)
  		sprintf(dp, ";sec=krb5");
  	else if (server->sec_mskerberos)
  		sprintf(dp, ";sec=mskrb5");
  	else {
  		cifs_dbg(VFS, "unknown or missing server auth type, use krb5\n");
  		sprintf(dp, ";sec=krb5");
  	}
  
  	dp = description + strlen(description);
  	sprintf(dp, ";uid=0x%x",
  		from_kuid_munged(&init_user_ns, sesInfo->linux_uid));
  
  	dp = description + strlen(description);
  	sprintf(dp, ";creduid=0x%x",
  		from_kuid_munged(&init_user_ns, sesInfo->cred_uid));
  
  	if (sesInfo->user_name) {
  		dp = description + strlen(description);
  		sprintf(dp, ";user=%s", sesInfo->user_name);
  	}
  
  	dp = description + strlen(description);
  	sprintf(dp, ";pid=0x%x", current->pid);
  
  	cifs_dbg(FYI, "key description = %s\n", description);
  	saved_cred = override_creds(spnego_cred);
  	spnego_key = request_key(&cifs_spnego_key_type, description, "");
  	revert_creds(saved_cred);
  
  #ifdef CONFIG_CIFS_DEBUG2
  	if (cifsFYI && !IS_ERR(spnego_key)) {
  		struct cifs_spnego_msg *msg = spnego_key->payload.data[0];
  		cifs_dump_mem("SPNEGO reply blob:", msg->data, min(1024U,
  				msg->secblob_len + msg->sesskey_len));
  	}
  #endif /* CONFIG_CIFS_DEBUG2 */
  
  out:
  	kfree(description);
  	return spnego_key;
  }
  
  int
  init_cifs_spnego(void)
  {
  	struct cred *cred;
  	struct key *keyring;
  	int ret;
  
  	cifs_dbg(FYI, "Registering the %s key type\n",
  		 cifs_spnego_key_type.name);
  
  	/*
  	 * Create an override credential set with special thread keyring for
  	 * spnego upcalls.
  	 */
  
  	cred = prepare_kernel_cred(NULL);
  	if (!cred)
  		return -ENOMEM;
  
  	keyring = keyring_alloc(".cifs_spnego",
  				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
  				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
  				KEY_USR_VIEW | KEY_USR_READ,
  				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
  	if (IS_ERR(keyring)) {
  		ret = PTR_ERR(keyring);
  		goto failed_put_cred;
  	}
  
  	ret = register_key_type(&cifs_spnego_key_type);
  	if (ret < 0)
  		goto failed_put_key;
  
  	/*
  	 * instruct request_key() to use this special keyring as a cache for
  	 * the results it looks up
  	 */
  	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
  	cred->thread_keyring = keyring;
  	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
  	spnego_cred = cred;
  
  	cifs_dbg(FYI, "cifs spnego keyring: %d\n", key_serial(keyring));
  	return 0;
  
  failed_put_key:
  	key_put(keyring);
  failed_put_cred:
  	put_cred(cred);
  	return ret;
  }
  
  void
  exit_cifs_spnego(void)
  {
  	key_revoke(spnego_cred->thread_keyring);
  	unregister_key_type(&cifs_spnego_key_type);
  	put_cred(spnego_cred);
  	cifs_dbg(FYI, "Unregistered %s key type\n", cifs_spnego_key_type.name);
  }
  