// 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 = kmemdup(prep->data, prep->datalen, GFP_KERNEL);

        if (!payload)
                return -ENOMEM;

        /* attach the data */
        key->payload.data[0] = payload;
        return 0;
}

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            6

/* 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

/* strlen of ";upcall_target=" */
#define UPCALL_TARGET_KEY_LEN   15

/* 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)
{
        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;

        /* 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);

        if (sesInfo->upcall_target == UPTARGET_MOUNT)
                desc_len += UPCALL_TARGET_KEY_LEN + 5; // strlen("mount")
        else
                desc_len += UPCALL_TARGET_KEY_LEN + 3; // strlen("app")

        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);
        dp += sprintf(dp, "ver=0x%x;host=%s;", CIFS_SPNEGO_UPCALL_VERSION,
                      hostname);

        /* add the server address */
        if (server->dstaddr.ss_family == AF_INET)
                dp += sprintf(dp, "ip4=%pI4", &sa->sin_addr);
        else if (server->dstaddr.ss_family == AF_INET6)
                dp += sprintf(dp, "ip6=%pI6", &sa6->sin6_addr);
        else
                goto out;

        /* for now, only sec=krb5 and sec=mskrb5 and iakerb are valid */
        if (server->sec_kerberos)
                dp += sprintf(dp, ";sec=krb5");
        else if (server->sec_mskerberos)
                dp += sprintf(dp, ";sec=mskrb5");
        else if (server->sec_iakerb)
                dp += sprintf(dp, ";sec=iakerb");
        else {
                cifs_dbg(VFS, "unknown or missing server auth type, use krb5\n");
                dp += sprintf(dp, ";sec=krb5");
        }

        dp += sprintf(dp, ";uid=0x%x",
                      from_kuid_munged(&init_user_ns, sesInfo->linux_uid));

        dp += sprintf(dp, ";creduid=0x%x",
                from_kuid_munged(&init_user_ns, sesInfo->cred_uid));

        if (sesInfo->user_name)
                dp += sprintf(dp, ";user=%s", sesInfo->user_name);

        dp += sprintf(dp, ";pid=0x%x", current->pid);

        if (sesInfo->upcall_target == UPTARGET_MOUNT)
                dp += sprintf(dp, ";upcall_target=mount");
        else
                dp += sprintf(dp, ";upcall_target=app");

        cifs_dbg(FYI, "key description = %s\n", description);
        scoped_with_creds(spnego_cred)
                spnego_key = request_key(&cifs_spnego_key_type, description, "");
        trace_smb3_kerberos_auth(server, sesInfo, PTR_ERR_OR_ZERO(spnego_key));

#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(&init_task);
        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);
}