// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/nfs/nfs4namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
 * - Modified by David Howells <dhowells@redhat.com>
 *
 * NFSv4 namespace
 */

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_mount.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/addr.h>
#include <linux/vfs.h>
#include <linux/inet.h>
#include "internal.h"
#include "nfs4_fs.h"
#include "dns_resolve.h"

#define NFSDBG_FACILITY         NFSDBG_VFS

/*
 * Convert the NFSv4 pathname components into a standard posix path.
 *
 * Note that the resulting string will be placed at the end of the buffer
 */
static inline char *nfs4_pathname_string(const struct nfs4_pathname *pathname,
                                         char *buffer, ssize_t buflen)
{
        char *end = buffer + buflen;
        int n;

        *--end = '\0';
        buflen--;

        n = pathname->ncomponents;
        while (--n >= 0) {
                const struct nfs4_string *component = &pathname->components[n];
                buflen -= component->len + 1;
                if (buflen < 0)
                        goto Elong;
                end -= component->len;
                memcpy(end, component->data, component->len);
                *--end = '/';
        }
        return end;
Elong:
        return ERR_PTR(-ENAMETOOLONG);
}

/*
 * return the path component of "<server>:<path>"
 *  nfspath - the "<server>:<path>" string
 *  end - one past the last char that could contain "<server>:"
 * returns NULL on failure
 */
static char *nfs_path_component(const char *nfspath, const char *end)
{
        char *p;

        if (*nfspath == '[') {
                /* parse [] escaped IPv6 addrs */
                p = strchr(nfspath, ']');
                if (p != NULL && ++p < end && *p == ':')
                        return p + 1;
        } else {
                /* otherwise split on first colon */
                p = strchr(nfspath, ':');
                if (p != NULL && p < end)
                        return p + 1;
        }
        return NULL;
}

/*
 * Determine the mount path as a string
 */
static char *nfs4_path(struct dentry *dentry, char *buffer, ssize_t buflen)
{
        char *limit;
        char *path = nfs_path(&limit, dentry, buffer, buflen,
                              NFS_PATH_CANONICAL);
        if (!IS_ERR(path)) {
                char *path_component = nfs_path_component(path, limit);
                if (path_component)
                        return path_component;
        }
        return path;
}

/*
 * Check that fs_locations::fs_root [RFC3530 6.3] is a prefix for what we
 * believe to be the server path to this dentry
 */
static int nfs4_validate_fspath(struct dentry *dentry,
                                const struct nfs4_fs_locations *locations,
                                char *page, char *page2)
{
        const char *path, *fs_path;

        path = nfs4_path(dentry, page, PAGE_SIZE);
        if (IS_ERR(path))
                return PTR_ERR(path);

        fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
        if (IS_ERR(fs_path))
                return PTR_ERR(fs_path);

        if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
                dprintk("%s: path %s does not begin with fsroot %s\n",
                        __func__, path, fs_path);
                return -ENOENT;
        }

        return 0;
}

static size_t nfs_parse_server_name(char *string, size_t len,
                struct sockaddr *sa, size_t salen, struct net *net)
{
        ssize_t ret;

        ret = rpc_pton(net, string, len, sa, salen);
        if (ret == 0) {
                ret = nfs_dns_resolve_name(net, string, len, sa, salen);
                if (ret < 0)
                        ret = 0;
        }
        return ret;
}

/**
 * nfs_find_best_sec - Find a security mechanism supported locally
 * @server: NFS server struct
 * @flavors: List of security tuples returned by SECINFO procedure
 *
 * Return an rpc client that uses the first security mechanism in
 * "flavors" that is locally supported.  The "flavors" array
 * is searched in the order returned from the server, per RFC 3530
 * recommendation and each flavor is checked for membership in the
 * sec= mount option list if it exists.
 *
 * Return -EPERM if no matching flavor is found in the array.
 *
 * Please call rpc_shutdown_client() when you are done with this rpc client.
 *
 */
static struct rpc_clnt *nfs_find_best_sec(struct rpc_clnt *clnt,
                                          struct nfs_server *server,
                                          struct nfs4_secinfo_flavors *flavors)
{
        rpc_authflavor_t pflavor;
        struct nfs4_secinfo4 *secinfo;
        unsigned int i;

        for (i = 0; i < flavors->num_flavors; i++) {
                secinfo = &flavors->flavors[i];

                switch (secinfo->flavor) {
                case RPC_AUTH_NULL:
                case RPC_AUTH_UNIX:
                case RPC_AUTH_GSS:
                        pflavor = rpcauth_get_pseudoflavor(secinfo->flavor,
                                                        &secinfo->flavor_info);
                        /* does the pseudoflavor match a sec= mount opt? */
                        if (pflavor != RPC_AUTH_MAXFLAVOR &&
                            nfs_auth_info_match(&server->auth_info, pflavor)) {
                                struct rpc_clnt *new;
                                struct rpc_cred *cred;

                                /* Cloning creates an rpc_auth for the flavor */
                                new = rpc_clone_client_set_auth(clnt, pflavor);
                                if (IS_ERR(new))
                                        continue;
                                /**
                                * Check that the user actually can use the
                                * flavor. This is mostly for RPC_AUTH_GSS
                                * where cr_init obtains a gss context
                                */
                                cred = rpcauth_lookupcred(new->cl_auth, 0);
                                if (IS_ERR(cred)) {
                                        rpc_shutdown_client(new);
                                        continue;
                                }
                                put_rpccred(cred);
                                return new;
                        }
                }
        }
        return ERR_PTR(-EPERM);
}

/**
 * nfs4_negotiate_security - in response to an NFS4ERR_WRONGSEC on lookup,
 * return an rpc_clnt that uses the best available security flavor with
 * respect to the secinfo flavor list and the sec= mount options.
 *
 * @clnt: RPC client to clone
 * @inode: directory inode
 * @name: lookup name
 *
 * Please call rpc_shutdown_client() when you are done with this rpc client.
 */
struct rpc_clnt *
nfs4_negotiate_security(struct rpc_clnt *clnt, struct inode *inode,
                                        const struct qstr *name)
{
        struct page *page;
        struct nfs4_secinfo_flavors *flavors;
        struct rpc_clnt *new;
        int err;

        page = alloc_page(GFP_KERNEL);
        if (!page)
                return ERR_PTR(-ENOMEM);

        flavors = page_address(page);

        err = nfs4_proc_secinfo(inode, name, flavors);
        if (err < 0) {
                new = ERR_PTR(err);
                goto out;
        }

        new = nfs_find_best_sec(clnt, NFS_SERVER(inode), flavors);

out:
        put_page(page);
        return new;
}

static struct vfsmount *try_location(struct nfs_clone_mount *mountdata,
                                     char *page, char *page2,
                                     const struct nfs4_fs_location *location)
{
        const size_t addr_bufsize = sizeof(struct sockaddr_storage);
        struct net *net = rpc_net_ns(NFS_SB(mountdata->sb)->client);
        struct vfsmount *mnt = ERR_PTR(-ENOENT);
        char *mnt_path;
        unsigned int maxbuflen;
        unsigned int s;

        mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
        if (IS_ERR(mnt_path))
                return ERR_CAST(mnt_path);
        mountdata->mnt_path = mnt_path;
        maxbuflen = mnt_path - 1 - page2;

        mountdata->addr = kmalloc(addr_bufsize, GFP_KERNEL);
        if (mountdata->addr == NULL)
                return ERR_PTR(-ENOMEM);

        for (s = 0; s < location->nservers; s++) {
                const struct nfs4_string *buf = &location->servers[s];

                if (buf->len <= 0 || buf->len >= maxbuflen)
                        continue;

                if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len))
                        continue;

                mountdata->addrlen = nfs_parse_server_name(buf->data, buf->len,
                                mountdata->addr, addr_bufsize, net);
                if (mountdata->addrlen == 0)
                        continue;

                rpc_set_port(mountdata->addr, NFS_PORT);

                memcpy(page2, buf->data, buf->len);
                page2[buf->len] = '\0';
                mountdata->hostname = page2;

                snprintf(page, PAGE_SIZE, "%s:%s",
                                mountdata->hostname,
                                mountdata->mnt_path);

                mnt = vfs_submount(mountdata->dentry, &nfs4_referral_fs_type, page, mountdata);
                if (!IS_ERR(mnt))
                        break;
        }
        kfree(mountdata->addr);
        return mnt;
}

/**
 * nfs_follow_referral - set up mountpoint when hitting a referral on moved error
 * @dentry - parent directory
 * @locations - array of NFSv4 server location information
 *
 */
static struct vfsmount *nfs_follow_referral(struct dentry *dentry,
                                            const struct nfs4_fs_locations *locations)
{
        struct vfsmount *mnt = ERR_PTR(-ENOENT);
        struct nfs_clone_mount mountdata = {
                .sb = dentry->d_sb,
                .dentry = dentry,
                .authflavor = NFS_SB(dentry->d_sb)->client->cl_auth->au_flavor,
        };
        char *page = NULL, *page2 = NULL;
        int loc, error;

        if (locations == NULL || locations->nlocations <= 0)
                goto out;

        dprintk("%s: referral at %pd2\n", __func__, dentry);

        page = (char *) __get_free_page(GFP_USER);
        if (!page)
                goto out;

        page2 = (char *) __get_free_page(GFP_USER);
        if (!page2)
                goto out;

        /* Ensure fs path is a prefix of current dentry path */
        error = nfs4_validate_fspath(dentry, locations, page, page2);
        if (error < 0) {
                mnt = ERR_PTR(error);
                goto out;
        }

        for (loc = 0; loc < locations->nlocations; loc++) {
                const struct nfs4_fs_location *location = &locations->locations[loc];

                if (location == NULL || location->nservers <= 0 ||
                    location->rootpath.ncomponents == 0)
                        continue;

                mnt = try_location(&mountdata, page, page2, location);
                if (!IS_ERR(mnt))
                        break;
        }

out:
        free_page((unsigned long) page);
        free_page((unsigned long) page2);
        return mnt;
}

/*
 * nfs_do_refmount - handle crossing a referral on server
 * @dentry - dentry of referral
 *
 */
static struct vfsmount *nfs_do_refmount(struct rpc_clnt *client, struct dentry *dentry)
{
        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
        struct dentry *parent;
        struct nfs4_fs_locations *fs_locations = NULL;
        struct page *page;
        int err;

        /* BUG_ON(IS_ROOT(dentry)); */
        page = alloc_page(GFP_KERNEL);
        if (page == NULL)
                return mnt;

        fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
        if (fs_locations == NULL)
                goto out_free;

        /* Get locations */
        mnt = ERR_PTR(-ENOENT);

        parent = dget_parent(dentry);
        dprintk("%s: getting locations for %pd2\n",
                __func__, dentry);

        err = nfs4_proc_fs_locations(client, d_inode(parent), &dentry->d_name, fs_locations, page);
        dput(parent);
        if (err != 0 ||
            fs_locations->nlocations <= 0 ||
            fs_locations->fs_path.ncomponents <= 0)
                goto out_free;

        mnt = nfs_follow_referral(dentry, fs_locations);
out_free:
        __free_page(page);
        kfree(fs_locations);
        return mnt;
}

struct vfsmount *nfs4_submount(struct nfs_server *server, struct dentry *dentry,
                               struct nfs_fh *fh, struct nfs_fattr *fattr)
{
        rpc_authflavor_t flavor = server->client->cl_auth->au_flavor;
        struct dentry *parent = dget_parent(dentry);
        struct inode *dir = d_inode(parent);
        const struct qstr *name = &dentry->d_name;
        struct rpc_clnt *client;
        struct vfsmount *mnt;

        /* Look it up again to get its attributes and sec flavor */
        client = nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);
        dput(parent);
        if (IS_ERR(client))
                return ERR_CAST(client);

        if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
                mnt = nfs_do_refmount(client, dentry);
                goto out;
        }

        if (client->cl_auth->au_flavor != flavor)
                flavor = client->cl_auth->au_flavor;
        mnt = nfs_do_submount(dentry, fh, fattr, flavor);
out:
        rpc_shutdown_client(client);
        return mnt;
}

/*
 * Try one location from the fs_locations array.
 *
 * Returns zero on success, or a negative errno value.
 */
static int nfs4_try_replacing_one_location(struct nfs_server *server,
                char *page, char *page2,
                const struct nfs4_fs_location *location)
{
        const size_t addr_bufsize = sizeof(struct sockaddr_storage);
        struct net *net = rpc_net_ns(server->client);
        struct sockaddr *sap;
        unsigned int s;
        size_t salen;
        int error;

        sap = kmalloc(addr_bufsize, GFP_KERNEL);
        if (sap == NULL)
                return -ENOMEM;

        error = -ENOENT;
        for (s = 0; s < location->nservers; s++) {
                const struct nfs4_string *buf = &location->servers[s];
                char *hostname;

                if (buf->len <= 0 || buf->len > PAGE_SIZE)
                        continue;

                if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len) != NULL)
                        continue;

                salen = nfs_parse_server_name(buf->data, buf->len,
                                                sap, addr_bufsize, net);
                if (salen == 0)
                        continue;
                rpc_set_port(sap, NFS_PORT);

                error = -ENOMEM;
                hostname = kstrndup(buf->data, buf->len, GFP_KERNEL);
                if (hostname == NULL)
                        break;

                error = nfs4_update_server(server, hostname, sap, salen, net);
                kfree(hostname);
                if (error == 0)
                        break;
        }

        kfree(sap);
        return error;
}

/**
 * nfs4_replace_transport - set up transport to destination server
 *
 * @server: export being migrated
 * @locations: fs_locations array
 *
 * Returns zero on success, or a negative errno value.
 *
 * The client tries all the entries in the "locations" array, in the
 * order returned by the server, until one works or the end of the
 * array is reached.
 */
int nfs4_replace_transport(struct nfs_server *server,
                           const struct nfs4_fs_locations *locations)
{
        char *page = NULL, *page2 = NULL;
        int loc, error;

        error = -ENOENT;
        if (locations == NULL || locations->nlocations <= 0)
                goto out;

        error = -ENOMEM;
        page = (char *) __get_free_page(GFP_USER);
        if (!page)
                goto out;
        page2 = (char *) __get_free_page(GFP_USER);
        if (!page2)
                goto out;

        for (loc = 0; loc < locations->nlocations; loc++) {
                const struct nfs4_fs_location *location =
                                                &locations->locations[loc];

                if (location == NULL || location->nservers <= 0 ||
                    location->rootpath.ncomponents == 0)
                        continue;

                error = nfs4_try_replacing_one_location(server, page,
                                                        page2, location);
                if (error == 0)
                        break;
        }

out:
        free_page((unsigned long)page);
        free_page((unsigned long)page2);
        return error;
}