// SPDX-License-Identifier: GPL-2.0
/*
 * The base64 encode/decode code was copied from fscrypt:
 * Copyright (C) 2015, Google, Inc.
 * Copyright (C) 2015, Motorola Mobility
 * Written by Uday Savagaonkar, 2014.
 * Modified by Jaegeuk Kim, 2015.
 */
#include <linux/ceph/ceph_debug.h>
#include <linux/xattr.h>
#include <linux/fscrypt.h>
#include <linux/ceph/striper.h>

#include "super.h"
#include "mds_client.h"
#include "crypto.h"

static int ceph_crypt_get_context(struct inode *inode, void *ctx, size_t len)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fscrypt_auth *cfa = (struct ceph_fscrypt_auth *)ci->fscrypt_auth;
        u32 ctxlen;

        /* Non existent or too short? */
        if (!cfa || (ci->fscrypt_auth_len < (offsetof(struct ceph_fscrypt_auth, cfa_blob) + 1)))
                return -ENOBUFS;

        /* Some format we don't recognize? */
        if (le32_to_cpu(cfa->cfa_version) != CEPH_FSCRYPT_AUTH_VERSION)
                return -ENOBUFS;

        ctxlen = le32_to_cpu(cfa->cfa_blob_len);
        if (len < ctxlen)
                return -ERANGE;

        memcpy(ctx, cfa->cfa_blob, ctxlen);
        return ctxlen;
}

static int ceph_crypt_set_context(struct inode *inode, const void *ctx,
                                  size_t len, void *fs_data)
{
        int ret;
        struct iattr attr = { };
        struct ceph_iattr cia = { };
        struct ceph_fscrypt_auth *cfa;

        WARN_ON_ONCE(fs_data);

        if (len > FSCRYPT_SET_CONTEXT_MAX_SIZE)
                return -EINVAL;

        cfa = kzalloc_obj(*cfa);
        if (!cfa)
                return -ENOMEM;

        cfa->cfa_version = cpu_to_le32(CEPH_FSCRYPT_AUTH_VERSION);
        cfa->cfa_blob_len = cpu_to_le32(len);
        memcpy(cfa->cfa_blob, ctx, len);

        cia.fscrypt_auth = cfa;

        ret = __ceph_setattr(&nop_mnt_idmap, inode, &attr, &cia);
        if (ret == 0)
                inode_set_flags(inode, S_ENCRYPTED, S_ENCRYPTED);
        kfree(cia.fscrypt_auth);
        return ret;
}

static bool ceph_crypt_empty_dir(struct inode *inode)
{
        struct ceph_inode_info *ci = ceph_inode(inode);

        return ci->i_rsubdirs + ci->i_rfiles == 1;
}

static const union fscrypt_policy *ceph_get_dummy_policy(struct super_block *sb)
{
        return ceph_sb_to_fs_client(sb)->fsc_dummy_enc_policy.policy;
}

static struct fscrypt_operations ceph_fscrypt_ops = {
        .inode_info_offs        = (int)offsetof(struct ceph_inode_info, i_crypt_info) -
                                  (int)offsetof(struct ceph_inode_info, netfs.inode),
        .needs_bounce_pages     = 1,
        .get_context            = ceph_crypt_get_context,
        .set_context            = ceph_crypt_set_context,
        .get_dummy_policy       = ceph_get_dummy_policy,
        .empty_dir              = ceph_crypt_empty_dir,
};

void ceph_fscrypt_set_ops(struct super_block *sb)
{
        fscrypt_set_ops(sb, &ceph_fscrypt_ops);
}

void ceph_fscrypt_free_dummy_policy(struct ceph_fs_client *fsc)
{
        fscrypt_free_dummy_policy(&fsc->fsc_dummy_enc_policy);
}

int ceph_fscrypt_prepare_context(struct inode *dir, struct inode *inode,
                                 struct ceph_acl_sec_ctx *as)
{
        int ret, ctxsize;
        bool encrypted = false;
        struct ceph_inode_info *ci = ceph_inode(inode);

        ret = fscrypt_prepare_new_inode(dir, inode, &encrypted);
        if (ret)
                return ret;
        if (!encrypted)
                return 0;

        as->fscrypt_auth = kzalloc_obj(*as->fscrypt_auth);
        if (!as->fscrypt_auth)
                return -ENOMEM;

        ctxsize = fscrypt_context_for_new_inode(as->fscrypt_auth->cfa_blob,
                                                inode);
        if (ctxsize < 0)
                return ctxsize;

        as->fscrypt_auth->cfa_version = cpu_to_le32(CEPH_FSCRYPT_AUTH_VERSION);
        as->fscrypt_auth->cfa_blob_len = cpu_to_le32(ctxsize);

        WARN_ON_ONCE(ci->fscrypt_auth);
        kfree(ci->fscrypt_auth);
        ci->fscrypt_auth_len = ceph_fscrypt_auth_len(as->fscrypt_auth);
        ci->fscrypt_auth = kmemdup(as->fscrypt_auth, ci->fscrypt_auth_len,
                                   GFP_KERNEL);
        if (!ci->fscrypt_auth)
                return -ENOMEM;

        inode->i_flags |= S_ENCRYPTED;

        return 0;
}

void ceph_fscrypt_as_ctx_to_req(struct ceph_mds_request *req,
                                struct ceph_acl_sec_ctx *as)
{
        swap(req->r_fscrypt_auth, as->fscrypt_auth);
}

/*
 * User-created snapshots can't start with '_'.  Snapshots that start with this
 * character are special (hint: there aren't real snapshots) and use the
 * following format:
 *
 *   _<SNAPSHOT-NAME>_<INODE-NUMBER>
 *
 * where:
 *  - <SNAPSHOT-NAME> - the real snapshot name that may need to be decrypted,
 *  - <INODE-NUMBER> - the inode number (in decimal) for the actual snapshot
 *
 * This function parses these snapshot names and returns the inode
 * <INODE-NUMBER>.  'name_len' will also bet set with the <SNAPSHOT-NAME>
 * length.
 */
static struct inode *parse_longname(const struct inode *parent,
                                    const char *name, int *name_len)
{
        struct ceph_client *cl = ceph_inode_to_client(parent);
        struct inode *dir = NULL;
        struct ceph_vino vino = { .snap = CEPH_NOSNAP };
        char *name_end, *inode_number;
        int ret = -EIO;
        /* Snapshot name must start with an underscore */
        if (*name_len <= 0 || name[0] != '_')
                return ERR_PTR(-EIO);
        /* Skip initial '_' and NUL-terminate */
        char *str __free(kfree) = kmemdup_nul(name + 1, *name_len - 1, GFP_KERNEL);
        if (!str)
                return ERR_PTR(-ENOMEM);
        name_end = strrchr(str, '_');
        if (!name_end) {
                doutc(cl, "failed to parse long snapshot name: %s\n", str);
                return ERR_PTR(-EIO);
        }
        *name_len = (name_end - str);
        if (*name_len <= 0) {
                pr_err_client(cl, "failed to parse long snapshot name\n");
                return ERR_PTR(-EIO);
        }

        /* Get the inode number */
        inode_number = name_end + 1;
        ret = kstrtou64(inode_number, 10, &vino.ino);
        if (ret) {
                doutc(cl, "failed to parse inode number: %s\n", str);
                return ERR_PTR(ret);
        }

        /* And finally the inode */
        dir = ceph_find_inode(parent->i_sb, vino);
        if (!dir) {
                /* This can happen if we're not mounting cephfs on the root */
                dir = ceph_get_inode(parent->i_sb, vino, NULL);
                if (IS_ERR(dir))
                        doutc(cl, "can't find inode %s (%s)\n", inode_number, name);
        }
        return dir;
}

int ceph_encode_encrypted_dname(struct inode *parent, char *buf, int elen)
{
        struct ceph_client *cl = ceph_inode_to_client(parent);
        struct inode *dir = parent;
        char *p = buf;
        u32 len;
        int name_len = elen;
        int ret;
        u8 *cryptbuf = NULL;

        /* Handle the special case of snapshot names that start with '_' */
        if (ceph_snap(dir) == CEPH_SNAPDIR && *p == '_') {
                dir = parse_longname(parent, p, &name_len);
                if (IS_ERR(dir))
                        return PTR_ERR(dir);
                p++; /* skip initial '_' */
        }

        if (!fscrypt_has_encryption_key(dir))
                goto out;

        /*
         * Convert cleartext d_name to ciphertext. If result is longer than
         * CEPH_NOHASH_NAME_MAX, sha256 the remaining bytes
         *
         * See: fscrypt_setup_filename
         */
        if (!fscrypt_fname_encrypted_size(dir, name_len, NAME_MAX, &len)) {
                elen = -ENAMETOOLONG;
                goto out;
        }

        /* Allocate a buffer appropriate to hold the result */
        cryptbuf = kmalloc(len > CEPH_NOHASH_NAME_MAX ? NAME_MAX : len,
                           GFP_KERNEL);
        if (!cryptbuf) {
                elen = -ENOMEM;
                goto out;
        }

        ret = fscrypt_fname_encrypt(dir,
                                    &(struct qstr)QSTR_INIT(p, name_len),
                                    cryptbuf, len);
        if (ret) {
                elen = ret;
                goto out;
        }

        /* hash the end if the name is long enough */
        if (len > CEPH_NOHASH_NAME_MAX) {
                u8 hash[SHA256_DIGEST_SIZE];
                u8 *extra = cryptbuf + CEPH_NOHASH_NAME_MAX;

                /*
                 * hash the extra bytes and overwrite crypttext beyond that
                 * point with it
                 */
                sha256(extra, len - CEPH_NOHASH_NAME_MAX, hash);
                memcpy(extra, hash, SHA256_DIGEST_SIZE);
                len = CEPH_NOHASH_NAME_MAX + SHA256_DIGEST_SIZE;
        }

        /* base64 encode the encrypted name */
        elen = base64_encode(cryptbuf, len, p, false, BASE64_IMAP);
        doutc(cl, "base64-encoded ciphertext name = %.*s\n", elen, p);

        /* To understand the 240 limit, see CEPH_NOHASH_NAME_MAX comments */
        WARN_ON(elen > 240);
        if (dir != parent) // leading _ is already there; append _<inum>
                elen += 1 + sprintf(p + elen, "_%ld", dir->i_ino);

out:
        kfree(cryptbuf);
        if (dir != parent) {
                if ((inode_state_read_once(dir) & I_NEW))
                        discard_new_inode(dir);
                else
                        iput(dir);
        }
        return elen;
}

/**
 * ceph_fname_to_usr - convert a filename for userland presentation
 * @fname: ceph_fname to be converted
 * @tname: temporary name buffer to use for conversion (may be NULL)
 * @oname: where converted name should be placed
 * @is_nokey: set to true if key wasn't available during conversion (may be NULL)
 *
 * Given a filename (usually from the MDS), format it for presentation to
 * userland. If @parent is not encrypted, just pass it back as-is.
 *
 * Otherwise, base64 decode the string, and then ask fscrypt to format it
 * for userland presentation.
 *
 * Returns 0 on success or negative error code on error.
 */
int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,
                      struct fscrypt_str *oname, bool *is_nokey)
{
        struct inode *dir = fname->dir;
        struct fscrypt_str _tname = FSTR_INIT(NULL, 0);
        struct fscrypt_str iname;
        char *name = fname->name;
        int name_len = fname->name_len;
        int ret;

        /* Sanity check that the resulting name will fit in the buffer */
        if (fname->name_len > NAME_MAX || fname->ctext_len > NAME_MAX)
                return -EIO;

        /* Handle the special case of snapshot names that start with '_' */
        if ((ceph_snap(dir) == CEPH_SNAPDIR) && (name_len > 0) &&
            (name[0] == '_')) {
                dir = parse_longname(dir, name, &name_len);
                if (IS_ERR(dir))
                        return PTR_ERR(dir);
                name++; /* skip initial '_' */
        }

        if (!IS_ENCRYPTED(dir)) {
                oname->name = fname->name;
                oname->len = fname->name_len;
                ret = 0;
                goto out_inode;
        }

        ret = ceph_fscrypt_prepare_readdir(dir);
        if (ret)
                goto out_inode;

        /*
         * Use the raw dentry name as sent by the MDS instead of
         * generating a nokey name via fscrypt.
         */
        if (!fscrypt_has_encryption_key(dir)) {
                if (fname->no_copy)
                        oname->name = fname->name;
                else
                        memcpy(oname->name, fname->name, fname->name_len);
                oname->len = fname->name_len;
                if (is_nokey)
                        *is_nokey = true;
                ret = 0;
                goto out_inode;
        }

        if (fname->ctext_len == 0) {
                int declen;

                if (!tname) {
                        ret = fscrypt_fname_alloc_buffer(NAME_MAX, &_tname);
                        if (ret)
                                goto out_inode;
                        tname = &_tname;
                }

                declen = base64_decode(name, name_len,
                                       tname->name, false, BASE64_IMAP);
                if (declen <= 0) {
                        ret = -EIO;
                        goto out;
                }
                iname.name = tname->name;
                iname.len = declen;
        } else {
                iname.name = fname->ctext;
                iname.len = fname->ctext_len;
        }

        ret = fscrypt_fname_disk_to_usr(dir, 0, 0, &iname, oname);
        if (!ret && (dir != fname->dir)) {
                char tmp_buf[BASE64_CHARS(NAME_MAX)];

                name_len = snprintf(tmp_buf, sizeof(tmp_buf), "_%.*s_%ld",
                                    oname->len, oname->name, dir->i_ino);
                memcpy(oname->name, tmp_buf, name_len);
                oname->len = name_len;
        }

out:
        fscrypt_fname_free_buffer(&_tname);
out_inode:
        if (dir != fname->dir) {
                if ((inode_state_read_once(dir) & I_NEW))
                        discard_new_inode(dir);
                else
                        iput(dir);
        }
        return ret;
}

/**
 * ceph_fscrypt_prepare_readdir - simple __fscrypt_prepare_readdir() wrapper
 * @dir: directory inode for readdir prep
 *
 * Simple wrapper around __fscrypt_prepare_readdir() that will mark directory as
 * non-complete if this call results in having the directory unlocked.
 *
 * Returns:
 *     1 - if directory was locked and key is now loaded (i.e. dir is unlocked)
 *     0 - if directory is still locked
 *   < 0 - if __fscrypt_prepare_readdir() fails
 */
int ceph_fscrypt_prepare_readdir(struct inode *dir)
{
        bool had_key = fscrypt_has_encryption_key(dir);
        int err;

        if (!IS_ENCRYPTED(dir))
                return 0;

        err = __fscrypt_prepare_readdir(dir);
        if (err)
                return err;
        if (!had_key && fscrypt_has_encryption_key(dir)) {
                /* directory just got unlocked, mark it as not complete */
                ceph_dir_clear_complete(dir);
                return 1;
        }
        return 0;
}

int ceph_fscrypt_decrypt_block_inplace(const struct inode *inode,
                                  struct page *page, unsigned int len,
                                  unsigned int offs, u64 lblk_num)
{
        struct ceph_client *cl = ceph_inode_to_client(inode);

        doutc(cl, "%p %llx.%llx len %u offs %u blk %llu\n", inode,
              ceph_vinop(inode), len, offs, lblk_num);
        return fscrypt_decrypt_block_inplace(inode, page, len, offs, lblk_num);
}

int ceph_fscrypt_encrypt_block_inplace(const struct inode *inode,
                                  struct page *page, unsigned int len,
                                  unsigned int offs, u64 lblk_num)
{
        struct ceph_client *cl = ceph_inode_to_client(inode);

        doutc(cl, "%p %llx.%llx len %u offs %u blk %llu\n", inode,
              ceph_vinop(inode), len, offs, lblk_num);
        return fscrypt_encrypt_block_inplace(inode, page, len, offs, lblk_num);
}

/**
 * ceph_fscrypt_decrypt_pages - decrypt an array of pages
 * @inode: pointer to inode associated with these pages
 * @page: pointer to page array
 * @off: offset into the file that the read data starts
 * @len: max length to decrypt
 *
 * Decrypt an array of fscrypt'ed pages and return the amount of
 * data decrypted. Any data in the page prior to the start of the
 * first complete block in the read is ignored. Any incomplete
 * crypto blocks at the end of the array are ignored (and should
 * probably be zeroed by the caller).
 *
 * Returns the length of the decrypted data or a negative errno.
 */
int ceph_fscrypt_decrypt_pages(struct inode *inode, struct page **page,
                               u64 off, int len)
{
        int i, num_blocks;
        u64 baseblk = off >> CEPH_FSCRYPT_BLOCK_SHIFT;
        int ret = 0;

        /*
         * We can't deal with partial blocks on an encrypted file, so mask off
         * the last bit.
         */
        num_blocks = ceph_fscrypt_blocks(off, len & CEPH_FSCRYPT_BLOCK_MASK);

        /* Decrypt each block */
        for (i = 0; i < num_blocks; ++i) {
                int blkoff = i << CEPH_FSCRYPT_BLOCK_SHIFT;
                int pgidx = blkoff >> PAGE_SHIFT;
                unsigned int pgoffs = offset_in_page(blkoff);
                int fret;

                fret = ceph_fscrypt_decrypt_block_inplace(inode, page[pgidx],
                                CEPH_FSCRYPT_BLOCK_SIZE, pgoffs,
                                baseblk + i);
                if (fret < 0) {
                        if (ret == 0)
                                ret = fret;
                        break;
                }
                ret += CEPH_FSCRYPT_BLOCK_SIZE;
        }
        return ret;
}

/**
 * ceph_fscrypt_decrypt_extents: decrypt received extents in given buffer
 * @inode: inode associated with pages being decrypted
 * @page: pointer to page array
 * @off: offset into the file that the data in page[0] starts
 * @map: pointer to extent array
 * @ext_cnt: length of extent array
 *
 * Given an extent map and a page array, decrypt the received data in-place,
 * skipping holes. Returns the offset into buffer of end of last decrypted
 * block.
 */
int ceph_fscrypt_decrypt_extents(struct inode *inode, struct page **page,
                                 u64 off, struct ceph_sparse_extent *map,
                                 u32 ext_cnt)
{
        struct ceph_client *cl = ceph_inode_to_client(inode);
        int i, ret = 0;
        struct ceph_inode_info *ci = ceph_inode(inode);
        u64 objno, objoff;
        u32 xlen;

        /* Nothing to do for empty array */
        if (ext_cnt == 0) {
                doutc(cl, "%p %llx.%llx empty array, ret 0\n", inode,
                      ceph_vinop(inode));
                return 0;
        }

        ceph_calc_file_object_mapping(&ci->i_layout, off, map[0].len,
                                      &objno, &objoff, &xlen);

        for (i = 0; i < ext_cnt; ++i) {
                struct ceph_sparse_extent *ext = &map[i];
                int pgsoff = ext->off - objoff;
                int pgidx = pgsoff >> PAGE_SHIFT;
                int fret;

                if ((ext->off | ext->len) & ~CEPH_FSCRYPT_BLOCK_MASK) {
                        pr_warn_client(cl,
                                "%p %llx.%llx bad encrypted sparse extent "
                                "idx %d off %llx len %llx\n",
                                inode, ceph_vinop(inode), i, ext->off,
                                ext->len);
                        return -EIO;
                }
                fret = ceph_fscrypt_decrypt_pages(inode, &page[pgidx],
                                                 off + pgsoff, ext->len);
                doutc(cl, "%p %llx.%llx [%d] 0x%llx~0x%llx fret %d\n", inode,
                      ceph_vinop(inode), i, ext->off, ext->len, fret);
                if (fret < 0) {
                        if (ret == 0)
                                ret = fret;
                        break;
                }
                ret = pgsoff + fret;
        }
        doutc(cl, "ret %d\n", ret);
        return ret;
}

/**
 * ceph_fscrypt_encrypt_pages - encrypt an array of pages
 * @inode: pointer to inode associated with these pages
 * @page: pointer to page array
 * @off: offset into the file that the data starts
 * @len: max length to encrypt
 *
 * Encrypt an array of cleartext pages and return the amount of
 * data encrypted. Any data in the page prior to the start of the
 * first complete block in the read is ignored. Any incomplete
 * crypto blocks at the end of the array are ignored.
 *
 * Returns the length of the encrypted data or a negative errno.
 */
int ceph_fscrypt_encrypt_pages(struct inode *inode, struct page **page, u64 off,
                                int len)
{
        int i, num_blocks;
        u64 baseblk = off >> CEPH_FSCRYPT_BLOCK_SHIFT;
        int ret = 0;

        /*
         * We can't deal with partial blocks on an encrypted file, so mask off
         * the last bit.
         */
        num_blocks = ceph_fscrypt_blocks(off, len & CEPH_FSCRYPT_BLOCK_MASK);

        /* Encrypt each block */
        for (i = 0; i < num_blocks; ++i) {
                int blkoff = i << CEPH_FSCRYPT_BLOCK_SHIFT;
                int pgidx = blkoff >> PAGE_SHIFT;
                unsigned int pgoffs = offset_in_page(blkoff);
                int fret;

                fret = ceph_fscrypt_encrypt_block_inplace(inode, page[pgidx],
                                CEPH_FSCRYPT_BLOCK_SIZE, pgoffs,
                                baseblk + i);
                if (fret < 0) {
                        if (ret == 0)
                                ret = fret;
                        break;
                }
                ret += CEPH_FSCRYPT_BLOCK_SIZE;
        }
        return ret;
}