/* * This contains functions for filename crypto management * * Copyright (C) 2015, Google, Inc. * Copyright (C) 2015, Motorola Mobility * * Written by Uday Savagaonkar, 2014. * Modified by Jaegeuk Kim, 2015. * * This has not yet undergone a rigorous security audit. */ #include <linux/scatterlist.h> #include <linux/ratelimit.h> #include <linux/fscrypto.h> /** * fname_crypt_complete() - completion callback for filename crypto * @req: The asynchronous cipher request context * @res: The result of the cipher operation */ static void fname_crypt_complete(struct crypto_async_request *req, int res) { struct fscrypt_completion_result *ecr = req->data; if (res == -EINPROGRESS) return; ecr->res = res; complete(&ecr->completion); } /** * fname_encrypt() - encrypt a filename * * The caller must have allocated sufficient memory for the @oname string. * * Return: 0 on success, -errno on failure */ static int fname_encrypt(struct inode *inode, const struct qstr *iname, struct fscrypt_str *oname) { u32 ciphertext_len; struct skcipher_request *req = NULL; DECLARE_FS_COMPLETION_RESULT(ecr); struct fscrypt_info *ci = inode->i_crypt_info; struct crypto_skcipher *tfm = ci->ci_ctfm; int res = 0; char iv[FS_CRYPTO_BLOCK_SIZE]; struct scatterlist src_sg, dst_sg; int padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK); char *workbuf, buf[32], *alloc_buf = NULL; unsigned lim; lim = inode->i_sb->s_cop->max_namelen(inode); if (iname->len <= 0 || iname->len > lim) return -EIO; ciphertext_len = max(iname->len, (u32)FS_CRYPTO_BLOCK_SIZE); ciphertext_len = round_up(ciphertext_len, padding); ciphertext_len = min(ciphertext_len, lim); if (ciphertext_len <= sizeof(buf)) { workbuf = buf; } else { alloc_buf = kmalloc(ciphertext_len, GFP_NOFS); if (!alloc_buf) return -ENOMEM; workbuf = alloc_buf; } /* Allocate request */ req = skcipher_request_alloc(tfm, GFP_NOFS); if (!req) { printk_ratelimited(KERN_ERR "%s: crypto_request_alloc() failed\n", __func__); kfree(alloc_buf); return -ENOMEM; } skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, fname_crypt_complete, &ecr); /* Copy the input */ memcpy(workbuf, iname->name, iname->len); if (iname->len < ciphertext_len) memset(workbuf + iname->len, 0, ciphertext_len - iname->len); /* Initialize IV */ memset(iv, 0, FS_CRYPTO_BLOCK_SIZE); /* Create encryption request */ sg_init_one(&src_sg, workbuf, ciphertext_len); sg_init_one(&dst_sg, oname->name, ciphertext_len); skcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv); res = crypto_skcipher_encrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { wait_for_completion(&ecr.completion); res = ecr.res; } kfree(alloc_buf); skcipher_request_free(req); if (res < 0) { printk_ratelimited(KERN_ERR "%s: Error (error code %d)\n", __func__, res); return res; } oname->len = ciphertext_len; return 0; } /** * fname_decrypt() - decrypt a filename * * The caller must have allocated sufficient memory for the @oname string. * * Return: 0 on success, -errno on failure */ static int fname_decrypt(struct inode *inode, const struct fscrypt_str *iname, struct fscrypt_str *oname) { struct skcipher_request *req = NULL; DECLARE_FS_COMPLETION_RESULT(ecr); struct scatterlist src_sg, dst_sg; struct fscrypt_info *ci = inode->i_crypt_info; struct crypto_skcipher *tfm = ci->ci_ctfm; int res = 0; char iv[FS_CRYPTO_BLOCK_SIZE]; unsigned lim; lim = inode->i_sb->s_cop->max_namelen(inode); if (iname->len <= 0 || iname->len > lim) return -EIO; /* Allocate request */ req = skcipher_request_alloc(tfm, GFP_NOFS); if (!req) { printk_ratelimited(KERN_ERR "%s: crypto_request_alloc() failed\n", __func__); return -ENOMEM; } skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, fname_crypt_complete, &ecr); /* Initialize IV */ memset(iv, 0, FS_CRYPTO_BLOCK_SIZE); /* Create decryption request */ sg_init_one(&src_sg, iname->name, iname->len); sg_init_one(&dst_sg, oname->name, oname->len); skcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv); res = crypto_skcipher_decrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { wait_for_completion(&ecr.completion); res = ecr.res; } skcipher_request_free(req); if (res < 0) { printk_ratelimited(KERN_ERR "%s: Error (error code %d)\n", __func__, res); return res; } oname->len = strnlen(oname->name, iname->len); return 0; } static const char *lookup_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,"; /** * digest_encode() - * * Encodes the input digest using characters from the set [a-zA-Z0-9_+]. * The encoded string is roughly 4/3 times the size of the input string. */ static int digest_encode(const char *src, int len, char *dst) { int i = 0, bits = 0, ac = 0; char *cp = dst; while (i < len) { ac += (((unsigned char) src[i]) << bits); bits += 8; do { *cp++ = lookup_table[ac & 0x3f]; ac >>= 6; bits -= 6; } while (bits >= 6); i++; } if (bits) *cp++ = lookup_table[ac & 0x3f]; return cp - dst; } static int digest_decode(const char *src, int len, char *dst) { int i = 0, bits = 0, ac = 0; const char *p; char *cp = dst; while (i < len) { p = strchr(lookup_table, src[i]); if (p == NULL || src[i] == 0) return -2; ac += (p - lookup_table) << bits; bits += 6; if (bits >= 8) { *cp++ = ac & 0xff; ac >>= 8; bits -= 8; } i++; } if (ac) return -1; return cp - dst; } u32 fscrypt_fname_encrypted_size(struct inode *inode, u32 ilen) { int padding = 32; struct fscrypt_info *ci = inode->i_crypt_info; if (ci) padding = 4 << (ci->ci_flags & FS_POLICY_FLAGS_PAD_MASK); ilen = max(ilen, (u32)FS_CRYPTO_BLOCK_SIZE); return round_up(ilen, padding); } EXPORT_SYMBOL(fscrypt_fname_encrypted_size); /** * fscrypt_fname_crypto_alloc_obuff() - * * Allocates an output buffer that is sufficient for the crypto operation * specified by the context and the direction. */ int fscrypt_fname_alloc_buffer(struct inode *inode, u32 ilen, struct fscrypt_str *crypto_str) { unsigned int olen = fscrypt_fname_encrypted_size(inode, ilen); crypto_str->len = olen; if (olen < FS_FNAME_CRYPTO_DIGEST_SIZE * 2) olen = FS_FNAME_CRYPTO_DIGEST_SIZE * 2; /* * Allocated buffer can hold one more character to null-terminate the * string */ crypto_str->name = kmalloc(olen + 1, GFP_NOFS); if (!(crypto_str->name)) return -ENOMEM; return 0; } EXPORT_SYMBOL(fscrypt_fname_alloc_buffer); /** * fscrypt_fname_crypto_free_buffer() - * * Frees the buffer allocated for crypto operation. */ void fscrypt_fname_free_buffer(struct fscrypt_str *crypto_str) { if (!crypto_str) return; kfree(crypto_str->name); crypto_str->name = NULL; } EXPORT_SYMBOL(fscrypt_fname_free_buffer); /** * fscrypt_fname_disk_to_usr() - converts a filename from disk space to user * space * * The caller must have allocated sufficient memory for the @oname string. * * Return: 0 on success, -errno on failure */ int fscrypt_fname_disk_to_usr(struct inode *inode, u32 hash, u32 minor_hash, const struct fscrypt_str *iname, struct fscrypt_str *oname) { const struct qstr qname = FSTR_TO_QSTR(iname); char buf[24]; if (fscrypt_is_dot_dotdot(&qname)) { oname->name[0] = '.'; oname->name[iname->len - 1] = '.'; oname->len = iname->len; return 0; } if (iname->len < FS_CRYPTO_BLOCK_SIZE) return -EUCLEAN; if (inode->i_crypt_info) return fname_decrypt(inode, iname, oname); if (iname->len <= FS_FNAME_CRYPTO_DIGEST_SIZE) { oname->len = digest_encode(iname->name, iname->len, oname->name); return 0; } if (hash) { memcpy(buf, &hash, 4); memcpy(buf + 4, &minor_hash, 4); } else { memset(buf, 0, 8); } memcpy(buf + 8, iname->name + iname->len - 16, 16); oname->name[0] = '_'; oname->len = 1 + digest_encode(buf, 24, oname->name + 1); return 0; } EXPORT_SYMBOL(fscrypt_fname_disk_to_usr); /** * fscrypt_fname_usr_to_disk() - converts a filename from user space to disk * space * * The caller must have allocated sufficient memory for the @oname string. * * Return: 0 on success, -errno on failure */ int fscrypt_fname_usr_to_disk(struct inode *inode, const struct qstr *iname, struct fscrypt_str *oname) { if (fscrypt_is_dot_dotdot(iname)) { oname->name[0] = '.'; oname->name[iname->len - 1] = '.'; oname->len = iname->len; return 0; } if (inode->i_crypt_info) return fname_encrypt(inode, iname, oname); /* * Without a proper key, a user is not allowed to modify the filenames * in a directory. Consequently, a user space name cannot be mapped to * a disk-space name */ return -EACCES; } EXPORT_SYMBOL(fscrypt_fname_usr_to_disk); int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname, int lookup, struct fscrypt_name *fname) { int ret = 0, bigname = 0; memset(fname, 0, sizeof(struct fscrypt_name)); fname->usr_fname = iname; if (!dir->i_sb->s_cop->is_encrypted(dir) || fscrypt_is_dot_dotdot(iname)) { fname->disk_name.name = (unsigned char *)iname->name; fname->disk_name.len = iname->len; return 0; } ret = get_crypt_info(dir); if (ret && ret != -EOPNOTSUPP) return ret; if (dir->i_crypt_info) { ret = fscrypt_fname_alloc_buffer(dir, iname->len, &fname->crypto_buf); if (ret) return ret; ret = fname_encrypt(dir, iname, &fname->crypto_buf); if (ret) goto errout; fname->disk_name.name = fname->crypto_buf.name; fname->disk_name.len = fname->crypto_buf.len; return 0; } if (!lookup) return -EACCES; /* * We don't have the key and we are doing a lookup; decode the * user-supplied name */ if (iname->name[0] == '_') bigname = 1; if ((bigname && (iname->len != 33)) || (!bigname && (iname->len > 43))) return -ENOENT; fname->crypto_buf.name = kmalloc(32, GFP_KERNEL); if (fname->crypto_buf.name == NULL) return -ENOMEM; ret = digest_decode(iname->name + bigname, iname->len - bigname, fname->crypto_buf.name); if (ret < 0) { ret = -ENOENT; goto errout; } fname->crypto_buf.len = ret; if (bigname) { memcpy(&fname->hash, fname->crypto_buf.name, 4); memcpy(&fname->minor_hash, fname->crypto_buf.name + 4, 4); } else { fname->disk_name.name = fname->crypto_buf.name; fname->disk_name.len = fname->crypto_buf.len; } return 0; errout: fscrypt_fname_free_buffer(&fname->crypto_buf); return ret; } EXPORT_SYMBOL(fscrypt_setup_filename); void fscrypt_free_filename(struct fscrypt_name *fname) { kfree(fname->crypto_buf.name); fname->crypto_buf.name = NULL; fname->usr_fname = NULL; fname->disk_name.name = NULL; } EXPORT_SYMBOL(fscrypt_free_filename);