/* * linux/fs/ext4/crypto_fname.c * * Copyright (C) 2015, Google, Inc. * * This contains functions for filename crypto management in ext4 * * Written by Uday Savagaonkar, 2014. * * This has not yet undergone a rigorous security audit. * */ #include <crypto/hash.h> #include <crypto/sha.h> #include <keys/encrypted-type.h> #include <keys/user-type.h> #include <linux/crypto.h> #include <linux/gfp.h> #include <linux/kernel.h> #include <linux/key.h> #include <linux/list.h> #include <linux/mempool.h> #include <linux/random.h> #include <linux/scatterlist.h> #include <linux/spinlock_types.h> #include "ext4.h" #include "ext4_crypto.h" #include "xattr.h" /** * ext4_dir_crypt_complete() - */ static void ext4_dir_crypt_complete(struct crypto_async_request *req, int res) { struct ext4_completion_result *ecr = req->data; if (res == -EINPROGRESS) return; ecr->res = res; complete(&ecr->completion); } bool ext4_valid_filenames_enc_mode(uint32_t mode) { return (mode == EXT4_ENCRYPTION_MODE_AES_256_CTS); } static unsigned max_name_len(struct inode *inode) { return S_ISLNK(inode->i_mode) ? inode->i_sb->s_blocksize : EXT4_NAME_LEN; } /** * ext4_fname_encrypt() - * * This function encrypts the input filename, and returns the length of the * ciphertext. Errors are returned as negative numbers. We trust the caller to * allocate sufficient memory to oname string. */ static int ext4_fname_encrypt(struct inode *inode, const struct qstr *iname, struct ext4_str *oname) { u32 ciphertext_len; struct ablkcipher_request *req = NULL; DECLARE_EXT4_COMPLETION_RESULT(ecr); struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info; struct crypto_ablkcipher *tfm = ci->ci_ctfm; int res = 0; char iv[EXT4_CRYPTO_BLOCK_SIZE]; struct scatterlist src_sg, dst_sg; int padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK); char *workbuf, buf[32], *alloc_buf = NULL; unsigned lim = max_name_len(inode); if (iname->len <= 0 || iname->len > lim) return -EIO; ciphertext_len = (iname->len < EXT4_CRYPTO_BLOCK_SIZE) ? EXT4_CRYPTO_BLOCK_SIZE : iname->len; ciphertext_len = ext4_fname_crypto_round_up(ciphertext_len, padding); ciphertext_len = (ciphertext_len > lim) ? lim : ciphertext_len; 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 = ablkcipher_request_alloc(tfm, GFP_NOFS); if (!req) { printk_ratelimited( KERN_ERR "%s: crypto_request_alloc() failed\n", __func__); kfree(alloc_buf); return -ENOMEM; } ablkcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, ext4_dir_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, EXT4_CRYPTO_BLOCK_SIZE); /* Create encryption request */ sg_init_one(&src_sg, workbuf, ciphertext_len); sg_init_one(&dst_sg, oname->name, ciphertext_len); ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, ciphertext_len, iv); res = crypto_ablkcipher_encrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { BUG_ON(req->base.data != &ecr); wait_for_completion(&ecr.completion); res = ecr.res; } kfree(alloc_buf); ablkcipher_request_free(req); if (res < 0) { printk_ratelimited( KERN_ERR "%s: Error (error code %d)\n", __func__, res); } oname->len = ciphertext_len; return res; } /* * ext4_fname_decrypt() * This function decrypts the input filename, and returns * the length of the plaintext. * Errors are returned as negative numbers. * We trust the caller to allocate sufficient memory to oname string. */ static int ext4_fname_decrypt(struct inode *inode, const struct ext4_str *iname, struct ext4_str *oname) { struct ext4_str tmp_in[2], tmp_out[1]; struct ablkcipher_request *req = NULL; DECLARE_EXT4_COMPLETION_RESULT(ecr); struct scatterlist src_sg, dst_sg; struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info; struct crypto_ablkcipher *tfm = ci->ci_ctfm; int res = 0; char iv[EXT4_CRYPTO_BLOCK_SIZE]; unsigned lim = max_name_len(inode); if (iname->len <= 0 || iname->len > lim) return -EIO; tmp_in[0].name = iname->name; tmp_in[0].len = iname->len; tmp_out[0].name = oname->name; /* Allocate request */ req = ablkcipher_request_alloc(tfm, GFP_NOFS); if (!req) { printk_ratelimited( KERN_ERR "%s: crypto_request_alloc() failed\n", __func__); return -ENOMEM; } ablkcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, ext4_dir_crypt_complete, &ecr); /* Initialize IV */ memset(iv, 0, EXT4_CRYPTO_BLOCK_SIZE); /* Create encryption request */ sg_init_one(&src_sg, iname->name, iname->len); sg_init_one(&dst_sg, oname->name, oname->len); ablkcipher_request_set_crypt(req, &src_sg, &dst_sg, iname->len, iv); res = crypto_ablkcipher_decrypt(req); if (res == -EINPROGRESS || res == -EBUSY) { BUG_ON(req->base.data != &ecr); wait_for_completion(&ecr.completion); res = ecr.res; } ablkcipher_request_free(req); if (res < 0) { printk_ratelimited( KERN_ERR "%s: Error in ext4_fname_encrypt (error code %d)\n", __func__, res); return res; } oname->len = strnlen(oname->name, iname->len); return oname->len; } static const char *lookup_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,"; /** * ext4_fname_encode_digest() - * * 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; } /** * ext4_fname_crypto_round_up() - * * Return: The next multiple of block size */ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize) { return ((size+blksize-1)/blksize)*blksize; } unsigned ext4_fname_encrypted_size(struct inode *inode, u32 ilen) { struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info; int padding = 32; if (ci) padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK); if (ilen < EXT4_CRYPTO_BLOCK_SIZE) ilen = EXT4_CRYPTO_BLOCK_SIZE; return ext4_fname_crypto_round_up(ilen, padding); } /* * ext4_fname_crypto_alloc_buffer() - * * Allocates an output buffer that is sufficient for the crypto operation * specified by the context and the direction. */ int ext4_fname_crypto_alloc_buffer(struct inode *inode, u32 ilen, struct ext4_str *crypto_str) { unsigned int olen = ext4_fname_encrypted_size(inode, ilen); crypto_str->len = olen; if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) olen = EXT4_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; } /** * ext4_fname_crypto_free_buffer() - * * Frees the buffer allocated for crypto operation. */ void ext4_fname_crypto_free_buffer(struct ext4_str *crypto_str) { if (!crypto_str) return; kfree(crypto_str->name); crypto_str->name = NULL; } /** * ext4_fname_disk_to_usr() - converts a filename from disk space to user space */ int _ext4_fname_disk_to_usr(struct inode *inode, struct dx_hash_info *hinfo, const struct ext4_str *iname, struct ext4_str *oname) { char buf[24]; int ret; if (iname->len < 3) { /*Check for . and .. */ if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') { oname->name[0] = '.'; oname->name[iname->len-1] = '.'; oname->len = iname->len; return oname->len; } } if (iname->len < EXT4_CRYPTO_BLOCK_SIZE) { EXT4_ERROR_INODE(inode, "encrypted inode too small"); return -EUCLEAN; } if (EXT4_I(inode)->i_crypt_info) return ext4_fname_decrypt(inode, iname, oname); if (iname->len <= EXT4_FNAME_CRYPTO_DIGEST_SIZE) { ret = digest_encode(iname->name, iname->len, oname->name); oname->len = ret; return ret; } if (hinfo) { memcpy(buf, &hinfo->hash, 4); memcpy(buf+4, &hinfo->minor_hash, 4); } else memset(buf, 0, 8); memcpy(buf + 8, iname->name + iname->len - 16, 16); oname->name[0] = '_'; ret = digest_encode(buf, 24, oname->name+1); oname->len = ret + 1; return ret + 1; } int ext4_fname_disk_to_usr(struct inode *inode, struct dx_hash_info *hinfo, const struct ext4_dir_entry_2 *de, struct ext4_str *oname) { struct ext4_str iname = {.name = (unsigned char *) de->name, .len = de->name_len }; return _ext4_fname_disk_to_usr(inode, hinfo, &iname, oname); } /** * ext4_fname_usr_to_disk() - converts a filename from user space to disk space */ int ext4_fname_usr_to_disk(struct inode *inode, const struct qstr *iname, struct ext4_str *oname) { int res; struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info; if (iname->len < 3) { /*Check for . and .. */ if (iname->name[0] == '.' && iname->name[iname->len-1] == '.') { oname->name[0] = '.'; oname->name[iname->len-1] = '.'; oname->len = iname->len; return oname->len; } } if (ci) { res = ext4_fname_encrypt(inode, iname, oname); return res; } /* 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; } int ext4_fname_setup_filename(struct inode *dir, const struct qstr *iname, int lookup, struct ext4_filename *fname) { struct ext4_crypt_info *ci; int ret = 0, bigname = 0; memset(fname, 0, sizeof(struct ext4_filename)); fname->usr_fname = iname; if (!ext4_encrypted_inode(dir) || ((iname->name[0] == '.') && ((iname->len == 1) || ((iname->name[1] == '.') && (iname->len == 2))))) { fname->disk_name.name = (unsigned char *) iname->name; fname->disk_name.len = iname->len; return 0; } ret = ext4_get_encryption_info(dir); if (ret) return ret; ci = EXT4_I(dir)->i_crypt_info; if (ci) { ret = ext4_fname_crypto_alloc_buffer(dir, iname->len, &fname->crypto_buf); if (ret < 0) return ret; ret = ext4_fname_encrypt(dir, iname, &fname->crypto_buf); if (ret < 0) 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->hinfo.hash, fname->crypto_buf.name, 4); memcpy(&fname->hinfo.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: kfree(fname->crypto_buf.name); fname->crypto_buf.name = NULL; return ret; } void ext4_fname_free_filename(struct ext4_filename *fname) { kfree(fname->crypto_buf.name); fname->crypto_buf.name = NULL; fname->usr_fname = NULL; fname->disk_name.name = NULL; }