1b4d0d230SThomas Gleixner // SPDX-License-Identifier: GPL-2.0-or-later 2ab3c3587SDavid Howells /* Large capacity key type 3ab3c3587SDavid Howells * 4*521fd61cSJason A. Donenfeld * Copyright (C) 2017-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. 5ab3c3587SDavid Howells * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. 6ab3c3587SDavid Howells * Written by David Howells (dhowells@redhat.com) 7ab3c3587SDavid Howells */ 8ab3c3587SDavid Howells 97df3e59cSDavid Howells #define pr_fmt(fmt) "big_key: "fmt 10ab3c3587SDavid Howells #include <linux/init.h> 11ab3c3587SDavid Howells #include <linux/seq_file.h> 12ab3c3587SDavid Howells #include <linux/file.h> 13ab3c3587SDavid Howells #include <linux/shmem_fs.h> 14ab3c3587SDavid Howells #include <linux/err.h> 15428490e3SJason A. Donenfeld #include <linux/random.h> 16ab3c3587SDavid Howells #include <keys/user-type.h> 17ab3c3587SDavid Howells #include <keys/big_key-type.h> 18*521fd61cSJason A. Donenfeld #include <crypto/chacha20poly1305.h> 19d9f4bb1aSDavid Howells 20ab3c3587SDavid Howells /* 21146aa8b1SDavid Howells * Layout of key payload words. 22146aa8b1SDavid Howells */ 23146aa8b1SDavid Howells enum { 24146aa8b1SDavid Howells big_key_data, 25146aa8b1SDavid Howells big_key_path, 26146aa8b1SDavid Howells big_key_path_2nd_part, 27146aa8b1SDavid Howells big_key_len, 28146aa8b1SDavid Howells }; 29146aa8b1SDavid Howells 30146aa8b1SDavid Howells /* 31ab3c3587SDavid Howells * If the data is under this limit, there's no point creating a shm file to 32ab3c3587SDavid Howells * hold it as the permanently resident metadata for the shmem fs will be at 33ab3c3587SDavid Howells * least as large as the data. 34ab3c3587SDavid Howells */ 35ab3c3587SDavid Howells #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) 36ab3c3587SDavid Howells 37ab3c3587SDavid Howells /* 38ab3c3587SDavid Howells * big_key defined keys take an arbitrary string as the description and an 39ab3c3587SDavid Howells * arbitrary blob of data as the payload 40ab3c3587SDavid Howells */ 41ab3c3587SDavid Howells struct key_type key_type_big_key = { 42ab3c3587SDavid Howells .name = "big_key", 43002edaf7SDavid Howells .preparse = big_key_preparse, 44002edaf7SDavid Howells .free_preparse = big_key_free_preparse, 45002edaf7SDavid Howells .instantiate = generic_key_instantiate, 46ab3c3587SDavid Howells .revoke = big_key_revoke, 47ab3c3587SDavid Howells .destroy = big_key_destroy, 48ab3c3587SDavid Howells .describe = big_key_describe, 49ab3c3587SDavid Howells .read = big_key_read, 50*521fd61cSJason A. Donenfeld /* no ->update(); don't add it without changing chacha20poly1305's nonce */ 51ab3c3587SDavid Howells }; 52ab3c3587SDavid Howells 53ab3c3587SDavid Howells /* 54002edaf7SDavid Howells * Preparse a big key 55ab3c3587SDavid Howells */ 56002edaf7SDavid Howells int big_key_preparse(struct key_preparsed_payload *prep) 57ab3c3587SDavid Howells { 58146aa8b1SDavid Howells struct path *path = (struct path *)&prep->payload.data[big_key_path]; 59ab3c3587SDavid Howells struct file *file; 60*521fd61cSJason A. Donenfeld u8 *buf, *enckey; 61ab3c3587SDavid Howells ssize_t written; 62*521fd61cSJason A. Donenfeld size_t datalen = prep->datalen; 63*521fd61cSJason A. Donenfeld size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE; 64ab3c3587SDavid Howells int ret; 65ab3c3587SDavid Howells 66ab3c3587SDavid Howells if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) 67d9f4bb1aSDavid Howells return -EINVAL; 68ab3c3587SDavid Howells 69ab3c3587SDavid Howells /* Set an arbitrary quota */ 70002edaf7SDavid Howells prep->quotalen = 16; 71ab3c3587SDavid Howells 72146aa8b1SDavid Howells prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; 73ab3c3587SDavid Howells 74ab3c3587SDavid Howells if (datalen > BIG_KEY_FILE_THRESHOLD) { 75ab3c3587SDavid Howells /* Create a shmem file to store the data in. This will permit the data 76ab3c3587SDavid Howells * to be swapped out if needed. 77ab3c3587SDavid Howells * 7813100a72SKirill Marinushkin * File content is stored encrypted with randomly generated key. 79*521fd61cSJason A. Donenfeld * Since the key is random for each file, we can set the nonce 80*521fd61cSJason A. Donenfeld * to zero, provided we never define a ->update() call. 81ab3c3587SDavid Howells */ 82e13ec939SChristoph Hellwig loff_t pos = 0; 8313100a72SKirill Marinushkin 84*521fd61cSJason A. Donenfeld buf = kvmalloc(enclen, GFP_KERNEL); 85d9f4bb1aSDavid Howells if (!buf) 8613100a72SKirill Marinushkin return -ENOMEM; 8713100a72SKirill Marinushkin 8813100a72SKirill Marinushkin /* generate random key */ 89*521fd61cSJason A. Donenfeld enckey = kmalloc(CHACHA20POLY1305_KEY_SIZE, GFP_KERNEL); 9013100a72SKirill Marinushkin if (!enckey) { 9113100a72SKirill Marinushkin ret = -ENOMEM; 92002edaf7SDavid Howells goto error; 93d2b86970SWei Yongjun } 94*521fd61cSJason A. Donenfeld ret = get_random_bytes_wait(enckey, CHACHA20POLY1305_KEY_SIZE); 95428490e3SJason A. Donenfeld if (unlikely(ret)) 9613100a72SKirill Marinushkin goto err_enckey; 9713100a72SKirill Marinushkin 98*521fd61cSJason A. Donenfeld /* encrypt data */ 99*521fd61cSJason A. Donenfeld chacha20poly1305_encrypt(buf, prep->data, datalen, NULL, 0, 100*521fd61cSJason A. Donenfeld 0, enckey); 10113100a72SKirill Marinushkin 10213100a72SKirill Marinushkin /* save aligned data to file */ 10313100a72SKirill Marinushkin file = shmem_kernel_file_setup("", enclen, 0); 10413100a72SKirill Marinushkin if (IS_ERR(file)) { 10513100a72SKirill Marinushkin ret = PTR_ERR(file); 10613100a72SKirill Marinushkin goto err_enckey; 10713100a72SKirill Marinushkin } 10813100a72SKirill Marinushkin 109*521fd61cSJason A. Donenfeld written = kernel_write(file, buf, enclen, &pos); 11013100a72SKirill Marinushkin if (written != enclen) { 11197826c82SDavid Howells ret = written; 112ab3c3587SDavid Howells if (written >= 0) 113*521fd61cSJason A. Donenfeld ret = -EIO; 114ab3c3587SDavid Howells goto err_fput; 115ab3c3587SDavid Howells } 116ab3c3587SDavid Howells 117ab3c3587SDavid Howells /* Pin the mount and dentry to the key so that we can open it again 118ab3c3587SDavid Howells * later 119ab3c3587SDavid Howells */ 12013100a72SKirill Marinushkin prep->payload.data[big_key_data] = enckey; 121ab3c3587SDavid Howells *path = file->f_path; 122ab3c3587SDavid Howells path_get(path); 123ab3c3587SDavid Howells fput(file); 124*521fd61cSJason A. Donenfeld memzero_explicit(buf, enclen); 125*521fd61cSJason A. Donenfeld kvfree(buf); 126ab3c3587SDavid Howells } else { 127ab3c3587SDavid Howells /* Just store the data in a buffer */ 128ab3c3587SDavid Howells void *data = kmalloc(datalen, GFP_KERNEL); 12913100a72SKirill Marinushkin 130002edaf7SDavid Howells if (!data) 131002edaf7SDavid Howells return -ENOMEM; 132ab3c3587SDavid Howells 133146aa8b1SDavid Howells prep->payload.data[big_key_data] = data; 134146aa8b1SDavid Howells memcpy(data, prep->data, prep->datalen); 135ab3c3587SDavid Howells } 136ab3c3587SDavid Howells return 0; 137ab3c3587SDavid Howells 138ab3c3587SDavid Howells err_fput: 139ab3c3587SDavid Howells fput(file); 14013100a72SKirill Marinushkin err_enckey: 14191080180SJason A. Donenfeld kzfree(enckey); 142ab3c3587SDavid Howells error: 143*521fd61cSJason A. Donenfeld memzero_explicit(buf, enclen); 144*521fd61cSJason A. Donenfeld kvfree(buf); 145ab3c3587SDavid Howells return ret; 146ab3c3587SDavid Howells } 147ab3c3587SDavid Howells 148ab3c3587SDavid Howells /* 149002edaf7SDavid Howells * Clear preparsement. 150002edaf7SDavid Howells */ 151002edaf7SDavid Howells void big_key_free_preparse(struct key_preparsed_payload *prep) 152002edaf7SDavid Howells { 153002edaf7SDavid Howells if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { 154146aa8b1SDavid Howells struct path *path = (struct path *)&prep->payload.data[big_key_path]; 15513100a72SKirill Marinushkin 156002edaf7SDavid Howells path_put(path); 157002edaf7SDavid Howells } 15891080180SJason A. Donenfeld kzfree(prep->payload.data[big_key_data]); 159002edaf7SDavid Howells } 160002edaf7SDavid Howells 161002edaf7SDavid Howells /* 162ab3c3587SDavid Howells * dispose of the links from a revoked keyring 163ab3c3587SDavid Howells * - called with the key sem write-locked 164ab3c3587SDavid Howells */ 165ab3c3587SDavid Howells void big_key_revoke(struct key *key) 166ab3c3587SDavid Howells { 167146aa8b1SDavid Howells struct path *path = (struct path *)&key->payload.data[big_key_path]; 168ab3c3587SDavid Howells 169ab3c3587SDavid Howells /* clear the quota */ 170ab3c3587SDavid Howells key_payload_reserve(key, 0); 171363b02daSDavid Howells if (key_is_positive(key) && 172146aa8b1SDavid Howells (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) 173ab3c3587SDavid Howells vfs_truncate(path, 0); 174ab3c3587SDavid Howells } 175ab3c3587SDavid Howells 176ab3c3587SDavid Howells /* 177ab3c3587SDavid Howells * dispose of the data dangling from the corpse of a big_key key 178ab3c3587SDavid Howells */ 179ab3c3587SDavid Howells void big_key_destroy(struct key *key) 180ab3c3587SDavid Howells { 181146aa8b1SDavid Howells size_t datalen = (size_t)key->payload.data[big_key_len]; 182146aa8b1SDavid Howells 18313100a72SKirill Marinushkin if (datalen > BIG_KEY_FILE_THRESHOLD) { 184146aa8b1SDavid Howells struct path *path = (struct path *)&key->payload.data[big_key_path]; 18513100a72SKirill Marinushkin 186ab3c3587SDavid Howells path_put(path); 187ab3c3587SDavid Howells path->mnt = NULL; 188ab3c3587SDavid Howells path->dentry = NULL; 18913100a72SKirill Marinushkin } 19091080180SJason A. Donenfeld kzfree(key->payload.data[big_key_data]); 191146aa8b1SDavid Howells key->payload.data[big_key_data] = NULL; 192ab3c3587SDavid Howells } 193ab3c3587SDavid Howells 194ab3c3587SDavid Howells /* 195ab3c3587SDavid Howells * describe the big_key key 196ab3c3587SDavid Howells */ 197ab3c3587SDavid Howells void big_key_describe(const struct key *key, struct seq_file *m) 198ab3c3587SDavid Howells { 199146aa8b1SDavid Howells size_t datalen = (size_t)key->payload.data[big_key_len]; 200ab3c3587SDavid Howells 201ab3c3587SDavid Howells seq_puts(m, key->description); 202ab3c3587SDavid Howells 203363b02daSDavid Howells if (key_is_positive(key)) 204146aa8b1SDavid Howells seq_printf(m, ": %zu [%s]", 205ab3c3587SDavid Howells datalen, 206ab3c3587SDavid Howells datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); 207ab3c3587SDavid Howells } 208ab3c3587SDavid Howells 209ab3c3587SDavid Howells /* 210ab3c3587SDavid Howells * read the key data 211ab3c3587SDavid Howells * - the key's semaphore is read-locked 212ab3c3587SDavid Howells */ 213d3ec10aaSWaiman Long long big_key_read(const struct key *key, char *buffer, size_t buflen) 214ab3c3587SDavid Howells { 215146aa8b1SDavid Howells size_t datalen = (size_t)key->payload.data[big_key_len]; 216ab3c3587SDavid Howells long ret; 217ab3c3587SDavid Howells 218ab3c3587SDavid Howells if (!buffer || buflen < datalen) 219ab3c3587SDavid Howells return datalen; 220ab3c3587SDavid Howells 221ab3c3587SDavid Howells if (datalen > BIG_KEY_FILE_THRESHOLD) { 222146aa8b1SDavid Howells struct path *path = (struct path *)&key->payload.data[big_key_path]; 223ab3c3587SDavid Howells struct file *file; 224*521fd61cSJason A. Donenfeld u8 *buf, *enckey = (u8 *)key->payload.data[big_key_data]; 225*521fd61cSJason A. Donenfeld size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE; 226bdd1d2d3SChristoph Hellwig loff_t pos = 0; 22713100a72SKirill Marinushkin 228*521fd61cSJason A. Donenfeld buf = kvmalloc(enclen, GFP_KERNEL); 229d9f4bb1aSDavid Howells if (!buf) 23013100a72SKirill Marinushkin return -ENOMEM; 231ab3c3587SDavid Howells 232ab3c3587SDavid Howells file = dentry_open(path, O_RDONLY, current_cred()); 23313100a72SKirill Marinushkin if (IS_ERR(file)) { 23413100a72SKirill Marinushkin ret = PTR_ERR(file); 23513100a72SKirill Marinushkin goto error; 23613100a72SKirill Marinushkin } 237ab3c3587SDavid Howells 23813100a72SKirill Marinushkin /* read file to kernel and decrypt */ 239*521fd61cSJason A. Donenfeld ret = kernel_read(file, buf, enclen, &pos); 240*521fd61cSJason A. Donenfeld if (ret != enclen) { 241*521fd61cSJason A. Donenfeld if (ret >= 0) 242ab3c3587SDavid Howells ret = -EIO; 24313100a72SKirill Marinushkin goto err_fput; 24413100a72SKirill Marinushkin } 24513100a72SKirill Marinushkin 246*521fd61cSJason A. Donenfeld ret = chacha20poly1305_decrypt(buf, buf, enclen, NULL, 0, 0, 247*521fd61cSJason A. Donenfeld enckey) ? 0 : -EBADMSG; 248*521fd61cSJason A. Donenfeld if (unlikely(ret)) 24913100a72SKirill Marinushkin goto err_fput; 25013100a72SKirill Marinushkin 25113100a72SKirill Marinushkin ret = datalen; 25213100a72SKirill Marinushkin 253d3ec10aaSWaiman Long /* copy out decrypted data */ 254*521fd61cSJason A. Donenfeld memcpy(buffer, buf, datalen); 25513100a72SKirill Marinushkin 25613100a72SKirill Marinushkin err_fput: 25713100a72SKirill Marinushkin fput(file); 25813100a72SKirill Marinushkin error: 259*521fd61cSJason A. Donenfeld memzero_explicit(buf, enclen); 260*521fd61cSJason A. Donenfeld kvfree(buf); 261ab3c3587SDavid Howells } else { 262ab3c3587SDavid Howells ret = datalen; 263d3ec10aaSWaiman Long memcpy(buffer, key->payload.data[big_key_data], datalen); 264ab3c3587SDavid Howells } 265ab3c3587SDavid Howells 266ab3c3587SDavid Howells return ret; 267ab3c3587SDavid Howells } 268ab3c3587SDavid Howells 26913100a72SKirill Marinushkin /* 27013100a72SKirill Marinushkin * Register key type 27113100a72SKirill Marinushkin */ 272ab3c3587SDavid Howells static int __init big_key_init(void) 273ab3c3587SDavid Howells { 274*521fd61cSJason A. Donenfeld return register_key_type(&key_type_big_key); 27513100a72SKirill Marinushkin } 27613100a72SKirill Marinushkin 2777df3e59cSDavid Howells late_initcall(big_key_init); 278