cregit-Linux how code gets into the kernel

Release 4.15 security/keys/big_key.c

Directory: security/keys
/* Large capacity key type
 *
 * Copyright (C) 2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */


#define pr_fmt(fmt) "big_key: "fmt
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/file.h>
#include <linux/shmem_fs.h>
#include <linux/err.h>
#include <linux/scatterlist.h>
#include <linux/random.h>
#include <keys/user-type.h>
#include <keys/big_key-type.h>
#include <crypto/aead.h>

/*
 * Layout of key payload words.
 */
enum {
	
big_key_data,
	
big_key_path,
	
big_key_path_2nd_part,
	
big_key_len,
};

/*
 * Crypto operation with big_key data
 */

enum big_key_op {
	
BIG_KEY_ENC,
	
BIG_KEY_DEC,
};

/*
 * If the data is under this limit, there's no point creating a shm file to
 * hold it as the permanently resident metadata for the shmem fs will be at
 * least as large as the data.
 */

#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))

/*
 * Key size for big_key data encryption
 */

#define ENC_KEY_SIZE 32

/*
 * Authentication tag length
 */

#define ENC_AUTHTAG_SIZE 16

/*
 * big_key defined keys take an arbitrary string as the description and an
 * arbitrary blob of data as the payload
 */

struct key_type key_type_big_key = {
	.name			= "big_key",
	.preparse		= big_key_preparse,
	.free_preparse		= big_key_free_preparse,
	.instantiate		= generic_key_instantiate,
	.revoke			= big_key_revoke,
	.destroy		= big_key_destroy,
	.describe		= big_key_describe,
	.read			= big_key_read,
	/* no ->update(); don't add it without changing big_key_crypt() nonce */
};

/*
 * Crypto names for big_key data authenticated encryption
 */

static const char big_key_alg_name[] = "gcm(aes)";

/*
 * Crypto algorithms for big_key data authenticated encryption
 */

static struct crypto_aead *big_key_aead;

/*
 * Since changing the key affects the entire object, we need a mutex.
 */
static DEFINE_MUTEX(big_key_aead_lock);

/*
 * Encrypt/decrypt big_key data
 */

static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key) { int ret; struct scatterlist sgio; struct aead_request *aead_req; /* We always use a zero nonce. The reason we can get away with this is * because we're using a different randomly generated key for every * different encryption. Notably, too, key_type_big_key doesn't define * an .update function, so there's no chance we'll wind up reusing the * key to encrypt updated data. Simply put: one key, one encryption. */ u8 zero_nonce[crypto_aead_ivsize(big_key_aead)]; aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL); if (!aead_req) return -ENOMEM; memset(zero_nonce, 0, sizeof(zero_nonce)); sg_init_one(&sgio, data, datalen + (op == BIG_KEY_ENC ? ENC_AUTHTAG_SIZE : 0)); aead_request_set_crypt(aead_req, &sgio, &sgio, datalen, zero_nonce); aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL); aead_request_set_ad(aead_req, 0); mutex_lock(&big_key_aead_lock); if (crypto_aead_setkey(big_key_aead, key, ENC_KEY_SIZE)) { ret = -EAGAIN; goto error; } if (op == BIG_KEY_ENC) ret = crypto_aead_encrypt(aead_req); else ret = crypto_aead_decrypt(aead_req); error: mutex_unlock(&big_key_aead_lock); aead_request_free(aead_req); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Jason A. Donenfeld10354.21%133.33%
Kirill Marinushkin6333.16%133.33%
Herbert Xu2412.63%133.33%
Total190100.00%3100.00%

/* * Preparse a big key */
int big_key_preparse(struct key_preparsed_payload *prep) { struct path *path = (struct path *)&prep->payload.data[big_key_path]; struct file *file; u8 *enckey; u8 *data = NULL; ssize_t written; size_t datalen = prep->datalen; int ret; ret = -EINVAL; if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) goto error; /* Set an arbitrary quota */ prep->quotalen = 16; prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; if (datalen > BIG_KEY_FILE_THRESHOLD) { /* Create a shmem file to store the data in. This will permit the data * to be swapped out if needed. * * File content is stored encrypted with randomly generated key. */ size_t enclen = datalen + ENC_AUTHTAG_SIZE; loff_t pos = 0; data = kmalloc(enclen, GFP_KERNEL); if (!data) return -ENOMEM; memcpy(data, prep->data, datalen); /* generate random key */ enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL); if (!enckey) { ret = -ENOMEM; goto error; } ret = get_random_bytes_wait(enckey, ENC_KEY_SIZE); if (unlikely(ret)) goto err_enckey; /* encrypt aligned data */ ret = big_key_crypt(BIG_KEY_ENC, data, datalen, enckey); if (ret) goto err_enckey; /* save aligned data to file */ file = shmem_kernel_file_setup("", enclen, 0); if (IS_ERR(file)) { ret = PTR_ERR(file); goto err_enckey; } written = kernel_write(file, data, enclen, &pos); if (written != enclen) { ret = written; if (written >= 0) ret = -ENOMEM; goto err_fput; } /* Pin the mount and dentry to the key so that we can open it again * later */ prep->payload.data[big_key_data] = enckey; *path = file->f_path; path_get(path); fput(file); kzfree(data); } else { /* Just store the data in a buffer */ void *data = kmalloc(datalen, GFP_KERNEL); if (!data) return -ENOMEM; prep->payload.data[big_key_data] = data; memcpy(data, prep->data, prep->datalen); } return 0; err_fput: fput(file); err_enckey: kzfree(enckey); error: kzfree(data); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells24259.90%440.00%
Kirill Marinushkin13332.92%110.00%
Jason A. Donenfeld122.97%220.00%
Wei Yongjun92.23%110.00%
Christoph Hellwig71.73%110.00%
Eric Paris10.25%110.00%
Total404100.00%10100.00%

/* * Clear preparsement. */
void big_key_free_preparse(struct key_preparsed_payload *prep) { if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { struct path *path = (struct path *)&prep->payload.data[big_key_path]; path_put(path); } kzfree(prep->payload.data[big_key_data]); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells5698.25%266.67%
Jason A. Donenfeld11.75%133.33%
Total57100.00%3100.00%

/* * dispose of the links from a revoked keyring * - called with the key sem write-locked */
void big_key_revoke(struct key *key) { struct path *path = (struct path *)&key->payload.data[big_key_path]; /* clear the quota */ key_payload_reserve(key, 0); if (key_is_positive(key) && (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) vfs_truncate(path, 0); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells66100.00%3100.00%
Total66100.00%3100.00%

/* * dispose of the data dangling from the corpse of a big_key key */
void big_key_destroy(struct key *key) { size_t datalen = (size_t)key->payload.data[big_key_len]; if (datalen > BIG_KEY_FILE_THRESHOLD) { struct path *path = (struct path *)&key->payload.data[big_key_path]; path_put(path); path->mnt = NULL; path->dentry = NULL; } kzfree(key->payload.data[big_key_data]); key->payload.data[big_key_data] = NULL; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells9096.77%250.00%
Kirill Marinushkin22.15%125.00%
Jason A. Donenfeld11.08%125.00%
Total93100.00%4100.00%

/* * describe the big_key key */
void big_key_describe(const struct key *key, struct seq_file *m) { size_t datalen = (size_t)key->payload.data[big_key_len]; seq_puts(m, key->description); if (key_is_positive(key)) seq_printf(m, ": %zu [%s]", datalen, datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells64100.00%3100.00%
Total64100.00%3100.00%

/* * read the key data * - the key's semaphore is read-locked */
long big_key_read(const struct key *key, char __user *buffer, size_t buflen) { size_t datalen = (size_t)key->payload.data[big_key_len]; long ret; if (!buffer || buflen < datalen) return datalen; if (datalen > BIG_KEY_FILE_THRESHOLD) { struct path *path = (struct path *)&key->payload.data[big_key_path]; struct file *file; u8 *data; u8 *enckey = (u8 *)key->payload.data[big_key_data]; size_t enclen = datalen + ENC_AUTHTAG_SIZE; loff_t pos = 0; data = kmalloc(enclen, GFP_KERNEL); if (!data) return -ENOMEM; file = dentry_open(path, O_RDONLY, current_cred()); if (IS_ERR(file)) { ret = PTR_ERR(file); goto error; } /* read file to kernel and decrypt */ ret = kernel_read(file, data, enclen, &pos); if (ret >= 0 && ret != enclen) { ret = -EIO; goto err_fput; } ret = big_key_crypt(BIG_KEY_DEC, data, enclen, enckey); if (ret) goto err_fput; ret = datalen; /* copy decrypted data to user */ if (copy_to_user(buffer, data, datalen) != 0) ret = -EFAULT; err_fput: fput(file); error: kzfree(data); } else { ret = datalen; if (copy_to_user(buffer, key->payload.data[big_key_data], datalen) != 0) ret = -EFAULT; } return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells16456.36%233.33%
Kirill Marinushkin11639.86%116.67%
Christoph Hellwig82.75%116.67%
Jason A. Donenfeld31.03%233.33%
Total291100.00%6100.00%

/* * Register key type */
static int __init big_key_init(void) { int ret; /* init block cipher */ big_key_aead = crypto_alloc_aead(big_key_alg_name, 0, CRYPTO_ALG_ASYNC); if (IS_ERR(big_key_aead)) { ret = PTR_ERR(big_key_aead); pr_err("Can't alloc crypto: %d\n", ret); return ret; } ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE); if (ret < 0) { pr_err("Can't set crypto auth tag len: %d\n", ret); goto free_aead; } ret = register_key_type(&key_type_big_key); if (ret < 0) { pr_err("Can't register type: %d\n", ret); goto free_aead; } return 0; free_aead: crypto_free_aead(big_key_aead); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells4639.66%250.00%
Kirill Marinushkin4538.79%125.00%
Jason A. Donenfeld2521.55%125.00%
Total116100.00%4100.00%

late_initcall(big_key_init);

Overall Contributors

PersonTokensPropCommitsCommitProp
David Howells82457.22%642.86%
Kirill Marinushkin39827.64%17.14%
Jason A. Donenfeld16711.60%214.29%
Herbert Xu261.81%17.14%
Christoph Hellwig151.04%214.29%
Wei Yongjun90.62%17.14%
Eric Paris10.07%17.14%
Total1440100.00%14100.00%
Directory: security/keys
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