cregit-Linux how code gets into the kernel

Release 4.15 net/dns_resolver/dns_key.c

Directory: net/dns_resolver
/* Key type used to cache DNS lookups made by the kernel
 *
 * See Documentation/networking/dns_resolver.txt
 *
 *   Copyright (c) 2007 Igor Mammedov
 *   Author(s): Igor Mammedov (niallain@gmail.com)
 *              Steve French (sfrench@us.ibm.com)
 *              Wang Lei (wang840925@gmail.com)
 *              David Howells (dhowells@redhat.com)
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, see <http://www.gnu.org/licenses/>.
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/keyctl.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <keys/dns_resolver-type.h>
#include <keys/user-type.h>
#include "internal.h"

MODULE_DESCRIPTION("DNS Resolver");
MODULE_AUTHOR("Wang Lei");
MODULE_LICENSE("GPL");


unsigned int dns_resolver_debug;
module_param_named(debug, dns_resolver_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");


const struct cred *dns_resolver_cache;


#define	DNS_ERRORNO_OPTION	"dnserror"

/*
 * Preparse instantiation data for a dns_resolver key.
 *
 * The data must be a NUL-terminated string, with the NUL char accounted in
 * datalen.
 *
 * If the data contains a '#' characters, then we take the clause after each
 * one to be an option of the form 'key=value'.  The actual data of interest is
 * the string leading up to the first '#'.  For instance:
 *
 *        "ip1,ip2,...#foo=bar"
 */

static int dns_resolver_preparse(struct key_preparsed_payload *prep) { struct user_key_payload *upayload; unsigned long derrno; int ret; int datalen = prep->datalen, result_len = 0; const char *data = prep->data, *end, *opt; kenter("'%*.*s',%u", datalen, datalen, data, datalen); if (datalen <= 1 || !data || data[datalen - 1] != '\0') return -EINVAL; datalen--; /* deal with any options embedded in the data */ end = data + datalen; opt = memchr(data, '#', datalen); if (!opt) { /* no options: the entire data is the result */ kdebug("no options"); result_len = datalen; } else { const char *next_opt; result_len = opt - data; opt++; kdebug("options: '%s'", opt); do { const char *eq; int opt_len, opt_nlen, opt_vlen, tmp; next_opt = memchr(opt, '#', end - opt) ?: end; opt_len = next_opt - opt; if (!opt_len) { printk(KERN_WARNING "Empty option to dns_resolver key\n"); return -EINVAL; } eq = memchr(opt, '=', opt_len) ?: end; opt_nlen = eq - opt; eq++; opt_vlen = next_opt - eq; /* will be -1 if no value */ tmp = opt_vlen >= 0 ? opt_vlen : 0; kdebug("option '%*.*s' val '%*.*s'", opt_nlen, opt_nlen, opt, tmp, tmp, eq); /* see if it's an error number representing a DNS error * that's to be recorded as the result in this key */ if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 && memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) { kdebug("dns error number option"); if (opt_vlen <= 0) goto bad_option_value; ret = kstrtoul(eq, 10, &derrno); if (ret < 0) goto bad_option_value; if (derrno < 1 || derrno > 511) goto bad_option_value; kdebug("dns error no. = %lu", derrno); prep->payload.data[dns_key_error] = ERR_PTR(-derrno); continue; } bad_option_value: printk(KERN_WARNING "Option '%*.*s' to dns_resolver key:" " bad/missing value\n", opt_nlen, opt_nlen, opt); return -EINVAL; } while (opt = next_opt + 1, opt < end); } /* don't cache the result if we're caching an error saying there's no * result */ if (prep->payload.data[dns_key_error]) { kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error])); return 0; } kdebug("store result"); prep->quotalen = result_len; upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL); if (!upayload) { kleave(" = -ENOMEM"); return -ENOMEM; } upayload->datalen = result_len; memcpy(upayload->data, data, result_len); upayload->data[result_len] = '\0'; prep->payload.data[dns_key_data] = upayload; kleave(" = 0"); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Wang Lei45889.80%228.57%
David Howells5110.00%457.14%
“Cosmin10.20%114.29%
Total510100.00%7100.00%

/* * Clean up the preparse data */
static void dns_resolver_free_preparse(struct key_preparsed_payload *prep) { pr_devel("==>%s()\n", __func__); kfree(prep->payload.data[dns_key_data]); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells30100.00%2100.00%
Total30100.00%2100.00%

/* * The description is of the form "[<type>:]<domain_name>" * * The domain name may be a simple name or an absolute domain name (which * should end with a period). The domain name is case-independent. */
static bool dns_resolver_cmp(const struct key *key, const struct key_match_data *match_data) { int slen, dlen, ret = 0; const char *src = key->description, *dsp = match_data->raw_data; kenter("%s,%s", src, dsp); if (!src || !dsp) goto no_match; if (strcasecmp(src, dsp) == 0) goto matched; slen = strlen(src); dlen = strlen(dsp); if (slen <= 0 || dlen <= 0) goto no_match; if (src[slen - 1] == '.') slen--; if (dsp[dlen - 1] == '.') dlen--; if (slen != dlen || strncasecmp(src, dsp, slen) != 0) goto no_match; matched: ret = 1; no_match: kleave(" = %d", ret); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Wang Lei16295.29%125.00%
David Howells84.71%375.00%
Total170100.00%4100.00%

/* * Preparse the match criterion. */
static int dns_resolver_match_preparse(struct key_match_data *match_data) { match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE; match_data->cmp = dns_resolver_cmp; return 0; }

Contributors

PersonTokensPropCommitsCommitProp
David Howells26100.00%1100.00%
Total26100.00%1100.00%

/* * Describe a DNS key */
static void dns_resolver_describe(const struct key *key, struct seq_file *m) { seq_puts(m, key->description); if (key_is_positive(key)) { int err = PTR_ERR(key->payload.data[dns_key_error]); if (err) seq_printf(m, ": %d", err); else seq_printf(m, ": %u", key->datalen); } }

Contributors

PersonTokensPropCommitsCommitProp
Wang Lei5168.00%125.00%
David Howells2432.00%375.00%
Total75100.00%4100.00%

/* * read the DNS data * - the key's semaphore is read-locked */
static long dns_resolver_read(const struct key *key, char __user *buffer, size_t buflen) { int err = PTR_ERR(key->payload.data[dns_key_error]); if (err) return err; return user_read(key, buffer, buflen); }

Contributors

PersonTokensPropCommitsCommitProp
David Howells52100.00%2100.00%
Total52100.00%2100.00%

struct key_type key_type_dns_resolver = { .name = "dns_resolver", .preparse = dns_resolver_preparse, .free_preparse = dns_resolver_free_preparse, .instantiate = generic_key_instantiate, .match_preparse = dns_resolver_match_preparse, .revoke = user_revoke, .destroy = user_destroy, .describe = dns_resolver_describe, .read = dns_resolver_read, };
static int __init init_dns_resolver(void) { struct cred *cred; struct key *keyring; int ret; /* create an override credential set with a special thread keyring in * which DNS requests are cached * * this is used to prevent malicious redirections from being installed * with add_key(). */ cred = prepare_kernel_cred(NULL); if (!cred) return -ENOMEM; keyring = keyring_alloc(".dns_resolver", GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, (KEY_POS_ALL & ~KEY_POS_SETATTR) | KEY_USR_VIEW | KEY_USR_READ, KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); if (IS_ERR(keyring)) { ret = PTR_ERR(keyring); goto failed_put_cred; } ret = register_key_type(&key_type_dns_resolver); if (ret < 0) goto failed_put_key; /* instruct request_key() to use this special keyring as a cache for * the results it looks up */ set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); cred->thread_keyring = keyring; cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; dns_resolver_cache = cred; kdebug("DNS resolver keyring: %d\n", key_serial(keyring)); return 0; failed_put_key: key_put(keyring); failed_put_cred: put_cred(cred); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Wang Lei14589.51%120.00%
David Howells159.26%360.00%
Eric W. Biedermann21.23%120.00%
Total162100.00%5100.00%


static void __exit exit_dns_resolver(void) { key_revoke(dns_resolver_cache->thread_keyring); unregister_key_type(&key_type_dns_resolver); put_cred(dns_resolver_cache); }

Contributors

PersonTokensPropCommitsCommitProp
Wang Lei27100.00%1100.00%
Total27100.00%1100.00%

module_init(init_dns_resolver) module_exit(exit_dns_resolver) MODULE_LICENSE("GPL");

Overall Contributors

PersonTokensPropCommitsCommitProp
Wang Lei97380.75%210.53%
David Howells22418.59%1263.16%
Stephen Rothwell30.25%15.26%
Eric W. Biedermann20.17%15.26%
Jeff Kirsher10.08%15.26%
“Cosmin10.08%15.26%
Eric Dumazet10.08%15.26%
Total1205100.00%19100.00%
Directory: net/dns_resolver
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