diff options
author | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
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committer | André Fabian Silva Delgado <emulatorman@parabola.nu> | 2015-08-05 17:04:01 -0300 |
commit | 57f0f512b273f60d52568b8c6b77e17f5636edc0 (patch) | |
tree | 5e910f0e82173f4ef4f51111366a3f1299037a7b /net/dns_resolver/dns_key.c |
Initial import
Diffstat (limited to 'net/dns_resolver/dns_key.c')
-rw-r--r-- | net/dns_resolver/dns_key.c | 319 |
1 files changed, 319 insertions, 0 deletions
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c new file mode 100644 index 000000000..31cd4fd75 --- /dev/null +++ b/net/dns_resolver/dns_key.c @@ -0,0 +1,319 @@ +/* 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->type_data[0] = 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->type_data[0]) { + kleave(" = 0 [h_error %ld]", PTR_ERR(prep->type_data[0])); + 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[0] = upayload; + kleave(" = 0"); + return 0; +} + +/* + * Clean up the preparse data + */ +static void dns_resolver_free_preparse(struct key_preparsed_payload *prep) +{ + pr_devel("==>%s()\n", __func__); + + kfree(prep->payload[0]); +} + +/* + * 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; +} + +/* + * 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; +} + +/* + * Describe a DNS key + */ +static void dns_resolver_describe(const struct key *key, struct seq_file *m) +{ + int err = key->type_data.x[0]; + + seq_puts(m, key->description); + if (key_is_instantiated(key)) { + if (err) + seq_printf(m, ": %d", err); + else + seq_printf(m, ": %u", key->datalen); + } +} + +/* + * 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) +{ + if (key->type_data.x[0]) + return key->type_data.x[0]; + + return user_read(key, buffer, buflen); +} + +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); + 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; +} + +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); +} + +module_init(init_dns_resolver) +module_exit(exit_dns_resolver) +MODULE_LICENSE("GPL"); + |