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-rw-r--r--net/dns_resolver/Kconfig27
-rw-r--r--net/dns_resolver/Makefile7
-rw-r--r--net/dns_resolver/dns_key.c210
-rw-r--r--net/dns_resolver/dns_query.c159
-rw-r--r--net/dns_resolver/internal.h44
5 files changed, 447 insertions, 0 deletions
diff --git a/net/dns_resolver/Kconfig b/net/dns_resolver/Kconfig
new file mode 100644
index 000000000000..2ec47cb5d0d6
--- /dev/null
+++ b/net/dns_resolver/Kconfig
@@ -0,0 +1,27 @@
+#
+# Configuration for DNS Resolver
+#
+config DNS_RESOLVER
+ tristate "DNS Resolver support"
+ depends on NET && KEYS
+ help
+ Saying Y here will include support for the DNS Resolver key type
+ which can be used to make upcalls to perform DNS lookups in
+ userspace.
+
+ DNS Resolver is used to query DNS server for information. Examples
+ being resolving a UNC hostname element to an IP address for CIFS or
+ performing a DNS query for AFSDB records so that AFS can locate a
+ cell's volume location database servers.
+
+ DNS Resolver is used by the CIFS and AFS modules, and would support
+ samba4 later. DNS Resolver is supported by the userspace upcall
+ helper "/sbin/dns.resolver" via /etc/request-key.conf.
+
+ See <file:Documentation/networking/dns_resolver.txt> for further
+ information.
+
+ To compile this as a module, choose M here: the module will be called
+ dnsresolver.
+
+ If unsure, say N.
diff --git a/net/dns_resolver/Makefile b/net/dns_resolver/Makefile
new file mode 100644
index 000000000000..c0ef4e71dc49
--- /dev/null
+++ b/net/dns_resolver/Makefile
@@ -0,0 +1,7 @@
+#
+# Makefile for the Linux DNS Resolver.
+#
+
+obj-$(CONFIG_DNS_RESOLVER) += dns_resolver.o
+
+dns_resolver-objs := dns_key.o dns_query.o
diff --git a/net/dns_resolver/dns_key.c b/net/dns_resolver/dns_key.c
new file mode 100644
index 000000000000..1b1b411adcf1
--- /dev/null
+++ b/net/dns_resolver/dns_key.c
@@ -0,0 +1,210 @@
+/* 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#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 <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 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;
+
+/*
+ * Instantiate a user defined key for dns_resolver.
+ *
+ * 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_instantiate(struct key *key, const void *_data, size_t datalen)
+{
+ struct user_key_payload *upayload;
+ int ret;
+ size_t result_len = 0;
+ const char *data = _data, *opt;
+
+ kenter("%%%d,%s,'%s',%zu",
+ key->serial, key->description, data, datalen);
+
+ if (datalen <= 1 || !data || data[datalen - 1] != '\0')
+ return -EINVAL;
+ datalen--;
+
+ /* deal with any options embedded in the data */
+ opt = memchr(data, '#', datalen);
+ if (!opt) {
+ kdebug("no options currently supported");
+ return -EINVAL;
+ }
+
+ result_len = datalen;
+ ret = key_payload_reserve(key, result_len);
+ if (ret < 0)
+ return -EINVAL;
+
+ 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';
+ rcu_assign_pointer(key->payload.data, upayload);
+
+ kleave(" = 0");
+ return 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 int
+dns_resolver_match(const struct key *key, const void *description)
+{
+ int slen, dlen, ret = 0;
+ const char *src = key->description, *dsp = description;
+
+ 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;
+}
+
+struct key_type key_type_dns_resolver = {
+ .name = "dns_resolver",
+ .instantiate = dns_resolver_instantiate,
+ .match = dns_resolver_match,
+ .revoke = user_revoke,
+ .destroy = user_destroy,
+ .describe = user_describe,
+ .read = user_read,
+};
+
+static int __init init_dns_resolver(void)
+{
+ struct cred *cred;
+ struct key *keyring;
+ int ret;
+
+ printk(KERN_NOTICE "Registering the %s key type\n",
+ key_type_dns_resolver.name);
+
+ /* 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 = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred,
+ (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ,
+ KEY_ALLOC_NOT_IN_QUOTA);
+ if (IS_ERR(keyring)) {
+ ret = PTR_ERR(keyring);
+ goto failed_put_cred;
+ }
+
+ ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
+ if (ret < 0)
+ goto failed_put_key;
+
+ 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 */
+ 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);
+ printk(KERN_NOTICE "Unregistered %s key type\n",
+ key_type_dns_resolver.name);
+}
+
+module_init(init_dns_resolver)
+module_exit(exit_dns_resolver)
+MODULE_LICENSE("GPL");
diff --git a/net/dns_resolver/dns_query.c b/net/dns_resolver/dns_query.c
new file mode 100644
index 000000000000..6c0cf31ea00d
--- /dev/null
+++ b/net/dns_resolver/dns_query.c
@@ -0,0 +1,159 @@
+/* Upcall routine, designed to work as a key type and working through
+ * /sbin/request-key to contact userspace when handling DNS queries.
+ *
+ * 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)
+ *
+ * The upcall wrapper used to make an arbitrary DNS query.
+ *
+ * This function requires the appropriate userspace tool dns.upcall to be
+ * installed and something like the following lines should be added to the
+ * /etc/request-key.conf file:
+ *
+ * create dns_resolver * * /sbin/dns.upcall %k
+ *
+ * For example to use this module to query AFSDB RR:
+ *
+ * create dns_resolver afsdb:* * /sbin/dns.afsdb %k
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/dns_resolver.h>
+#include <keys/dns_resolver-type.h>
+#include <keys/user-type.h>
+
+#include "internal.h"
+
+/*
+ * dns_query - Query the DNS
+ * @type: Query type (or NULL for straight host->IP lookup)
+ * @name: Name to look up
+ * @namelen: Length of name
+ * @options: Request options (or NULL if no options)
+ * @_result: Where to place the returned data.
+ * @_expiry: Where to store the result expiry time (or NULL)
+ *
+ * The data will be returned in the pointer at *result, and the caller is
+ * responsible for freeing it.
+ *
+ * The description should be of the form "[<query_type>:]<domain_name>", and
+ * the options need to be appropriate for the query type requested. If no
+ * query_type is given, then the query is a straight hostname to IP address
+ * lookup.
+ *
+ * The DNS resolution lookup is performed by upcalling to userspace by way of
+ * requesting a key of type dns_resolver.
+ *
+ * Returns the size of the result on success, -ve error code otherwise.
+ */
+int dns_query(const char *type, const char *name, size_t namelen,
+ const char *options, char **_result, time_t *_expiry)
+{
+ struct key *rkey;
+ struct user_key_payload *upayload;
+ const struct cred *saved_cred;
+ size_t typelen, desclen;
+ char *desc, *cp;
+ int ret, len;
+
+ kenter("%s,%*.*s,%zu,%s",
+ type, (int)namelen, (int)namelen, name, namelen, options);
+
+ if (!name || namelen == 0 || !_result)
+ return -EINVAL;
+
+ /* construct the query key description as "[<type>:]<name>" */
+ typelen = 0;
+ desclen = 0;
+ if (type) {
+ typelen = strlen(type);
+ if (typelen < 1)
+ return -EINVAL;
+ desclen += typelen + 1;
+ }
+
+ if (!namelen)
+ namelen = strlen(name);
+ if (namelen < 3)
+ return -EINVAL;
+ desclen += namelen + 1;
+
+ desc = kmalloc(desclen, GFP_KERNEL);
+ if (!desc)
+ return -ENOMEM;
+
+ cp = desc;
+ if (type) {
+ memcpy(cp, type, typelen);
+ cp += typelen;
+ *cp++ = ':';
+ }
+ memcpy(cp, name, namelen);
+ cp += namelen;
+ *cp = '\0';
+
+ if (!options)
+ options = "";
+ kdebug("call request_key(,%s,%s)", desc, options);
+
+ /* make the upcall, using special credentials to prevent the use of
+ * add_key() to preinstall malicious redirections
+ */
+ saved_cred = override_creds(dns_resolver_cache);
+ rkey = request_key(&key_type_dns_resolver, desc, options);
+ revert_creds(saved_cred);
+ kfree(desc);
+ if (IS_ERR(rkey)) {
+ ret = PTR_ERR(rkey);
+ goto out;
+ }
+
+ down_read(&rkey->sem);
+ rkey->perm |= KEY_USR_VIEW;
+
+ ret = key_validate(rkey);
+ if (ret < 0)
+ goto put;
+
+ upayload = rcu_dereference_protected(rkey->payload.data,
+ lockdep_is_held(&rkey->sem));
+ len = upayload->datalen;
+
+ ret = -ENOMEM;
+ *_result = kmalloc(len + 1, GFP_KERNEL);
+ if (!*_result)
+ goto put;
+
+ memcpy(*_result, upayload->data, len + 1);
+ if (_expiry)
+ *_expiry = rkey->expiry;
+
+ ret = len;
+put:
+ up_read(&rkey->sem);
+ key_put(rkey);
+out:
+ kleave(" = %d", ret);
+ return ret;
+}
+EXPORT_SYMBOL(dns_query);
diff --git a/net/dns_resolver/internal.h b/net/dns_resolver/internal.h
new file mode 100644
index 000000000000..189ca9e9b785
--- /dev/null
+++ b/net/dns_resolver/internal.h
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2010 Wang Lei
+ * Author(s): Wang Lei (wang840925@gmail.com). All Rights Reserved.
+ *
+ * Internal DNS Rsolver stuff
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/compiler.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+
+/*
+ * dns_key.c
+ */
+extern const struct cred *dns_resolver_cache;
+
+/*
+ * debug tracing
+ */
+extern unsigned dns_resolver_debug;
+
+#define kdebug(FMT, ...) \
+do { \
+ if (unlikely(dns_resolver_debug)) \
+ printk(KERN_DEBUG "[%-6.6s] "FMT"\n", \
+ current->comm, ##__VA_ARGS__); \
+} while (0)
+
+#define kenter(FMT, ...) kdebug("==> %s("FMT")", __func__, ##__VA_ARGS__)
+#define kleave(FMT, ...) kdebug("<== %s()"FMT"", __func__, ##__VA_ARGS__)

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