1 /* 2 * Copyright (C) 2014 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #pragma once 30 31 #include <android-base/format.h> 32 #include <arpa/nameser.h> 33 #include <netinet/in.h> 34 35 /* 36 * Passing NETID_UNSET as the netId causes system/netd/resolv/DnsProxyListener.cpp to 37 * fill in the appropriate default netId for the query. 38 */ 39 #define NETID_UNSET 0u 40 41 /* 42 * MARK_UNSET represents the default (i.e. unset) value for a socket mark. 43 */ 44 #define MARK_UNSET 0u 45 46 #define NET_CONTEXT_INVALID_UID ((uid_t)-1) 47 #define NET_CONTEXT_INVALID_PID ((pid_t)-1) 48 49 /* 50 * A struct to capture context relevant to network operations. 51 * 52 * Application and DNS netids/marks can differ from one another under certain 53 * circumstances, notably when a VPN applies to the given uid's traffic but the 54 * VPN network does not have its own DNS servers explicitly provisioned. 55 * 56 * The introduction of per-UID routing means the uid is also an essential part 57 * of the evaluation context. Its proper uninitialized value is 58 * NET_CONTEXT_INVALID_UID. 59 */ 60 struct android_net_context { 61 unsigned app_netid; 62 unsigned app_mark; 63 unsigned dns_netid; 64 unsigned dns_mark; 65 uid_t uid = NET_CONTEXT_INVALID_UID; 66 unsigned flags; 67 // Variable to store the pid of the application sending DNS query. 68 pid_t pid = NET_CONTEXT_INVALID_PID; 69 toStringandroid_net_context70 std::string toString() const { 71 return fmt::format("{} {} {} {} {} {}", app_netid, app_mark, dns_netid, dns_mark, uid, 72 flags); 73 } 74 }; 75 76 #define NET_CONTEXT_FLAG_USE_LOCAL_NAMESERVERS 0x00000001 77 #define NET_CONTEXT_FLAG_USE_EDNS 0x00000002 78 #define NET_CONTEXT_FLAG_USE_DNS_OVER_TLS 0x00000004 79 80 // TODO: investigate having the resolver check permissions itself, either by adding support to 81 // libbinder_ndk or by converting IPermissionController into a stable AIDL interface. 82 typedef bool (*check_calling_permission_callback)(const char* permission); 83 typedef void (*get_network_context_callback)(unsigned netid, uid_t uid, 84 android_net_context* netcontext); 85 typedef void (*log_callback)(const char* msg); 86 typedef int (*tagSocketCallback)(int sockFd, uint32_t tag, uid_t uid, pid_t pid); 87 88 // The DnsResolver module invokes this callback once before starting each DNS 89 // lookup. The callback receives the android_net_context associated with the 90 // request, and the (possibly unqualified) hostname requested by the app via 91 // getaddrinfo() or gethostbyname(). 92 // 93 // If the callback returns false, the DnsResolver will abort the request 94 // returning EAI_SYSTEM. If the callback returns true, the query will proceed as 95 // usual. 96 // 97 // If this callback is not present (i.e. set to nullptr), the effect is the same 98 // of returning true. 99 // 100 // This callback *will* be invoked concurrently from multiple threads. It must 101 // peform its own locking when accessing shared data structures. Furthermore, 102 // the callback must not sleep nor perform RPC requests. 103 // 104 // Be mindful that hostnames could contain sensitive user data. Do not log them 105 // and do not transmit them to third parties without explicit user 106 // authorization. 107 // 108 typedef bool (*evaluate_domain_name_callback)( 109 const android_net_context &netcontext, const char *host); 110 111 /* 112 * Some functions needed by the resolver (e.g. checkCallingPermission()) live in 113 * libraries with no ABI stability guarantees, such as libbinder.so. 114 * As a temporary workaround, we keep these functions in netd and call them via 115 * function pointers. 116 */ 117 struct ResolverNetdCallbacks { 118 check_calling_permission_callback check_calling_permission; 119 get_network_context_callback get_network_context; 120 log_callback log; 121 tagSocketCallback tagSocket; 122 evaluate_domain_name_callback evaluate_domain_name; 123 }; 124 125 #define TAG_SYSTEM_DNS 0xFFFFFF82 126 127 #define LIBNETD_RESOLV_PUBLIC extern "C" [[gnu::visibility("default")]] 128 129 LIBNETD_RESOLV_PUBLIC bool resolv_has_nameservers(unsigned netid); 130 131 // Set callbacks and bring DnsResolver up. 132 LIBNETD_RESOLV_PUBLIC bool resolv_init(const ResolverNetdCallbacks* callbacks); 133 134 // Function that performs RDNS in local cache. The |domain_name_size| is the size of domain_name 135 // buffer, which is recommended to NS_MAXDNAME. Function return false if hostname not found or 136 // domain_name_size > NS_MAXDNAME. 137 LIBNETD_RESOLV_PUBLIC bool resolv_gethostbyaddr_from_cache(unsigned netId, char domain_name[], 138 size_t domain_name_size, 139 const char* ip_address, int af); 140