Support for name lookups in -connect and -addnode

* A new option -dns is introduced that enables name lookups in
  -connect and -addnode, which is not enabled by default,
  as it may be considered a security issue.
* A Lookup function is added that supports retrieving one or
  more addresses based on a host name
* CAddress constructors (optionally) support name lookups.
* The different places in the source code that did name lookups
  are refactored to use NameLookup or CAddress instead (dns seeding,
  irc server lookup, getexternalip, ...).
* Removed ToStringLog() from CAddress, and switched to ToString(),
  since it was empty.

src/init.cpp

@@ -158,6 +158,7 @@ bool AppInit2(int argc, char* argv[])
             "  -min             \t\t  " + _("Start minimized\n") +
             "  -datadir=<dir>   \t\t  " + _("Specify data directory\n") +
             "  -proxy=<ip:port> \t  "   + _("Connect through socks4 proxy\n") +
+            "  -dns             \t  "   + _("Allow DNS lookups for addnode and connect\n") +
             "  -addnode=<ip>    \t  "   + _("Add a node to connect to\n") +
             "  -connect=<ip>    \t\t  " + _("Connect only to the specified node\n") +
             "  -nolisten        \t  "   + _("Don't accept connections from outside\n") +
@@ -208,6 +209,7 @@ bool AppInit2(int argc, char* argv[])
     }
 
     fDebug = GetBoolArg("-debug");
+    fAllowDNS = GetBoolArg("-dns");
 
 #ifndef __WXMSW__
     fDaemon = GetBoolArg("-daemon");
@@ -458,7 +460,7 @@ bool AppInit2(int argc, char* argv[])
     {
         foreach(string strAddr, mapMultiArgs["-addnode"])
         {
-            CAddress addr(strAddr, NODE_NETWORK);
+            CAddress addr(strAddr, fAllowDNS);
             addr.nTime = 0; // so it won't relay unless successfully connected
             if (addr.IsValid())
                 AddAddress(addr);

src/irc.cpp

@@ -41,7 +41,7 @@ bool DecodeAddress(string str, CAddress& addr)
         return false;
     memcpy(&tmp, &vch[0], sizeof(tmp));
 
-    addr = CAddress(tmp.ip, tmp.port, NODE_NETWORK);
+    addr = CAddress(tmp.ip, ntohs(tmp.port), NODE_NETWORK);
     return true;
 }
 
@@ -215,25 +215,15 @@ bool GetIPFromIRC(SOCKET hSocket, string strMyName, unsigned int& ipRet)
         return false;
     string strHost = str.substr(str.rfind("@")+1);
 
-    unsigned int a=0, b=0, c=0, d=0;
-    if (sscanf(strHost.c_str(), "%u.%u.%u.%u", &a, &b, &c, &d) == 4 &&
-        inet_addr(strHost.c_str()) != INADDR_NONE)
-    {
-        printf("GetIPFromIRC() userhost is IP %s\n", strHost.c_str());
-        ipRet = CAddress(strHost).ip;
-    }
-    else
-    {
-        // Hybrid IRC used by lfnet always returns IP when you userhost yourself,
-        // but in case another IRC is ever used this should work.
-        printf("GetIPFromIRC() got userhost %s\n", strHost.c_str());
-        if (fUseProxy)
-            return false;
-        struct hostent* phostent = gethostbyname(strHost.c_str());
-        if (!phostent || !phostent->h_addr_list || !phostent->h_addr_list[0])
-            return false;
-        ipRet = *(u_long*)phostent->h_addr_list[0];
-    }
+    // Hybrid IRC used by lfnet always returns IP when you userhost yourself,
+    // but in case another IRC is ever used this should work.
+    printf("GetIPFromIRC() got userhost %s\n", strHost.c_str());
+    if (fUseProxy)
+        return false;
+    CAddress addr(strHost, 0, true);
+    if (!addr.IsValid())
+        return false;
+    ipRet = addr.ip;
 
     return true;
 }
@@ -276,9 +266,9 @@ void ThreadIRCSeed2(void* parg)
         if (!fTOR)
         {
             //struct hostent* phostent = gethostbyname("chat.freenode.net");
-            struct hostent* phostent = gethostbyname("irc.lfnet.org");
-            if (phostent && phostent->h_addr_list && phostent->h_addr_list[0])
-                addrConnect = CAddress(*(u_long*)phostent->h_addr_list[0], htons(6667));
+            CAddress addrIRC("irc.lfnet.org:6667", 0, true);
+            if (addrIRC.IsValid())
+                addrConnect = addrIRC;
         }
 
         SOCKET hSocket;
@@ -390,7 +380,7 @@ void ThreadIRCSeed2(void* parg)
                 {
                     addr.nTime = GetAdjustedTime();
                     if (AddAddress(addr, 51 * 60))
-                        printf("IRC got new address\n");
+                        printf("IRC got new address: %s\n", addr.ToString().c_str());
                     nGotIRCAddresses++;
                 }
                 else

src/net.cpp

@@ -29,8 +29,9 @@ bool OpenNetworkConnection(const CAddress& addrConnect);
 // Global state variables
 //
 bool fClient = false;
+bool fAllowDNS = false;
 uint64 nLocalServices = (fClient ? 0 : NODE_NETWORK);
-CAddress addrLocalHost(0, 0, nLocalServices);
+CAddress addrLocalHost("0.0.0.0", 0, false, nLocalServices);
 CNode* pnodeLocalHost = NULL;
 uint64 nLocalHostNonce = 0;
 array<int, 10> vnThreadsRunning;
@@ -47,7 +48,7 @@ map<CInv, int64> mapAlreadyAskedFor;
 
 // Settings
 int fUseProxy = false;
-CAddress addrProxy("127.0.0.1:9050");
+CAddress addrProxy("127.0.0.1",9050);
 
 
 
@@ -92,7 +93,7 @@ bool ConnectSocket(const CAddress& addrConnect, SOCKET& hSocketRet)
 
     if (fProxy)
     {
-        printf("proxy connecting %s\n", addrConnect.ToStringLog().c_str());
+        printf("proxy connecting %s\n", addrConnect.ToString().c_str());
         char pszSocks4IP[] = "\4\1\0\0\0\0\0\0user";
         memcpy(pszSocks4IP + 2, &addrConnect.port, 2);
         memcpy(pszSocks4IP + 4, &addrConnect.ip, 4);
@@ -118,14 +119,81 @@ bool ConnectSocket(const CAddress& addrConnect, SOCKET& hSocketRet)
                 printf("ERROR: Proxy returned error %d\n", pchRet[1]);
             return false;
         }
-        printf("proxy connected %s\n", addrConnect.ToStringLog().c_str());
+        printf("proxy connected %s\n", addrConnect.ToString().c_str());
     }
 
     hSocketRet = hSocket;
     return true;
 }
 
+// portDefault is in host order
+bool Lookup(const char *pszName, vector<CAddress>& vaddr, int nServices, int nMaxSolutions, bool fAllowLookup, int portDefault, bool fAllowPort)
+{
+    vaddr.clear();
+    int port = portDefault;
+    char psz[256];
+    char *pszHost = psz;
+    strlcpy(psz, pszName, sizeof(psz));
+    if (fAllowPort)
+    {
+        char* pszColon = strrchr(psz+1,':');
+        char *pszPortEnd = NULL;
+        int portParsed = pszColon ? strtoul(pszColon+1, &pszPortEnd, 10) : 0;
+        if (pszColon && pszPortEnd && pszPortEnd[0] == 0)
+        {
+            if (psz[0] == '[' && pszColon[-1] == ']')
+            {
+                // Future: enable IPv6 colon-notation inside []
+                pszHost = psz+1;
+                pszColon[-1] = 0;
+            }
+            else
+                pszColon[0] = 0;
+            port = portParsed;
+            if (port < 0 || port > USHRT_MAX)
+                port = USHRT_MAX;
+        }
+    }
+
+    struct in_addr addrIP;
+    if (inet_aton(pszHost, &addrIP))
+    {
+        // valid IP address passed
+        vaddr.push_back(CAddress(addrIP.s_addr, port, nServices));
+        return true;
+    }
+
+    if (!fAllowLookup)
+        return false;
+
+    struct hostent* phostent = gethostbyname(pszHost);
+    if (!phostent)
+        return false;
+
+    if (phostent->h_addrtype != AF_INET)
+        return false;
 
+    char** ppAddr = phostent->h_addr_list;
+    while (*ppAddr != NULL && vaddr.size() != nMaxSolutions)
+    {
+        CAddress addr(((struct in_addr*)ppAddr[0])->s_addr, port, nServices);
+        if (addr.IsValid())
+            vaddr.push_back(addr);
+        ppAddr++;
+    }
+
+    return (vaddr.size() > 0);
+}
+
+// portDefault is in host order
+bool Lookup(const char *pszName, CAddress& addr, int nServices, bool fAllowLookup, int portDefault, bool fAllowPort)
+{
+    vector<CAddress> vaddr;
+    bool fRet = Lookup(pszName, vaddr, nServices, 1, fAllowLookup, portDefault, fAllowPort);
+    if (fRet)
+        addr = vaddr[0];
+    return fRet;
+}
 
 bool GetMyExternalIP2(const CAddress& addrConnect, const char* pszGet, const char* pszKeyword, unsigned int& ipRet)
 {
@@ -161,7 +229,7 @@ bool GetMyExternalIP2(const CAddress& addrConnect, const char* pszGet, const cha
             strLine = strLine.substr(strspn(strLine.c_str(), " \t\n\r"));
             while (strLine.size() > 0 && isspace(strLine[strLine.size()-1]))
                 strLine.resize(strLine.size()-1);
-            CAddress addr(strLine.c_str());
+            CAddress addr(strLine,0,true);
             printf("GetMyExternalIP() received [%s] %s\n", strLine.c_str(), addr.ToString().c_str());
             if (addr.ip == 0 || addr.ip == INADDR_NONE || !addr.IsRoutable())
                 return false;
@@ -192,13 +260,13 @@ bool GetMyExternalIP(unsigned int& ipRet)
         //  <?php echo $_SERVER["REMOTE_ADDR"]; ?>
         if (nHost == 1)
         {
-            addrConnect = CAddress("91.198.22.70:80"); // checkip.dyndns.org
+            addrConnect = CAddress("91.198.22.70",80); // checkip.dyndns.org
 
             if (nLookup == 1)
             {
-                struct hostent* phostent = gethostbyname("checkip.dyndns.org");
-                if (phostent && phostent->h_addr_list && phostent->h_addr_list[0])
-                    addrConnect = CAddress(*(u_long*)phostent->h_addr_list[0], htons(80));
+                CAddress addrIP("checkip.dyndns.org", 80, true);
+                if (addrIP.IsValid())
+                    addrConnect = addrIP;
             }
 
             pszGet = "GET / HTTP/1.1\r\n"
@@ -211,13 +279,13 @@ bool GetMyExternalIP(unsigned int& ipRet)
         }
         else if (nHost == 2)
         {
-            addrConnect = CAddress("74.208.43.192:80"); // www.showmyip.com
+            addrConnect = CAddress("74.208.43.192", 80); // www.showmyip.com
 
             if (nLookup == 1)
             {
-                struct hostent* phostent = gethostbyname("www.showmyip.com");
-                if (phostent && phostent->h_addr_list && phostent->h_addr_list[0])
-                    addrConnect = CAddress(*(u_long*)phostent->h_addr_list[0], htons(80));
+                CAddress addrIP("www.showmyip.com", 80, true);
+                if (addrIP.IsValid())
+                    addrConnect = addrIP;
             }
 
             pszGet = "GET /simple/ HTTP/1.1\r\n"
@@ -283,7 +351,7 @@ bool AddAddress(CAddress addr, int64 nTimePenalty)
         if (it == mapAddresses.end())
         {
             // New address
-            printf("AddAddress(%s)\n", addr.ToStringLog().c_str());
+            printf("AddAddress(%s)\n", addr.ToString().c_str());
             mapAddresses.insert(make_pair(addr.GetKey(), addr));
             CAddrDB().WriteAddress(addr);
             return true;
@@ -479,7 +547,7 @@ CNode* ConnectNode(CAddress addrConnect, int64 nTimeout)
 
     /// debug print
     printf("trying connection %s lastseen=%.1fhrs lasttry=%.1fhrs\n",
-        addrConnect.ToStringLog().c_str(),
+        addrConnect.ToString().c_str(),
         (double)(addrConnect.nTime - GetAdjustedTime())/3600.0,
         (double)(addrConnect.nLastTry - GetAdjustedTime())/3600.0);
 
@@ -491,7 +559,7 @@ CNode* ConnectNode(CAddress addrConnect, int64 nTimeout)
     if (ConnectSocket(addrConnect, hSocket))
     {
         /// debug print
-        printf("connected %s\n", addrConnect.ToStringLog().c_str());
+        printf("connected %s\n", addrConnect.ToString().c_str());
 
         // Set to nonblocking
 #ifdef __WXMSW__
@@ -528,7 +596,7 @@ void CNode::CloseSocketDisconnect()
     {
         if (fDebug)
             printf("%s ", DateTimeStrFormat("%x %H:%M:%S", GetTime()).c_str());
-        printf("disconnecting node %s\n", addr.ToStringLog().c_str());
+        printf("disconnecting node %s\n", addr.ToString().c_str());
         closesocket(hSocket);
         hSocket = INVALID_SOCKET;
     }
@@ -715,7 +783,7 @@ void ThreadSocketHandler2(void* parg)
             }
             else
             {
-                printf("accepted connection %s\n", addr.ToStringLog().c_str());
+                printf("accepted connection %s\n", addr.ToString().c_str());
                 CNode* pnode = new CNode(hSocket, addr, true);
                 pnode->AddRef();
                 CRITICAL_BLOCK(cs_vNodes)
@@ -892,7 +960,7 @@ void ThreadMapPort2(void* parg)
     printf("ThreadMapPort started\n");
 
     char port[6];
-    sprintf(port, "%d", ntohs(GetDefaultPort()));
+    sprintf(port, "%d", GetDefaultPort());
 
     const char * rootdescurl = 0;
     const char * multicastif = 0;
@@ -984,17 +1052,17 @@ void DNSAddressSeed()
     printf("Loading addresses from DNS seeds (could take a while)\n");
 
     for (int seed_idx = 0; seed_idx < ARRAYLEN(strDNSSeed); seed_idx++) {
-        struct hostent* phostent = gethostbyname(strDNSSeed[seed_idx]);
-        if (!phostent)
-            continue;
-
-        for (int host = 0; phostent->h_addr_list[host] != NULL; host++) {
-            CAddress addr(*(unsigned int*)phostent->h_addr_list[host],
-                          GetDefaultPort(), NODE_NETWORK);
-            addr.nTime = 0;
-            if (addr.IsValid() && addr.GetByte(3) != 127) {
-                AddAddress(addr);
-                found++;
+        vector<CAddress> vaddr;
+        if (Lookup(strDNSSeed[seed_idx], vaddr, NODE_NETWORK, true))
+        {
+            foreach (CAddress& addr, vaddr)
+            {
+                if (addr.GetByte(3) != 127)
+                {
+                    addr.nTime = 0;
+                    AddAddress(addr);
+                    found++;
+                }
             }
         }
     }
@@ -1080,7 +1148,7 @@ void ThreadOpenConnections2(void* parg)
         {
             foreach(string strAddr, mapMultiArgs["-connect"])
             {
-                CAddress addr(strAddr, NODE_NETWORK);
+                CAddress addr(strAddr, fAllowDNS);
                 if (addr.IsValid())
                     OpenNetworkConnection(addr);
                 for (int i = 0; i < 10 && i < nLoop; i++)
@@ -1098,7 +1166,7 @@ void ThreadOpenConnections2(void* parg)
     {
         foreach(string strAddr, mapMultiArgs["-addnode"])
         {
-            CAddress addr(strAddr, NODE_NETWORK);
+            CAddress addr(strAddr, fAllowDNS);
             if (addr.IsValid())
             {
                 OpenNetworkConnection(addr);
@@ -1209,7 +1277,7 @@ void ThreadOpenConnections2(void* parg)
 
                 // Randomize the order in a deterministic way, putting the standard port first
                 int64 nRandomizer = (uint64)(nStart * 4951 + addr.nLastTry * 9567851 + addr.ip * 7789) % (2 * 60 * 60);
-                if (addr.port != GetDefaultPort())
+                if (addr.port != htons(GetDefaultPort()))
                     nRandomizer += 2 * 60 * 60;
 
                 // Last seen  Base retry frequency
@@ -1369,7 +1437,7 @@ bool BindListenPort(string& strError)
 {
     strError = "";
     int nOne = 1;
-    addrLocalHost.port = GetDefaultPort();
+    addrLocalHost.port = htons(GetDefaultPort());
 
 #ifdef __WXMSW__
     // Initialize Windows Sockets
@@ -1421,7 +1489,7 @@ bool BindListenPort(string& strError)
     memset(&sockaddr, 0, sizeof(sockaddr));
     sockaddr.sin_family = AF_INET;
     sockaddr.sin_addr.s_addr = INADDR_ANY; // bind to all IPs on this computer
-    sockaddr.sin_port = GetDefaultPort();
+    sockaddr.sin_port = htons(GetDefaultPort());
     if (::bind(hListenSocket, (struct sockaddr*)&sockaddr, sizeof(sockaddr)) == SOCKET_ERROR)
     {
         int nErr = WSAGetLastError();
@@ -1448,29 +1516,21 @@ bool BindListenPort(string& strError)
 void StartNode(void* parg)
 {
     if (pnodeLocalHost == NULL)
-        pnodeLocalHost = new CNode(INVALID_SOCKET, CAddress("127.0.0.1", nLocalServices));
+        pnodeLocalHost = new CNode(INVALID_SOCKET, CAddress("127.0.0.1", 0, false, nLocalServices));
 
 #ifdef __WXMSW__
     // Get local host ip
     char pszHostName[1000] = "";
     if (gethostname(pszHostName, sizeof(pszHostName)) != SOCKET_ERROR)
     {
-        struct hostent* phostent = gethostbyname(pszHostName);
-        if (phostent)
-        {
-            // Take the first IP that isn't loopback 127.x.x.x
-            for (int i = 0; phostent->h_addr_list[i] != NULL; i++)
-                printf("host ip %d: %s\n", i, CAddress(*(unsigned int*)phostent->h_addr_list[i]).ToStringIP().c_str());
-            for (int i = 0; phostent->h_addr_list[i] != NULL; i++)
-            {
-                CAddress addr(*(unsigned int*)phostent->h_addr_list[i], GetDefaultPort(), nLocalServices);
-                if (addr.IsValid() && addr.GetByte(3) != 127)
+        vector<CAddress> vaddr;
+        if (NameLookup(pszHostName, vaddr, nLocalServices))
+            foreach (const CAddress &addr, vaddr)
+                if (addr.GetByte(3) != 127)
                 {
                     addrLocalHost = addr;
                     break;
                 }
-            }
-        }
     }
 #else
     // Get local host ip
@@ -1491,7 +1551,7 @@ void StartNode(void* parg)
                     printf("ipv4 %s: %s\n", ifa->ifa_name, pszIP);
 
                 // Take the first IP that isn't loopback 127.x.x.x
-                CAddress addr(*(unsigned int*)&s4->sin_addr, GetDefaultPort(), nLocalServices);
+                CAddress addr(*(unsigned int*)&s4->sin_addr, 0, nLocalServices);
                 if (addr.IsValid() && addr.GetByte(3) != 127)
                 {
                     addrLocalHost = addr;

src/net.h

@@ -12,7 +12,7 @@ extern int nBestHeight;
 
 
 
-inline unsigned short GetDefaultPort() { return fTestNet ? htons(18333) : htons(8333); }
+inline unsigned short GetDefaultPort() { return fTestNet ? 18333 : 8333; }
 static const unsigned int PUBLISH_HOPS = 5;
 enum
 {
@@ -23,6 +23,8 @@ enum
 
 
 bool ConnectSocket(const CAddress& addrConnect, SOCKET& hSocketRet);
+bool Lookup(const char *pszName, vector<CAddress>& vaddr, int nServices, int nMaxSolutions, bool fAllowLookup = false, int portDefault = 0, bool fAllowPort = false);
+bool Lookup(const char *pszName, CAddress& addr, int nServices, bool fAllowLookup = false, int portDefault = 0, bool fAllowPort = false);
 bool GetMyExternalIP(unsigned int& ipRet);
 bool AddAddress(CAddress addr, int64 nTimePenalty=0);
 void AddressCurrentlyConnected(const CAddress& addr);
@@ -156,7 +158,7 @@ public:
     {
         Init();
         ip = ipIn;
-        port = (portIn == 0 ? GetDefaultPort() : portIn);
+        port = htons(portIn == 0 ? GetDefaultPort() : portIn);
         nServices = nServicesIn;
     }
 
@@ -168,54 +170,38 @@ public:
         nServices = nServicesIn;
     }
 
-    explicit CAddress(const char* pszIn, uint64 nServicesIn=NODE_NETWORK)
+    explicit CAddress(const char* pszIn, int portIn, bool fNameLookup = false, uint64 nServicesIn=NODE_NETWORK)
     {
         Init();
-        SetAddress(pszIn);
-        nServices = nServicesIn;
+        Lookup(pszIn, *this, nServicesIn, fNameLookup, portIn);
     }
 
-    explicit CAddress(string strIn, uint64 nServicesIn=NODE_NETWORK)
+    explicit CAddress(const char* pszIn, bool fNameLookup = false, uint64 nServicesIn=NODE_NETWORK)
     {
         Init();
-        SetAddress(strIn.c_str());
-        nServices = nServicesIn;
+        Lookup(pszIn, *this, nServicesIn, fNameLookup, 0, true);
     }
 
-    void Init()
+    explicit CAddress(string strIn, int portIn, bool fNameLookup = false, uint64 nServicesIn=NODE_NETWORK)
     {
-        nServices = NODE_NETWORK;
-        memcpy(pchReserved, pchIPv4, sizeof(pchReserved));
-        ip = INADDR_NONE;
-        port = GetDefaultPort();
-        nTime = 100000000;
-        nLastTry = 0;
+        Init();
+        Lookup(strIn.c_str(), *this, nServicesIn, fNameLookup, portIn);
     }
 
-    bool SetAddress(const char* pszIn)
+    explicit CAddress(string strIn, bool fNameLookup = false, uint64 nServicesIn=NODE_NETWORK)
     {
-        ip = INADDR_NONE;
-        port = GetDefaultPort();
-        char psz[100];
-        strlcpy(psz, pszIn, sizeof(psz));
-        unsigned int a=0, b=0, c=0, d=0, e=0;
-        if (sscanf(psz, "%u.%u.%u.%u:%u", &a, &b, &c, &d, &e) < 4)
-            return false;
-        char* pszPort = strchr(psz, ':');
-        if (pszPort)
-        {
-            *pszPort++ = '\0';
-            port = htons(atoi(pszPort));
-            if (atoi(pszPort) < 0 || atoi(pszPort) > USHRT_MAX)
-                port = htons(USHRT_MAX);
-        }
-        ip = inet_addr(psz);
-        return IsValid();
+        Init();
+        Lookup(strIn.c_str(), *this, nServicesIn, fNameLookup, 0, true);
     }
 
-    bool SetAddress(string strIn)
+    void Init()
     {
-        return SetAddress(strIn.c_str());
+        nServices = NODE_NETWORK;
+        memcpy(pchReserved, pchIPv4, sizeof(pchReserved));
+        ip = INADDR_NONE;
+        port = htons(GetDefaultPort());
+        nTime = 100000000;
+        nLastTry = 0;
     }
 
     IMPLEMENT_SERIALIZE
@@ -330,11 +316,6 @@ public:
         return strprintf("%u", ntohs(port));
     }
 
-    string ToStringLog() const
-    {
-        return "";
-    }
-
     string ToString() const
     {
         return strprintf("%u.%u.%u.%u:%u", GetByte(3), GetByte(2), GetByte(1), GetByte(0), ntohs(port));
@@ -460,6 +441,7 @@ public:
 
 
 extern bool fClient;
+extern bool fAllowDNS;
 extern uint64 nLocalServices;
 extern CAddress addrLocalHost;
 extern CNode* pnodeLocalHost;