Merge #17754: net: Don't allow resolving of std::string with embedded NUL characters. Add tests.

7a046cdc1423963bdcbcf9bb98560af61fa90b37 tests: Avoid using C-style NUL-terminated strings as arguments (practicalswift)
fefb9165f23fe9d10ad092ec31715f906e0d2ee7 tests: Add tests to make sure lookup methods fail on std::string parameters with embedded NUL characters (practicalswift)
9574de86ad703ad942cdd0eca79f48c0d42b102b net: Avoid using C-style NUL-terminated strings as arguments in the netbase interface (practicalswift)

Pull request description:

  Don't allow resolving of `std::string`:s with embedded `NUL` characters.

  Avoid using C-style `NUL`-terminated strings as arguments in the `netbase` interface

  Add tests.

  The only place in where C-style `NUL`-terminated strings are actually needed is here:

  ```diff
  +    if (!ValidAsCString(name)) {
  +        return false;
  +    }
  ...
  -    int nErr = getaddrinfo(pszName, nullptr, &aiHint, &aiRes);
  +    int nErr = getaddrinfo(name.c_str(), nullptr, &aiHint, &aiRes);
       if (nErr)
           return false;
  ```

  Interface changes:

  ```diff
  -bool LookupHost(const char *pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup);
  +bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup);

  -bool LookupHost(const char *pszName, CNetAddr& addr, bool fAllowLookup);
  +bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup);

  -bool Lookup(const char *pszName, CService& addr, int portDefault, bool fAllowLookup);
  +bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup);

  -bool Lookup(const char *pszName, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);
  +bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);

  -bool LookupSubNet(const char *pszName, CSubNet& subnet);
  +bool LookupSubNet(const std::string& strSubnet, CSubNet& subnet);

  -CService LookupNumeric(const char *pszName, int portDefault = 0);
  +CService LookupNumeric(const std::string& name, int portDefault = 0);

  -bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed);
  +bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocketRet, int nTimeout, bool& outProxyConnectionFailed);
  ```

  It should be noted that the `ConnectThroughProxy` change (from `bool *outProxyConnectionFailed` to `bool& outProxyConnectionFailed`) has nothing to do with `NUL` handling but I thought it was worth doing when touching this file :)

ACKs for top commit:
  EthanHeilman:
    ACK 7a046cdc1423963bdcbcf9bb98560af61fa90b37
  laanwj:
    ACK 7a046cdc1423963bdcbcf9bb98560af61fa90b37

Tree-SHA512: 66556e290db996917b54091acd591df221f72230f6b9f6b167b9195ee870ebef6e26f4cda2f6f54d00e1c362e1743bf56785d0de7cae854e6bf7d26f6caccaba

13 files changed, 99 insertions, 69 deletions

diff --git a/src/httpserver.cpp b/src/httpserver.cpp
index 7179949eaf..0e13b85806 100644
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -172,7 +172,7 @@ static bool InitHTTPAllowList()
     rpc_allow_subnets.push_back(CSubNet(localv6));         // always allow IPv6 localhost
     for (const std::string& strAllow : gArgs.GetArgs("-rpcallowip")) {
         CSubNet subnet;
-        LookupSubNet(strAllow.c_str(), subnet);
+        LookupSubNet(strAllow, subnet);
         if (!subnet.IsValid()) {
             uiInterface.ThreadSafeMessageBox(
                 strprintf("Invalid -rpcallowip subnet specification: %s. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).", strAllow),
@@ -324,7 +324,7 @@ static bool HTTPBindAddresses(struct evhttp* http)
         evhttp_bound_socket *bind_handle = evhttp_bind_socket_with_handle(http, i->first.empty() ? nullptr : i->first.c_str(), i->second);
         if (bind_handle) {
             CNetAddr addr;
-            if (i->first.empty() || (LookupHost(i->first.c_str(), addr, false) && addr.IsBindAny())) {
+            if (i->first.empty() || (LookupHost(i->first, addr, false) && addr.IsBindAny())) {
                 LogPrintf("WARNING: the RPC server is not safe to expose to untrusted networks such as the public internet\n");
             }
             boundSockets.push_back(bind_handle);
diff --git a/src/init.cpp b/src/init.cpp
index 539546117b..18c32b34ed 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1358,7 +1358,7 @@ bool AppInitMain(NodeContext& node)
     SetReachable(NET_ONION, false);
     if (proxyArg != "" && proxyArg != "0") {
         CService proxyAddr;
-        if (!Lookup(proxyArg.c_str(), proxyAddr, 9050, fNameLookup)) {
+        if (!Lookup(proxyArg, proxyAddr, 9050, fNameLookup)) {
             return InitError(strprintf(_("Invalid -proxy address or hostname: '%s'").translated, proxyArg));
         }
 
@@ -1382,7 +1382,7 @@ bool AppInitMain(NodeContext& node)
             SetReachable(NET_ONION, false);
         } else {
             CService onionProxy;
-            if (!Lookup(onionArg.c_str(), onionProxy, 9050, fNameLookup)) {
+            if (!Lookup(onionArg, onionProxy, 9050, fNameLookup)) {
                 return InitError(strprintf(_("Invalid -onion address or hostname: '%s'").translated, onionArg));
             }
             proxyType addrOnion = proxyType(onionProxy, proxyRandomize);
@@ -1400,7 +1400,7 @@ bool AppInitMain(NodeContext& node)
 
     for (const std::string& strAddr : gArgs.GetArgs("-externalip")) {
         CService addrLocal;
-        if (Lookup(strAddr.c_str(), addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
+        if (Lookup(strAddr, addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
             AddLocal(addrLocal, LOCAL_MANUAL);
         else
             return InitError(ResolveErrMsg("externalip", strAddr));
@@ -1780,7 +1780,7 @@ bool AppInitMain(NodeContext& node)
 
     for (const std::string& strBind : gArgs.GetArgs("-bind")) {
         CService addrBind;
-        if (!Lookup(strBind.c_str(), addrBind, GetListenPort(), false)) {
+        if (!Lookup(strBind, addrBind, GetListenPort(), false)) {
             return InitError(ResolveErrMsg("bind", strBind));
         }
         connOptions.vBinds.push_back(addrBind);
diff --git a/src/net.cpp b/src/net.cpp
index 75b230d0be..68764bf5cb 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -410,7 +410,7 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
             if (hSocket == INVALID_SOCKET) {
                 return nullptr;
             }
-            connected = ConnectThroughProxy(proxy, addrConnect.ToStringIP(), addrConnect.GetPort(), hSocket, nConnectTimeout, &proxyConnectionFailed);
+            connected = ConnectThroughProxy(proxy, addrConnect.ToStringIP(), addrConnect.GetPort(), hSocket, nConnectTimeout, proxyConnectionFailed);
         } else {
             // no proxy needed (none set for target network)
             hSocket = CreateSocket(addrConnect);
@@ -432,7 +432,8 @@ CNode* CConnman::ConnectNode(CAddress addrConnect, const char *pszDest, bool fCo
         std::string host;
         int port = default_port;
         SplitHostPort(std::string(pszDest), port, host);
-        connected = ConnectThroughProxy(proxy, host, port, hSocket, nConnectTimeout, nullptr);
+        bool proxyConnectionFailed;
+        connected = ConnectThroughProxy(proxy, host, port, hSocket, nConnectTimeout, proxyConnectionFailed);
     }
     if (!connected) {
         CloseSocket(hSocket);
@@ -1609,7 +1610,7 @@ void CConnman::ThreadDNSAddressSeed()
                 continue;
             }
             unsigned int nMaxIPs = 256; // Limits number of IPs learned from a DNS seed
-            if (LookupHost(host.c_str(), vIPs, nMaxIPs, true)) {
+            if (LookupHost(host, vIPs, nMaxIPs, true)) {
                 for (const CNetAddr& ip : vIPs) {
                     int nOneDay = 24*3600;
                     CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
@@ -1907,7 +1908,7 @@ std::vector<AddedNodeInfo> CConnman::GetAddedNodeInfo()
     }
 
     for (const std::string& strAddNode : lAddresses) {
-        CService service(LookupNumeric(strAddNode.c_str(), Params().GetDefaultPort()));
+        CService service(LookupNumeric(strAddNode, Params().GetDefaultPort()));
         AddedNodeInfo addedNode{strAddNode, CService(), false, false};
         if (service.IsValid()) {
             // strAddNode is an IP:port
diff --git a/src/net_permissions.cpp b/src/net_permissions.cpp
index c3947173de..22fa5ee73b 100644
--- a/src/net_permissions.cpp
+++ b/src/net_permissions.cpp
@@ -71,7 +71,7 @@ bool NetWhitebindPermissions::TryParse(const std::string str, NetWhitebindPermis
 
     const std::string strBind = str.substr(offset);
     CService addrBind;
-    if (!Lookup(strBind.c_str(), addrBind, 0, false)) {
+    if (!Lookup(strBind, addrBind, 0, false)) {
         error = ResolveErrMsg("whitebind", strBind);
         return false;
     }
@@ -94,7 +94,7 @@ bool NetWhitelistPermissions::TryParse(const std::string str, NetWhitelistPermis
 
     const std::string net = str.substr(offset);
     CSubNet subnet;
-    LookupSubNet(net.c_str(), subnet);
+    LookupSubNet(net, subnet);
     if (!subnet.IsValid()) {
         error = strprintf(_("Invalid netmask specified in -whitelist: '%s'").translated, net);
         return false;
diff --git a/src/netbase.cpp b/src/netbase.cpp
index f0c91e0619..a70179cb16 100644
--- a/src/netbase.cpp
+++ b/src/netbase.cpp
@@ -7,8 +7,9 @@
 
 #include <sync.h>
 #include <tinyformat.h>
-#include <util/system.h>
 #include <util/strencodings.h>
+#include <util/string.h>
+#include <util/system.h>
 
 #include <atomic>
 
@@ -59,10 +60,14 @@ std::string GetNetworkName(enum Network net) {
     }
 }
 
-bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
+bool static LookupIntern(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
 {
     vIP.clear();
 
+    if (!ValidAsCString(name)) {
+        return false;
+    }
+
     {
         CNetAddr addr;
         // From our perspective, onion addresses are not hostnames but rather
@@ -71,7 +76,7 @@ bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsign
         // getaddrinfo to decode them and it wouldn't make sense to resolve
         // them, we return a network address representing it instead. See
         // CNetAddr::SetSpecial(const std::string&) for more details.
-        if (addr.SetSpecial(std::string(pszName))) {
+        if (addr.SetSpecial(name)) {
             vIP.push_back(addr);
             return true;
         }
@@ -93,7 +98,7 @@ bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsign
     // hostname lookups.
     aiHint.ai_flags = fAllowLookup ? AI_ADDRCONFIG : AI_NUMERICHOST;
     struct addrinfo *aiRes = nullptr;
-    int nErr = getaddrinfo(pszName, nullptr, &aiHint, &aiRes);
+    int nErr = getaddrinfo(name.c_str(), nullptr, &aiHint, &aiRes);
     if (nErr)
         return false;
 
@@ -131,7 +136,7 @@ bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsign
 /**
  * Resolve a host string to its corresponding network addresses.
  *
- * @param pszName The string representing a host. Could be a name or a numerical
+ * @param name    The string representing a host. Could be a name or a numerical
  *                IP address (IPv6 addresses in their bracketed form are
  *                allowed).
  * @param[out] vIP The resulting network addresses to which the specified host
@@ -143,28 +148,34 @@ bool static LookupIntern(const char *pszName, std::vector<CNetAddr>& vIP, unsign
  * @see Lookup(const char *, std::vector<CService>&, int, bool, unsigned int)
  *      for additional parameter descriptions.
  */
-bool LookupHost(const char *pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
+bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup)
 {
-    std::string strHost(pszName);
+    if (!ValidAsCString(name)) {
+        return false;
+    }
+    std::string strHost = name;
     if (strHost.empty())
         return false;
     if (strHost.front() == '[' && strHost.back() == ']') {
         strHost = strHost.substr(1, strHost.size() - 2);
     }
 
-    return LookupIntern(strHost.c_str(), vIP, nMaxSolutions, fAllowLookup);
+    return LookupIntern(strHost, vIP, nMaxSolutions, fAllowLookup);
 }
 
  /**
  * Resolve a host string to its first corresponding network address.
  *
- * @see LookupHost(const char *, std::vector<CNetAddr>&, unsigned int, bool) for
+ * @see LookupHost(const std::string&, std::vector<CNetAddr>&, unsigned int, bool) for
  *      additional parameter descriptions.
  */
-bool LookupHost(const char *pszName, CNetAddr& addr, bool fAllowLookup)
+bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup)
 {
+    if (!ValidAsCString(name)) {
+        return false;
+    }
     std::vector<CNetAddr> vIP;
-    LookupHost(pszName, vIP, 1, fAllowLookup);
+    LookupHost(name, vIP, 1, fAllowLookup);
     if(vIP.empty())
         return false;
     addr = vIP.front();
@@ -174,7 +185,7 @@ bool LookupHost(const char *pszName, CNetAddr& addr, bool fAllowLookup)
 /**
  * Resolve a service string to its corresponding service.
  *
- * @param pszName The string representing a service. Could be a name or a
+ * @param name    The string representing a service. Could be a name or a
  *                numerical IP address (IPv6 addresses should be in their
  *                disambiguated bracketed form), optionally followed by a port
  *                number. (e.g. example.com:8333 or
@@ -191,16 +202,17 @@ bool LookupHost(const char *pszName, CNetAddr& addr, bool fAllowLookup)
  * @returns Whether or not the service string successfully resolved to any
  *          resulting services.
  */
-bool Lookup(const char *pszName, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions)
+bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions)
 {
-    if (pszName[0] == 0)
+    if (name.empty() || !ValidAsCString(name)) {
         return false;
+    }
     int port = portDefault;
     std::string hostname;
-    SplitHostPort(std::string(pszName), port, hostname);
+    SplitHostPort(name, port, hostname);
 
     std::vector<CNetAddr> vIP;
-    bool fRet = LookupIntern(hostname.c_str(), vIP, nMaxSolutions, fAllowLookup);
+    bool fRet = LookupIntern(hostname, vIP, nMaxSolutions, fAllowLookup);
     if (!fRet)
         return false;
     vAddr.resize(vIP.size());
@@ -215,10 +227,13 @@ bool Lookup(const char *pszName, std::vector<CService>& vAddr, int portDefault,
  * @see Lookup(const char *, std::vector<CService>&, int, bool, unsigned int)
  *      for additional parameter descriptions.
  */
-bool Lookup(const char *pszName, CService& addr, int portDefault, bool fAllowLookup)
+bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup)
 {
+    if (!ValidAsCString(name)) {
+        return false;
+    }
     std::vector<CService> vService;
-    bool fRet = Lookup(pszName, vService, portDefault, fAllowLookup, 1);
+    bool fRet = Lookup(name, vService, portDefault, fAllowLookup, 1);
     if (!fRet)
         return false;
     addr = vService[0];
@@ -235,12 +250,15 @@ bool Lookup(const char *pszName, CService& addr, int portDefault, bool fAllowLoo
  * @see Lookup(const char *, CService&, int, bool) for additional parameter
  *      descriptions.
  */
-CService LookupNumeric(const char *pszName, int portDefault)
+CService LookupNumeric(const std::string& name, int portDefault)
 {
+    if (!ValidAsCString(name)) {
+        return {};
+    }
     CService addr;
     // "1.2:345" will fail to resolve the ip, but will still set the port.
     // If the ip fails to resolve, re-init the result.
-    if(!Lookup(pszName, addr, portDefault, false))
+    if(!Lookup(name, addr, portDefault, false))
         addr = CService();
     return addr;
 }
@@ -768,12 +786,11 @@ bool IsProxy(const CNetAddr &addr) {
  *
  * @returns Whether or not the operation succeeded.
  */
-bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocket, int nTimeout, bool *outProxyConnectionFailed)
+bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocket, int nTimeout, bool& outProxyConnectionFailed)
 {
     // first connect to proxy server
     if (!ConnectSocketDirectly(proxy.proxy, hSocket, nTimeout, true)) {
-        if (outProxyConnectionFailed)
-            *outProxyConnectionFailed = true;
+        outProxyConnectionFailed = true;
         return false;
     }
     // do socks negotiation
@@ -796,23 +813,25 @@ bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int
  * Parse and resolve a specified subnet string into the appropriate internal
  * representation.
  *
- * @param pszName A string representation of a subnet of the form `network
+ * @param strSubnet A string representation of a subnet of the form `network
  *                address [ "/", ( CIDR-style suffix | netmask ) ]`(e.g.
  *                `2001:db8::/32`, `192.0.2.0/255.255.255.0`, or `8.8.8.8`).
  * @param ret The resulting internal representation of a subnet.
  *
  * @returns Whether the operation succeeded or not.
  */
-bool LookupSubNet(const char* pszName, CSubNet& ret)
+bool LookupSubNet(const std::string& strSubnet, CSubNet& ret)
 {
-    std::string strSubnet(pszName);
+    if (!ValidAsCString(strSubnet)) {
+        return false;
+    }
     size_t slash = strSubnet.find_last_of('/');
     std::vector<CNetAddr> vIP;
 
     std::string strAddress = strSubnet.substr(0, slash);
-    // TODO: Use LookupHost(const char *, CNetAddr&, bool) instead to just get
+    // TODO: Use LookupHost(const std::string&, CNetAddr&, bool) instead to just get
     //       one CNetAddr.
-    if (LookupHost(strAddress.c_str(), vIP, 1, false))
+    if (LookupHost(strAddress, vIP, 1, false))
     {
         CNetAddr network = vIP[0];
         if (slash != strSubnet.npos)
@@ -827,7 +846,7 @@ bool LookupSubNet(const char* pszName, CSubNet& ret)
             else // If not a valid number, try full netmask syntax
             {
                 // Never allow lookup for netmask
-                if (LookupHost(strNetmask.c_str(), vIP, 1, false)) {
+                if (LookupHost(strNetmask, vIP, 1, false)) {
                     ret = CSubNet(network, vIP[0]);
                     return ret.IsValid();
                 }
diff --git a/src/netbase.h b/src/netbase.h
index 8f9d65bf3a..ac4cd97673 100644
--- a/src/netbase.h
+++ b/src/netbase.h
@@ -45,15 +45,15 @@ bool IsProxy(const CNetAddr &addr);
 bool SetNameProxy(const proxyType &addrProxy);
 bool HaveNameProxy();
 bool GetNameProxy(proxyType &nameProxyOut);
-bool LookupHost(const char *pszName, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup);
-bool LookupHost(const char *pszName, CNetAddr& addr, bool fAllowLookup);
-bool Lookup(const char *pszName, CService& addr, int portDefault, bool fAllowLookup);
-bool Lookup(const char *pszName, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);
-CService LookupNumeric(const char *pszName, int portDefault = 0);
-bool LookupSubNet(const char *pszName, CSubNet& subnet);
+bool LookupHost(const std::string& name, std::vector<CNetAddr>& vIP, unsigned int nMaxSolutions, bool fAllowLookup);
+bool LookupHost(const std::string& name, CNetAddr& addr, bool fAllowLookup);
+bool Lookup(const std::string& name, CService& addr, int portDefault, bool fAllowLookup);
+bool Lookup(const std::string& name, std::vector<CService>& vAddr, int portDefault, bool fAllowLookup, unsigned int nMaxSolutions);
+CService LookupNumeric(const std::string& name, int portDefault = 0);
+bool LookupSubNet(const std::string& strSubnet, CSubNet& subnet);
 SOCKET CreateSocket(const CService &addrConnect);
 bool ConnectSocketDirectly(const CService &addrConnect, const SOCKET& hSocketRet, int nTimeout, bool manual_connection);
-bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocketRet, int nTimeout, bool *outProxyConnectionFailed);
+bool ConnectThroughProxy(const proxyType &proxy, const std::string& strDest, int port, const SOCKET& hSocketRet, int nTimeout, bool& outProxyConnectionFailed);
 /** Return readable error string for a network error code */
 std::string NetworkErrorString(int err);
 /** Close socket and set hSocket to INVALID_SOCKET */
diff --git a/src/qt/optionsdialog.cpp b/src/qt/optionsdialog.cpp
index 2f612664df..8ee6c947e6 100644
--- a/src/qt/optionsdialog.cpp
+++ b/src/qt/optionsdialog.cpp
@@ -375,7 +375,7 @@ QValidator::State ProxyAddressValidator::validate(QString &input, int &pos) cons
 {
     Q_UNUSED(pos);
     // Validate the proxy
-    CService serv(LookupNumeric(input.toStdString().c_str(), DEFAULT_GUI_PROXY_PORT));
+    CService serv(LookupNumeric(input.toStdString(), DEFAULT_GUI_PROXY_PORT));
     proxyType addrProxy = proxyType(serv, true);
     if (addrProxy.IsValid())
         return QValidator::Acceptable;
diff --git a/src/qt/rpcconsole.cpp b/src/qt/rpcconsole.cpp
index 31c9e65140..e1f783b0e5 100644
--- a/src/qt/rpcconsole.cpp
+++ b/src/qt/rpcconsole.cpp
@@ -1236,7 +1236,7 @@ void RPCConsole::unbanSelectedNode()
         QString strNode = nodes.at(i).data().toString();
         CSubNet possibleSubnet;
 
-        LookupSubNet(strNode.toStdString().c_str(), possibleSubnet);
+        LookupSubNet(strNode.toStdString(), possibleSubnet);
         if (possibleSubnet.IsValid() && m_node.unban(possibleSubnet))
         {
             clientModel->getBanTableModel()->refresh();
diff --git a/src/rpc/net.cpp b/src/rpc/net.cpp
index 5e53fa5f5d..e0c1976f1a 100644
--- a/src/rpc/net.cpp
+++ b/src/rpc/net.cpp
@@ -562,11 +562,11 @@ static UniValue setban(const JSONRPCRequest& request)
 
     if (!isSubnet) {
         CNetAddr resolved;
-        LookupHost(request.params[0].get_str().c_str(), resolved, false);
+        LookupHost(request.params[0].get_str(), resolved, false);
         netAddr = resolved;
     }
     else
-        LookupSubNet(request.params[0].get_str().c_str(), subNet);
+        LookupSubNet(request.params[0].get_str(), subNet);
 
     if (! (isSubnet ? subNet.IsValid() : netAddr.IsValid()) )
         throw JSONRPCError(RPC_CLIENT_INVALID_IP_OR_SUBNET, "Error: Invalid IP/Subnet");
diff --git a/src/test/addrman_tests.cpp b/src/test/addrman_tests.cpp
index c034216bc1..f44ed712d9 100644
--- a/src/test/addrman_tests.cpp
+++ b/src/test/addrman_tests.cpp
@@ -59,29 +59,20 @@ public:
      }
 };
 
-static CNetAddr ResolveIP(const char* ip)
+static CNetAddr ResolveIP(const std::string& ip)
 {
     CNetAddr addr;
     BOOST_CHECK_MESSAGE(LookupHost(ip, addr, false), strprintf("failed to resolve: %s", ip));
     return addr;
 }
 
-static CNetAddr ResolveIP(std::string ip)
-{
-    return ResolveIP(ip.c_str());
-}
-
-static CService ResolveService(const char* ip, int port = 0)
+static CService ResolveService(const std::string& ip, const int port = 0)
 {
     CService serv;
     BOOST_CHECK_MESSAGE(Lookup(ip, serv, port, false), strprintf("failed to resolve: %s:%i", ip, port));
     return serv;
 }
 
-static CService ResolveService(std::string ip, int port = 0)
-{
-    return ResolveService(ip.c_str(), port);
-}
 
 BOOST_FIXTURE_TEST_SUITE(addrman_tests, BasicTestingSetup)
 
diff --git a/src/test/net_tests.cpp b/src/test/net_tests.cpp
index daf7fea6ad..cb1ef5dcf3 100644
--- a/src/test/net_tests.cpp
+++ b/src/test/net_tests.cpp
@@ -99,6 +99,8 @@ BOOST_AUTO_TEST_CASE(caddrdb_read)
     BOOST_CHECK(Lookup("250.7.1.1", addr1, 8333, false));
     BOOST_CHECK(Lookup("250.7.2.2", addr2, 9999, false));
     BOOST_CHECK(Lookup("250.7.3.3", addr3, 9999, false));
+    BOOST_CHECK(Lookup(std::string("250.7.3.3", 9), addr3, 9999, false));
+    BOOST_CHECK(!Lookup(std::string("250.7.3.3\0example.com", 21), addr3, 9999, false));
 
     // Add three addresses to new table.
     CService source;
diff --git a/src/test/netbase_tests.cpp b/src/test/netbase_tests.cpp
index 481dedc356..58e0565bda 100644
--- a/src/test/netbase_tests.cpp
+++ b/src/test/netbase_tests.cpp
@@ -13,21 +13,21 @@
 
 BOOST_FIXTURE_TEST_SUITE(netbase_tests, BasicTestingSetup)
 
-static CNetAddr ResolveIP(const char* ip)
+static CNetAddr ResolveIP(const std::string& ip)
 {
     CNetAddr addr;
     LookupHost(ip, addr, false);
     return addr;
 }
 
-static CSubNet ResolveSubNet(const char* subnet)
+static CSubNet ResolveSubNet(const std::string& subnet)
 {
     CSubNet ret;
     LookupSubNet(subnet, ret);
     return ret;
 }
 
-static CNetAddr CreateInternal(const char* host)
+static CNetAddr CreateInternal(const std::string& host)
 {
     CNetAddr addr;
     addr.SetInternal(host);
@@ -105,7 +105,7 @@ BOOST_AUTO_TEST_CASE(netbase_splithost)
 
 bool static TestParse(std::string src, std::string canon)
 {
-    CService addr(LookupNumeric(src.c_str(), 65535));
+    CService addr(LookupNumeric(src, 65535));
     return canon == addr.ToString();
 }
 
@@ -127,7 +127,6 @@ BOOST_AUTO_TEST_CASE(netbase_lookupnumeric)
 
 BOOST_AUTO_TEST_CASE(onioncat_test)
 {
-
     // values from https://web.archive.org/web/20121122003543/http://www.cypherpunk.at/onioncat/wiki/OnionCat
     CNetAddr addr1(ResolveIP("5wyqrzbvrdsumnok.onion"));
     CNetAddr addr2(ResolveIP("FD87:D87E:EB43:edb1:8e4:3588:e546:35ca"));
@@ -402,4 +401,22 @@ BOOST_AUTO_TEST_CASE(netpermissions_test)
     BOOST_CHECK(std::find(strings.begin(), strings.end(), "mempool") != strings.end());
 }
 
+BOOST_AUTO_TEST_CASE(netbase_dont_resolve_strings_with_embedded_nul_characters)
+{
+    CNetAddr addr;
+    BOOST_CHECK(LookupHost(std::string("127.0.0.1", 9), addr, false));
+    BOOST_CHECK(!LookupHost(std::string("127.0.0.1\0", 10), addr, false));
+    BOOST_CHECK(!LookupHost(std::string("127.0.0.1\0example.com", 21), addr, false));
+    BOOST_CHECK(!LookupHost(std::string("127.0.0.1\0example.com\0", 22), addr, false));
+    CSubNet ret;
+    BOOST_CHECK(LookupSubNet(std::string("1.2.3.0/24", 10), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("1.2.3.0/24\0", 11), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("1.2.3.0/24\0example.com", 22), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("1.2.3.0/24\0example.com\0", 23), ret));
+    BOOST_CHECK(LookupSubNet(std::string("5wyqrzbvrdsumnok.onion", 22), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("5wyqrzbvrdsumnok.onion\0", 23), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("5wyqrzbvrdsumnok.onion\0example.com", 34), ret));
+    BOOST_CHECK(!LookupSubNet(std::string("5wyqrzbvrdsumnok.onion\0example.com\0", 35), ret));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/torcontrol.cpp b/src/torcontrol.cpp
index d06b3cd20d..84118b36ef 100644
--- a/src/torcontrol.cpp
+++ b/src/torcontrol.cpp
@@ -501,7 +501,7 @@ void TorController::add_onion_cb(TorControlConnection& _conn, const TorControlRe
             }
             return;
         }
-        service = LookupNumeric(std::string(service_id+".onion").c_str(), Params().GetDefaultPort());
+        service = LookupNumeric(std::string(service_id+".onion"), Params().GetDefaultPort());
         LogPrintf("tor: Got service ID %s, advertising service %s\n", service_id, service.ToString());
         if (WriteBinaryFile(GetPrivateKeyFile(), private_key)) {
             LogPrint(BCLog::TOR, "tor: Cached service private key to %s\n", GetPrivateKeyFile().string());