Add channel TS to server-to-server INVITE to detect and drop unauthorized invites

The syntax of the server-to-server INVITE command changes from
:<source> INVITE <target> <channel> [<expire>]
to
:<source> INVITE <target> <channel> <chants> [<expire>]

3 files changed, 44 insertions, 4 deletions

diff --git a/src/coremods/core_channel/cmd_invite.cpp b/src/coremods/core_channel/cmd_invite.cpp
index 3260d7862..ea4692d04 100644
--- a/src/coremods/core_channel/cmd_invite.cpp
+++ b/src/coremods/core_channel/cmd_invite.cpp
@@ -36,7 +36,7 @@ CmdResult CommandInvite::Handle (const std::vector<std::string>& parameters, Use
 {
 	ModResult MOD_RESULT;
 
-	if (parameters.size() == 2 || parameters.size() == 3)
+	if (parameters.size() >= 2)
 	{
 		User* u;
 		if (IS_LOCAL(user))
@@ -46,12 +46,12 @@ CmdResult CommandInvite::Handle (const std::vector<std::string>& parameters, Use
 
 		Channel* c = ServerInstance->FindChan(parameters[1]);
 		time_t timeout = 0;
-		if (parameters.size() == 3)
+		if (parameters.size() >= 3)
 		{
 			if (IS_LOCAL(user))
 				timeout = ServerInstance->Time() + InspIRCd::Duration(parameters[2]);
-			else
-				timeout = ConvToInt(parameters[2]);
+			else if (parameters.size() > 3)
+				timeout = ConvToInt(parameters[3]);
 		}
 
 		if ((!c) || (!u) || (u->registered != REG_ALL))
@@ -60,6 +60,19 @@ CmdResult CommandInvite::Handle (const std::vector<std::string>& parameters, Use
 			return CMD_FAILURE;
 		}
 
+		// Verify channel timestamp if the INVITE is coming from a remote server
+		if (!IS_LOCAL(user))
+		{
+			// Remote INVITE commands must carry a channel timestamp
+			if (parameters.size() < 3)
+				return CMD_INVALID;
+
+			// Drop the invite if our channel TS is lower
+			time_t RemoteTS = ConvToInt(parameters[2]);
+			if (c->age < RemoteTS)
+				return CMD_FAILURE;
+		}
+
 		if ((IS_LOCAL(user)) && (!c->HasUser(user)))
 		{
 			user->WriteNumeric(ERR_NOTONCHANNEL, "%s :You're not on that channel!", c->name.c_str());
diff --git a/src/modules/m_spanningtree/compat.cpp b/src/modules/m_spanningtree/compat.cpp
index 98b6826e2..ca9fbfa6a 100644
--- a/src/modules/m_spanningtree/compat.cpp
+++ b/src/modules/m_spanningtree/compat.cpp
@@ -169,6 +169,25 @@ void TreeSocket::WriteLine(const std::string& original_line)
 						line.erase(colon, 1);
 					}
 				}
+				else if (command == "INVITE")
+				{
+					// :22D INVITE 22DAAAAAN #chan TS ExpirationTime
+					//     A      B         C     D  E
+					if (b == std::string::npos)
+						return;
+
+					std::string::size_type c = line.find(' ', b + 1);
+					if (c == std::string::npos)
+						return;
+
+					std::string::size_type d = line.find(' ', c + 1);
+					if (d == std::string::npos)
+						return;
+
+					std::string::size_type e = line.find(' ', d + 1);
+					// If there is no expiration time then everything will be erased from 'd'
+					line.erase(d, e-d);
+				}
 			}
 			ServerInstance->Logs->Log(MODNAME, LOG_RAWIO, "S[%d] O %s", this->GetFd(), line.c_str());
 			this->WriteData(line);
@@ -297,6 +316,13 @@ bool TreeSocket::PreProcessOldProtocolMessage(User*& who, std::string& cmd, std:
 	{
 		return false;
 	}
+	else if (cmd == "INVITE")
+	{
+		// :20D INVITE 22DAAABBB #chan
+		// :20D INVITE 22DAAABBB #chan 123456789
+		// Insert channel timestamp after the channel name; the 3rd parameter, if there, is the invite expiration time
+		return InsertCurrentChannelTS(params, 1, 2);
+	}
 
 	return true; // Passthru
 }
diff --git a/src/modules/m_spanningtree/main.cpp b/src/modules/m_spanningtree/main.cpp
index 0dc680ca0..46f46e0e0 100644
--- a/src/modules/m_spanningtree/main.cpp
+++ b/src/modules/m_spanningtree/main.cpp
@@ -415,6 +415,7 @@ void ModuleSpanningTree::OnUserInvite(User* source,User* dest,Channel* channel,
 		CmdBuilder params(source, "INVITE");
 		params.push_back(dest->uuid);
 		params.push_back(channel->name);
+		params.push_int(channel->age);
 		params.push_back(ConvToStr(expiry));
 		params.Broadcast();
 	}