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bugfix(network): Deny players with invalid names from joining a LAN game room #1595

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bugfix(network): Deny players with invalid names from joining a LAN game room #1595

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45fb971
bugfix(network): Deny players with invalid names to join game
slurmlord Sep 18, 2025
26f5d4c
Expand list of illegal chars, plus PR feedback
slurmlord Sep 18, 2025
a7866d6
Re-order comments a bit.
slurmlord Sep 19, 2025
27d8827
Refactor for better readability
slurmlord Sep 20, 2025
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23 changes: 22 additions & 1 deletion Generals/Code/GameEngine/Source/GameNetwork/LANAPIhandlers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -289,7 +289,28 @@ void LANAPI::handleRequestJoin( LANMessage *msg, UnsignedInt senderIP )
}
#endif

// We're the host, so see if he has a duplicate name
// TheSuperHackers @bugfix slurmlord 18/09/2025 need to validate the name of the connecting player before
// allowing them to join to prevent messing up the format of game state string. Commas, colons, semicolons etc.
// should not be in a player name. It should also not consist of only space characters.
if (canJoin)
{
constexpr WideChar IllegalNameChars[] = L",:;|\f\n\r\t\v";
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@xezon xezon Sep 20, 2025 •
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Why is the pipe character disallowed? I created a network match and was able to match 2 players with pipes (before this change). The pipe character is popular to separate clan names.

shot_20250920_112024_1

shot_20250920_112127_2

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This one was included via a suggestion, any thoughts on this @roossienb?.
I think it would be OK to allow pipe for the parsing functionality at least - as far as I know it's ,:; that would mess up the string splitting.

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@xezon xezon Sep 24, 2025 •
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roossienb asked if pipe was a problem. It is not after testing it.

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Instead of banning \f\n\r\t\v, how about banning all characters less than 32 ? That includes all control characters.

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Yes, that makes sense. As these are wide chars, are there other values or sequences beyond the traditional ASCII control characters that we should consider as well?

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@xezon xezon Sep 24, 2025 •
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I think this needs testing. I just tested Network lobby with nickname öäü and it triggered Asserts in Debug, but otherwise worked.

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Yes, testing is definitely needed here.
I was thinking of things like Surrogate pairs and Unicode special characters that will require a lot more validation/handling that what is proposed in this PR right now.
Should we limit names to only characters in the BMP for example? Require the string to be normalized to a specific normalization form?

const Bool containsIllegalChars = wcscspn(msg->name, IllegalNameChars);
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Can simplify further to wcscspn(msg->name, L",:;|\f\n\r\t\v");

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Should also be... != wcslen(msg->name)

const Bool isEffectivelyEmpty = wcsspn(msg->name, L" ") == wcslen(msg->name);
if (containsIllegalChars || isEffectivelyEmpty)
{
// Just deny with a duplicate name reason, for backwards compatibility with retail
reply.LANMessageType = LANMessage::MSG_JOIN_DENY;
reply.GameNotJoined.reason = LANAPIInterface::RET_DUPLICATE_NAME;
reply.GameNotJoined.gameIP = m_localIP;
reply.GameNotJoined.playerIP = senderIP;
canJoin = false;

DEBUG_LOG(("LANAPI::handleRequestJoin - join denied because of illegal characters in the player name."));
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This code only affects LAN lobby, correct? If so, does this need to be replicated anywhere in Online Lobby code?

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I haven't seen the online lobby code use the string representation of the GameInfo, which is the root of this problem. On the other hand I haven't looked really closely at the online lobby code either.
There might be 2 cases here:

  • Excluding ;:, because it causes trouble for the string parsing. If the online lobby does not use string parsing it strictly does not need to be replicated, other than maybe for consistency across the two lobbies.
  • Control characters and maybe other troublesome characters that could cause issues in the UI or other representations. These ones I think would be beneficial to replicate.

}
}

// Then see if the player has a duplicate name
for (player = 0; canJoin && player<MAX_SLOTS; ++player)
{
LANGameSlot *slot = m_currentGame->getLANSlot(player);
Expand Down
23 changes: 22 additions & 1 deletion GeneralsMD/Code/GameEngine/Source/GameNetwork/LANAPIhandlers.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -290,7 +290,28 @@ void LANAPI::handleRequestJoin( LANMessage *msg, UnsignedInt senderIP )
}
#endif

// We're the host, so see if he has a duplicate name
// TheSuperHackers @bugfix slurmlord 18/09/2025 need to validate the name of the connecting player before
// allowing them to join to prevent messing up the format of game state string. Commas, colons, semicolons etc.
// should not be in a player name. It should also not consist of only space characters.
if (canJoin)
{
constexpr WideChar IllegalNameChars[] = L",:;|\f\n\r\t\v";
const Bool containsIllegalChars = wcscspn(msg->name, IllegalNameChars);
const Bool isEffectivelyEmpty = wcsspn(msg->name, L" ") == wcslen(msg->name);
if (containsIllegalChars || isEffectivelyEmpty)
{
// Just deny with a duplicate name reason, for backwards compatibility with retail
reply.LANMessageType = LANMessage::MSG_JOIN_DENY;
reply.GameNotJoined.reason = LANAPIInterface::RET_DUPLICATE_NAME;
reply.GameNotJoined.gameIP = m_localIP;
reply.GameNotJoined.playerIP = senderIP;
canJoin = false;

DEBUG_LOG(("LANAPI::handleRequestJoin - join denied because of illegal characters in the player name."));
}
}

// Then see if the player has a duplicate name
for (player = 0; canJoin && player<MAX_SLOTS; ++player)
{
LANGameSlot *slot = m_currentGame->getLANSlot(player);
Expand Down
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