Fix ws binary/base64 subprotocol priority #595
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bk138
requested changes
Oct 25, 2023
src/libvncserver/websockets.c
Outdated
| @@ -289,13 +291,15 @@ webSocketsHandshake(rfbClientPtr cl, char *scheme) | |||
| return FALSE; | |||
| } | |||
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| if ((protocol) && (strstr(protocol, "base64"))) { | |||
| proto_binary = strstr(protocol, "binary"); | |||
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I think that's UB if protocol is NULL. Maybe just inline those calls?
| if ((protocol) && (strstr(protocol, "base64"))) { | ||
| proto_binary = strstr(protocol, "binary"); | ||
| proto_base64 = strstr(protocol, "base64"); | ||
| if ((protocol) && (proto_base64 && (!proto_binary || proto_base64 < proto_binary))) { |
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After the ||, you're comparing char*? That can't be right.
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Comparing pointers is the priority check: the one that comes first has the priority.
| @@ -289,13 +291,15 @@ webSocketsHandshake(rfbClientPtr cl, char *scheme) | |||
| return FALSE; | |||
| } | |||
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| if ((protocol) && (strstr(protocol, "base64"))) { | |||
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All in all: why not simply swap the if and else blocks?
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Some articles mention the list of protocols like "a list of sub-protocols that the client can handle in the priority order". So it's logical to respect the priority.
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The problem is when the client advertises
"protocol": ["binary", "base64"], the server picksbase64. The server should prefer the first one.It's an issue when the client had this configuration as a fix to the
400 Client must support 'binary' or 'base64' protocolerror with noVNC and old websockify + VNC: novnc/noVNC#1276 (comment) . Today it seems that noVNC doesn't dobase64any more. Although it's now incorrect for the client to advertise both protocols, it's not intuitive that"protocol": ["binary", "base64"]doesn't work while"protocol": ["binary"]does.Relevant PR/issue:
#342
novnc/noVNC#1310