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WebSocketClient: fix undefined read order in frame length

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Multiple read() calls in one expression have unspecified evaluation order
in C++, so the length bytes could be combined wrong. Read each byte into
its own variable before combining them.
This commit is contained in:
pennam
2026-07-13 15:50:01 +02:00
parent d3de6c8bfe
commit eed84b6cd6
1 changed files with 21 additions and 9 deletions
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30
src/WebSocketClient.cpp
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@@ -213,18 +213,30 @@ int WebSocketClient::parseMessage()
}
else if (length == 126)
{
iRxSize = (HttpClient::read() << 8) | HttpClient::read();
// read each byte in a well-defined order (the evaluation order of
// multiple read() calls in a single expression is unspecified)
uint8_t b1 = HttpClient::read();
uint8_t b0 = HttpClient::read();
iRxSize = ((uint64_t)b1 << 8) | b0;
}
else
{
iRxSize = ((uint64_t)HttpClient::read() << 56) |
((uint64_t)HttpClient::read() << 48) |
((uint64_t)HttpClient::read() << 40) |
((uint64_t)HttpClient::read() << 32) |
((uint64_t)HttpClient::read() << 24) |
((uint64_t)HttpClient::read() << 16) |
((uint64_t)HttpClient::read() << 8) |
(uint64_t)HttpClient::read();
uint8_t b7 = HttpClient::read();
uint8_t b6 = HttpClient::read();
uint8_t b5 = HttpClient::read();
uint8_t b4 = HttpClient::read();
uint8_t b3 = HttpClient::read();
uint8_t b2 = HttpClient::read();
uint8_t b1 = HttpClient::read();
uint8_t b0 = HttpClient::read();
iRxSize = ((uint64_t)b7 << 56) |
((uint64_t)b6 << 48) |
((uint64_t)b5 << 40) |
((uint64_t)b4 << 32) |
((uint64_t)b3 << 24) |
((uint64_t)b2 << 16) |
((uint64_t)b1 << 8) |
(uint64_t)b0;
}
// read in the mask, if present