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Fuzzer 01 - Dispatcher, Packet: always check if we have enough 'len' before pulling bytes out of a frame #3267

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Fuzzer 01 - Dispatcher, Packet: always check if we have enough 'len' before pulling bytes out of a frame #3267

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c7f1abe
Dispatcher: always verify len before pulling out bytes from a frame
Aug 21, 2026
05da523
Packet: always verify len before pulling out bytes from a frame
Aug 21, 2026
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3 changes: 3 additions & 0 deletions src/Dispatcher.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -147,6 +147,7 @@ void Dispatcher::loop() {
}

bool Dispatcher::tryParsePacket(Packet* pkt, const uint8_t* raw, int len) {
if (len < 1) return false; // bad encoding
int i = 0;

pkt->header = raw[i++];
Expand All @@ -156,12 +157,14 @@ bool Dispatcher::tryParsePacket(Packet* pkt, const uint8_t* raw, int len) {
}

if (pkt->hasTransportCodes()) {
if (i + 4 > len) return false; // bad encoding
memcpy(&pkt->transport_codes[0], &raw[i], 2); i += 2;
memcpy(&pkt->transport_codes[1], &raw[i], 2); i += 2;
} else {
pkt->transport_codes[0] = pkt->transport_codes[1] = 0;
}

if (i + 1 > len) return false; // bad encoding
pkt->path_len = raw[i++];
uint8_t path_mode = pkt->path_len >> 6; // upper 2 bits (legacy firmware: 00)
if (path_mode == 3) { // Reserved for future
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7 changes: 7 additions & 0 deletions src/Packet.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -63,18 +63,25 @@ uint8_t Packet::writeTo(uint8_t dest[]) const {
}

bool Packet::readFrom(const uint8_t src[], uint8_t len) {
if (len < 1) return false; // bad encoding

uint8_t i = 0;

header = src[i++];
if (hasTransportCodes()) {
if (i + 4 > len) return false; // bad encoding
memcpy(&transport_codes[0], &src[i], 2); i += 2;
memcpy(&transport_codes[1], &src[i], 2); i += 2;
} else {
transport_codes[0] = transport_codes[1] = 0;
}

if (i + 1 > len) return false; // bad encoding
path_len = src[i++];
if (!isValidPathLen(path_len)) return false; // bad encoding

uint8_t bl = getPathByteLen();
if (i + bl > len) return false; // bad encoding
memcpy(path, &src[i], bl); i += bl;

if (i >= len) return false; // bad encoding
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