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G1: R02 — fix txt_type empty-slice (uncrypted[4:4] -> [4:5])

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`uncrypted[4:4]` is the empty slice. `int.from_bytes(b"", "little")`
returns 0, so `txt_type` was always 0 for every decrypted channel
message — silently masking the upper 6 bits of byte 4. The line
immediately above (`attempt = uncrypted[4] & 3`) already proves byte
4 is in range, so widening the slice to `[4:5]` is safe.

This is a one-character fix and changes the observable value of
`txt_type` for all callers. Existing consumers that branched on
`txt_type` were effectively dead code; this restores the intended
behavior.

Finding: R02 (Info)
File: src/meshcore/meshcore_parser.py
This commit is contained in:
Matthew Wolter 2026-04-11 18:30:54 -07:00
parent 865c1b21b4
commit 1a3a665b17
1 changed files with 1 additions and 1 deletions
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2
src/meshcore/meshcore_parser.py
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@ -150,7 +150,7 @@ class MeshcorePacketParser:
uncrypted = cipher.decrypt(msg)
timestamp = int.from_bytes(uncrypted[0:4], "little", signed=False)
attempt = uncrypted[4] & 3
txt_type = int.from_bytes(uncrypted[4:4], "little", signed=False) >> 2
txt_type = int.from_bytes(uncrypted[4:5], "little", signed=False) >> 2
message = uncrypted[5:].strip(b"\0")
msg_hash = int.from_bytes(SHA256.new(timestamp.to_bytes(4, "little", signed=False) + message).digest()[0:4], "little", signed=False)
log_data["message"] = message.decode("utf-8", "ignore")