Fix HomeMatic Script injection in hmscript_escapeString - #132
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hmscript_escapeString escaped quotes but never escaped the backslash character itself. A user-supplied string value containing a backslash positioned before a quote would, once the quote was escaped to \", be decoded by ReGa as an escaped backslash that closes the generated `var name = "...";` literal early — turning the remainder of the input into executable HomeMatic Script. Because the API funnels user input through this helper, an authenticated low-privilege (LEVEL USER) caller could reach system.Exec and run OS commands as root. Escape backslash first so backslashes introduced by escaping are themselves escaped. This also fixes silent loss of literal backslashes in benign values (e.g. Windows-style paths).
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What
Escape the backslash character (first) in
hmscript_escapeString.Why
hmscript_escapeStringescaped the quote character but not the backslash. Because the generated HomeMatic Scriptvar name = "<value>";declarations are decoded by ReGa (which performs its own backslash-escape handling), a crafted string value could terminate the literal early and have the remainder executed as live HomeMatic Script — reachable by aLEVEL USERJSON-RPC caller and able to run OS commands as root.Escaping the backslash first ensures any backslash introduced by the escaping step is itself escaped, so crafted input stays inert inside the literal. This also fixes a pre-existing bug where legitimate backslashes in values (e.g. Windows-style paths) were silently dropped.
Verification
The fix was validated by sourcing the real
hmscript_escapeStringproc, emitting thevar name = "...";line for a breakout vector and benign values, and modelling ReGa's string-literal decoding:The change is ASCII-only and the file's existing ISO-8859-1 encoding is preserved.
Refs #131