readFieldText does not validate row/col against screen bounds

[p0dalirius]

Summary

ScriptExecutor::readFieldText(row, col) forwards the caller-supplied row and col to the ScreenInterface without validating them against the screen's rows() / cols(). This is inconsistent with the sibling helper readScreenText(row, col, length) which does range-check row and rejects out-of-range coordinates before dispatching. As a result, EXPECT FIELD AT ... and EXTRACT $var FIELD AT ... pass negative or out-of-screen coordinates straight to the embedding application's screen implementation.

Location

• File: src/script_executor.cpp
• Lines / functions:
  • readFieldText() at L805–L808 (no bounds check)
  • Compare readScreenText() at L799–L802 (does bounds-check row and reject negative col)
  • Callers: ExtractType::FieldAt at L513, ExpectType::FieldContains at L591

Category

error-handling

Severity

medium

Impact: malformed coordinates (e.g., EXPECT FIELD AT 999 999 CONTAINS "X") cross the library boundary into the host's ScreenInterface implementation. Whether this crashes or silently misbehaves depends on the host — but the library should not rely on host-side validation when it already validates similar inputs for a neighbouring helper.

Reproduction / Evidence

Verified by code analysis.

readScreenText(row, col, length) (L799):

if (row < 0 || row >= m_screen->rows() || col < 0) return {};
return m_screen->readText(row, col, length);

readFieldText(row, col) (L805):

if (!m_screen) return {};
return m_screen->readFieldText(row, col);   // no row/col validation

A script like EXPECT FIELD AT -1 -1 CONTAINS "x" converts to readFieldText(-2, -2) (1-based → 0-based subtraction at L513/L591) and hands (-2, -2) directly to the host screen.

Expected Behavior

readFieldText should perform the same bounds check as readScreenText and return an empty QString for out-of-range coordinates. The EXPECT FIELD comparison and EXTRACT FIELD extraction should then treat the field as empty / not-found, not trigger unpredictable host behavior.

Actual Behavior

Out-of-range coordinates are forwarded to the host's ScreenInterface::readFieldText, producing host-dependent behavior (potential crash, potential garbage).