OverrunWriteFloat.ql

/**
 * @name Potentially overrunning write with float to string conversion
 * @description Buffer write operations that do not control the length
 *              of data written may overflow when floating point inputs
 *              take extreme values.
 * @kind problem
 * @problem.severity error
 * @security-severity 9.3
 * @precision medium
 * @id cpp/overrunning-write-with-float
 * @tags reliability
 *       security
 *       external/cwe/cwe-120
 *       external/cwe/cwe-787
 *       external/cwe/cwe-805
 */

import semmle.code.cpp.security.BufferWrite

/*
 * See CWE-120/UnboundedWrite.ql for a summary of CWE-120 alert cases.
 */

from BufferWrite bw, int destSize, int estimated, BufferWriteEstimationReason reason
where
  not bw.hasExplicitLimit() and
  // has no explicit size limit
  destSize = getBufferSize(bw.getDest(), _) and
  estimated = bw.getMaxData(reason) and
  estimated > destSize and
  // and we can deduce that too much data may be copied
  bw.getMaxDataLimited(reason) <= destSize // but it would fit without long '%f' conversions
select bw,
  "This '" + bw.getBWDesc() + "' operation may require " + estimated +
    " bytes because of float conversions, but the target is only " + destSize + " bytes."