Enforce the byte range for numeric string escapes

engine/compiler.c

@@ -678,8 +678,10 @@ static sxi32 PH7_GenStateCompileString(ph7_gen_state *pGen) {
 					{
 						const char *zPtr = zIn;
 						sxu32 c = 0;
+						unsigned char cByte;
 						sxi32 iBase = 8;
 						sxi32 bBraced = FALSE;
+						sxi32 bOutOfRange = FALSE;
 						sxu32 nDigit = 0;
 						sxu32 nLimit = 3;
 						if(zIn[0] < '0' || zIn[0] > '7') {
@@ -706,8 +708,12 @@ static sxi32 PH7_GenStateCompileString(ph7_gen_state *pGen) {
 								}
 								break;
 							}
-							/* Unsigned accumulation avoids signed overflow on long digit streams. */
-							c = c * (sxu32)iBase + (sxu32)iDigit;
+							/* Keep scanning for syntax errors without overflowing the byte value. */
+							if(c > (255 - (sxu32)iDigit) / (sxu32)iBase) {
+								bOutOfRange = TRUE;
+							} else if(!bOutOfRange) {
+								c = c * (sxu32)iBase + (sxu32)iDigit;
+							}
 							nDigit++;
 							zPtr++;
 						}
@@ -722,7 +728,12 @@ static sxi32 PH7_GenStateCompileString(ph7_gen_state *pGen) {
 							}
 							zPtr++;
 						}
-						PH7_MemObjStringAppend(pObj, (const char *)&c, sizeof(char));
+						if(bOutOfRange) {
+							PH7_GenCompileError(pGen, E_ERROR, pGen->pIn->nLine, "Numeric escape value exceeds 255");
+							return SXERR_ABORT;
+						}
+						cByte = (unsigned char)c;
+						PH7_MemObjStringAppend(pObj, (const char *)&cByte, sizeof(cByte));
 						n = (sxu32)(zPtr - zIn);
 					}
 					break;