Security: Invalid read in trim comparison functions.

This is a back port of the changes from the 0.7. development branch commit 4d19713c7c113481124958284f7390b8bdc48e97.

The unit tests might also be back ported at a later time.

Writing unit tests exposed this problem.

The last1 and last2 positions could be the exclusive stop points.
The comparison checks fail to handle this situation and expect the last1 and last2 variables to not be positioned at an exclusive stop point.
This results in an invalid read.

diff --git a/level_1/fl_string/c/private-string.c b/level_1/fl_string/c/private-string.c
index 3d1315d53a184b05b9fc217ddbc7dfe09b3b4fe2..73186d8b90abb6e8a2dfe1bf1ef9917c63270d8b 100644 (file)
--- a/level_1/fl_string/c/private-string.c
+++ b/level_1/fl_string/c/private-string.c
@@ -307,9 +307,7 @@ extern "C" {
         status = f_utf_is_whitespace(string2 + j, width_max, F_false);
 
         if (F_status_is_error(status)) {
-          if (F_status_set_fine(status) == F_maybe) {
-            return F_status_set_error(F_utf_not);
-          }
+          if (F_status_set_fine(status) == F_maybe) return F_status_set_error(F_utf_not);
 
           return status;
         }
@@ -322,71 +320,73 @@ extern "C" {
         }
       } // for
 
-      if (size1 != size2) {
-        return F_equal_to_not;
-      }
+      if (size1 != size2) return F_equal_to_not;
     }
 
-    while (i1 <= last1 && i2 <= last2) {
+    if (last1 < stop1 && last2 < stop2) {
+      while (i1 <= last1 && i2 <= last2) {
 
-      // Skip past NULL in string1.
-      while (i1 <= last1 && !string1[i1]) ++i1;
-      if (i1 > last1) break;
+        // Skip past NULL in string1.
+        while (i1 <= last1 && !string1[i1]) ++i1;
+        if (i1 > last1) break;
 
-      // Skip past NULL in string2.
-      while (i2 <= last2 && !string2[i2]) ++i2;
-      if (i2 > last2) break;
+        // Skip past NULL in string2.
+        while (i2 <= last2 && !string2[i2]) ++i2;
+        if (i2 > last2) break;
 
-      // Skip past except characters in string1.
-      while (e1 < except1.used && except1.array[e1] < i1) ++e1;
+        // Skip past except characters in string1.
+        while (e1 < except1.used && except1.array[e1] < i1) ++e1;
 
-      if (e1 < except1.used && except1.array[e1] == i1) {
-        ++i1;
+        if (e1 < except1.used && except1.array[e1] == i1) {
+          ++i1;
 
-        continue;
-      }
+          continue;
+        }
 
-      // Skip past except characters in string2.
-      while (e2 < except2.used && except2.array[e2] < i2) ++e2;
+        // Skip past except characters in string2.
+        while (e2 < except2.used && except2.array[e2] < i2) ++e2;
 
-      if (e2 < except2.used && except2.array[e2] == i2) {
-        ++i2;
+        if (e2 < except2.used && except2.array[e2] == i2) {
+          ++i2;
 
-        continue;
-      }
+          continue;
+        }
 
-      if (string1[i1] != string2[i2]) {
-        return F_equal_to_not;
-      }
+        if (string1[i1] != string2[i2]) return F_equal_to_not;
 
-      ++i1;
-      ++i2;
-    } // while
+        ++i1;
+        ++i2;
+      } // while
+    }
 
     // Only return F_equal_to if all remaining characters are NULL.
-    for (; i1 <= last1; ++i1) {
+    if (last1 < stop1) {
+      for (; i1 <= last1; ++i1) {
 
-      if (string1[i1] != 0) {
+        if (string1[i1] != 0) {
 
-        // Skip past except characters in string1.
-        while (e1 < except1.used && except1.array[e1] < i1) ++e1;
-        if (e1 < except1.used && except1.array[e1] == i1) continue;
+          // Skip past except characters in string1.
+          while (e1 < except1.used && except1.array[e1] < i1) ++e1;
+          if (e1 < except1.used && except1.array[e1] == i1) continue;
 
-        return F_equal_to_not;
-      }
-    } // for
+          return F_equal_to_not;
+        }
+      } // for
+    }
 
-    for (; i2 <= last2; ++i2) {
+    if (last2 < stop2) {
+      for (; i2 <= last2; ++i2) {
 
-      if (string2[i2] != 0) {
+        if (string2[i2] != 0) {
 
-        // Skip past except characters in string1.
-        while (e2 < except2.used && except2.array[e2] < i2) ++e2;
-        if (e2 < except2.used && except2.array[e2] == i2) continue;
+          // Skip past except characters in string1.
+          while (e2 < except2.used && except2.array[e2] < i2) ++e2;
+          if (e2 < except2.used && except2.array[e2] == i2) continue;
 
-        return F_equal_to_not;
-      }
-    } // for
+          return F_equal_to_not;
+        }
+      } // for
+    }
 
     return F_equal_to;
   }
@@ -572,34 +572,36 @@ extern "C" {
         }
       } // for
 
-      if (size1 != size2) {
-        return F_equal_to_not;
-      }
+      if (size1 != size2) return F_equal_to_not;
     }
 
-    for (; i1 < last1 && i2 < last2; ++i1, ++i2) {
+    if (last1 < stop1 && last2 < stop2) {
+      for (; i1 < last1 && i2 < last2; ++i1, ++i2) {
 
-      // Skip past NULL in string1.
-      while (i1 < last1 && !string1[i1]) ++i1;
-      if (i1 == last1) break;
+        // Skip past NULL in string1.
+        while (i1 < last1 && !string1[i1]) ++i1;
+        if (i1 == last1) break;
 
-      // Skip past NULL in string2.
-      while (i2 < last2 && !string2[i2]) ++i2;
-      if (i2 == last2) break;
+        // Skip past NULL in string2.
+        while (i2 < last2 && !string2[i2]) ++i2;
+        if (i2 == last2) break;
 
-      if (string1[i1] != string2[i2]) {
-        return F_equal_to_not;
-      }
-    } // for
+        if (string1[i1] != string2[i2]) return F_equal_to_not;
+      } // for
+    }
 
     // Only return F_equal_to if all remaining characters are NULL.
-    for (; i1 < last1; ++i1) {
-      if (string1[i1] != 0) return F_equal_to_not;
-    } // for
+    if (last1 < stop1) {
+      for (; i1 < last1; ++i1) {
+        if (string1[i1] != 0) return F_equal_to_not;
+      } // for
+    }
 
-    for (; i2 < last2; ++i2) {
-      if (string2[i2] != 0) return F_equal_to_not;
-    } // for
+    if (last2 < stop2) {
+      for (; i2 < last2; ++i2) {
+        if (string2[i2] != 0) return F_equal_to_not;
+      } // for
+    }
 
     return F_equal_to;
   }