Fix overrun bug caused by conditional with assertion using too much memory.

ChangeLog

@@ -83,6 +83,13 @@ copied).
   (i) An insufficient memory size was being computed for compiling with 
       PCRE2_AUTO_CALLOUT. 
       
+  (j) A conditional group with an assertion condition used more memory than was 
+      allowed for it during parsing, so too many of them could therefore 
+      overrun a buffer.
+      
+  (k) If parsing a pattern exactly filled the buffer, the internal test for 
+      overrun did not check when the final META_END item was added.
+
 4. Back references are now permitted in lookbehind assertions when there are 
 no duplicated group numbers (that is, (?| has not been used), and, if the 
 reference is by name, there is only one group of that name. The referenced

HACKING

@@ -186,6 +186,7 @@ META_CLASS_EMPTY_NOT  [^] negative empty class - ditto
 META_CLASS_END        ] end of non-empty class
 META_CLASS_NOT        [^ start non-empty negative class
 META_COMMIT           (*COMMIT)
+META_COND_ASSERT      (?(?assertion)
 META_DOLLAR           $ metacharacter
 META_DOT              . metacharacter
 META_END              End of pattern (this value is 0x80000000)
@@ -274,9 +275,8 @@ This one is followed by an offset, for use in error messages, then a number:
 
 META_COND_NUMBER       (?([+-]digits)
 
-The following are followed just by an offset, for use in error messages:
+The following is followed just by an offset, for use in error messages:
 
-META_COND_ASSERT      (?(?assertion)
 META_COND_DEFINE      (?(DEFINE)
 
 In fact, META_COND_ASSERT is used for any group starting (?( that does not

src/pcre2_compile.c

@@ -856,6 +856,7 @@ for (;;)
 
     case META_BIGVALUE: fprintf(stderr, "META_BIGVALUE %.8x", *pptr++); break;
     case META_CIRCUMFLEX: fprintf(stderr, "META_CIRCUMFLEX"); break;
+    case META_COND_ASSERT: fprintf(stderr, "META_COND_ASSERT"); break;
     case META_DOLLAR: fprintf(stderr, "META_DOLLAR"); break;
     case META_DOT: fprintf(stderr, "META_DOT"); break;
     case META_ASTERISK: fprintf(stderr, "META *"); break;
@@ -949,12 +950,6 @@ for (;;)
     fprintf(stderr, "%zd", offset);
     break;
 
-    case META_COND_ASSERT:
-    fprintf(stderr, "META_COND_ASSERT offset=");
-    GETOFFSET(offset, pptr);
-    fprintf(stderr, "%zd", offset);
-    break;
-
     case META_COND_VERSION:
     fprintf(stderr, "META (?(VERSION%s", (*pptr++ == 0)? "=" : ">=");
     fprintf(stderr, "%d.", *pptr++);
@@ -2368,6 +2363,42 @@ while (ptr < ptrend)
         parsed_pattern, cb);
     }
 
+  /* If expect_cond_assert is 2, we have just passed (?( and are expecting an
+  assertion, possibly preceded by a callout. If the value is 1, we have just
+  had the callout and expect an assertion. There must be at least 3 more
+  characters in all cases. We know that the current character is an opening
+  parenthesis, as otherwise we wouldn't be here. Note that expect_cond_assert 
+  may be negative, since all callouts just decrement it. */
+
+  if (expect_cond_assert > 0)
+    {
+    BOOL ok = ptrend - ptr >= 3 && ptr[0] == CHAR_QUESTION_MARK;
+    if (ok) switch(ptr[1])
+      {
+      case CHAR_C:
+      ok = expect_cond_assert == 2;
+      break;  
+ 
+      case CHAR_EQUALS_SIGN:
+      case CHAR_EXCLAMATION_MARK:
+      break;
+      
+      case CHAR_LESS_THAN_SIGN:
+      ok = ptr[2] == CHAR_EQUALS_SIGN || ptr[2] == CHAR_EXCLAMATION_MARK;
+      break;
+      
+      default:
+      ok = FALSE;       
+      }   
+
+    if (!ok)
+      {
+      ptr--;   /* Adjust error offset */ 
+      errorcode = ERR28;
+      goto FAILED;
+      }
+    }
+
   /* Remember whether we are expecting a conditional assertion, and set the
   default for this item. */
 
@@ -3519,18 +3550,16 @@ while (ptr < ptrend)
       nest_depth++;
 
       /* If the next character is ? there must be an assertion next (optionally
-      preceded by a callout). We do not check this here, but instead we just
+      preceded by a callout). We do not check this here, but instead we set
-      preserve the offset so that the later check can give a sensible error
+      expect_cond_assert to 2. If this is still greater than zero (callouts
-      message. Pull back the pointer to the start of the assertion (or
+      decrement it) when the next assertion is read, it will be marked as a
-      callout), and set expect_cond_assert to 2. If this is still greater than
+      condition that must not be repeated. A value greater than zero also
-      zero (callouts decrement it) when the next assertion is read, it will be
+      causes checking that an assertion (possibly with callout) follows. */
-      marked as a condition that must not be repeated. */
 
       if (*ptr == CHAR_QUESTION_MARK)
         {
         *parsed_pattern++ = META_COND_ASSERT;
-        offset = (PCRE2_SIZE)(--ptr - cb->start_pattern - 2);
+        ptr--;   /* Pull pointer back to the opening parenthesis. */ 
-        PUTOFFSET(offset, parsed_pattern);
         expect_cond_assert = 2;
         break;  /* End of conditional */
         }
@@ -3902,6 +3931,11 @@ parsed_pattern = manage_callouts(ptr, &previous_callout, options,
 /* Terminate the parsed pattern, then return success if all groups are closed.
 Otherwise we have unclosed parentheses. */
 
+if (parsed_pattern >= parsed_pattern_end)
+  {
+  errorcode = ERR63;  /* Internal error (parsed pattern overflow) */
+  goto FAILED;
+  }
 *parsed_pattern = META_END;
 if (nest_depth == 0) return 0;
 
@@ -5806,23 +5840,10 @@ for (;; pptr++)
     pptr += 3;
     goto GROUP_PROCESS;
 
-    /* The condition is alleged to be an assertion, possibly preceded by a
+    /* The condition is an assertion, possibly preceded by a callout. */
-    callout, because it's not one of the others, and began with (?(?. This is
-    where the check for the next thing being an assertion (with optional
-    callout) is done. */
 
     case META_COND_ASSERT:
     bravalue = OP_COND;
-    GETPLUSOFFSET(offset, pptr);
-    i = (pptr[1] == META_CALLOUT_NUMBER)? 5 :
-        (pptr[1] == META_CALLOUT_STRING)? (5 + SIZEOFFSET) : 1;
-    if (META_CODE(pptr[i]) < META_LOOKAHEAD ||
-        META_CODE(pptr[i]) > META_LOOKBEHINDNOT)
-      {
-      *errorcodeptr = ERR28;         /* Assertion expected */
-      cb->erroroffset = offset + 2;  /* Point after initial (? */
-      return FALSE;
-      }
     goto GROUP_PROCESS;
 
 
@@ -8563,7 +8584,7 @@ for (;; pptr++)
     goto CHECK_GROUP;
 
     case META_COND_ASSERT:
-    pptr += 1 + SIZEOFFSET;
+    pptr += 1;
     goto CHECK_GROUP;
 
     case META_COND_VERSION:
@@ -8733,6 +8754,7 @@ for (pptr = cb->parsed_pattern; *pptr != META_END; pptr++)
     case META_CLASS_END:
     case META_CLASS_NOT:
     case META_COMMIT:
+    case META_COND_ASSERT:
     case META_DOLLAR:
     case META_DOT:
     case META_FAIL:
@@ -8753,7 +8775,6 @@ for (pptr = cb->parsed_pattern; *pptr != META_END; pptr++)
     case META_THEN:
     break;
 
-    case META_COND_ASSERT:
     case META_RECURSE:
     pptr += SIZEOFFSET;
     break;

testdata/testinput2

@@ -4912,4 +4912,8 @@ a)"xI
 \=get=i00000000000000000000000000000000
 \=get=i2345678901234567890123456789012,get=i1245678901234567890123456789012
 
+"(?(?C))"
+
+/(?(?(?(?(?(?))))))/
+
 # End of testinput2 

testdata/testoutput18

@@ -145,7 +145,7 @@ Failed: POSIX code 9: bad escape sequence at offset 4
 Failed: POSIX code 11: unbalanced () at offset 6     
 
 "(?(?C))"
-Failed: POSIX code 3: pattern error at offset 2     
+Failed: POSIX code 3: pattern error at offset 6     
 
 /abcd/substitute_extended
 ** Ignored with POSIX interface: substitute_extended

testdata/testoutput2

@@ -556,7 +556,7 @@ Failed: error 128 at offset 2: assertion expected after (?( or (?(?C)
 Failed: error 115 at offset 3: reference to non-existent subpattern
 
 /(?(?<ab))/
-Failed: error 142 at offset 7: syntax error in subpattern name (missing terminator)
+Failed: error 128 at offset 2: assertion expected after (?( or (?(?C)
 
 /((?s)blah)\s+\1/I
 Capturing subpattern count = 1
@@ -15361,6 +15361,12 @@ Failed: error 157 at offset 6: \g is not followed by a braced, angle-bracketed,
 \=get=i2345678901234567890123456789012,get=i1245678901234567890123456789012
 ** Too many characters in named 'get' modifiers
 
+"(?(?C))"
+Failed: error 128 at offset 6: assertion expected after (?( or (?(?C)
+
+/(?(?(?(?(?(?))))))/
+Failed: error 128 at offset 2: assertion expected after (?( or (?(?C)
+
 # End of testinput2 
 Error -63: PCRE2_ERROR_BADDATA (unknown error number)
 Error -62: bad serialized data