Change 583480615 by sungyc@sungyc:fig-export-icing-153-change-459:7032:citc on 2023/11/17 13:59:58

	[hunspell][vulnerability fix] Fix heap buffer overflow in AffixMgr::compound_check
	
	## Test plan
	```
	sso_client -location 'https://clusterfuzz.corp.google.com/testcase-detail/download-testcase?id=5877288434466816' > /tmp/testcase-5877288434466816 && \
	blaze --blazerc=/dev/null test -c opt --config=asan-fuzzer --test_strategy=local --test_sharding_strategy=disabled \
	  --test_env=ENABLE_BLAZE_TEST_FUZZING=1  --test_arg=-runs=100 --test_arg=/tmp/testcase-5877288434466816 \
	  //third_party/hunspell/fuzzers:suggestions_fuzzer
	```
	
	## Description
	- Variable `i`, `cmin`, `cmax` are changed in every iteration.
	- Originally buffer `word` has length `len`.
	- It is possible that `i >= len` and makes all `word + i` or `word[i]` invalid. This is the heap buffer overflow reason.
	- So we must check if `i < len` before using `word + i` (or any possibility that accesses `word + i` or later.
	- Also `len` is changed at L1604, so we should copy it out (as `word_len`) in the beginning of the function.
	
	Also double check the [latest hunspell AffixMgr](https://github.com/hunspell/hunspell/blob/master/src/hunspell/affixmgr.cxx#L1570), verifying this change is similar to the current solution.
	
	PRESUBMIT=passed
	BUG=298635289
	R=adorokhine,mghiware
	APPROVED=adorokhine,mghiware
	REQUIRED_REVIEW=1
	DELTA=18 (10 added, 0 deleted, 8 changed)
	DELTA_BY_EXTENSION=cxx=18
	OCL=582895680
	FIG_CHANGESET=4ab7f2818e7d826b55a4701f0d97153534ff41fd
	FIG_WORKSPACE=sungyc/153:icing
	MARKDOWN=true

Affected files ...

... //depot//src/hunspell/affixmgr.cxx#15 edit

==== //depot//src/hunspell/affixmgr.cxx#14 - /google/src/files/583480615/depot//src/hunspell/affixmgr.cxx ====
--- /google/src/files/553210266/depot//src/hunspell/affixmgr.cxx	2023-08-02 14:42:00.000000000 -0400
+++ /google/src/files/583480615/depot//src/hunspell/affixmgr.cxx	2023-11-17 16:59:58.000000000 -0500
@@ -1527,6 +1527,10 @@
     short wordnum, short numsyllable, short maxwordnum, short wnum, hentry ** words = NULL,
     char hu_mov_rule = 0, char is_sug = 0, int * info = NULL)
 {
+    // Since len will be modified later, let's copy it out to preserve the
+    // word's len info.
+    int word_len = len;
+
     int i; 
     short oldnumsyllable, oldnumsyllable2, oldwordnum, oldwordnum2;
     struct hentry * rv = NULL;
@@ -1586,7 +1590,7 @@
         do { // simplified checkcompoundpattern loop
 
         if (scpd > 0) {
-          for (; scpd <= numcheckcpd && (!checkcpdtable[scpd-1].pattern3 ||
+          for (; scpd <= numcheckcpd && (!checkcpdtable[scpd-1].pattern3 || i > word_len ||
             strncmp(word + i, checkcpdtable[scpd-1].pattern3, strlen(checkcpdtable[scpd-1].pattern3)) != 0); scpd++);
 
           if (scpd > numcheckcpd) break; // break simplified checkcompoundpattern loop
@@ -1865,15 +1869,19 @@
             // perhaps second word has prefix or/and suffix
             sfx = NULL;
             sfxflag = FLAG_NULL;
-            rv = (compoundflag && !onlycpdrule) ? affix_check((word+i),strlen(word+i), compoundflag, IN_CPD_END) : NULL;
+            rv = (compoundflag && !onlycpdrule && i < word_len) ? affix_check((word+i),strlen(word+i), compoundflag, IN_CPD_END) : NULL;
             if (!rv && compoundend && !onlycpdrule) {
                 sfx = NULL;
                 pfx = NULL;
+                if (i < word_len) {
                 rv = affix_check((word+i),strlen(word+i), compoundend, IN_CPD_END);
             }
+            }
 
             if (!rv && numdefcpd && words) {
+                if (i < word_len) {
                 rv = affix_check((word+i),strlen(word+i), 0, IN_CPD_END);
+                }
                 if (rv && defcpd_check(&words, wnum + 1, rv, NULL, 1)) {
                   free(rwords);
                   return rv_first;
@@ -1886,7 +1894,7 @@
                 TESTAFF(rv->astr, checkcpdtable[scpd-1].cond2, rv->alen))) rv = NULL;
 
             // test CHECKCOMPOUNDPATTERN conditions (forbidden compounds)
-            if (rv && numcheckcpd && scpd == 0 && cpdpat_check(word, i, rv_first, rv, affixed)) rv = NULL;
+            if (rv && numcheckcpd && scpd == 0 && i < word_len && cpdpat_check(word, i, rv_first, rv, affixed)) rv = NULL;
 
             // check non_compound flag in suffix and prefix
             if ((rv) && 
@@ -1918,7 +1926,9 @@
 
             if (langnum == LANG_hu) {
                 // calculate syllable number of the word
+                if (i < word_len) {
                 numsyllable += get_syllable(word + i, strlen(word + i));
+                }
 
                 // - affix syllable num.
                 // XXX only second suffix (inflections, not derivations)
@@ -1979,7 +1989,7 @@
                 rv = compound_check((st+i),strlen(st+i), wordnum+1,
                      numsyllable, maxwordnum, wnum + 1, words, 0, is_sug, info);
                 
-                if (rv && numcheckcpd && ((scpd == 0 && cpdpat_check(word, i, rv_first, rv, affixed)) ||
+                if (rv && numcheckcpd && i < word_len && ((scpd == 0 && cpdpat_check(word, i, rv_first, rv, affixed)) ||
                    (scpd != 0 && !cpdpat_check(word, i, rv_first, rv, affixed)))) rv = NULL;
             } else {
                 rv=NULL;
@@ -1995,7 +2005,7 @@
                     }
                     
                     // check first part
-                    if (strncmp(rv->word, word + i, rv->blen) == 0) {
+                    if (i < word_len && strncmp(rv->word, word + i, rv->blen) == 0) {
                         char r = *(st + i + rv->blen);
                         *(st + i + rv->blen) = '\0';