Fix security issues in bundled expat

Specifically, the following patches from the Debian 2.1.0-6+deb8u6 package
were applied:

CVE-2018-20843.patch
CVE-2015-1283.patch
CVE-2015-1283-refix.patch
CVE-2016-0718-v2-2-1.patch
cve-2012-6702-plus-cve-2016-5300-v1.patch
CVE-2017-9233.patch
CVE-2016-9063.patch
CVE-2019-15903.patch

Additionally, hashing code has been changed to use size_t instead of
unsigned long (which is 32-bit on 64-bit Windows).

5 files changed, 260 insertions, 115 deletions

diff --git a/libstudxml/details/expat/config.h b/libstudxml/details/expat/config.h
index 99fa673..eb32265 100644
--- a/libstudxml/details/expat/config.h
+++ b/libstudxml/details/expat/config.h
@@ -24,6 +24,7 @@
 #undef WIN32_LEAN_AND_MEAN
 
 #define HAVE_MEMMOVE 1
+#define COMPILED_FROM_DSP 1
 
 #else
 /* POSIX
diff --git a/libstudxml/details/expat/xmlparse.c b/libstudxml/details/expat/xmlparse.c
index 5bc6373..46871c1 100644
--- a/libstudxml/details/expat/xmlparse.c
+++ b/libstudxml/details/expat/xmlparse.c
@@ -6,12 +6,19 @@
 #include <string.h>                     /* memset(), memcpy() */
 #include <assert.h>
 #include <limits.h>                     /* UINT_MAX */
-#include <time.h>                       /* time() */
 
 #define XML_BUILDING_EXPAT 1
 
 #include <libstudxml/details/expat/config.h>
 
+#ifdef COMPILED_FROM_DSP
+#define getpid GetCurrentProcessId
+#else
+#include <sys/time.h>                   /* gettimeofday() */
+#include <sys/types.h>                  /* getpid() */
+#include <unistd.h>                     /* getpid() */
+#endif
+
 #include <libstudxml/details/expat/ascii.h>
 #include <libstudxml/details/expat/expat.h>
 
@@ -236,7 +243,7 @@ typedef struct {
 
 typedef struct {
   unsigned long version;
-  unsigned long hash;
+  size_t hash;
   const XML_Char *uriName;
 } NS_ATT;
 
@@ -321,7 +328,7 @@ initializeEncoding(XML_Parser parser);
 static enum XML_Error
 doProlog(XML_Parser parser, const ENCODING *enc, const char *s,
          const char *end, int tok, const char *next, const char **nextPtr,
-         XML_Bool haveMore);
+         XML_Bool haveMore, XML_Bool allowClosingDoctype);
 static enum XML_Error
 processInternalEntity(XML_Parser parser, ENTITY *entity,
                       XML_Bool betweenDecl);
@@ -422,7 +429,7 @@ static ELEMENT_TYPE *
 getElementType(XML_Parser parser, const ENCODING *enc,
                const char *ptr, const char *end);
 
-static unsigned long generate_hash_secret_salt(void);
+static size_t generate_hash_secret_salt(XML_Parser parser);
 static XML_Bool startParsing(XML_Parser parser);
 
 static XML_Parser
@@ -546,7 +553,7 @@ struct XML_ParserStruct {
   XML_Bool m_useForeignDTD;
   enum XML_ParamEntityParsing m_paramEntityParsing;
 #endif
-  unsigned long m_hash_secret_salt;
+  size_t m_hash_secret_salt;
 };
 
 #define MALLOC(s) (parser->m_mem.malloc_fcn((s)))
@@ -680,12 +687,39 @@ static const XML_Char implicitContext[] = {
   ASCII_s, ASCII_p, ASCII_a, ASCII_c, ASCII_e, '\0'
 };
 
-static unsigned long
-generate_hash_secret_salt(void)
+static size_t
+gather_time_entropy(void)
 {
-  unsigned int seed = time(NULL) % UINT_MAX;
-  srand(seed);
-  return rand();
+#ifdef COMPILED_FROM_DSP
+  FILETIME ft;
+  GetSystemTimeAsFileTime(&ft); /* never fails */
+  return ft.dwHighDateTime ^ ft.dwLowDateTime;
+#else
+  struct timeval tv;
+  int gettimeofday_res;
+
+  gettimeofday_res = gettimeofday(&tv, NULL);
+  assert (gettimeofday_res == 0);
+
+  /* Microseconds time is <20 bits entropy */
+  return tv.tv_usec;
+#endif
+}
+
+static size_t
+generate_hash_secret_salt(XML_Parser parser)
+{
+  /* Process ID is 0 bits entropy if attacker has local access
+   * XML_Parser address is few bits of entropy if attacker has local access */
+  const size_t entropy =
+      gather_time_entropy() ^ getpid() ^ (size_t)parser;
+
+  /* Factors are 2^31-1 and 2^61-1 (Mersenne primes M31 and M61) */
+  if (sizeof(size_t) == 4) {
+    return entropy * (size_t)2147483647;
+  } else {
+    return entropy * (size_t)2305843009213693951;
+  }
 }
 
 static XML_Bool  /* only valid for root parser */
@@ -693,7 +727,7 @@ startParsing(XML_Parser parser)
 {
     /* hash functions must be initialized before setContext() is called */
     if (hash_secret_salt == 0)
-      hash_secret_salt = generate_hash_secret_salt();
+      hash_secret_salt = generate_hash_secret_salt(parser);
     if (ns) {
       /* implicit context only set for root parser, since child
          parsers (i.e. external entity parsers) will inherit it
@@ -1018,7 +1052,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser,
      from hash tables associated with either parser without us having
      to worry which hash secrets each table has.
   */
-  unsigned long oldhash_secret_salt = hash_secret_salt;
+  size_t oldhash_secret_salt = hash_secret_salt;
 
 #ifdef XML_DTD
   if (!context)
@@ -1477,7 +1511,7 @@ XML_SetParamEntityParsing(XML_Parser parser,
 
 int XMLCALL
 XML_SetHashSalt(XML_Parser parser,
-                unsigned long hash_salt)
+                unsigned long hash_salt) /* should be size_t */
 {
   /* block after XML_Parse()/XML_ParseBuffer() has been called */
   if (ps_parsing == XML_PARSING || ps_parsing == XML_SUSPENDED)
@@ -1573,11 +1607,14 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal)
     nLeftOver = s + len - end;
     if (nLeftOver) {
       if (buffer == NULL || nLeftOver > bufferLim - buffer) {
-        /* FIXME avoid integer overflow */
-        char *temp;
-        temp = (buffer == NULL
-                ? (char *)MALLOC(len * 2)
-                : (char *)REALLOC(buffer, len * 2));
+        /* avoid _signed_ integer overflow */
+        char *temp = NULL;
+        const int bytesToAllocate = (int)((unsigned)len * 2U);
+        if (bytesToAllocate > 0) {
+          temp = (buffer == NULL
+                ? (char *)MALLOC(bytesToAllocate)
+                : (char *)REALLOC(buffer, bytesToAllocate));
+        }
         if (temp == NULL) {
           errorCode = XML_ERROR_NO_MEMORY;
           eventPtr = eventEndPtr = NULL;
@@ -1585,7 +1622,7 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal)
           return XML_STATUS_ERROR;
         }
         buffer = temp;
-        bufferLim = buffer + len * 2;
+        bufferLim = buffer + bytesToAllocate;
       }
       memcpy(buffer, end, nLeftOver);
     }
@@ -1668,6 +1705,12 @@ XML_ParseBuffer(XML_Parser parser, int len, int isFinal)
 void * XMLCALL
 XML_GetBuffer(XML_Parser parser, int len)
 {
+/* BEGIN MOZILLA CHANGE (sanity check len) */
+  if (len < 0) {
+    errorCode = XML_ERROR_NO_MEMORY;
+    return NULL;
+  }
+/* END MOZILLA CHANGE */
   switch (ps_parsing) {
   case XML_SUSPENDED:
     errorCode = XML_ERROR_SUSPENDED;
@@ -1679,8 +1722,14 @@ XML_GetBuffer(XML_Parser parser, int len)
   }
 
   if (len > bufferLim - bufferEnd) {
-    /* FIXME avoid integer overflow */
-    int neededSize = len + (int)(bufferEnd - bufferPtr);
+    /* Do not invoke signed arithmetic overflow: */
+    int neededSize = (int) ((unsigned)len + (unsigned)(bufferEnd - bufferPtr));
+/* BEGIN MOZILLA CHANGE (sanity check neededSize) */
+    if (neededSize < 0) {
+      errorCode = XML_ERROR_NO_MEMORY;
+      return NULL;
+    }
+/* END MOZILLA CHANGE */
 #ifdef XML_CONTEXT_BYTES
     int keep = (int)(bufferPtr - buffer);
 
@@ -1708,8 +1757,17 @@ XML_GetBuffer(XML_Parser parser, int len)
       if (bufferSize == 0)
         bufferSize = INIT_BUFFER_SIZE;
       do {
-        bufferSize *= 2;
-      } while (bufferSize < neededSize);
+        /* Do not invoke signed arithmetic overflow: */
+        bufferSize = (int) (2U * (unsigned) bufferSize);
+/* BEGIN MOZILLA CHANGE (prevent infinite loop on overflow) */
+      } while (bufferSize < neededSize && bufferSize > 0);
+/* END MOZILLA CHANGE */
+/* BEGIN MOZILLA CHANGE (sanity check bufferSize) */
+      if (bufferSize <= 0) {
+        errorCode = XML_ERROR_NO_MEMORY;
+        return NULL;
+      }
+/* END MOZILLA CHANGE */
       newBuf = (char *)MALLOC(bufferSize);
       if (newBuf == 0) {
         errorCode = XML_ERROR_NO_MEMORY;
@@ -2405,11 +2463,11 @@ doContent(XML_Parser parser,
           for (;;) {
             int bufSize;
             int convLen;
-            XmlConvert(enc,
+            const enum XML_Convert_Result convert_res = XmlConvert(enc,
                        &fromPtr, rawNameEnd,
                        (ICHAR **)&toPtr, (ICHAR *)tag->bufEnd - 1);
             convLen = (int)(toPtr - (XML_Char *)tag->buf);
-            if (fromPtr == rawNameEnd) {
+            if ((convert_res == XML_CONVERT_COMPLETED) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE)) {
               tag->name.strLen = convLen;
               break;
             }
@@ -2630,11 +2688,11 @@ doContent(XML_Parser parser,
           if (MUST_CONVERT(enc, s)) {
             for (;;) {
               ICHAR *dataPtr = (ICHAR *)dataBuf;
-              XmlConvert(enc, &s, next, &dataPtr, (ICHAR *)dataBufEnd);
+              const enum XML_Convert_Result convert_res = XmlConvert(enc, &s, next, &dataPtr, (ICHAR *)dataBufEnd);
               *eventEndPP = s;
               charDataHandler(handlerArg, dataBuf,
                               (int)(dataPtr - (ICHAR *)dataBuf));
-              if (s == next)
+              if ((convert_res == XML_CONVERT_COMPLETED) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE))
                 break;
               *eventPP = s;
             }
@@ -2867,7 +2925,7 @@ storeAtts(XML_Parser parser, const ENCODING *enc,
      and clear flags that say whether attributes were specified */
   i = 0;
   if (nPrefixes) {
-    int j;  /* hash table index */
+    size_t j;  /* hash table index */
     unsigned long version = nsAttsVersion;
     int nsAttsSize = (int)1 << nsAttsPower;
     /* size of hash table must be at least 2 * (# of prefixed attributes) */
@@ -2898,7 +2956,7 @@ storeAtts(XML_Parser parser, const ENCODING *enc,
       if (s[-1] == 2) {  /* prefixed */
         ATTRIBUTE_ID *id;
         const BINDING *b;
-        unsigned long uriHash = hash_secret_salt;
+        size_t uriHash = hash_secret_salt;
         ((XML_Char *)s)[-1] = 0;  /* clear flag */
         id = (ATTRIBUTE_ID *)lookup(parser, &dtd->attributeIds, s, 0);
         b = id->prefix->binding;
@@ -2906,7 +2964,7 @@ storeAtts(XML_Parser parser, const ENCODING *enc,
           return XML_ERROR_UNBOUND_PREFIX;
 
         /* as we expand the name we also calculate its hash value */
-        for (j = 0; j < b->uriLen; j++) {
+        for (j = 0; j < (size_t)b->uriLen; j++) {
           const XML_Char c = b->uri[j];
           if (!poolAppendChar(&tempPool, c))
             return XML_ERROR_NO_MEMORY;
@@ -2925,7 +2983,7 @@ storeAtts(XML_Parser parser, const ENCODING *enc,
              Derived from code in lookup(parser, HASH_TABLE *table, ...).
           */
           unsigned char step = 0;
-          unsigned long mask = nsAttsSize - 1;
+          size_t mask = nsAttsSize - 1;
           j = uriHash & mask;  /* index into hash table */
           while (nsAtts[j].version == version) {
             /* for speed we compare stored hash values first */
@@ -3238,11 +3296,11 @@ doCdataSection(XML_Parser parser,
           if (MUST_CONVERT(enc, s)) {
             for (;;) {
               ICHAR *dataPtr = (ICHAR *)dataBuf;
-              XmlConvert(enc, &s, next, &dataPtr, (ICHAR *)dataBufEnd);
+              const enum XML_Convert_Result convert_res = XmlConvert(enc, &s, next, &dataPtr, (ICHAR *)dataBufEnd);
               *eventEndPP = next;
               charDataHandler(handlerArg, dataBuf,
                               (int)(dataPtr - (ICHAR *)dataBuf));
-              if (s == next)
+              if ((convert_res == XML_CONVERT_COMPLETED) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE))
                 break;
               *eventPP = s;
             }
@@ -3634,6 +3692,14 @@ entityValueInitProcessor(XML_Parser parser,
       *nextPtr = next;
       return XML_ERROR_NONE;
     }
+    /* If we get this token, we have the start of what might be a
+       normal tag, but not a declaration (i.e. it doesn't begin with
+       "<!").  In a DTD context, that isn't legal.
+    */
+    else if (tok == XML_TOK_INSTANCE_START) {
+      *nextPtr = next;
+      return XML_ERROR_SYNTAX;
+    }
     start = next;
     eventPtr = start;
   }
@@ -3677,7 +3743,7 @@ externalParEntProcessor(XML_Parser parser,
 
   processor = prologProcessor;
   return doProlog(parser, encoding, s, end, tok, next,
-                  nextPtr, (XML_Bool)!ps_finalBuffer);
+                  nextPtr, (XML_Bool)!ps_finalBuffer, XML_TRUE);
 }
 
 static enum XML_Error PTRCALL
@@ -3727,7 +3793,7 @@ prologProcessor(XML_Parser parser,
   const char *next = s;
   int tok = XmlPrologTok(encoding, s, end, &next);
   return doProlog(parser, encoding, s, end, tok, next,
-                  nextPtr, (XML_Bool)!ps_finalBuffer);
+                  nextPtr, (XML_Bool)!ps_finalBuffer, XML_TRUE);
 }
 
 static enum XML_Error
@@ -3738,7 +3804,8 @@ doProlog(XML_Parser parser,
          int tok,
          const char *next,
          const char **nextPtr,
-         XML_Bool haveMore)
+         XML_Bool haveMore,
+         XML_Bool allowClosingDoctype)
 {
 #ifdef XML_DTD
   static const XML_Char externalSubsetName[] = { ASCII_HASH , '\0' };
@@ -3914,6 +3981,11 @@ doProlog(XML_Parser parser,
       }
       break;
     case XML_ROLE_DOCTYPE_CLOSE:
+      if (allowClosingDoctype != XML_TRUE) {
+        /* Must not close doctype from within expanded parameter entities */
+        return XML_ERROR_INVALID_TOKEN;
+      }
+
       if (doctypeName) {
         startDoctypeDeclHandler(handlerArg, doctypeName,
                                 doctypeSysid, doctypePubid, 0);
@@ -4815,7 +4887,7 @@ processInternalEntity(XML_Parser parser, ENTITY *entity,
   if (entity->is_param) {
     int tok = XmlPrologTok(internalEncoding, textStart, textEnd, &next);
     result = doProlog(parser, internalEncoding, textStart, textEnd, tok,
-                      next, &next, XML_FALSE);
+                      next, &next, XML_FALSE, XML_FALSE);
   }
   else
 #endif /* XML_DTD */
@@ -4860,7 +4932,7 @@ internalEntityProcessor(XML_Parser parser,
   if (entity->is_param) {
     int tok = XmlPrologTok(internalEncoding, textStart, textEnd, &next);
     result = doProlog(parser, internalEncoding, textStart, textEnd, tok,
-                      next, &next, XML_FALSE);
+                      next, &next, XML_FALSE, XML_TRUE);
   }
   else
 #endif /* XML_DTD */
@@ -4887,7 +4959,7 @@ internalEntityProcessor(XML_Parser parser,
     processor = prologProcessor;
     tok = XmlPrologTok(encoding, s, end, &next);
     return doProlog(parser, encoding, s, end, tok, next, nextPtr,
-                    (XML_Bool)!ps_finalBuffer);
+                    (XML_Bool)!ps_finalBuffer, XML_TRUE);
   }
   else
 #endif /* XML_DTD */
@@ -5323,6 +5395,7 @@ reportDefault(XML_Parser parser, const ENCODING *enc,
               const char *s, const char *end)
 {
   if (MUST_CONVERT(enc, s)) {
+    enum XML_Convert_Result convert_res;
     const char **eventPP;
     const char **eventEndPP;
     if (enc == encoding) {
@@ -5335,11 +5408,11 @@ reportDefault(XML_Parser parser, const ENCODING *enc,
     }
     do {
       ICHAR *dataPtr = (ICHAR *)dataBuf;
-      XmlConvert(enc, &s, end, &dataPtr, (ICHAR *)dataBufEnd);
+      convert_res = XmlConvert(enc, &s, end, &dataPtr, (ICHAR *)dataBufEnd);
       *eventEndPP = s;
       defaultHandler(handlerArg, dataBuf, (int)(dataPtr - (ICHAR *)dataBuf));
       *eventPP = s;
-    } while (s != end);
+    } while ((convert_res != XML_CONVERT_COMPLETED) && (convert_res != XML_CONVERT_INPUT_INCOMPLETE));
   }
   else
     defaultHandler(handlerArg, (XML_Char *)s, (int)((XML_Char *)end - (XML_Char *)s));
@@ -5414,6 +5487,7 @@ setElementTypePrefix(XML_Parser parser, ELEMENT_TYPE *elementType)
       else
         poolDiscard(&dtd->pool);
       elementType->prefix = prefix;
+      break;
 
     }
   }
@@ -5951,10 +6025,10 @@ keyeq(KEY s1, KEY s2)
   return XML_FALSE;
 }
 
-static unsigned long FASTCALL
+static size_t FASTCALL
 hash(XML_Parser parser, KEY s)
 {
-  unsigned long h = hash_secret_salt;
+  size_t h = hash_secret_salt;
   while (*s)
     h = CHAR_HASH(h, *s++);
   return h;
@@ -5981,8 +6055,8 @@ lookup(XML_Parser parser, HASH_TABLE *table, KEY name, size_t createSize)
     i = hash(parser, name) & ((unsigned long)table->size - 1);
   }
   else {
-    unsigned long h = hash(parser, name);
-    unsigned long mask = (unsigned long)table->size - 1;
+    size_t h = hash(parser, name);
+    size_t mask = table->size - 1;
     unsigned char step = 0;
     i = h & mask;
     while (table->v[i]) {
@@ -5999,7 +6073,7 @@ lookup(XML_Parser parser, HASH_TABLE *table, KEY name, size_t createSize)
     if (table->used >> (table->power - 1)) {
       unsigned char newPower = table->power + 1;
       size_t newSize = (size_t)1 << newPower;
-      unsigned long newMask = (unsigned long)newSize - 1;
+      size_t newMask = newSize - 1;
       size_t tsize = newSize * sizeof(NAMED *);
       NAMED **newV = (NAMED **)table->mem->malloc_fcn(tsize);
       if (!newV)
@@ -6007,7 +6081,7 @@ lookup(XML_Parser parser, HASH_TABLE *table, KEY name, size_t createSize)
       memset(newV, 0, tsize);
       for (i = 0; i < table->size; i++)
         if (table->v[i]) {
-          unsigned long newHash = hash(parser, table->v[i]->name);
+          size_t newHash = hash(parser, table->v[i]->name);
           size_t j = newHash & newMask;
           step = 0;
           while (newV[j]) {
@@ -6142,8 +6216,8 @@ poolAppend(STRING_POOL *pool, const ENCODING *enc,
   if (!pool->ptr && !poolGrow(pool))
     return NULL;
   for (;;) {
-    XmlConvert(enc, &ptr, end, (ICHAR **)&(pool->ptr), (ICHAR *)pool->end);
-    if (ptr == end)
+    const enum XML_Convert_Result convert_res = XmlConvert(enc, &ptr, end, (ICHAR **)&(pool->ptr), (ICHAR *)pool->end);
+    if ((convert_res == XML_CONVERT_COMPLETED) || (convert_res == XML_CONVERT_INPUT_INCOMPLETE))
       break;
     if (!poolGrow(pool))
       return NULL;
@@ -6227,8 +6301,13 @@ poolGrow(STRING_POOL *pool)
     }
   }
   if (pool->blocks && pool->start == pool->blocks->s) {
-    int blockSize = (int)(pool->end - pool->start)*2;
-    BLOCK *temp = (BLOCK *)
+    BLOCK *temp;
+    int blockSize = (int)((unsigned)(pool->end - pool->start)*2U);
+
+    if (blockSize < 0)
+      return XML_FALSE;
+
+    temp = (BLOCK *)
       pool->mem->realloc_fcn(pool->blocks,
                              (offsetof(BLOCK, s)
                               + blockSize * sizeof(XML_Char)));
@@ -6243,6 +6322,10 @@ poolGrow(STRING_POOL *pool)
   else {
     BLOCK *tem;
     int blockSize = (int)(pool->end - pool->start);
+
+    if (blockSize < 0)
+      return XML_FALSE;
+
     if (blockSize < INIT_BLOCK_SIZE)
       blockSize = INIT_BLOCK_SIZE;
     else
diff --git a/libstudxml/details/expat/xmltok.c b/libstudxml/details/expat/xmltok.c
index 5a8f36f..a36735c 100644
--- a/libstudxml/details/expat/xmltok.c
+++ b/libstudxml/details/expat/xmltok.c
@@ -336,11 +336,12 @@ enum {  /* UTF8_cvalN is value of masked first byte of N byte sequence */
   UTF8_cval4 = 0xf0
 };
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 utf8_toUtf8(const ENCODING *enc,
             const char **fromP, const char *fromLim,
             char **toP, const char *toLim)
 {
+  enum XML_Convert_Result res = XML_CONVERT_COMPLETED;
   char *to;
   const char *from;
 
@@ -348,30 +349,45 @@ utf8_toUtf8(const ENCODING *enc,
 
   if (fromLim - *fromP > toLim - *toP) {
     /* Avoid copying partial characters. */
+    res = XML_CONVERT_OUTPUT_EXHAUSTED;
     for (fromLim = *fromP + (toLim - *toP); fromLim > *fromP; fromLim--)
       if (((unsigned char)fromLim[-1] & 0xc0) != 0x80)
         break;
   }
-  for (to = *toP, from = *fromP; from != fromLim; from++, to++)
+  for (to = *toP, from = *fromP; (from < fromLim) && (to < toLim); from++, to++)
     *to = *from;
   *fromP = from;
   *toP = to;
+
+  if ((to == toLim) && (from < fromLim))
+    return XML_CONVERT_OUTPUT_EXHAUSTED;
+  else
+    return res;
 }
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 utf8_toUtf16(const ENCODING *enc,
              const char **fromP, const char *fromLim,
              unsigned short **toP, const unsigned short *toLim)
 {
+  enum XML_Convert_Result res = XML_CONVERT_COMPLETED;
   unsigned short *to = *toP;
   const char *from = *fromP;
-  while (from != fromLim && to != toLim) {
+  while (from < fromLim && to < toLim) {
     switch (((struct normal_encoding *)enc)->type[(unsigned char)*from]) {
     case BT_LEAD2:
+      if (fromLim - from < 2) {
+        res = XML_CONVERT_INPUT_INCOMPLETE;
+        break;
+      }
       *to++ = (unsigned short)(((from[0] & 0x1f) << 6) | (from[1] & 0x3f));
       from += 2;
       break;
     case BT_LEAD3:
+      if (fromLim - from < 3) {
+        res = XML_CONVERT_INPUT_INCOMPLETE;
+        break;
+      }
       *to++ = (unsigned short)(((from[0] & 0xf) << 12)
                                | ((from[1] & 0x3f) << 6) | (from[2] & 0x3f));
       from += 3;
@@ -379,8 +395,14 @@ utf8_toUtf16(const ENCODING *enc,
     case BT_LEAD4:
       {
         unsigned long n;
-        if (to + 1 == toLim)
+        if (toLim - to < 2) {
+          res = XML_CONVERT_OUTPUT_EXHAUSTED;
           goto after;
+        }
+        if (fromLim - from < 4) {
+          res = XML_CONVERT_INPUT_INCOMPLETE;
+          goto after;
+        }
         n = ((from[0] & 0x7) << 18) | ((from[1] & 0x3f) << 12)
             | ((from[2] & 0x3f) << 6) | (from[3] & 0x3f);
         n -= 0x10000;
@@ -398,6 +420,7 @@ utf8_toUtf16(const ENCODING *enc,
 after:
   *fromP = from;
   *toP = to;
+  return res;
 }
 
 #ifdef XML_NS
@@ -446,7 +469,7 @@ static const struct normal_encoding internal_utf8_encoding = {
   STANDARD_VTABLE(sb_) NORMAL_VTABLE(utf8_)
 };
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 latin1_toUtf8(const ENCODING *enc,
               const char **fromP, const char *fromLim,
               char **toP, const char *toLim)
@@ -456,32 +479,37 @@ latin1_toUtf8(const ENCODING *enc,
   for (;;) {
     unsigned char c;
     if (*fromP == fromLim)
-      break;
+      return XML_CONVERT_COMPLETED;
     c = (unsigned char)**fromP;
     if (c & 0x80) {
       if (toLim - *toP < 2)
-        break;
+        return XML_CONVERT_OUTPUT_EXHAUSTED;
       *(*toP)++ = (char)((c >> 6) | UTF8_cval2);
       *(*toP)++ = (char)((c & 0x3f) | 0x80);
       (*fromP)++;
     }
     else {
       if (*toP == toLim)
-        break;
+        return XML_CONVERT_OUTPUT_EXHAUSTED;
       *(*toP)++ = *(*fromP)++;
     }
   }
 }
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 latin1_toUtf16(const ENCODING *enc,
                const char **fromP, const char *fromLim,
                unsigned short **toP, const unsigned short *toLim)
 {
   UNUSED(enc);
 
-  while (*fromP != fromLim && *toP != toLim)
+  while (*fromP < fromLim && *toP < toLim)
     *(*toP)++ = (unsigned char)*(*fromP)++;
+
+  if ((*toP == toLim) && (*fromP < fromLim))
+    return XML_CONVERT_OUTPUT_EXHAUSTED;
+  else
+    return XML_CONVERT_COMPLETED;
 }
 
 #ifdef XML_NS
@@ -508,15 +536,20 @@ static const struct normal_encoding latin1_encoding = {
   STANDARD_VTABLE(sb_) ZERO_VTABLE
 };
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 ascii_toUtf8(const ENCODING *enc,
              const char **fromP, const char *fromLim,
              char **toP, const char *toLim)
 {
   UNUSED(enc);
 
-  while (*fromP != fromLim && *toP != toLim)
+  while (*fromP < fromLim && *toP < toLim)
     *(*toP)++ = *(*fromP)++;
+
+  if ((*toP == toLim) && (*fromP < fromLim))
+    return XML_CONVERT_OUTPUT_EXHAUSTED;
+  else
+    return XML_CONVERT_COMPLETED;
 }
 
 #ifdef XML_NS
@@ -563,14 +596,15 @@ unicode_byte_type(char hi, char lo)
 }
 
 #define DEFINE_UTF16_TO_UTF8(E) \
-static void  PTRCALL \
+static enum XML_Convert_Result  PTRCALL \
 E ## toUtf8(const ENCODING *enc, \
             const char **fromP, const char *fromLim, \
             char **toP, const char *toLim) \
 { \
-  const char *from; \
+  const char *from = *fromP; \
   UNUSED(enc); \
-  for (from = *fromP; from != fromLim; from += 2) { \
+  fromLim = from + (((fromLim - from) >> 1) << 1);  /* shrink to even */ \
+  for (; from < fromLim; from += 2) { \
     int plane; \
     unsigned char lo2; \
     unsigned char lo = GET_LO(from); \
@@ -580,7 +614,7 @@ E ## toUtf8(const ENCODING *enc, \
       if (lo < 0x80) { \
         if (*toP == toLim) { \
           *fromP = from; \
-          return; \
+          return XML_CONVERT_OUTPUT_EXHAUSTED; \
         } \
         *(*toP)++ = lo; \
         break; \
@@ -590,7 +624,7 @@ E ## toUtf8(const ENCODING *enc, \
     case 0x4: case 0x5: case 0x6: case 0x7: \
       if (toLim -  *toP < 2) { \
         *fromP = from; \
-        return; \
+        return XML_CONVERT_OUTPUT_EXHAUSTED; \
       } \
       *(*toP)++ = ((lo >> 6) | (hi << 2) |  UTF8_cval2); \
       *(*toP)++ = ((lo & 0x3f) | 0x80); \
@@ -598,7 +632,7 @@ E ## toUtf8(const ENCODING *enc, \
     default: \
       if (toLim -  *toP < 3)  { \
         *fromP = from; \
-        return; \
+        return XML_CONVERT_OUTPUT_EXHAUSTED; \
       } \
       /* 16 bits divided 4, 6, 6 amongst 3 bytes */ \
       *(*toP)++ = ((hi >> 4) | UTF8_cval3); \
@@ -608,7 +642,11 @@ E ## toUtf8(const ENCODING *enc, \
     case 0xD8: case 0xD9: case 0xDA: case 0xDB: \
       if (toLim -  *toP < 4) { \
         *fromP = from; \
-        return; \
+        return XML_CONVERT_OUTPUT_EXHAUSTED; \
+      } \
+      if (fromLim - from < 4) { \
+        *fromP = from; \
+        return XML_CONVERT_INPUT_INCOMPLETE; \
       } \
       plane = (((hi & 0x3) << 2) | ((lo >> 6) & 0x3)) + 1; \
       *(*toP)++ = ((plane >> 2) | UTF8_cval4); \
@@ -624,21 +662,33 @@ E ## toUtf8(const ENCODING *enc, \
     } \
   } \
   *fromP = from; \
+  if (from < fromLim) \
+    return XML_CONVERT_INPUT_INCOMPLETE; \
+  else \
+    return XML_CONVERT_COMPLETED; \
 }
 
 #define DEFINE_UTF16_TO_UTF16(E) \
-static void  PTRCALL \
+static enum XML_Convert_Result  PTRCALL \
 E ## toUtf16(const ENCODING *enc, \
              const char **fromP, const char *fromLim, \
              unsigned short **toP, const unsigned short *toLim) \
 { \
-   UNUSED(enc); \
+  enum XML_Convert_Result res = XML_CONVERT_COMPLETED; \
+  UNUSED(enc); \
+  fromLim = *fromP + (((fromLim - *fromP) >> 1) << 1);  /* shrink to even */ \
   /* Avoid copying first half only of surrogate */ \
   if (fromLim - *fromP > ((toLim - *toP) << 1) \
-      && (GET_HI(fromLim - 2) & 0xF8) == 0xD8) \
+      && (GET_HI(fromLim - 2) & 0xF8) == 0xD8) { \
     fromLim -= 2; \
-  for (; *fromP != fromLim && *toP != toLim; *fromP += 2) \
+    res = XML_CONVERT_INPUT_INCOMPLETE; \
+  } \
+  for (; *fromP < fromLim && *toP < toLim; *fromP += 2) \
     *(*toP)++ = (GET_HI(*fromP) << 8) | GET_LO(*fromP); \
+  if ((*toP == toLim) && (*fromP < fromLim)) \
+    return XML_CONVERT_OUTPUT_EXHAUSTED; \
+  else \
+    return res; \
 }
 
 #define SET2(ptr, ch) \
@@ -1318,7 +1368,7 @@ unknown_isInvalid(const ENCODING *enc, const char *p)
   return (c & ~0xFFFF) || checkCharRefNumber(c) < 0;
 }
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 unknown_toUtf8(const ENCODING *enc,
                const char **fromP, const char *fromLim,
                char **toP, const char *toLim)
@@ -1329,21 +1379,21 @@ unknown_toUtf8(const ENCODING *enc,
     const char *utf8;
     int n;
     if (*fromP == fromLim)
-      break;
+      return XML_CONVERT_COMPLETED;
     utf8 = uenc->utf8[(unsigned char)**fromP];
     n = *utf8++;
     if (n == 0) {
       int c = uenc->convert(uenc->userData, *fromP);
       n = XmlUtf8Encode(c, buf);
       if (n > toLim - *toP)
-        break;
+        return XML_CONVERT_OUTPUT_EXHAUSTED;
       utf8 = buf;
       *fromP += (AS_NORMAL_ENCODING(enc)->type[(unsigned char)**fromP]
                  - (BT_LEAD2 - 2));
     }
     else {
       if (n > toLim - *toP)
-        break;
+        return XML_CONVERT_OUTPUT_EXHAUSTED;
       (*fromP)++;
     }
     do {
@@ -1352,13 +1402,13 @@ unknown_toUtf8(const ENCODING *enc,
   }
 }
 
-static void PTRCALL
+static enum XML_Convert_Result PTRCALL
 unknown_toUtf16(const ENCODING *enc,
                 const char **fromP, const char *fromLim,
                 unsigned short **toP, const unsigned short *toLim)
 {
   const struct unknown_encoding *uenc = AS_UNKNOWN_ENCODING(enc);
-  while (*fromP != fromLim && *toP != toLim) {
+  while (*fromP < fromLim && *toP < toLim) {
     unsigned short c = uenc->utf16[(unsigned char)**fromP];
     if (c == 0) {
       c = (unsigned short)
@@ -1370,6 +1420,11 @@ unknown_toUtf16(const ENCODING *enc,
       (*fromP)++;
     *(*toP)++ = c;
   }
+
+  if ((*toP == toLim) && (*fromP < fromLim))
+    return XML_CONVERT_OUTPUT_EXHAUSTED;
+  else
+    return XML_CONVERT_COMPLETED;
 }
 
 ENCODING *
@@ -1533,7 +1588,7 @@ initScan(const ENCODING * const *encodingTable,
 {
   const ENCODING **encPtr;
 
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   encPtr = enc->encPtr;
   if (ptr + 1 == end) {
diff --git a/libstudxml/details/expat/xmltok.h b/libstudxml/details/expat/xmltok.h
index ca867aa..752007e 100644
--- a/libstudxml/details/expat/xmltok.h
+++ b/libstudxml/details/expat/xmltok.h
@@ -130,6 +130,12 @@ typedef int (PTRCALL *SCANNER)(const ENCODING *,
                                const char *,
                                const char **);
 
+enum XML_Convert_Result {
+  XML_CONVERT_COMPLETED = 0,
+  XML_CONVERT_INPUT_INCOMPLETE = 1,
+  XML_CONVERT_OUTPUT_EXHAUSTED = 2  /* and therefore potentially input remaining as well */
+};
+
 struct encoding {
   SCANNER scanners[XML_N_STATES];
   SCANNER literalScanners[XML_N_LITERAL_TYPES];
@@ -158,12 +164,12 @@ struct encoding {
                             const char *ptr,
                             const char *end,
                             const char **badPtr);
-  void (PTRCALL *utf8Convert)(const ENCODING *enc,
+  enum XML_Convert_Result (PTRCALL *utf8Convert)(const ENCODING *enc,
                               const char **fromP,
                               const char *fromLim,
                               char **toP,
                               const char *toLim);
-  void (PTRCALL *utf16Convert)(const ENCODING *enc,
+  enum XML_Convert_Result (PTRCALL *utf16Convert)(const ENCODING *enc,
                                const char **fromP,
                                const char *fromLim,
                                unsigned short **toP,
diff --git a/libstudxml/details/expat/xmltok_impl.c b/libstudxml/details/expat/xmltok_impl.c
index de4d21a..5410278 100644
--- a/libstudxml/details/expat/xmltok_impl.c
+++ b/libstudxml/details/expat/xmltok_impl.c
@@ -93,13 +93,13 @@ static int PTRCALL
 PREFIX(scanComment)(const ENCODING *enc, const char *ptr,
                     const char *end, const char **nextTokPtr)
 {
-  if (ptr != end) {
+  if (ptr < end) {
     if (!CHAR_MATCHES(enc, ptr, ASCII_MINUS)) {
       *nextTokPtr = ptr;
       return XML_TOK_INVALID;
     }
     ptr += MINBPC(enc);
-    while (ptr != end) {
+    while (ptr < end) {
       switch (BYTE_TYPE(enc, ptr)) {
       INVALID_CASES(ptr, nextTokPtr)
       case BT_MINUS:
@@ -147,7 +147,7 @@ PREFIX(scanDecl)(const ENCODING *enc, const char *ptr,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     case BT_PERCNT:
       if (ptr + MINBPC(enc) == end)
@@ -236,7 +236,7 @@ PREFIX(scanPi)(const ENCODING *enc, const char *ptr,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_S: case BT_CR: case BT_LF:
@@ -245,7 +245,7 @@ PREFIX(scanPi)(const ENCODING *enc, const char *ptr,
         return XML_TOK_INVALID;
       }
       ptr += MINBPC(enc);
-      while (ptr != end) {
+      while (ptr < end) {
         switch (BYTE_TYPE(enc, ptr)) {
         INVALID_CASES(ptr, nextTokPtr)
         case BT_QUEST:
@@ -311,7 +311,7 @@ static int PTRCALL
 PREFIX(cdataSectionTok)(const ENCODING *enc, const char *ptr,
                         const char *end, const char **nextTokPtr)
 {
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   if (MINBPC(enc) > 1) {
     size_t n = end - ptr;
@@ -354,7 +354,7 @@ PREFIX(cdataSectionTok)(const ENCODING *enc, const char *ptr,
     ptr += MINBPC(enc);
     break;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
 #define LEAD_CASE(n) \
     case BT_LEAD ## n: \
@@ -397,11 +397,11 @@ PREFIX(scanEndTag)(const ENCODING *enc, const char *ptr,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_S: case BT_CR: case BT_LF:
-      for (ptr += MINBPC(enc); ptr != end; ptr += MINBPC(enc)) {
+      for (ptr += MINBPC(enc); ptr < end; ptr += MINBPC(enc)) {
         switch (BYTE_TYPE(enc, ptr)) {
         case BT_S: case BT_CR: case BT_LF:
           break;
@@ -438,7 +438,7 @@ static int PTRCALL
 PREFIX(scanHexCharRef)(const ENCODING *enc, const char *ptr,
                        const char *end, const char **nextTokPtr)
 {
-  if (ptr != end) {
+  if (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     case BT_DIGIT:
     case BT_HEX:
@@ -447,7 +447,7 @@ PREFIX(scanHexCharRef)(const ENCODING *enc, const char *ptr,
       *nextTokPtr = ptr;
       return XML_TOK_INVALID;
     }
-    for (ptr += MINBPC(enc); ptr != end; ptr += MINBPC(enc)) {
+    for (ptr += MINBPC(enc); ptr < end; ptr += MINBPC(enc)) {
       switch (BYTE_TYPE(enc, ptr)) {
       case BT_DIGIT:
       case BT_HEX:
@@ -470,7 +470,7 @@ static int PTRCALL
 PREFIX(scanCharRef)(const ENCODING *enc, const char *ptr,
                     const char *end, const char **nextTokPtr)
 {
-  if (ptr != end) {
+  if (ptr < end) {
     if (CHAR_MATCHES(enc, ptr, ASCII_x))
       return PREFIX(scanHexCharRef)(enc, ptr + MINBPC(enc), end, nextTokPtr);
     switch (BYTE_TYPE(enc, ptr)) {
@@ -480,7 +480,7 @@ PREFIX(scanCharRef)(const ENCODING *enc, const char *ptr,
       *nextTokPtr = ptr;
       return XML_TOK_INVALID;
     }
-    for (ptr += MINBPC(enc); ptr != end; ptr += MINBPC(enc)) {
+    for (ptr += MINBPC(enc); ptr < end; ptr += MINBPC(enc)) {
       switch (BYTE_TYPE(enc, ptr)) {
       case BT_DIGIT:
         break;
@@ -512,7 +512,7 @@ PREFIX(scanRef)(const ENCODING *enc, const char *ptr, const char *end,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_SEMI:
@@ -535,7 +535,7 @@ PREFIX(scanAtts)(const ENCODING *enc, const char *ptr, const char *end,
 #ifdef XML_NS
   int hadColon = 0;
 #endif
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
 #ifdef XML_NS
@@ -722,7 +722,7 @@ PREFIX(scanLt)(const ENCODING *enc, const char *ptr, const char *end,
   hadColon = 0;
 #endif
   /* we have a start-tag */
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
 #ifdef XML_NS
@@ -746,7 +746,7 @@ PREFIX(scanLt)(const ENCODING *enc, const char *ptr, const char *end,
     case BT_S: case BT_CR: case BT_LF:
       {
         ptr += MINBPC(enc);
-        while (ptr != end) {
+        while (ptr < end) {
           switch (BYTE_TYPE(enc, ptr)) {
           CHECK_NMSTRT_CASES(enc, ptr, end, nextTokPtr)
           case BT_GT:
@@ -791,7 +791,7 @@ static int PTRCALL
 PREFIX(contentTok)(const ENCODING *enc, const char *ptr, const char *end,
                    const char **nextTokPtr)
 {
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   if (MINBPC(enc) > 1) {
     size_t n = end - ptr;
@@ -838,7 +838,7 @@ PREFIX(contentTok)(const ENCODING *enc, const char *ptr, const char *end,
     ptr += MINBPC(enc);
     break;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
 #define LEAD_CASE(n) \
     case BT_LEAD ## n: \
@@ -901,7 +901,7 @@ PREFIX(scanPercent)(const ENCODING *enc, const char *ptr, const char *end,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_SEMI:
@@ -927,7 +927,7 @@ PREFIX(scanPoundName)(const ENCODING *enc, const char *ptr, const char *end,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_CR: case BT_LF: case BT_S:
@@ -947,7 +947,7 @@ PREFIX(scanLit)(int open, const ENCODING *enc,
                 const char *ptr, const char *end,
                 const char **nextTokPtr)
 {
-  while (ptr != end) {
+  while (ptr < end) {
     int t = BYTE_TYPE(enc, ptr);
     switch (t) {
     INVALID_CASES(ptr, nextTokPtr)
@@ -979,7 +979,7 @@ PREFIX(prologTok)(const ENCODING *enc, const char *ptr, const char *end,
                   const char **nextTokPtr)
 {
   int tok;
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   if (MINBPC(enc) > 1) {
     size_t n = end - ptr;
@@ -1147,7 +1147,7 @@ PREFIX(prologTok)(const ENCODING *enc, const char *ptr, const char *end,
     *nextTokPtr = ptr;
     return XML_TOK_INVALID;
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     CHECK_NAME_CASES(enc, ptr, end, nextTokPtr)
     case BT_GT: case BT_RPAR: case BT_COMMA:
@@ -1210,10 +1210,10 @@ PREFIX(attributeValueTok)(const ENCODING *enc, const char *ptr,
                           const char *end, const char **nextTokPtr)
 {
   const char *start;
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   start = ptr;
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
 #define LEAD_CASE(n) \
     case BT_LEAD ## n: ptr += n; break;
@@ -1268,10 +1268,10 @@ PREFIX(entityValueTok)(const ENCODING *enc, const char *ptr,
                        const char *end, const char **nextTokPtr)
 {
   const char *start;
-  if (ptr == end)
+  if (ptr >= end)
     return XML_TOK_NONE;
   start = ptr;
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
 #define LEAD_CASE(n) \
     case BT_LEAD ## n: ptr += n; break;
@@ -1332,7 +1332,7 @@ PREFIX(ignoreSectionTok)(const ENCODING *enc, const char *ptr,
       end = ptr + n;
     }
   }
-  while (ptr != end) {
+  while (ptr < end) {
     switch (BYTE_TYPE(enc, ptr)) {
     INVALID_CASES(ptr, nextTokPtr)
     case BT_LT:
@@ -1379,7 +1379,7 @@ PREFIX(isPublicId)(const ENCODING *enc, const char *ptr, const char *end,
 {
   ptr += MINBPC(enc);
   end -= MINBPC(enc);
-  for (; ptr != end; ptr += MINBPC(enc)) {
+  for (; ptr < end; ptr += MINBPC(enc)) {
     switch (BYTE_TYPE(enc, ptr)) {
     case BT_DIGIT:
     case BT_HEX:
@@ -1773,7 +1773,7 @@ PREFIX(updatePosition)(const ENCODING *enc,
     case BT_CR:
       pos->lineNumber++;
       ptr += MINBPC(enc);
-      if (ptr != end && BYTE_TYPE(enc, ptr) == BT_LF)
+      if (ptr < end && BYTE_TYPE(enc, ptr) == BT_LF)
         ptr += MINBPC(enc);
       pos->columnNumber = (XML_Size)-1;
       break;