CVE-2023-52426 (published 2024-02-04T20:15Z)

libexpat through 2.5.0 allows recursive XML Entity Expansion if XML_DTD is undefined at compile time.

CVSS v3 base score: 5.5, MEDIUM (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-776
cwe_name: Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
description: The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.
extended_description: If the DTD contains a large number of nested or recursive entities, this can lead to explosive growth of data when parsed, causing a denial of service.
         

Fix information:
repo_url: https://github.com/libexpat/libexpat
commit_details: repo_url: https://github.com/libexpat/libexpat
author: Sebastian Pipping
author_date: 2023-10-26 00:43:22+02:00
msg: lib|xmlwf|cmake: Extend scope of billion laughs attack protection

.. from "defined(XML_DTD)" to "defined(XML_DTD) || XML_GE==1".
repository: repo_url: https://github.com/libexpat/libexpat
repo_name: libexpat/libexpat
description: :herb: Fast streaming XML parser written in C99 with >90% test coverage; moved from SourceForge to GitHub
repo_language: C
owner: libexpat
file_changes: filename: CMakeLists.txt
change_type: ModificationType.MODIFY
diff: @@ -403,7 +403,13 @@ if(EXPAT_SHARED_LIBS)
             endif()
         endmacro()
 
-        _expat_def_file_toggle(EXPAT_DTD _EXPAT_COMMENT_DTD)
+        if(EXPAT_DTD OR EXPAT_GE)
+            set(_EXPAT_DTD_OR_GE TRUE)
+        else()
+            set(_EXPAT_DTD_OR_GE FALSE)
+        endif()
+
+        _expat_def_file_toggle(_EXPAT_DTD_OR_GE _EXPAT_COMMENT_DTD_OR_GE)
         _expat_def_file_toggle(EXPAT_ATTR_INFO _EXPAT_COMMENT_ATTR_INFO)
 
         configure_file("${CMAKE_CURRENT_SOURCE_DIR}/lib/libexpat.def.cmake" "${CMAKE_CURRENT_BINARY_DIR}/lib/libexpat.def")

programming_language: Shell
filename: expat.h
change_type: ModificationType.MODIFY
diff: @@ -1038,13 +1038,15 @@ typedef struct {
 XMLPARSEAPI(const XML_Feature *)
 XML_GetFeatureList(void);
 
-#ifdef XML_DTD
-/* Added in Expat 2.4.0. */
+#if defined(XML_DTD) || XML_GE == 1
+/* Added in Expat 2.4.0 for XML_DTD defined and
+ * added in Expat 2.6.0 for XML_GE == 1. */
 XMLPARSEAPI(XML_Bool)
 XML_SetBillionLaughsAttackProtectionMaximumAmplification(
     XML_Parser parser, float maximumAmplificationFactor);
 
-/* Added in Expat 2.4.0. */
+/* Added in Expat 2.4.0 for XML_DTD defined and
+ * added in Expat 2.6.0 for XML_GE == 1. */
 XMLPARSEAPI(XML_Bool)
 XML_SetBillionLaughsAttackProtectionActivationThreshold(
     XML_Parser parser, unsigned long long activationThresholdBytes);

programming_language: C
filename: internal.h
change_type: ModificationType.MODIFY
diff: @@ -154,7 +154,7 @@ extern "C" {
 void _INTERNAL_trim_to_complete_utf8_characters(const char *from,
                                                 const char **fromLimRef);
 
-#if defined(XML_DTD)
+#if defined(XML_DTD) || XML_GE == 1
 unsigned long long testingAccountingGetCountBytesDirect(XML_Parser parser);
 unsigned long long testingAccountingGetCountBytesIndirect(XML_Parser parser);
 const char *unsignedCharToPrintable(unsigned char c);

programming_language: C++
filename: libexpat.def.cmake
change_type: ModificationType.MODIFY
diff: @@ -75,5 +75,5 @@ EXPORTS
   XML_SetHashSalt @67
 ; internal @68 removed with version 2.3.1
 ; added with version 2.4.0
-@_EXPAT_COMMENT_DTD@ XML_SetBillionLaughsAttackProtectionActivationThreshold @69
-@_EXPAT_COMMENT_DTD@ XML_SetBillionLaughsAttackProtectionMaximumAmplification @70
+@_EXPAT_COMMENT_DTD_OR_GE@ XML_SetBillionLaughsAttackProtectionActivationThreshold @69
+@_EXPAT_COMMENT_DTD_OR_GE@ XML_SetBillionLaughsAttackProtectionMaximumAmplification @70

programming_language: PowerShell
filename: xmlparse.c
change_type: ModificationType.MODIFY
diff: @@ -416,7 +416,7 @@ enum XML_Account {
   XML_ACCOUNT_NONE              /* i.e. do not account, was accounted already */
 };
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
 typedef unsigned long long XmlBigCount;
 typedef struct accounting {
   XmlBigCount countBytesDirect;
@@ -432,7 +432,7 @@ typedef struct entity_stats {
   unsigned int maximumDepthSeen;
   unsigned long debugLevel;
 } ENTITY_STATS;
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
 
 typedef enum XML_Error PTRCALL Processor(XML_Parser parser, const char *start,
                                          const char *end, const char **endPtr);
@@ -570,7 +570,7 @@ static XML_Parser parserCreate(const XML_Char *encodingName,
 
 static void parserInit(XML_Parser parser, const XML_Char *encodingName);
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
 static float accountingGetCurrentAmplification(XML_Parser rootParser);
 static void accountingReportStats(XML_Parser originParser, const char *epilog);
 static void accountingOnAbort(XML_Parser originParser);
@@ -593,7 +593,7 @@ static void entityTrackingOnClose(XML_Parser parser, ENTITY *entity,
 
 static XML_Parser getRootParserOf(XML_Parser parser,
                                   unsigned int *outLevelDiff);
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
 
 static unsigned long getDebugLevel(const char *variableName,
                                    unsigned long defaultDebugLevel);
@@ -718,7 +718,7 @@ struct XML_ParserStruct {
   enum XML_ParamEntityParsing m_paramEntityParsing;
 #endif
   unsigned long m_hash_secret_salt;
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
   ACCOUNTING m_accounting;
   ENTITY_STATS m_entity_stats;
 #endif
@@ -1178,7 +1178,7 @@ parserInit(XML_Parser parser, const XML_Char *encodingName) {
 #endif
   parser->m_hash_secret_salt = 0;
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
   memset(&parser->m_accounting, 0, sizeof(ACCOUNTING));
   parser->m_accounting.debugLevel = getDebugLevel("EXPAT_ACCOUNTING_DEBUG", 0u);
   parser->m_accounting.maximumAmplificationFactor
@@ -2534,8 +2534,9 @@ XML_GetFeatureList(void) {
 #ifdef XML_ATTR_INFO
     {XML_FEATURE_ATTR_INFO, XML_L("XML_ATTR_INFO"), 0},
 #endif
-#ifdef XML_DTD
-    /* Added in Expat 2.4.0. */
+#if defined(XML_DTD) || XML_GE == 1
+    /* Added in Expat 2.4.0 for XML_DTD defined and
+     * added in Expat 2.6.0 for XML_GE == 1. */
     {XML_FEATURE_BILLION_LAUGHS_ATTACK_PROTECTION_MAXIMUM_AMPLIFICATION_DEFAULT,
      XML_L("XML_BLAP_MAX_AMP"),
      (long int)
@@ -2550,7 +2551,7 @@ XML_GetFeatureList(void) {
   return features;
 }
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
 XML_Bool XMLCALL
 XML_SetBillionLaughsAttackProtectionMaximumAmplification(
     XML_Parser parser, float maximumAmplificationFactor) {
@@ -2572,7 +2573,7 @@ XML_SetBillionLaughsAttackProtectionActivationThreshold(
   parser->m_accounting.activationThresholdBytes = activationThresholdBytes;
   return XML_TRUE;
 }
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
 
 /* Initially tag->rawName always points into the parse buffer;
    for those TAG instances opened while the current parse buffer was
@@ -2658,13 +2659,13 @@ externalEntityInitProcessor2(XML_Parser parser, const char *start,
   int tok = XmlContentTok(parser->m_encoding, start, end, &next);
   switch (tok) {
   case XML_TOK_BOM:
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     if (! accountingDiffTolerated(parser, tok, start, next, __LINE__,
                                   XML_ACCOUNT_DIRECT)) {
       accountingOnAbort(parser);
       return XML_ERROR_AMPLIFICATION_LIMIT_BREACH;
     }
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
 
     /* If we are at the end of the buffer, this would cause the next stage,
        i.e. externalEntityInitProcessor3, to pass control directly to
@@ -2778,7 +2779,7 @@ doContent(XML_Parser parser, int startTagLevel, const ENCODING *enc,
   for (;;) {
     const char *next = s; /* XmlContentTok doesn't always set the last arg */
     int tok = XmlContentTok(enc, s, end, &next);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     const char *accountAfter
         = ((tok == XML_TOK_TRAILING_RSQB) || (tok == XML_TOK_TRAILING_CR))
               ? (haveMore ? s /* i.e. 0 bytes */ : end)
@@ -2844,14 +2845,14 @@ doContent(XML_Parser parser, int startTagLevel, const ENCODING *enc,
       XML_Char ch = (XML_Char)XmlPredefinedEntityName(
           enc, s + enc->minBytesPerChar, next - enc->minBytesPerChar);
       if (ch) {
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
         /* NOTE: We are replacing 4-6 characters original input for 1 character
          *       so there is no amplification and hence recording without
          *       protection. */
         accountingDiffTolerated(parser, tok, (char *)&ch,
                                 ((char *)&ch) + sizeof(XML_Char), __LINE__,
                                 XML_ACCOUNT_ENTITY_EXPANSION);
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
         if (parser->m_characterDataHandler)
           parser->m_characterDataHandler(parser->m_handlerArg, &ch, 1);
         else if (parser->m_defaultHandler)
@@ -4053,7 +4054,7 @@ doCdataSection(XML_Parser parser, const ENCODING *enc, const char **startPtr,
   for (;;) {
     const char *next = s; /* in case of XML_TOK_NONE or XML_TOK_PARTIAL */
     int tok = XmlCdataSectionTok(enc, s, end, &next);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     if (! accountingDiffTolerated(parser, tok, s, next, __LINE__, account)) {
       accountingOnAbort(parser);
       return XML_ERROR_AMPLIFICATION_LIMIT_BREACH;
@@ -4205,7 +4206,7 @@ doIgnoreSection(XML_Parser parser, const ENCODING *enc, const char **startPtr,
   *eventPP = s;
   *startPtr = NULL;
   tok = XmlIgnoreSectionTok(enc, s, end, &next);
-#  ifdef XML_DTD
+#  if defined(XML_DTD) || XML_GE == 1
   if (! accountingDiffTolerated(parser, tok, s, next, __LINE__,
                                 XML_ACCOUNT_DIRECT)) {
     accountingOnAbort(parser);
@@ -4297,7 +4298,7 @@ processXmlDecl(XML_Parser parser, int isGeneralTextEntity, const char *s,
   const XML_Char *storedversion = NULL;
   int standalone = -1;
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
   if (! accountingDiffTolerated(parser, XML_TOK_XML_DECL, s, next, __LINE__,
                                 XML_ACCOUNT_DIRECT)) {
     accountingOnAbort(parser);
@@ -4504,7 +4505,7 @@ entityValueInitProcessor(XML_Parser parser, const char *s, const char *end,
        is not valid to have multiple BOMs.
     */
     else if (tok == XML_TOK_BOM) {
-#  ifdef XML_DTD
+#  if defined(XML_DTD) || XML_GE == 1
       if (! accountingDiffTolerated(parser, tok, s, next, __LINE__,
                                     XML_ACCOUNT_DIRECT)) {
         accountingOnAbort(parser);
@@ -4720,11 +4721,13 @@ doProlog(XML_Parser parser, const ENCODING *enc, const char *s, const char *end,
       }
     }
     role = XmlTokenRole(&parser->m_prologState, tok, s, next, enc);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     switch (role) {
     case XML_ROLE_INSTANCE_START: // bytes accounted in contentProcessor
     case XML_ROLE_XML_DECL:       // bytes accounted in processXmlDecl
-    case XML_ROLE_TEXT_DECL:      // bytes accounted in processXmlDecl
+#  ifdef XML_DTD
+    case XML_ROLE_TEXT_DECL: // bytes accounted in processXmlDecl
+#  endif
       break;
     default:
       if (! accountingDiffTolerated(parser, tok, s, next, __LINE__, account)) {
@@ -5661,7 +5664,7 @@ epilogProcessor(XML_Parser parser, const char *s, const char *end,
   for (;;) {
     const char *next = NULL;
     int tok = XmlPrologTok(parser->m_encoding, s, end, &next);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     if (! accountingDiffTolerated(parser, tok, s, next, __LINE__,
                                   XML_ACCOUNT_DIRECT)) {
       accountingOnAbort(parser);
@@ -5741,7 +5744,7 @@ processInternalEntity(XML_Parser parser, ENTITY *entity, XML_Bool betweenDecl) {
       return XML_ERROR_NO_MEMORY;
   }
   entity->open = XML_TRUE;
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
   entityTrackingOnOpen(parser, entity, __LINE__);
 #endif
   entity->processed = 0;
@@ -5775,9 +5778,9 @@ processInternalEntity(XML_Parser parser, ENTITY *entity, XML_Bool betweenDecl) {
       entity->processed = (int)(next - textStart);
       parser->m_processor = internalEntityProcessor;
     } else {
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
       entityTrackingOnClose(parser, entity, __LINE__);
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
       entity->open = XML_FALSE;
       parser->m_openInternalEntities = openEntity->next;
       /* put openEntity back in list of free instances */
@@ -5826,7 +5829,7 @@ internalEntityProcessor(XML_Parser parser, const char *s, const char *end,
     return result;
   }
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
   entityTrackingOnClose(parser, entity, __LINE__);
 #endif
   entity->open = XML_FALSE;
@@ -5905,7 +5908,7 @@ appendAttributeValue(XML_Parser parser, const ENCODING *enc, XML_Bool isCdata,
     const char *next
         = ptr; /* XmlAttributeValueTok doesn't always set the last arg */
     int tok = XmlAttributeValueTok(enc, ptr, end, &next);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     if (! accountingDiffTolerated(parser, tok, ptr, next, __LINE__, account)) {
       accountingOnAbort(parser);
       return XML_ERROR_AMPLIFICATION_LIMIT_BREACH;
@@ -5970,14 +5973,14 @@ appendAttributeValue(XML_Parser parser, const ENCODING *enc, XML_Bool isCdata,
       XML_Char ch = (XML_Char)XmlPredefinedEntityName(
           enc, ptr + enc->minBytesPerChar, next - enc->minBytesPerChar);
       if (ch) {
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
         /* NOTE: We are replacing 4-6 characters original input for 1 character
          *       so there is no amplification and hence recording without
          *       protection. */
         accountingDiffTolerated(parser, tok, (char *)&ch,
                                 ((char *)&ch) + sizeof(XML_Char), __LINE__,
                                 XML_ACCOUNT_ENTITY_EXPANSION);
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
         if (! poolAppendChar(pool, ch))
           return XML_ERROR_NO_MEMORY;
         break;
@@ -6055,14 +6058,14 @@ appendAttributeValue(XML_Parser parser, const ENCODING *enc, XML_Bool isCdata,
         enum XML_Error result;
         const XML_Char *textEnd = entity->textPtr + entity->textLen;
         entity->open = XML_TRUE;
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
         entityTrackingOnOpen(parser, entity, __LINE__);
 #endif
         result = appendAttributeValue(parser, parser->m_internalEncoding,
                                       isCdata, (const char *)entity->textPtr,
                                       (const char *)textEnd, pool,
                                       XML_ACCOUNT_ENTITY_EXPANSION);
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
         entityTrackingOnClose(parser, entity, __LINE__);
 #endif
         entity->open = XML_FALSE;
@@ -6118,7 +6121,7 @@ storeEntityValue(XML_Parser parser, const ENCODING *enc,
         = entityTextPtr; /* XmlEntityValueTok doesn't always set the last arg */
     int tok = XmlEntityValueTok(enc, entityTextPtr, entityTextEnd, &next);
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
     if (! accountingDiffTolerated(parser, tok, entityTextPtr, next, __LINE__,
                                   account)) {
       accountingOnAbort(parser);
@@ -7669,7 +7672,7 @@ copyString(const XML_Char *s, const XML_Memory_Handling_Suite *memsuite) {
   return result;
 }
 
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
 
 static float
 accountingGetCurrentAmplification(XML_Parser rootParser) {
@@ -8400,7 +8403,7 @@ unsignedCharToPrintable(unsigned char c) {
   assert(0); /* never gets here */
 }
 
-#endif /* XML_DTD */
+#endif /* defined(XML_DTD) || XML_GE == 1 */
 
 static unsigned long
 getDebugLevel(const char *variableName, unsigned long defaultDebugLevel) {

programming_language: C++
filename: xmlwf.c
change_type: ModificationType.MODIFY
diff: @@ -1096,9 +1096,10 @@ tmain(int argc, XML_Char **argv) {
             " (needs a floating point number greater or equal than 1.0)"));
         exit(XMLWF_EXIT_USAGE_ERROR);
       }
-#ifndef XML_DTD
-      ftprintf(stderr, T("Warning: Given amplification limit ignored") T(
-                           ", xmlwf has been compiled without DTD support.\n"));
+#if ! defined(XML_DTD) && XML_GE == 0
+      ftprintf(stderr,
+               T("Warning: Given amplification limit ignored")
+                   T(", xmlwf has been compiled without DTD/GE support.\n"));
 #endif
       break;
     }
@@ -1117,9 +1118,10 @@ tmain(int argc, XML_Char **argv) {
         exit(XMLWF_EXIT_USAGE_ERROR);
       }
       attackThresholdGiven = XML_TRUE;
-#ifndef XML_DTD
-      ftprintf(stderr, T("Warning: Given attack threshold ignored") T(
-                           ", xmlwf has been compiled without DTD support.\n"));
+#if ! defined(XML_DTD) && XML_GE == 0
+      ftprintf(stderr,
+               T("Warning: Given attack threshold ignored")
+                   T(", xmlwf has been compiled without DTD/GE support.\n"));
 #endif
       break;
     }
@@ -1155,13 +1157,13 @@ tmain(int argc, XML_Char **argv) {
     }
 
     if (attackMaximumAmplification != -1.0f) {
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
       XML_SetBillionLaughsAttackProtectionMaximumAmplification(
           parser, attackMaximumAmplification);
 #endif
     }
     if (attackThresholdGiven) {
-#ifdef XML_DTD
+#if defined(XML_DTD) || XML_GE == 1
       XML_SetBillionLaughsAttackProtectionActivationThreshold(
           parser, attackThresholdBytes);
 #else

programming_language: C