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xerces-c
xerces-c-CVE-2018-1311.patch
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File xerces-c-CVE-2018-1311.patch of Package xerces-c
From e0024267504188e42ace4dd9031d936786914835 Mon Sep 17 00:00:00 2001 From: Karen Arutyunov <karen@codesynthesis.com> Date: Wed, 13 Dec 2023 09:59:07 +0200 Subject: [PATCH] XERCESC-2188 - Use-after-free on external DTD scan (CVE-2018-1311) These are the instructions for observing the bug (before this commit): $ git clone https://github.com/apache/xerces-c.git $ cd xerces-c $ mkdir build $ cd build $ cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=Debug .. $ make -j8 $ cp ../samples/data/personal.xml . $ cat <<EOF >personal.dtd <?xml encoding="ISO-8859-1"?> <!ENTITY % nonExistentEntity SYSTEM "non-existent.ent"> %nonExistentEntity; EOF $ gdb samples/StdInParse (gdb) b IGXMLScanner.cpp:1544 (gdb) run <personal.xml 1544 fReaderMgr.pushReader(reader, declDTD); (gdb) p declDTD $1 = (xercesc_4_0::DTDEntityDecl *) 0x49ac68 (gdb) n 1547 dtdScanner.scanExtSubsetDecl(false, true); (gdb) n 1548 } (gdb) s ... (gdb) s # The Janitor is about to delete the above declDTD. 90 delete fData; (gdb) p fData $1 = (xercesc_4_0::DTDEntityDecl *) 0x49ac68 (gdb) b ReaderMgr.cpp:1024 (gdb) n ... (gdb) n # Now we about to dereference the deleted declDTD. 1024 if (curEntity && !curEntity->isExternal()) (gdb) p curEntity $2 = (const xercesc_4_0::XMLEntityDecl *) 0x49ac68 --- src/xercesc/internal/DGXMLScanner.cpp | 6 +- src/xercesc/internal/IGXMLScanner.cpp | 6 +- src/xercesc/internal/ReaderMgr.cpp | 207 ++++++++++++++++++-------- src/xercesc/internal/ReaderMgr.hpp | 92 ++++++++++-- 4 files changed, 229 insertions(+), 82 deletions(-) diff --git a/src/xercesc/internal/DGXMLScanner.cpp b/src/xercesc/internal/DGXMLScanner.cpp index 43342235a..895dfeb06 100644 --- a/src/xercesc/internal/DGXMLScanner.cpp +++ b/src/xercesc/internal/DGXMLScanner.cpp @@ -1052,13 +1052,12 @@ void DGXMLScanner::scanDocTypeDecl() DTDEntityDecl* declDTD = new (fMemoryManager) DTDEntityDecl(gDTDStr, false, fMemoryManager); declDTD->setSystemId(sysId); declDTD->setIsExternal(true); - Janitor<DTDEntityDecl> janDecl(declDTD); // Mark this one as a throw at end reader->setThrowAtEnd(true); // And push it onto the stack, with its pseudo name - fReaderMgr.pushReader(reader, declDTD); + fReaderMgr.pushReaderAdoptEntity(reader, declDTD); // Tell it its not in an include section dtdScanner.scanExtSubsetDecl(false, true); @@ -2131,13 +2130,12 @@ Grammar* DGXMLScanner::loadDTDGrammar(const InputSource& src, DTDEntityDecl* declDTD = new (fMemoryManager) DTDEntityDecl(gDTDStr, false, fMemoryManager); declDTD->setSystemId(src.getSystemId()); declDTD->setIsExternal(true); - Janitor<DTDEntityDecl> janDecl(declDTD); // Mark this one as a throw at end newReader->setThrowAtEnd(true); // And push it onto the stack, with its pseudo name - fReaderMgr.pushReader(newReader, declDTD); + fReaderMgr.pushReaderAdoptEntity(newReader, declDTD); // If we have a doc type handler and advanced callbacks are enabled, // call the doctype event. diff --git a/src/xercesc/internal/IGXMLScanner.cpp b/src/xercesc/internal/IGXMLScanner.cpp index 912ec0c62..d694b23e6 100644 --- a/src/xercesc/internal/IGXMLScanner.cpp +++ b/src/xercesc/internal/IGXMLScanner.cpp @@ -1535,13 +1535,12 @@ void IGXMLScanner::scanDocTypeDecl() DTDEntityDecl* declDTD = new (fMemoryManager) DTDEntityDecl(gDTDStr, false, fMemoryManager); declDTD->setSystemId(sysId); declDTD->setIsExternal(true); - Janitor<DTDEntityDecl> janDecl(declDTD); // Mark this one as a throw at end reader->setThrowAtEnd(true); // And push it onto the stack, with its pseudo name - fReaderMgr.pushReader(reader, declDTD); + fReaderMgr.pushReaderAdoptEntity(reader, declDTD); // Tell it its not in an include section dtdScanner.scanExtSubsetDecl(false, true); @@ -3098,13 +3097,12 @@ Grammar* IGXMLScanner::loadDTDGrammar(const InputSource& src, DTDEntityDecl* declDTD = new (fMemoryManager) DTDEntityDecl(gDTDStr, false, fMemoryManager); declDTD->setSystemId(src.getSystemId()); declDTD->setIsExternal(true); - Janitor<DTDEntityDecl> janDecl(declDTD); // Mark this one as a throw at end newReader->setThrowAtEnd(true); // And push it onto the stack, with its pseudo name - fReaderMgr.pushReader(newReader, declDTD); + fReaderMgr.pushReaderAdoptEntity(newReader, declDTD); // If we have a doc type handler and advanced callbacks are enabled, // call the doctype event. diff --git a/src/xercesc/internal/ReaderMgr.cpp b/src/xercesc/internal/ReaderMgr.cpp index d14483e3c..9f363a071 100644 --- a/src/xercesc/internal/ReaderMgr.cpp +++ b/src/xercesc/internal/ReaderMgr.cpp @@ -45,12 +45,61 @@ XERCES_CPP_NAMESPACE_BEGIN +// --------------------------------------------------------------------------- +// ReaderMgr::ReaderData: Constructors and Destructor +// --------------------------------------------------------------------------- +ReaderMgr::ReaderData::ReaderData( XMLReader* const reader + , XMLEntityDecl* const entity + , const bool adoptEntity) : + + fReader(reader) + , fEntity(entity) + , fEntityAdopted(adoptEntity) +{ +} + +ReaderMgr::ReaderData::~ReaderData() +{ + delete fReader; + + if (fEntityAdopted) + delete fEntity; +} + +// --------------------------------------------------------------------------- +// ReaderMgr::ReaderData: Getter methods +// --------------------------------------------------------------------------- +XMLReader* ReaderMgr::ReaderData::getReader() const +{ + return fReader; +} + +XMLEntityDecl* ReaderMgr::ReaderData::getEntity() const +{ + return fEntity; +} + +bool ReaderMgr::ReaderData::getEntityAdopted() const +{ + return fEntityAdopted; +} + +// +// This method gives up the entity object ownership but leaves the fEntity +// pointer intact. +// +XMLEntityDecl* ReaderMgr::ReaderData::releaseEntity() +{ + fEntityAdopted = false; + return fEntity; +} + // --------------------------------------------------------------------------- // ReaderMgr: Constructors and Destructor // --------------------------------------------------------------------------- ReaderMgr::ReaderMgr(MemoryManager* const manager) : - fCurEntity(0) + fCurReaderData(0) , fCurReader(0) , fEntityHandler(0) , fEntityStack(0) @@ -66,12 +115,11 @@ ReaderMgr::ReaderMgr(MemoryManager* const manager) : ReaderMgr::~ReaderMgr() { // - // Clean up the reader and entity stacks. Note that we don't own the - // entities, so we don't delete the current entity (and the entity stack - // does not own its elements either, so deleting it will not delete the - // entities it still references!) + // Clean up the reader stack and orphan entities container. Note that + // all adopted entities (potentially contained in fCurReaderData, + // fReaderStack, and fEntityStack) are deleted here. // - delete fCurReader; + delete fCurReaderData; delete fReaderStack; delete fEntityStack; } @@ -357,9 +405,9 @@ void ReaderMgr::cleanStackBackTo(const XMLSize_t readerNum) if (fReaderStack->empty()) ThrowXMLwithMemMgr(RuntimeException, XMLExcepts::RdrMgr_ReaderIdNotFound, fMemoryManager); - delete fCurReader; - fCurReader = fReaderStack->pop(); - fCurEntity = fEntityStack->pop(); + delete fCurReaderData; + fCurReaderData = fReaderStack->pop(); + fCurReader = fCurReaderData->getReader (); } } @@ -795,20 +843,20 @@ const XMLCh* ReaderMgr::getCurrentEncodingStr() const const XMLEntityDecl* ReaderMgr::getCurrentEntity() const { - return fCurEntity; + return fCurReaderData? fCurReaderData->getEntity() : 0; } XMLEntityDecl* ReaderMgr::getCurrentEntity() { - return fCurEntity; + return fCurReaderData? fCurReaderData->getEntity() : 0; } XMLSize_t ReaderMgr::getReaderDepth() const { // If the stack doesn't exist, its obviously zero - if (!fEntityStack) + if (!fReaderStack) return 0; // @@ -816,7 +864,7 @@ XMLSize_t ReaderMgr::getReaderDepth() const // reader. So if there is no current reader and none on the stack, // its zero, else its some non-zero value. // - XMLSize_t retVal = fEntityStack->size(); + XMLSize_t retVal = fReaderStack->size(); if (fCurReader) retVal++; return retVal; @@ -852,7 +900,7 @@ void ReaderMgr::getLastExtEntityInfo(LastExtEntityInfo& lastInfo) const bool ReaderMgr::isScanningPERefOutOfLiteral() const { // If the current reader is not for an entity, then definitely not - if (!fCurEntity) + if (!fCurReaderData || !fCurReaderData->getEntity()) return false; // @@ -867,13 +915,19 @@ bool ReaderMgr::isScanningPERefOutOfLiteral() const return false; } - bool ReaderMgr::pushReader( XMLReader* const reader , XMLEntityDecl* const entity) +{ + return pushReaderAdoptEntity(reader, entity, false); +} + +bool ReaderMgr::pushReaderAdoptEntity( XMLReader* const reader + , XMLEntityDecl* const entity + , const bool adoptEntity) { // // First, if an entity was passed, we have to confirm that this entity - // is not already on the entity stack. If so, then this is a recursive + // is not already on the reader stack. If so, then this is a recursive // entity expansion, so we issue an error and refuse to put the reader // on the stack. // @@ -881,19 +935,30 @@ bool ReaderMgr::pushReader( XMLReader* const reader // nothing to do. If there is no entity stack yet, then of coures it // cannot already be there. // - if (entity && fEntityStack) + if (entity && fReaderStack) { - const XMLSize_t count = fEntityStack->size(); + // @@ Strangely, we don't check the entity at the top of the stack + // (fCurReaderData). Is it a bug? + // + const XMLSize_t count = fReaderStack->size(); const XMLCh* const theName = entity->getName(); for (XMLSize_t index = 0; index < count; index++) { - const XMLEntityDecl* curDecl = fEntityStack->elementAt(index); + const XMLEntityDecl* curDecl = + fReaderStack->elementAt(index)->getEntity(); + if (curDecl) { if (XMLString::equals(theName, curDecl->getName())) { - // Oops, already there so delete reader and return + // Oops, already there so delete reader and entity and + // return. + // delete reader; + + if (adoptEntity) + delete entity; + return false; } } @@ -905,52 +970,37 @@ bool ReaderMgr::pushReader( XMLReader* const reader // tell it it does own its elements. // if (!fReaderStack) - fReaderStack = new (fMemoryManager) RefStackOf<XMLReader>(16, true, fMemoryManager); - - // And the entity stack, which does not own its elements - if (!fEntityStack) - fEntityStack = new (fMemoryManager) RefStackOf<XMLEntityDecl>(16, false, fMemoryManager); + fReaderStack = new (fMemoryManager) RefStackOf<ReaderData>(16, true, fMemoryManager); // - // Push the current reader and entity onto their respective stacks. - // Note that the the current entity can be null if the current reader - // is not for an entity. + // Push the current reader and entity onto the stack. Note that + // the current entity can be null if the current reader is not for + // an entity. // - if (fCurReader) - { - fReaderStack->push(fCurReader); - fEntityStack->push(fCurEntity); - } + if (fCurReaderData) + fReaderStack->push(fCurReaderData); // // Make the passed reader and entity the current top of stack. The // passed entity can (and often is) null. // + fCurReaderData = new (fMemoryManager) ReaderData(reader, entity, adoptEntity); fCurReader = reader; - fCurEntity = entity; return true; } - void ReaderMgr::reset() { // Reset all of the flags fThrowEOE = false; // Delete the current reader and flush the reader stack - delete fCurReader; + delete fCurReaderData; + fCurReaderData = 0; fCurReader = 0; if (fReaderStack) fReaderStack->removeAllElements(); - - // - // And do the same for the entity stack, but don't delete the current - // entity (if any) since we don't own them. - // - fCurEntity = 0; - if (fEntityStack) - fEntityStack->removeAllElements(); } @@ -1014,7 +1064,9 @@ ReaderMgr::getLastExtEntity(const XMLEntityDecl*& itsEntity) const // search the stack; else, keep the reader that we've got since its // either an external entity reader or the main file reader. // - const XMLEntityDecl* curEntity = fCurEntity; + const XMLEntityDecl* curEntity = + fCurReaderData? fCurReaderData->getEntity() : 0; + if (curEntity && !curEntity->isExternal()) { XMLSize_t index = fReaderStack->size(); @@ -1024,7 +1076,7 @@ ReaderMgr::getLastExtEntity(const XMLEntityDecl*& itsEntity) const { // Move down to the previous element and get a pointer to it index--; - curEntity = fEntityStack->elementAt(index); + curEntity = fReaderStack->elementAt(index)->getEntity(); // // If its null or its an external entity, then this reader @@ -1032,12 +1084,12 @@ ReaderMgr::getLastExtEntity(const XMLEntityDecl*& itsEntity) const // if (!curEntity) { - theReader = fReaderStack->elementAt(index); + theReader = fReaderStack->elementAt(index)->getReader (); break; } else if (curEntity->isExternal()) { - theReader = fReaderStack->elementAt(index); + theReader = fReaderStack->elementAt(index)->getReader (); break; } @@ -1048,6 +1100,11 @@ ReaderMgr::getLastExtEntity(const XMLEntityDecl*& itsEntity) const } } + // @@ It feels like we may end up with theReader being from the top of + // the stack (fCurReader) and itsEntity being from the bottom of the + // stack (if there are no null or external entities on the stack). + // Is it a bug? + // itsEntity = curEntity; return theReader; } @@ -1059,31 +1116,59 @@ bool ReaderMgr::popReader() // We didn't get any more, so try to pop off a reader. If the reader // stack is empty, then we are at the end, so return false. // + // @@ It feels like we never pop the reader pushed to the stack first + // (think of fReaderStack empty but fCurReader not null). Is it a + // bug? + // if (fReaderStack->empty()) return false; // - // Remember the current entity, before we pop off a new one. We might + // Remember the current reader, before we pop off a new one. We might // need this to throw the end of entity exception at the end. // - XMLEntityDecl* prevEntity = fCurEntity; + ReaderData* prevReaderData = fCurReaderData; const bool prevReaderThrowAtEnd = fCurReader->getThrowAtEnd(); const XMLSize_t readerNum = fCurReader->getReaderNum(); // - // Delete the current reader and pop a new reader and entity off - // the stacks. + // Pop a new reader and entity off the stack. // - delete fCurReader; - fCurReader = fReaderStack->pop(); - fCurEntity = fEntityStack->pop(); + fCurReaderData = fReaderStack->pop(); + fCurReader = fCurReaderData->getReader(); // // If there was a previous entity, and either the fThrowEOE flag is set - // or reader was marked as such, then throw an end of entity. + // or reader was marked as such, then throw an end of entity. Otherwise, + // delete the previous reader data. // - if (prevEntity && (fThrowEOE || prevReaderThrowAtEnd)) - throw EndOfEntityException(prevEntity, readerNum); + if (prevReaderData->getEntity() && (fThrowEOE || prevReaderThrowAtEnd)) + { + // + // If the entity is adopted, then move it to fEntityStack so that + // its life-time is prolonged to the life-time of this reader + // manager. Also delete the previous reader data before throwing + // EndOfEntityException. + // + XMLEntityDecl* entity; + + if (prevReaderData->getEntityAdopted()) + { + if (!fEntityStack) + fEntityStack = new (fMemoryManager) RefStackOf<XMLEntityDecl>(16, true, fMemoryManager); + + entity = prevReaderData->releaseEntity(); + fEntityStack->push(entity); + } + else + entity = prevReaderData->getEntity(); + + delete prevReaderData; + + throw EndOfEntityException(entity, readerNum); + } + else + delete prevReaderData; while (true) { @@ -1113,9 +1198,9 @@ bool ReaderMgr::popReader() return false; // Else pop again and try it one more time - delete fCurReader; - fCurReader = fReaderStack->pop(); - fCurEntity = fEntityStack->pop(); + delete fCurReaderData; + fCurReaderData = fReaderStack->pop(); + fCurReader = fCurReaderData->getReader(); } return true; } diff --git a/src/xercesc/internal/ReaderMgr.hpp b/src/xercesc/internal/ReaderMgr.hpp index f63b2194e..0855ed77a 100644 --- a/src/xercesc/internal/ReaderMgr.hpp +++ b/src/xercesc/internal/ReaderMgr.hpp @@ -160,6 +160,12 @@ public : XMLReader* const reader , XMLEntityDecl* const entity ); + bool pushReaderAdoptEntity + ( + XMLReader* const reader + , XMLEntityDecl* const entity + , const bool adoptEntity = true + ); void reset(); @@ -208,16 +214,72 @@ private : ReaderMgr(const ReaderMgr&); ReaderMgr& operator=(const ReaderMgr&); + // ----------------------------------------------------------------------- + // Private data types + // ----------------------------------------------------------------------- + class ReaderData : public XMemory + { + public : + // --------------------------------------------------------------------- + // Constructors and Destructor + // --------------------------------------------------------------------- + ReaderData + ( XMLReader* const reader + , XMLEntityDecl* const entity + , const bool adoptEntity + ); + + ~ReaderData(); + + // ---------------------------------------------------------------------- + // Getter methods + // ---------------------------------------------------------------------- + XMLReader* getReader() const; + XMLEntityDecl* getEntity() const; + bool getEntityAdopted() const; + + XMLEntityDecl* releaseEntity(); + + private : + // --------------------------------------------------------------------- + // Unimplemented constructors and operators + // --------------------------------------------------------------------- + ReaderData(); + ReaderData(const ReaderData&); + ReaderData& operator=(const ReaderData&); + + // --------------------------------------------------------------------- + // Private data members + // + // fReader + // This is the pointer to the reader object that must be destroyed + // when this object is destroyed. + // + // fEntity + // fEntityAdopted + // This is the pointer to the entity object that, if adopted, must + // be destroyed when this object is destroyed. + // + // Note that we need to keep up with which of the pushed readers + // are pushed entity values that are being spooled. This is done + // to avoid the problem of recursive definitions. + // --------------------------------------------------------------------- + XMLReader* fReader; + XMLEntityDecl* fEntity; + bool fEntityAdopted; + }; + // ----------------------------------------------------------------------- // Private data members // - // fCurEntity - // This is the current top of stack entity. We pull it off the stack - // and store it here for efficiency. + // fCurReaderData + // This is the current top of the reader data stack. We pull it off + // the stack and store it here for efficiency. // // fCurReader - // This is the current top of stack reader. We pull it off the - // stack and store it here for efficiency. + // This is the reader of the current top of the reader data stack. + // It contains the same value as fCurReaderData->fReader or NULL, + // if fCurReaderData is NULL. We store it here for efficiency. // // fEntityHandler // This is the installed entity handler. Its installed via the @@ -225,10 +287,14 @@ private : // process of creating external entity readers. // // fEntityStack - // We need to keep up with which of the pushed readers are pushed - // entity values that are being spooled. This is done to avoid the - // problem of recursive definitions. This stack consists of refs to - // EntityDecl objects for the pushed entities. + // This is a storage of orphaned XMLEntityDecl objects. The + // popReader() function adds a reader manager-adopted entity object + // to this storage before passing its pointer to the constructor + // of the being thrown EndOfEntityException exception. This makes + // sure that the life-time of an entity exposed to the exception + // handlers is the same as the life-time of reader manager (and so + // normally the life-time of the scanner which embeds the reader + // manager). // // fNextReaderNum // This is the reader serial number value. Each new reader that is @@ -236,8 +302,8 @@ private : // us catch things like partial markup errors and such. // // fReaderStack - // This is the stack of reader references. We own all the readers - // and destroy them when they are used up. + // This is the stack of reader data references. We own all the + // entries and destroy them when they are used up. // // fThrowEOE // This flag controls whether we throw an exception when we hit an @@ -252,12 +318,12 @@ private : // fStandardUriConformant // This flag controls whether we force conformant URI // ----------------------------------------------------------------------- - XMLEntityDecl* fCurEntity; + ReaderData* fCurReaderData; XMLReader* fCurReader; XMLEntityHandler* fEntityHandler; RefStackOf<XMLEntityDecl>* fEntityStack; unsigned int fNextReaderNum; - RefStackOf<XMLReader>* fReaderStack; + RefStackOf<ReaderData>* fReaderStack; bool fThrowEOE; XMLReader::XMLVersion fXMLVersion; bool fStandardUriConformant;
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