Merge pull request #300500 from LeSuisse/expat-CVE-2023-52425-23.11

[23.11] expat: apply patch for CVE-2023-52425

2 files changed, 1451 insertions, 0 deletions

diff --git a/pkgs/development/libraries/expat/CVE-2023-52425.patch b/pkgs/development/libraries/expat/CVE-2023-52425.patch
new file mode 100644
index 0000000000000..741535fd21289
--- /dev/null
+++ b/pkgs/development/libraries/expat/CVE-2023-52425.patch
@@ -0,0 +1,1450 @@
+commit 678a2f7efcaaa977886e055613f2332615aef82c
+Author: Tomas Korbar <tkorbar@redhat.com>
+Date:   Tue Feb 13 13:52:28 2024 +0100
+
+    Fix CVE-2023-52425
+
+diff --git a/doc/reference.html b/doc/reference.html
+index 8b0d47d..a10f3cb 100644
+--- a/doc/reference.html
++++ b/doc/reference.html
+@@ -151,10 +151,11 @@ interface.</p>
+     </ul>
+     </li>
+     <li>
+-      <a href="#billion-laughs">Billion Laughs Attack Protection</a>
++      <a href="#attack-protection">Attack Protection</a>
+       <ul>
+         <li><a href="#XML_SetBillionLaughsAttackProtectionMaximumAmplification">XML_SetBillionLaughsAttackProtectionMaximumAmplification</a></li>
+         <li><a href="#XML_SetBillionLaughsAttackProtectionActivationThreshold">XML_SetBillionLaughsAttackProtectionActivationThreshold</a></li>
++        <li><a href="#XML_SetReparseDeferralEnabled">XML_SetReparseDeferralEnabled</a></li>
+       </ul>
+     </li>
+     <li><a href="#miscellaneous">Miscellaneous Functions</a>
+@@ -2096,11 +2097,7 @@ parse position may be before the beginning of the buffer.</p>
+ return NULL.</p>
+ </div>
+ 
+-<h3><a name="billion-laughs">Billion Laughs Attack Protection</a></h3>
+-
+-<p>The functions in this section configure the built-in
+-  protection against various forms of
+-  <a href="https://en.wikipedia.org/wiki/Billion_laughs_attack">billion laughs attacks</a>.</p>
++<h3><a name="attack-protection">Attack Protection</a><a name="billion-laughs"></a></h3>
+ 
+ <h4 id="XML_SetBillionLaughsAttackProtectionMaximumAmplification">XML_SetBillionLaughsAttackProtectionMaximumAmplification</h4>
+ <pre class="fcndec">
+@@ -2188,6 +2185,27 @@ XML_SetBillionLaughsAttackProtectionActivationThreshold(XML_Parser p,
+   </p>
+ </div>
+ 
++<h4 id="XML_SetReparseDeferralEnabled">XML_SetReparseDeferralEnabled</h4>
++<pre class="fcndec">
++/* Added in Expat 2.6.0. */
++XML_Bool XMLCALL
++XML_SetReparseDeferralEnabled(XML_Parser parser, XML_Bool enabled);
++</pre>
++<div class="fcndef">
++  <p>
++    Large tokens may require many parse calls before enough data is available for Expat to parse it in full.
++    If Expat retried parsing the token on every parse call, parsing could take quadratic time.
++    To avoid this, Expat only retries once a significant amount of new data is available.
++    This function allows disabling this behavior.
++  </p>
++  <p>
++    The <code>enabled</code> argument should be <code>XML_TRUE</code> or <code>XML_FALSE</code>.
++  </p>
++  <p>
++    Returns <code>XML_TRUE</code> on success, and <code>XML_FALSE</code> on error.
++  </p>
++</div>
++
+ <h3><a name="miscellaneous">Miscellaneous functions</a></h3>
+ 
+ <p>The functions in this section either obtain state information from
+diff --git a/doc/xmlwf.xml b/doc/xmlwf.xml
+index 9603abf..3d35393 100644
+--- a/doc/xmlwf.xml
++++ b/doc/xmlwf.xml
+@@ -313,6 +313,16 @@ supports both.
+         </listitem>
+       </varlistentry>
+ 
++      <varlistentry>
++        <term><option>-q</option></term>
++        <listitem>
++          <para>
++            Disable reparse deferral, and allow quadratic parse runtime
++            on large tokens (default: reparse deferral enabled).
++          </para>
++        </listitem>
++      </varlistentry>
++
+       <varlistentry>
+         <term><option>-r</option></term>
+         <listitem>
+diff --git a/lib/expat.h b/lib/expat.h
+index 1c83563..842dd70 100644
+--- a/lib/expat.h
++++ b/lib/expat.h
+@@ -16,6 +16,7 @@
+    Copyright (c) 2016      Thomas Beutlich <tc@tbeu.de>
+    Copyright (c) 2017      Rhodri James <rhodri@wildebeest.org.uk>
+    Copyright (c) 2022      Thijs Schreijer <thijs@thijsschreijer.nl>
++   Copyright (c) 2023      Sony Corporation / Snild Dolkow <snild@sony.com>
+    Licensed under the MIT license:
+ 
+    Permission is  hereby granted,  free of charge,  to any  person obtaining
+@@ -1050,6 +1051,10 @@ XML_SetBillionLaughsAttackProtectionActivationThreshold(
+     XML_Parser parser, unsigned long long activationThresholdBytes);
+ #endif
+ 
++/* Added in Expat 2.6.0. */
++XMLPARSEAPI(XML_Bool)
++XML_SetReparseDeferralEnabled(XML_Parser parser, XML_Bool enabled);
++
+ /* Expat follows the semantic versioning convention.
+    See http://semver.org.
+ */
+diff --git a/lib/internal.h b/lib/internal.h
+index e09f533..e2709c8 100644
+--- a/lib/internal.h
++++ b/lib/internal.h
+@@ -31,6 +31,7 @@
+    Copyright (c) 2016-2022 Sebastian Pipping <sebastian@pipping.org>
+    Copyright (c) 2018      Yury Gribov <tetra2005@gmail.com>
+    Copyright (c) 2019      David Loffredo <loffredo@steptools.com>
++   Copyright (c) 2023      Sony Corporation / Snild Dolkow <snild@sony.com>
+    Licensed under the MIT license:
+ 
+    Permission is  hereby granted,  free of charge,  to any  person obtaining
+@@ -160,6 +161,9 @@ unsigned long long testingAccountingGetCountBytesIndirect(XML_Parser parser);
+ const char *unsignedCharToPrintable(unsigned char c);
+ #endif
+ 
++extern XML_Bool g_reparseDeferralEnabledDefault; // written ONLY in runtests.c
++extern unsigned int g_parseAttempts;             // used for testing only
++
+ #ifdef __cplusplus
+ }
+ #endif
+diff --git a/lib/libexpat.def.cmake b/lib/libexpat.def.cmake
+index cf434a2..3ff4d55 100644
+--- a/lib/libexpat.def.cmake
++++ b/lib/libexpat.def.cmake
+@@ -77,3 +77,4 @@ EXPORTS
+ ; added with version 2.4.0
+ @_EXPAT_COMMENT_DTD@ XML_SetBillionLaughsAttackProtectionActivationThreshold @69
+ @_EXPAT_COMMENT_DTD@ XML_SetBillionLaughsAttackProtectionMaximumAmplification @70
++XML_SetReparseDeferralEnabled @71
+diff --git a/lib/xmlparse.c b/lib/xmlparse.c
+index b6c2eca..2ae64e9 100644
+--- a/lib/xmlparse.c
++++ b/lib/xmlparse.c
+@@ -73,6 +73,7 @@
+ #  endif
+ #endif
+ 
++#include <stdbool.h>
+ #include <stddef.h>
+ #include <string.h> /* memset(), memcpy() */
+ #include <assert.h>
+@@ -196,6 +197,8 @@ typedef char ICHAR;
+ /* Do safe (NULL-aware) pointer arithmetic */
+ #define EXPAT_SAFE_PTR_DIFF(p, q) (((p) && (q)) ? ((p) - (q)) : 0)
+ 
++#define EXPAT_MIN(a, b) (((a) < (b)) ? (a) : (b))
++
+ #include "internal.h"
+ #include "xmltok.h"
+ #include "xmlrole.h"
+@@ -602,6 +605,9 @@ static unsigned long getDebugLevel(const char *variableName,
+        ? 0                                                                     \
+        : ((*((pool)->ptr)++ = c), 1))
+ 
++XML_Bool g_reparseDeferralEnabledDefault = XML_TRUE; // write ONLY in runtests.c
++unsigned int g_parseAttempts = 0;                    // used for testing only
++
+ struct XML_ParserStruct {
+   /* The first member must be m_userData so that the XML_GetUserData
+      macro works. */
+@@ -617,6 +623,9 @@ struct XML_ParserStruct {
+   const char *m_bufferLim;
+   XML_Index m_parseEndByteIndex;
+   const char *m_parseEndPtr;
++  size_t m_partialTokenBytesBefore; /* used in heuristic to avoid O(n^2) */
++  XML_Bool m_reparseDeferralEnabled;
++  int m_lastBufferRequestSize;
+   XML_Char *m_dataBuf;
+   XML_Char *m_dataBufEnd;
+   XML_StartElementHandler m_startElementHandler;
+@@ -948,6 +957,47 @@ get_hash_secret_salt(XML_Parser parser) {
+   return parser->m_hash_secret_salt;
+ }
+ 
++static enum XML_Error
++callProcessor(XML_Parser parser, const char *start, const char *end,
++              const char **endPtr) {
++  const size_t have_now = EXPAT_SAFE_PTR_DIFF(end, start);
++
++  if (parser->m_reparseDeferralEnabled
++      && ! parser->m_parsingStatus.finalBuffer) {
++    // Heuristic: don't try to parse a partial token again until the amount of
++    // available data has increased significantly.
++    const size_t had_before = parser->m_partialTokenBytesBefore;
++    // ...but *do* try anyway if we're close to causing a reallocation.
++    size_t available_buffer
++        = EXPAT_SAFE_PTR_DIFF(parser->m_bufferPtr, parser->m_buffer);
++#if XML_CONTEXT_BYTES > 0
++    available_buffer -= EXPAT_MIN(available_buffer, XML_CONTEXT_BYTES);
++#endif
++    available_buffer
++        += EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_bufferEnd);
++    // m_lastBufferRequestSize is never assigned a value < 0, so the cast is ok
++    const bool enough
++        = (have_now >= 2 * had_before)
++          || ((size_t)parser->m_lastBufferRequestSize > available_buffer);
++
++    if (! enough) {
++      *endPtr = start; // callers may expect this to be set
++      return XML_ERROR_NONE;
++    }
++  }
++  g_parseAttempts += 1;
++  const enum XML_Error ret = parser->m_processor(parser, start, end, endPtr);
++  if (ret == XML_ERROR_NONE) {
++    // if we consumed nothing, remember what we had on this parse attempt.
++    if (*endPtr == start) {
++      parser->m_partialTokenBytesBefore = have_now;
++    } else {
++      parser->m_partialTokenBytesBefore = 0;
++    }
++  }
++  return ret;
++}
++
+ static XML_Bool /* only valid for root parser */
+ startParsing(XML_Parser parser) {
+   /* hash functions must be initialized before setContext() is called */
+@@ -1129,6 +1179,9 @@ parserInit(XML_Parser parser, const XML_Char *encodingName) {
+   parser->m_bufferEnd = parser->m_buffer;
+   parser->m_parseEndByteIndex = 0;
+   parser->m_parseEndPtr = NULL;
++  parser->m_partialTokenBytesBefore = 0;
++  parser->m_reparseDeferralEnabled = g_reparseDeferralEnabledDefault;
++  parser->m_lastBufferRequestSize = 0;
+   parser->m_declElementType = NULL;
+   parser->m_declAttributeId = NULL;
+   parser->m_declEntity = NULL;
+@@ -1298,6 +1351,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser, const XML_Char *context,
+      to worry which hash secrets each table has.
+   */
+   unsigned long oldhash_secret_salt;
++  XML_Bool oldReparseDeferralEnabled;
+ 
+   /* Validate the oldParser parameter before we pull everything out of it */
+   if (oldParser == NULL)
+@@ -1342,6 +1396,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser, const XML_Char *context,
+      to worry which hash secrets each table has.
+   */
+   oldhash_secret_salt = parser->m_hash_secret_salt;
++  oldReparseDeferralEnabled = parser->m_reparseDeferralEnabled;
+ 
+ #ifdef XML_DTD
+   if (! context)
+@@ -1394,6 +1449,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser, const XML_Char *context,
+   parser->m_defaultExpandInternalEntities = oldDefaultExpandInternalEntities;
+   parser->m_ns_triplets = oldns_triplets;
+   parser->m_hash_secret_salt = oldhash_secret_salt;
++  parser->m_reparseDeferralEnabled = oldReparseDeferralEnabled;
+   parser->m_parentParser = oldParser;
+ #ifdef XML_DTD
+   parser->m_paramEntityParsing = oldParamEntityParsing;
+@@ -1848,55 +1904,8 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal) {
+     parser->m_parsingStatus.parsing = XML_PARSING;
+   }
+ 
+-  if (len == 0) {
+-    parser->m_parsingStatus.finalBuffer = (XML_Bool)isFinal;
+-    if (! isFinal)
+-      return XML_STATUS_OK;
+-    parser->m_positionPtr = parser->m_bufferPtr;
+-    parser->m_parseEndPtr = parser->m_bufferEnd;
+-
+-    /* If data are left over from last buffer, and we now know that these
+-       data are the final chunk of input, then we have to check them again
+-       to detect errors based on that fact.
+-    */
+-    parser->m_errorCode
+-        = parser->m_processor(parser, parser->m_bufferPtr,
+-                              parser->m_parseEndPtr, &parser->m_bufferPtr);
+-
+-    if (parser->m_errorCode == XML_ERROR_NONE) {
+-      switch (parser->m_parsingStatus.parsing) {
+-      case XML_SUSPENDED:
+-        /* It is hard to be certain, but it seems that this case
+-         * cannot occur.  This code is cleaning up a previous parse
+-         * with no new data (since len == 0).  Changing the parsing
+-         * state requires getting to execute a handler function, and
+-         * there doesn't seem to be an opportunity for that while in
+-         * this circumstance.
+-         *
+-         * Given the uncertainty, we retain the code but exclude it
+-         * from coverage tests.
+-         *
+-         * LCOV_EXCL_START
+-         */
+-        XmlUpdatePosition(parser->m_encoding, parser->m_positionPtr,
+-                          parser->m_bufferPtr, &parser->m_position);
+-        parser->m_positionPtr = parser->m_bufferPtr;
+-        return XML_STATUS_SUSPENDED;
+-        /* LCOV_EXCL_STOP */
+-      case XML_INITIALIZED:
+-      case XML_PARSING:
+-        parser->m_parsingStatus.parsing = XML_FINISHED;
+-        /* fall through */
+-      default:
+-        return XML_STATUS_OK;
+-      }
+-    }
+-    parser->m_eventEndPtr = parser->m_eventPtr;
+-    parser->m_processor = errorProcessor;
+-    return XML_STATUS_ERROR;
+-  }
+ #ifndef XML_CONTEXT_BYTES
+-  else if (parser->m_bufferPtr == parser->m_bufferEnd) {
++  if (parser->m_bufferPtr == parser->m_bufferEnd) {
+     const char *end;
+     int nLeftOver;
+     enum XML_Status result;
+@@ -1907,12 +1916,15 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal) {
+       parser->m_processor = errorProcessor;
+       return XML_STATUS_ERROR;
+     }
++    // though this isn't a buffer request, we assume that `len` is the app's
++    // preferred buffer fill size, and therefore save it here.
++    parser->m_lastBufferRequestSize = len;
+     parser->m_parseEndByteIndex += len;
+     parser->m_positionPtr = s;
+     parser->m_parsingStatus.finalBuffer = (XML_Bool)isFinal;
+ 
+     parser->m_errorCode
+-        = parser->m_processor(parser, s, parser->m_parseEndPtr = s + len, &end);
++        = callProcessor(parser, s, parser->m_parseEndPtr = s + len, &end);
+ 
+     if (parser->m_errorCode != XML_ERROR_NONE) {
+       parser->m_eventEndPtr = parser->m_eventPtr;
+@@ -1939,23 +1951,25 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal) {
+                       &parser->m_position);
+     nLeftOver = s + len - end;
+     if (nLeftOver) {
+-      if (parser->m_buffer == NULL
+-          || nLeftOver > parser->m_bufferLim - parser->m_buffer) {
+-        /* avoid _signed_ integer overflow */
+-        char *temp = NULL;
+-        const int bytesToAllocate = (int)((unsigned)len * 2U);
+-        if (bytesToAllocate > 0) {
+-          temp = (char *)REALLOC(parser, parser->m_buffer, bytesToAllocate);
+-        }
+-        if (temp == NULL) {
+-          parser->m_errorCode = XML_ERROR_NO_MEMORY;
+-          parser->m_eventPtr = parser->m_eventEndPtr = NULL;
+-          parser->m_processor = errorProcessor;
+-          return XML_STATUS_ERROR;
+-        }
+-        parser->m_buffer = temp;
+-        parser->m_bufferLim = parser->m_buffer + bytesToAllocate;
++      // Back up and restore the parsing status to avoid XML_ERROR_SUSPENDED
++      // (and XML_ERROR_FINISHED) from XML_GetBuffer.
++      const enum XML_Parsing originalStatus = parser->m_parsingStatus.parsing;
++      parser->m_parsingStatus.parsing = XML_PARSING;
++      void *const temp = XML_GetBuffer(parser, nLeftOver);
++      parser->m_parsingStatus.parsing = originalStatus;
++      // GetBuffer may have overwritten this, but we want to remember what the
++      // app requested, not how many bytes were left over after parsing.
++      parser->m_lastBufferRequestSize = len;
++      if (temp == NULL) {
++        // NOTE: parser->m_errorCode has already been set by XML_GetBuffer().
++        parser->m_eventPtr = parser->m_eventEndPtr = NULL;
++        parser->m_processor = errorProcessor;
++        return XML_STATUS_ERROR;
+       }
++      // Since we know that the buffer was empty and XML_CONTEXT_BYTES is 0, we
++      // don't have any data to preserve, and can copy straight into the start
++      // of the buffer rather than the GetBuffer return pointer (which may be
++      // pointing further into the allocated buffer).
+       memcpy(parser->m_buffer, end, nLeftOver);
+     }
+     parser->m_bufferPtr = parser->m_buffer;
+@@ -1967,15 +1981,14 @@ XML_Parse(XML_Parser parser, const char *s, int len, int isFinal) {
+     return result;
+   }
+ #endif /* not defined XML_CONTEXT_BYTES */
+-  else {
+-    void *buff = XML_GetBuffer(parser, len);
+-    if (buff == NULL)
+-      return XML_STATUS_ERROR;
+-    else {
+-      memcpy(buff, s, len);
+-      return XML_ParseBuffer(parser, len, isFinal);
+-    }
++  void *buff = XML_GetBuffer(parser, len);
++  if (buff == NULL)
++    return XML_STATUS_ERROR;
++  if (len > 0) {
++    assert(s != NULL); // make sure s==NULL && len!=0 was rejected above
++    memcpy(buff, s, len);
+   }
++  return XML_ParseBuffer(parser, len, isFinal);
+ }
+ 
+ enum XML_Status XMLCALL
+@@ -2015,8 +2028,8 @@ XML_ParseBuffer(XML_Parser parser, int len, int isFinal) {
+   parser->m_parseEndByteIndex += len;
+   parser->m_parsingStatus.finalBuffer = (XML_Bool)isFinal;
+ 
+-  parser->m_errorCode = parser->m_processor(
+-      parser, start, parser->m_parseEndPtr, &parser->m_bufferPtr);
++  parser->m_errorCode = callProcessor(parser, start, parser->m_parseEndPtr,
++                                      &parser->m_bufferPtr);
+ 
+   if (parser->m_errorCode != XML_ERROR_NONE) {
+     parser->m_eventEndPtr = parser->m_eventPtr;
+@@ -2061,10 +2074,14 @@ XML_GetBuffer(XML_Parser parser, int len) {
+   default:;
+   }
+ 
+-  if (len > EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_bufferEnd)) {
+-#ifdef XML_CONTEXT_BYTES
++  // whether or not the request succeeds, `len` seems to be the app's preferred
++  // buffer fill size; remember it.
++  parser->m_lastBufferRequestSize = len;
++  if (len > EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_bufferEnd)
++      || parser->m_buffer == NULL) {
++#if XML_CONTEXT_BYTES > 0
+     int keep;
+-#endif /* defined XML_CONTEXT_BYTES */
++#endif /* XML_CONTEXT_BYTES > 0 */
+     /* Do not invoke signed arithmetic overflow: */
+     int neededSize = (int)((unsigned)len
+                            + (unsigned)EXPAT_SAFE_PTR_DIFF(
+@@ -2073,7 +2090,7 @@ XML_GetBuffer(XML_Parser parser, int len) {
+       parser->m_errorCode = XML_ERROR_NO_MEMORY;
+       return NULL;
+     }
+-#ifdef XML_CONTEXT_BYTES
++#if XML_CONTEXT_BYTES > 0
+     keep = (int)EXPAT_SAFE_PTR_DIFF(parser->m_bufferPtr, parser->m_buffer);
+     if (keep > XML_CONTEXT_BYTES)
+       keep = XML_CONTEXT_BYTES;
+@@ -2083,10 +2100,11 @@ XML_GetBuffer(XML_Parser parser, int len) {
+       return NULL;
+     }
+     neededSize += keep;
+-#endif /* defined XML_CONTEXT_BYTES */
+-    if (neededSize
+-        <= EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_buffer)) {
+-#ifdef XML_CONTEXT_BYTES
++#endif /* XML_CONTEXT_BYTES > 0 */
++    if (parser->m_buffer && parser->m_bufferPtr
++        && neededSize
++               <= EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_buffer)) {
++#if XML_CONTEXT_BYTES > 0
+       if (keep < EXPAT_SAFE_PTR_DIFF(parser->m_bufferPtr, parser->m_buffer)) {
+         int offset
+             = (int)EXPAT_SAFE_PTR_DIFF(parser->m_bufferPtr, parser->m_buffer)
+@@ -2099,19 +2117,17 @@ XML_GetBuffer(XML_Parser parser, int len) {
+         parser->m_bufferPtr -= offset;
+       }
+ #else
+-      if (parser->m_buffer && parser->m_bufferPtr) {
+-        memmove(parser->m_buffer, parser->m_bufferPtr,
+-                EXPAT_SAFE_PTR_DIFF(parser->m_bufferEnd, parser->m_bufferPtr));
+-        parser->m_bufferEnd
+-            = parser->m_buffer
+-              + EXPAT_SAFE_PTR_DIFF(parser->m_bufferEnd, parser->m_bufferPtr);
+-        parser->m_bufferPtr = parser->m_buffer;
+-      }
+-#endif /* not defined XML_CONTEXT_BYTES */
++      memmove(parser->m_buffer, parser->m_bufferPtr,
++              EXPAT_SAFE_PTR_DIFF(parser->m_bufferEnd, parser->m_bufferPtr));
++      parser->m_bufferEnd
++          = parser->m_buffer
++            + EXPAT_SAFE_PTR_DIFF(parser->m_bufferEnd, parser->m_bufferPtr);
++      parser->m_bufferPtr = parser->m_buffer;
++#endif /* XML_CONTEXT_BYTES > 0 */
+     } else {
+       char *newBuf;
+       int bufferSize
+-          = (int)EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_bufferPtr);
++          = (int)EXPAT_SAFE_PTR_DIFF(parser->m_bufferLim, parser->m_buffer);
+       if (bufferSize == 0)
+         bufferSize = INIT_BUFFER_SIZE;
+       do {
+@@ -2128,7 +2144,7 @@ XML_GetBuffer(XML_Parser parser, int len) {
+         return NULL;
+       }
+       parser->m_bufferLim = newBuf + bufferSize;
+-#ifdef XML_CONTEXT_BYTES
++#if XML_CONTEXT_BYTES > 0
+       if (parser->m_bufferPtr) {
+         memcpy(newBuf, &parser->m_bufferPtr[-keep],
+                EXPAT_SAFE_PTR_DIFF(parser->m_bufferEnd, parser->m_bufferPtr)
+@@ -2158,7 +2174,7 @@ XML_GetBuffer(XML_Parser parser, int len) {
+         parser->m_bufferEnd = newBuf;
+       }
+       parser->m_bufferPtr = parser->m_buffer = newBuf;
+-#endif /* not defined XML_CONTEXT_BYTES */
++#endif /* XML_CONTEXT_BYTES > 0 */
+     }
+     parser->m_eventPtr = parser->m_eventEndPtr = NULL;
+     parser->m_positionPtr = NULL;
+@@ -2208,7 +2224,7 @@ XML_ResumeParser(XML_Parser parser) {
+   }
+   parser->m_parsingStatus.parsing = XML_PARSING;
+ 
+-  parser->m_errorCode = parser->m_processor(
++  parser->m_errorCode = callProcessor(
+       parser, parser->m_bufferPtr, parser->m_parseEndPtr, &parser->m_bufferPtr);
+ 
+   if (parser->m_errorCode != XML_ERROR_NONE) {
+@@ -2561,6 +2577,15 @@ XML_SetBillionLaughsAttackProtectionActivationThreshold(
+ }
+ #endif /* XML_DTD */
+ 
++XML_Bool XMLCALL
++XML_SetReparseDeferralEnabled(XML_Parser parser, XML_Bool enabled) {
++  if (parser != NULL && (enabled == XML_TRUE || enabled == XML_FALSE)) {
++    parser->m_reparseDeferralEnabled = enabled;
++    return XML_TRUE;
++  }
++  return XML_FALSE;
++}
++
+ /* Initially tag->rawName always points into the parse buffer;
+    for those TAG instances opened while the current parse buffer was
+    processed, and not yet closed, we need to store tag->rawName in a more
+@@ -4482,15 +4507,15 @@ entityValueInitProcessor(XML_Parser parser, const char *s, const char *end,
+       parser->m_processor = entityValueProcessor;
+       return entityValueProcessor(parser, next, end, nextPtr);
+     }
+-    /* If we are at the end of the buffer, this would cause XmlPrologTok to
+-       return XML_TOK_NONE on the next call, which would then cause the
+-       function to exit with *nextPtr set to s - that is what we want for other
+-       tokens, but not for the BOM - we would rather like to skip it;
+-       then, when this routine is entered the next time, XmlPrologTok will
+-       return XML_TOK_INVALID, since the BOM is still in the buffer
++    /* XmlPrologTok has now set the encoding based on the BOM it found, and we
++       must move s and nextPtr forward to consume the BOM.
++
++       If we didn't, and got XML_TOK_NONE from the next XmlPrologTok call, we
++       would leave the BOM in the buffer and return. On the next call to this
++       function, our XmlPrologTok call would return XML_TOK_INVALID, since it
++       is not valid to have multiple BOMs.
+     */
+-    else if (tok == XML_TOK_BOM && next == end
+-             && ! parser->m_parsingStatus.finalBuffer) {
++    else if (tok == XML_TOK_BOM) {
+ #  ifdef XML_DTD
+       if (! accountingDiffTolerated(parser, tok, s, next, __LINE__,
+                                     XML_ACCOUNT_DIRECT)) {
+@@ -4500,7 +4525,7 @@ entityValueInitProcessor(XML_Parser parser, const char *s, const char *end,
+ #  endif
+ 
+       *nextPtr = next;
+-      return XML_ERROR_NONE;
++      s = next;
+     }
+     /* 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
+diff --git a/tests/minicheck.c b/tests/minicheck.c
+index 1c65748..f383380 100644
+--- a/tests/minicheck.c
++++ b/tests/minicheck.c
+@@ -208,6 +208,21 @@ srunner_run_all(SRunner *runner, int verbosity) {
+   }
+ }
+ 
++void
++_fail(const char *file, int line, const char *msg) {
++  /* Always print the error message so it isn't lost.  In this case,
++     we have a failure, so there's no reason to be quiet about what
++     it is.
++  */
++  _check_current_filename = file;
++  _check_current_lineno = line;
++  if (msg != NULL) {
++    const int has_newline = (msg[strlen(msg) - 1] == '\n');
++    fprintf(stderr, "ERROR: %s%s", msg, has_newline ? "" : "\n");
++  }
++  longjmp(env, 1);
++}
++
+ void
+ _fail_unless(int condition, const char *file, int line, const char *msg) {
+   /* Always print the error message so it isn't lost.  In this case,
+diff --git a/tests/minicheck.h b/tests/minicheck.h
+index cc1f835..032b54e 100644
+--- a/tests/minicheck.h
++++ b/tests/minicheck.h
+@@ -64,7 +64,14 @@ extern "C" {
+   }                                                                            \
+   }
+ 
+-#define fail(msg) _fail_unless(0, __FILE__, __LINE__, msg)
++
++#  define fail(msg) _fail(__FILE__, __LINE__, msg)
++#  define assert_true(cond)                                                    \
++    do {                                                                       \
++      if (! (cond)) {                                                          \
++        _fail(__FILE__, __LINE__, "check failed: " #cond);                     \
++      }                                                                        \
++    } while (0)
+ 
+ typedef void (*tcase_setup_function)(void);
+ typedef void (*tcase_teardown_function)(void);
+@@ -103,6 +110,11 @@ void _check_set_test_info(char const *function, char const *filename,
+  * Prototypes for the actual implementation.
+  */
+ 
++#  if defined(__GNUC__)
++__attribute__((noreturn))
++#  endif
++void
++_fail(const char *file, int line, const char *msg);
+ void _fail_unless(int condition, const char *file, int line, const char *msg);
+ Suite *suite_create(const char *name);
+ TCase *tcase_create(const char *name);
+diff --git a/tests/runtests.c b/tests/runtests.c
+index 915fa52..941f61d 100644
+--- a/tests/runtests.c
++++ b/tests/runtests.c
+@@ -54,6 +54,7 @@
+ #include <ctype.h>
+ #include <limits.h>
+ #include <stdint.h> /* intptr_t uint64_t */
++#include <time.h>
+ 
+ #if ! defined(__cplusplus)
+ #  include <stdbool.h>
+@@ -1071,7 +1072,7 @@ START_TEST(test_column_number_after_parse) {
+   const char *text = "<tag></tag>";
+   XML_Size colno;
+ 
+-  if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_FALSE)
++  if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_TRUE)
+       == XML_STATUS_ERROR)
+     xml_failure(g_parser);
+   colno = XML_GetCurrentColumnNumber(g_parser);
+@@ -2582,7 +2583,7 @@ START_TEST(test_default_current) {
+   if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_TRUE)
+       == XML_STATUS_ERROR)
+     xml_failure(g_parser);
+-  CharData_CheckXMLChars(&storage, XCS("DCDCDCDCDCDD"));
++  CharData_CheckXMLChars(&storage, XCS("DCDCDCDD"));
+ 
+   /* Again, without the defaulting */
+   XML_ParserReset(g_parser, NULL);
+@@ -2593,7 +2594,7 @@ START_TEST(test_default_current) {
+   if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_TRUE)
+       == XML_STATUS_ERROR)
+     xml_failure(g_parser);
+-  CharData_CheckXMLChars(&storage, XCS("DcccccD"));
++  CharData_CheckXMLChars(&storage, XCS("DcccD"));
+ 
+   /* Now with an internal entity to complicate matters */
+   XML_ParserReset(g_parser, NULL);
+@@ -3946,6 +3947,19 @@ START_TEST(test_get_buffer_3_overflow) {
+ END_TEST
+ #endif // defined(XML_CONTEXT_BYTES)
+ 
++START_TEST(test_getbuffer_allocates_on_zero_len) {
++  for (int first_len = 1; first_len >= 0; first_len--) {
++    XML_Parser parser = XML_ParserCreate(NULL);
++    assert_true(parser != NULL);
++    assert_true(XML_GetBuffer(parser, first_len) != NULL);
++    assert_true(XML_GetBuffer(parser, 0) != NULL);
++    if (XML_ParseBuffer(parser, 0, XML_FALSE) != XML_STATUS_OK)
++      xml_failure(parser);
++    XML_ParserFree(parser);
++  }
++}
++END_TEST
++
+ /* Test position information macros */
+ START_TEST(test_byte_info_at_end) {
+   const char *text = "<doc></doc>";
+@@ -6205,6 +6219,12 @@ START_TEST(test_utf8_in_start_tags) {
+   char doc[1024];
+   size_t failCount = 0;
+ 
++  // we need all the bytes to be parsed, but we don't want the errors that can
++  // trigger on isFinal=XML_TRUE, so we skip the test if the heuristic is on.
++  if (g_reparseDeferralEnabledDefault) {
++    return;
++  }
++
+   for (; i < sizeof(cases) / sizeof(cases[0]); i++) {
+     size_t j = 0;
+     for (; j < sizeof(atNameStart) / sizeof(atNameStart[0]); j++) {
+@@ -6830,6 +6850,613 @@ START_TEST(test_nested_entity_suspend) {
+ }
+ END_TEST
+ 
++/* Regression test for quadratic parsing on large tokens */
++START_TEST(test_big_tokens_take_linear_time) {
++  const char *const too_slow_failure_message
++      = "Compared to the baseline runtime of the first test, this test has a "
++        "slowdown of more than <max_slowdown>. "
++        "Please keep increasing the value by 1 until it reliably passes the "
++        "test on your hardware and open a bug sharing that number with us. "
++        "Thanks in advance!";
++  const struct {
++    const char *pre;
++    const char *post;
++  } text[] = {
++      {"<a>", "</a>"},                      // assumed good, used as baseline
++      {"<b><![CDATA[ value: ", " ]]></b>"}, // CDATA, performed OK before patch
++      {"<c attr='", "'></c>"},              // big attribute, used to be O(N²)
++      {"<d><!-- ", " --></d>"},             // long comment, used to be O(N²)
++      {"<e><", "/></e>"},                   // big elem name, used to be O(N²)
++  };
++  const int num_cases = sizeof(text) / sizeof(text[0]);
++  // For the test we need a <max_slowdown> value that is:
++  // (1) big enough that the test passes reliably (avoiding flaky tests), and
++  // (2) small enough that the test actually catches regressions.
++  const int max_slowdown = 15;
++  char aaaaaa[4096];
++  const int fillsize = (int)sizeof(aaaaaa);
++  const int fillcount = 100;
++
++  memset(aaaaaa, 'a', fillsize);
++
++  if (! g_reparseDeferralEnabledDefault) {
++    return; // heuristic is disabled; we would get O(n^2) and fail.
++  }
++#if defined(_WIN32)
++  if (CLOCKS_PER_SEC < 100000) {
++    // Skip this test if clock() doesn't have reasonably good resolution.
++    // This workaround is only applied to Windows targets, since XSI requires
++    // the value to be 1 000 000 (10x the condition here), and we want to be
++    // very sure that at least one platform in CI can catch regressions.
++    return;
++  }
++#endif
++
++  clock_t baseline = 0;
++  for (int i = 0; i < num_cases; ++i) {
++    XML_Parser parser = XML_ParserCreate(NULL);
++    assert_true(parser != NULL);
++    enum XML_Status status;
++    const clock_t start = clock();
++
++    // parse the start text
++    status = _XML_Parse_SINGLE_BYTES(parser, text[i].pre,
++                                     (int)strlen(text[i].pre), XML_FALSE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++    // parse lots of 'a', failing the test early if it takes too long
++    for (int f = 0; f < fillcount; ++f) {
++      status = _XML_Parse_SINGLE_BYTES(parser, aaaaaa, fillsize, XML_FALSE);
++      if (status != XML_STATUS_OK) {
++        xml_failure(parser);
++      }
++      // i == 0 means we're still calculating the baseline value
++      if (i > 0) {
++        const clock_t now = clock();
++        const clock_t clocks_so_far = now - start;
++        const int slowdown = clocks_so_far / baseline;
++        if (slowdown >= max_slowdown) {
++          fprintf(
++              stderr,
++              "fill#%d: clocks_so_far=%d baseline=%d slowdown=%d max_slowdown=%d\n",
++              f, (int)clocks_so_far, (int)baseline, slowdown, max_slowdown);
++          fail(too_slow_failure_message);
++        }
++      }
++    }
++    // parse the end text
++    status = _XML_Parse_SINGLE_BYTES(parser, text[i].post,
++                                     (int)strlen(text[i].post), XML_TRUE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++
++    // how long did it take in total?
++    const clock_t end = clock();
++    const clock_t taken = end - start;
++    if (i == 0) {
++      assert_true(taken > 0); // just to make sure we don't div-by-0 later
++      baseline = taken;
++    }
++    const int slowdown = taken / baseline;
++    if (slowdown >= max_slowdown) {
++      fprintf(stderr, "taken=%d baseline=%d slowdown=%d max_slowdown=%d\n",
++              (int)taken, (int)baseline, slowdown, max_slowdown);
++      fail(too_slow_failure_message);
++    }
++
++    XML_ParserFree(parser);
++  }
++}
++END_TEST
++
++START_TEST(test_set_reparse_deferral) {
++  const char *const pre = "<d>";
++  const char *const start = "<x attr='";
++  const char *const end = "'></x>";
++  char eeeeee[100];
++  const int fillsize = (int)sizeof(eeeeee);
++  memset(eeeeee, 'e', fillsize);
++
++  for (int enabled = 0; enabled <= 1; enabled += 1) {
++
++    XML_Parser parser = XML_ParserCreate(NULL);
++    assert_true(parser != NULL);
++    assert_true(XML_SetReparseDeferralEnabled(parser, enabled));
++    // pre-grow the buffer to avoid reparsing due to almost-fullness
++    assert_true(XML_GetBuffer(parser, fillsize * 10103) != NULL);
++
++    CharData storage;
++    CharData_Init(&storage);
++    XML_SetUserData(parser, &storage);
++    XML_SetStartElementHandler(parser, start_element_event_handler);
++
++    enum XML_Status status;
++    // parse the start text
++    status = XML_Parse(parser, pre, (int)strlen(pre), XML_FALSE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++    CharData_CheckXMLChars(&storage, XCS("d")); // first element should be done
++
++    // ..and the start of the token
++    status = XML_Parse(parser, start, (int)strlen(start), XML_FALSE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++    CharData_CheckXMLChars(&storage, XCS("d")); // still just the first one
++
++    // try to parse lots of 'e', but the token isn't finished
++    for (int c = 0; c < 100; ++c) {
++      status = XML_Parse(parser, eeeeee, fillsize, XML_FALSE);
++      if (status != XML_STATUS_OK) {
++        xml_failure(parser);
++      }
++    }
++    CharData_CheckXMLChars(&storage, XCS("d")); // *still* just the first one
++
++    // end the <x> token.
++    status = XML_Parse(parser, end, (int)strlen(end), XML_FALSE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++
++    if (enabled) {
++      // In general, we may need to push more data to trigger a reparse attempt,
++      // but in this test, the data is constructed to always require it.
++      CharData_CheckXMLChars(&storage, XCS("d")); // or the test is incorrect
++      // 2x the token length should suffice; the +1 covers the start and end.
++      for (int c = 0; c < 101; ++c) {
++        status = XML_Parse(parser, eeeeee, fillsize, XML_FALSE);
++        if (status != XML_STATUS_OK) {
++          xml_failure(parser);
++        }
++      }
++    }
++    CharData_CheckXMLChars(&storage, XCS("dx")); // the <x> should be done
++
++    XML_ParserFree(parser);
++  }
++}
++END_TEST
++
++struct element_decl_data {
++  XML_Parser parser;
++  int count;
++};
++
++static void
++element_decl_counter(void *userData, const XML_Char *name, XML_Content *model) {
++  UNUSED_P(name);
++  struct element_decl_data *testdata = (struct element_decl_data *)userData;
++  testdata->count += 1;
++  XML_FreeContentModel(testdata->parser, model);
++}
++
++static int
++external_inherited_parser(XML_Parser p, const XML_Char *context,
++                          const XML_Char *base, const XML_Char *systemId,
++                          const XML_Char *publicId) {
++  UNUSED_P(base);
++  UNUSED_P(systemId);
++  UNUSED_P(publicId);
++  const char *const pre = "<!ELEMENT document ANY>\n";
++  const char *const start = "<!ELEMENT ";
++  const char *const end = " ANY>\n";
++  const char *const post = "<!ELEMENT xyz ANY>\n";
++  const int enabled = *(int *)XML_GetUserData(p);
++  char eeeeee[100];
++  char spaces[100];
++  const int fillsize = (int)sizeof(eeeeee);
++  assert_true(fillsize == (int)sizeof(spaces));
++  memset(eeeeee, 'e', fillsize);
++  memset(spaces, ' ', fillsize);
++
++  XML_Parser parser = XML_ExternalEntityParserCreate(p, context, NULL);
++  assert_true(parser != NULL);
++  // pre-grow the buffer to avoid reparsing due to almost-fullness
++  assert_true(XML_GetBuffer(parser, fillsize * 10103) != NULL);
++
++  struct element_decl_data testdata;
++  testdata.parser = parser;
++  testdata.count = 0;
++  XML_SetUserData(parser, &testdata);
++  XML_SetElementDeclHandler(parser, element_decl_counter);
++
++  enum XML_Status status;
++  // parse the initial text
++  status = XML_Parse(parser, pre, (int)strlen(pre), XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  assert_true(testdata.count == 1); // first element should be done
++
++  // ..and the start of the big token
++  status = XML_Parse(parser, start, (int)strlen(start), XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  assert_true(testdata.count == 1); // still just the first one
++
++  // try to parse lots of 'e', but the token isn't finished
++  for (int c = 0; c < 100; ++c) {
++    status = XML_Parse(parser, eeeeee, fillsize, XML_FALSE);
++    if (status != XML_STATUS_OK) {
++      xml_failure(parser);
++    }
++  }
++  assert_true(testdata.count == 1); // *still* just the first one
++
++  // end the big token.
++  status = XML_Parse(parser, end, (int)strlen(end), XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++
++  if (enabled) {
++    // In general, we may need to push more data to trigger a reparse attempt,
++    // but in this test, the data is constructed to always require it.
++    assert_true(testdata.count == 1); // or the test is incorrect
++    // 2x the token length should suffice; the +1 covers the start and end.
++    for (int c = 0; c < 101; ++c) {
++      status = XML_Parse(parser, spaces, fillsize, XML_FALSE);
++      if (status != XML_STATUS_OK) {
++        xml_failure(parser);
++      }
++    }
++  }
++  assert_true(testdata.count == 2); // the big token should be done
++
++  // parse the final text
++  status = XML_Parse(parser, post, (int)strlen(post), XML_TRUE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  assert_true(testdata.count == 3); // after isFinal=XML_TRUE, all must be done
++
++  XML_ParserFree(parser);
++  return XML_STATUS_OK;
++}
++
++START_TEST(test_reparse_deferral_is_inherited) {
++  const char *const text
++      = "<!DOCTYPE document SYSTEM 'something.ext'><document/>";
++  for (int enabled = 0; enabled <= 1; ++enabled) {
++
++    XML_Parser parser = XML_ParserCreate(NULL);
++    assert_true(parser != NULL);
++    XML_SetUserData(parser, (void *)&enabled);
++    XML_SetParamEntityParsing(parser, XML_PARAM_ENTITY_PARSING_ALWAYS);
++    // this handler creates a sub-parser and checks that its deferral behavior
++    // is what we expected, based on the value of `enabled` (in userdata).
++    XML_SetExternalEntityRefHandler(parser, external_inherited_parser);
++    assert_true(XML_SetReparseDeferralEnabled(parser, enabled));
++    if (XML_Parse(parser, text, (int)strlen(text), XML_TRUE) != XML_STATUS_OK)
++      xml_failure(parser);
++
++    XML_ParserFree(parser);
++  }
++}
++END_TEST
++
++START_TEST(test_set_reparse_deferral_on_null_parser) {
++  assert_true(XML_SetReparseDeferralEnabled(NULL, 0) == XML_FALSE);
++  assert_true(XML_SetReparseDeferralEnabled(NULL, 1) == XML_FALSE);
++  assert_true(XML_SetReparseDeferralEnabled(NULL, 10) == XML_FALSE);
++  assert_true(XML_SetReparseDeferralEnabled(NULL, 100) == XML_FALSE);
++  assert_true(XML_SetReparseDeferralEnabled(NULL, (XML_Bool)INT_MIN)
++              == XML_FALSE);
++  assert_true(XML_SetReparseDeferralEnabled(NULL, (XML_Bool)INT_MAX)
++              == XML_FALSE);
++}
++END_TEST
++
++START_TEST(test_set_reparse_deferral_on_the_fly) {
++  const char *const pre = "<d><x attr='";
++  const char *const end = "'></x>";
++  char iiiiii[100];
++  const int fillsize = (int)sizeof(iiiiii);
++  memset(iiiiii, 'i', fillsize);
++
++  XML_Parser parser = XML_ParserCreate(NULL);
++  assert_true(parser != NULL);
++  assert_true(XML_SetReparseDeferralEnabled(parser, XML_TRUE));
++
++  CharData storage;
++  CharData_Init(&storage);
++  XML_SetUserData(parser, &storage);
++  XML_SetStartElementHandler(parser, start_element_event_handler);
++
++  enum XML_Status status;
++  // parse the start text
++  status = XML_Parse(parser, pre, (int)strlen(pre), XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  CharData_CheckXMLChars(&storage, XCS("d")); // first element should be done
++
++  // try to parse some 'i', but the token isn't finished
++  status = XML_Parse(parser, iiiiii, fillsize, XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  CharData_CheckXMLChars(&storage, XCS("d")); // *still* just the first one
++
++  // end the <x> token.
++  status = XML_Parse(parser, end, (int)strlen(end), XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  CharData_CheckXMLChars(&storage, XCS("d")); // not yet.
++
++  // now change the heuristic setting and add *no* data
++  assert_true(XML_SetReparseDeferralEnabled(parser, XML_FALSE));
++  // we avoid isFinal=XML_TRUE, because that would force-bypass the heuristic.
++  status = XML_Parse(parser, "", 0, XML_FALSE);
++  if (status != XML_STATUS_OK) {
++    xml_failure(parser);
++  }
++  CharData_CheckXMLChars(&storage, XCS("dx"));
++
++  XML_ParserFree(parser);
++}
++END_TEST
++
++START_TEST(test_set_bad_reparse_option) {
++  XML_Parser parser = XML_ParserCreate(NULL);
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 2));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 3));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 99));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 127));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 128));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 129));
++  assert_true(XML_FALSE == XML_SetReparseDeferralEnabled(parser, 255));
++  assert_true(XML_TRUE == XML_SetReparseDeferralEnabled(parser, 0));
++  assert_true(XML_TRUE == XML_SetReparseDeferralEnabled(parser, 1));
++  XML_ParserFree(parser);
++}
++END_TEST
++
++static size_t g_totalAlloc = 0;
++static size_t g_biggestAlloc = 0;
++
++static void *
++counting_realloc(void *ptr, size_t size) {
++  g_totalAlloc += size;
++  if (size > g_biggestAlloc) {
++    g_biggestAlloc = size;
++  }
++  return realloc(ptr, size);
++}
++
++static void *
++counting_malloc(size_t size) {
++  return counting_realloc(NULL, size);
++}
++
++START_TEST(test_bypass_heuristic_when_close_to_bufsize) {
++  if (! g_reparseDeferralEnabledDefault) {
++    return; // this test is irrelevant when the deferral heuristic is disabled.
++  }
++
++  const int document_length = 65536;
++  char *const document = (char *)malloc(document_length);
++
++  const XML_Memory_Handling_Suite memfuncs = {
++      counting_malloc,
++      counting_realloc,
++      free,
++  };
++
++  const int leading_list[] = {0, 3, 61, 96, 400, 401, 4000, 4010, 4099, -1};
++  const int bigtoken_list[] = {3000, 4000, 4001, 4096, 4099, 5000, 20000, -1};
++  const int fillsize_list[] = {131, 256, 399, 400, 401, 1025, 4099, 4321, -1};
++
++  for (const int *leading = leading_list; *leading >= 0; leading++) {
++    for (const int *bigtoken = bigtoken_list; *bigtoken >= 0; bigtoken++) {
++      for (const int *fillsize = fillsize_list; *fillsize >= 0; fillsize++) {
++        // start by checking that the test looks reasonably valid
++        assert_true(*leading + *bigtoken <= document_length);
++
++        // put 'x' everywhere; some will be overwritten by elements.
++        memset(document, 'x', document_length);
++        // maybe add an initial tag
++        if (*leading) {
++          assert_true(*leading >= 3); // or the test case is invalid
++          memcpy(document, "<a>", 3);
++        }
++        // add the large token
++        document[*leading + 0] = '<';
++        document[*leading + 1] = 'b';
++        memset(&document[*leading + 2], ' ', *bigtoken - 2); // a spacy token
++        document[*leading + *bigtoken - 1] = '>';
++
++        // 1 for 'b', plus 1 or 0 depending on the presence of 'a'
++        const int expected_elem_total = 1 + (*leading ? 1 : 0);
++
++        XML_Parser parser = XML_ParserCreate_MM(NULL, &memfuncs, NULL);
++        assert_true(parser != NULL);
++
++        CharData storage;
++        CharData_Init(&storage);
++        XML_SetUserData(parser, &storage);
++        XML_SetStartElementHandler(parser, start_element_event_handler);
++
++        g_biggestAlloc = 0;
++        g_totalAlloc = 0;
++        int offset = 0;
++        // fill data until the big token is covered (but not necessarily parsed)
++        while (offset < *leading + *bigtoken) {
++          assert_true(offset + *fillsize <= document_length);
++          const enum XML_Status status
++              = XML_Parse(parser, &document[offset], *fillsize, XML_FALSE);
++          if (status != XML_STATUS_OK) {
++            xml_failure(parser);
++          }
++          offset += *fillsize;
++        }
++        // Now, check that we've had a buffer allocation that could fit the
++        // context bytes and our big token. In order to detect a special case,
++        // we need to know how many bytes of our big token were included in the
++        // first push that contained _any_ bytes of the big token:
++        const int bigtok_first_chunk_bytes = *fillsize - (*leading % *fillsize);
++        if (bigtok_first_chunk_bytes >= *bigtoken && XML_CONTEXT_BYTES == 0) {
++          // Special case: we aren't saving any context, and the whole big token
++          // was covered by a single fill, so Expat may have parsed directly
++          // from our input pointer, without allocating an internal buffer.
++        } else if (*leading < XML_CONTEXT_BYTES) {
++          assert_true(g_biggestAlloc >= *leading + (size_t)*bigtoken);
++        } else {
++          assert_true(g_biggestAlloc >= XML_CONTEXT_BYTES + (size_t)*bigtoken);
++        }
++        // fill data until the big token is actually parsed
++        while (storage.count < expected_elem_total) {
++          const size_t alloc_before = g_totalAlloc;
++          assert_true(offset + *fillsize <= document_length);
++          const enum XML_Status status
++              = XML_Parse(parser, &document[offset], *fillsize, XML_FALSE);
++          if (status != XML_STATUS_OK) {
++            xml_failure(parser);
++          }
++          offset += *fillsize;
++          // since all the bytes of the big token are already in the buffer,
++          // the bufsize ceiling should make us finish its parsing without any
++          // further buffer allocations. We assume that there will be no other
++          // large allocations in this test.
++          assert_true(g_totalAlloc - alloc_before < 4096);
++        }
++        // test-the-test: was our alloc even called?
++        assert_true(g_totalAlloc > 0);
++        // test-the-test: there shouldn't be any extra start elements
++        assert_true(storage.count == expected_elem_total);
++
++        XML_ParserFree(parser);
++      }
++    }
++  }
++  free(document);
++}
++END_TEST
++
++START_TEST(test_varying_buffer_fills) {
++  const int KiB = 1024;
++  const int MiB = 1024 * KiB;
++  const int document_length = 16 * MiB;
++  const int big = 7654321; // arbitrarily chosen between 4 and 8 MiB
++
++  char *const document = (char *)malloc(document_length);
++  assert_true(document != NULL);
++  memset(document, 'x', document_length);
++  document[0] = '<';
++  document[1] = 't';
++  memset(&document[2], ' ', big - 2); // a very spacy token
++  document[big - 1] = '>';
++
++  // Each testcase is a list of buffer fill sizes, terminated by a value < 0.
++  // When reparse deferral is enabled, the final (negated) value is the expected
++  // maximum number of bytes scanned in parse attempts.
++  const int testcases[][30] = {
++      {8 * MiB, -8 * MiB},
++      {4 * MiB, 4 * MiB, -12 * MiB}, // try at 4MB, then 8MB = 12 MB total
++      // zero-size fills shouldn't trigger the bypass
++      {4 * MiB, 0, 4 * MiB, -12 * MiB},
++      {4 * MiB, 0, 0, 4 * MiB, -12 * MiB},
++      {4 * MiB, 0, 1 * MiB, 0, 3 * MiB, -12 * MiB},
++      // try to hit the buffer ceiling only once (at the end)
++      {4 * MiB, 2 * MiB, 1 * MiB, 512 * KiB, 256 * KiB, 256 * KiB, -12 * MiB},
++      // try to hit the same buffer ceiling multiple times
++      {4 * MiB + 1, 2 * MiB, 1 * MiB, 512 * KiB, -25 * MiB},
++
++      // try to hit every ceiling, by always landing 1K shy of the buffer size
++      {1 * KiB, 2 * KiB, 4 * KiB, 8 * KiB, 16 * KiB, 32 * KiB, 64 * KiB,
++       128 * KiB, 256 * KiB, 512 * KiB, 1 * MiB, 2 * MiB, 4 * MiB, -16 * MiB},
++
++      // try to avoid every ceiling, by always landing 1B past the buffer size
++      // the normal 2x heuristic threshold still forces parse attempts.
++      {2 * KiB + 1,          // will attempt 2KiB + 1 ==> total 2KiB + 1
++       2 * KiB, 4 * KiB,     // will attempt 8KiB + 1 ==> total 10KiB + 2
++       8 * KiB, 16 * KiB,    // will attempt 32KiB + 1 ==> total 42KiB + 3
++       32 * KiB, 64 * KiB,   // will attempt 128KiB + 1 ==> total 170KiB + 4
++       128 * KiB, 256 * KiB, // will attempt 512KiB + 1 ==> total 682KiB + 5
++       512 * KiB, 1 * MiB,   // will attempt 2MiB + 1 ==> total 2M + 682K + 6
++       2 * MiB, 4 * MiB,     // will attempt 8MiB + 1 ==> total 10M + 682K + 7
++       -(10 * MiB + 682 * KiB + 7)},
++      // try to avoid every ceiling again, except on our last fill.
++      {2 * KiB + 1,          // will attempt 2KiB + 1 ==> total 2KiB + 1
++       2 * KiB, 4 * KiB,     // will attempt 8KiB + 1 ==> total 10KiB + 2
++       8 * KiB, 16 * KiB,    // will attempt 32KiB + 1 ==> total 42KiB + 3
++       32 * KiB, 64 * KiB,   // will attempt 128KiB + 1 ==> total 170KiB + 4
++       128 * KiB, 256 * KiB, // will attempt 512KiB + 1 ==> total 682KiB + 5
++       512 * KiB, 1 * MiB,   // will attempt 2MiB + 1 ==> total 2M + 682K + 6
++       2 * MiB, 4 * MiB - 1, // will attempt 8MiB ==> total 10M + 682K + 6
++       -(10 * MiB + 682 * KiB + 6)},
++
++      // try to hit ceilings on the way multiple times
++      {512 * KiB + 1, 256 * KiB, 128 * KiB, 128 * KiB - 1, // 1 MiB buffer
++       512 * KiB + 1, 256 * KiB, 128 * KiB, 128 * KiB - 1, // 2 MiB buffer
++       1 * MiB + 1, 512 * KiB, 256 * KiB, 256 * KiB - 1,   // 4 MiB buffer
++       2 * MiB + 1, 1 * MiB, 512 * KiB,                    // 8 MiB buffer
++       // we'll make a parse attempt at every parse call
++       -(45 * MiB + 12)},
++  };
++  const int testcount = sizeof(testcases) / sizeof(testcases[0]);
++  for (int test_i = 0; test_i < testcount; test_i++) {
++    const int *fillsize = testcases[test_i];
++    XML_Parser parser = XML_ParserCreate(NULL);
++    assert_true(parser != NULL);
++    g_parseAttempts = 0;
++
++    CharData storage;
++    CharData_Init(&storage);
++    XML_SetUserData(parser, &storage);
++    XML_SetStartElementHandler(parser, start_element_event_handler);
++
++    int worstcase_bytes = 0; // sum of (buffered bytes at each XML_Parse call)
++    int scanned_bytes = 0;   // sum of (buffered bytes at each actual parse)
++    int offset = 0;
++    while (*fillsize >= 0) {
++      assert_true(offset + *fillsize <= document_length); // or test is invalid
++      const unsigned attempts_before = g_parseAttempts;
++      const enum XML_Status status
++          = XML_Parse(parser, &document[offset], *fillsize, XML_FALSE);
++      if (status != XML_STATUS_OK) {
++        xml_failure(parser);
++      }
++      offset += *fillsize;
++      fillsize++;
++      assert_true(offset <= INT_MAX - worstcase_bytes); // avoid overflow
++      worstcase_bytes += offset; // we might've tried to parse all pending bytes
++      if (g_parseAttempts != attempts_before) {
++        assert_true(g_parseAttempts == attempts_before + 1); // max 1/XML_Parse
++        assert_true(offset <= INT_MAX - scanned_bytes);      // avoid overflow
++        scanned_bytes += offset; // we *did* try to parse all pending bytes
++      }
++    }
++    assert_true(storage.count == 1); // the big token should've been parsed
++    assert_true(scanned_bytes > 0);  // test-the-test: does our counter work?
++    if (g_reparseDeferralEnabledDefault) {
++      // heuristic is enabled; some XML_Parse calls may have deferred reparsing
++      const int max_bytes_scanned = -*fillsize;
++      if (scanned_bytes > max_bytes_scanned) {
++        fprintf(stderr,
++                "bytes scanned in parse attempts: actual=%d limit=%d \n",
++                scanned_bytes, max_bytes_scanned);
++        fail("too many bytes scanned in parse attempts");
++      }
++      assert_true(scanned_bytes <= worstcase_bytes);
++    } else {
++      // heuristic is disabled; every XML_Parse() will have reparsed
++      assert_true(scanned_bytes == worstcase_bytes);
++    }
++
++    XML_ParserFree(parser);
++  }
++  free(document);
++}
++END_TEST
++
++
+ /*
+  * Namespaces tests.
+  */
+@@ -6902,13 +7529,13 @@ START_TEST(test_return_ns_triplet) {
+   if (_XML_Parse_SINGLE_BYTES(g_parser, text, (int)strlen(text), XML_FALSE)
+       == XML_STATUS_ERROR)
+     xml_failure(g_parser);
+-  if (! triplet_start_flag)
+-    fail("triplet_start_checker not invoked");
+   /* Check that unsetting "return triplets" fails while still parsing */
+   XML_SetReturnNSTriplet(g_parser, XML_FALSE);
+   if (_XML_Parse_SINGLE_BYTES(g_parser, epilog, (int)strlen(epilog), XML_TRUE)
+       == XML_STATUS_ERROR)
+     xml_failure(g_parser);
++  if (! triplet_start_flag)
++    fail("triplet_start_checker not invoked");
+   if (! triplet_end_flag)
+     fail("triplet_end_checker not invoked");
+   if (dummy_handler_flags
+@@ -12219,6 +12846,7 @@ make_suite(void) {
+ #if defined(XML_CONTEXT_BYTES)
+   tcase_add_test(tc_basic, test_get_buffer_3_overflow);
+ #endif
++  tcase_add_test(tc_basic, test_getbuffer_allocates_on_zero_len);
+   tcase_add_test(tc_basic, test_byte_info_at_end);
+   tcase_add_test(tc_basic, test_byte_info_at_error);
+   tcase_add_test(tc_basic, test_byte_info_at_cdata);
+@@ -12337,7 +12965,14 @@ make_suite(void) {
+   tcase_add_test__ifdef_xml_dtd(tc_basic,
+                                 test_pool_integrity_with_unfinished_attr);
+   tcase_add_test(tc_basic, test_nested_entity_suspend);
+-
++  tcase_add_test(tc_basic, test_big_tokens_take_linear_time);
++  tcase_add_test(tc_basic, test_set_reparse_deferral);
++  tcase_add_test(tc_basic, test_reparse_deferral_is_inherited);
++  tcase_add_test(tc_basic, test_set_reparse_deferral_on_null_parser);
++  tcase_add_test(tc_basic, test_set_reparse_deferral_on_the_fly);
++  tcase_add_test(tc_basic, test_set_bad_reparse_option);
++  tcase_add_test(tc_basic, test_bypass_heuristic_when_close_to_bufsize);
++  tcase_add_test(tc_basic, test_varying_buffer_fills);
+   suite_add_tcase(s, tc_namespace);
+   tcase_add_checked_fixture(tc_namespace, namespace_setup, namespace_teardown);
+   tcase_add_test(tc_namespace, test_return_ns_triplet);
+diff --git a/xmlwf/xmlwf.c b/xmlwf/xmlwf.c
+index 471f2a2..7c62919 100644
+--- a/xmlwf/xmlwf.c
++++ b/xmlwf/xmlwf.c
+@@ -914,6 +914,9 @@ usage(const XML_Char *prog, int rc) {
+       T("  -a FACTOR     set maximum tolerated [a]mplification factor (default: 100.0)\n")
+       T("  -b BYTES      set number of output [b]ytes needed to activate (default: 8 MiB)\n")
+       T("\n")
++      T("reparse deferral:\n")
++      T("  -q             disable reparse deferral, and allow [q]uadratic parse runtime with large tokens\n")
++      T("\n")
+       T("info arguments:\n")
+       T("  -h            show this [h]elp message and exit\n")
+       T("  -v            show program's [v]ersion number and exit\n")
+@@ -967,6 +970,8 @@ tmain(int argc, XML_Char **argv) {
+   unsigned long long attackThresholdBytes;
+   XML_Bool attackThresholdGiven = XML_FALSE;
+ 
++  XML_Bool disableDeferral = XML_FALSE;
++
+   int exitCode = XMLWF_EXIT_SUCCESS;
+   enum XML_ParamEntityParsing paramEntityParsing
+       = XML_PARAM_ENTITY_PARSING_NEVER;
+@@ -1089,6 +1094,11 @@ tmain(int argc, XML_Char **argv) {
+ #endif
+       break;
+     }
++    case T('q'): {
++      disableDeferral = XML_TRUE;
++      j++;
++      break;
++    }
+     case T('\0'):
+       if (j > 1) {
+         i++;
+@@ -1134,6 +1144,16 @@ tmain(int argc, XML_Char **argv) {
+ #endif
+     }
+ 
++    if (disableDeferral) {
++      const XML_Bool success = XML_SetReparseDeferralEnabled(parser, XML_FALSE);
++      if (! success) {
++        // This prevents tperror(..) from reporting misleading "[..]: Success"
++        errno = EINVAL;
++        tperror(T("Failed to disable reparse deferral"));
++        exit(XMLWF_EXIT_INTERNAL_ERROR);
++      }
++    }
++
+     if (requireStandalone)
+       XML_SetNotStandaloneHandler(parser, notStandalone);
+     XML_SetParamEntityParsing(parser, paramEntityParsing);
+diff --git a/xmlwf/xmlwf_helpgen.py b/xmlwf/xmlwf_helpgen.py
+index c2a527f..1bd0a0a 100755
+--- a/xmlwf/xmlwf_helpgen.py
++++ b/xmlwf/xmlwf_helpgen.py
+@@ -81,6 +81,10 @@ billion_laughs.add_argument('-a', metavar='FACTOR',
+                             help='set maximum tolerated [a]mplification factor (default: 100.0)')
+ billion_laughs.add_argument('-b', metavar='BYTES', help='set number of output [b]ytes needed to activate (default: 8 MiB)')
+ 
++reparse_deferral = parser.add_argument_group('reparse deferral')
++reparse_deferral.add_argument('-q', metavar='FACTOR',
++                            help='disable reparse deferral, and allow [q]uadratic parse runtime with large tokens')
++
+ parser.add_argument('files', metavar='FILE', nargs='*', help='file to process (default: STDIN)')
+ 
+ info = parser.add_argument_group('info arguments')
+diff --git a/testdata/largefiles/aaaaaa_attr.xml b/testdata/largefiles/aaaaaa_attr.xml
+new file mode 100644
+index 0000000..66e3d25
+--- /dev/null
++++ b/testdata/largefiles/aaaaaa_attr.xml
+@@ -0,0 +1 @@
++<myFile><attack value="ACHARS"></attack></myFile>
+\ No newline at end of file
+diff --git a/testdata/largefiles/aaaaaa_cdata.xml b/testdata/largefiles/aaaaaa_cdata.xml
+new file mode 100644
+index 0000000..66f64bd
+--- /dev/null
++++ b/testdata/largefiles/aaaaaa_cdata.xml
+@@ -0,0 +1 @@
++<myFile><attack><![CDATA[ value: ACHARS ]]></attack></myFile>
+\ No newline at end of file
+diff --git a/testdata/largefiles/aaaaaa_comment.xml b/testdata/largefiles/aaaaaa_comment.xml
+new file mode 100644
+index 0000000..bb9af13
+--- /dev/null
++++ b/testdata/largefiles/aaaaaa_comment.xml
+@@ -0,0 +1 @@
++<myFile><attack><!-- value: ACHARS --></attack></myFile>
+\ No newline at end of file
+diff --git a/testdata/largefiles/aaaaaa_tag.xml b/testdata/largefiles/aaaaaa_tag.xml
+new file mode 100644
+index 0000000..946f701
+--- /dev/null
++++ b/testdata/largefiles/aaaaaa_tag.xml
+@@ -0,0 +1 @@
++<myFile><attack><ACHARS /></attack></myFile>
+\ No newline at end of file
+diff --git a/testdata/largefiles/aaaaaa_text.xml b/testdata/largefiles/aaaaaa_text.xml
+new file mode 100644
+index 0000000..e266acb
+--- /dev/null
++++ b/testdata/largefiles/aaaaaa_text.xml
+@@ -0,0 +1 @@
++<myFile><attack>ACHARS</attack></myFile>
+\ No newline at end of file
diff --git a/pkgs/development/libraries/expat/default.nix b/pkgs/development/libraries/expat/default.nix
index d55addc41cc1a..417127d3d2e32 100644
--- a/pkgs/development/libraries/expat/default.nix
+++ b/pkgs/development/libraries/expat/default.nix
@@ -24,6 +24,7 @@ stdenv.mkDerivation rec {
   };
 
   patches = [
+    ./CVE-2023-52425.patch
     ./CVE-2024-28757.patch
   ];