The Tor Browser / file revision

 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* vim: set sw=4 ts=8 et tw=80 : */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #include <string.h>

 #include "prmem.h"

 #include "prprf.h"

 #include "plstr.h"

 #include "plbase64.h"

 #include "nsCRT.h"

 #include "nsMemory.h"

 #include "nsTArray.h"

 #include "nsCOMPtr.h"

 #include "nsEscape.h"

 #include "nsIUTF8ConverterService.h"

 #include "nsUConvCID.h"

 #include "nsIServiceManager.h"

 #include "nsMIMEHeaderParamImpl.h"

 #include "nsReadableUtils.h"

 #include "nsNativeCharsetUtils.h"

 #include "nsError.h"

 #include "nsIUnicodeDecoder.h"

 #include "mozilla/dom/EncodingUtils.h"

 using mozilla::dom::EncodingUtils;

 // static functions declared below are moved from mailnews/mime/src/comi18n.cpp

 static char *DecodeQ(const char *, uint32_t);

 static bool Is7bitNonAsciiString(const char *, uint32_t);

 static void CopyRawHeader(const char *, uint32_t, const char *, nsACString &);

 static nsresult DecodeRFC2047Str(const char *, const char *, bool, nsACString&);

 static nsresult internalDecodeParameter(const nsACString&, const char*,

                                         const char*, bool, bool, nsACString&);

 // XXX The chance of UTF-7 being used in the message header is really

 // low, but in theory it's possible. 

 #define IS_7BIT_NON_ASCII_CHARSET(cset)            \

     (!nsCRT::strncasecmp((cset), "ISO-2022", 8) || \

      !nsCRT::strncasecmp((cset), "HZ-GB", 5)    || \

      !nsCRT::strncasecmp((cset), "UTF-7", 5))   

 NS_IMPL_ISUPPORTS(nsMIMEHeaderParamImpl, nsIMIMEHeaderParam)

 NS_IMETHODIMP 

 nsMIMEHeaderParamImpl::GetParameter(const nsACString& aHeaderVal, 

                                     const char *aParamName,

                                     const nsACString& aFallbackCharset, 

                                     bool aTryLocaleCharset, 

                                     char **aLang, nsAString& aResult)

 {

   return DoGetParameter(aHeaderVal, aParamName, MIME_FIELD_ENCODING,

                         aFallbackCharset, aTryLocaleCharset, aLang, aResult);

 }

 NS_IMETHODIMP 

 nsMIMEHeaderParamImpl::GetParameterHTTP(const nsACString& aHeaderVal, 

                                         const char *aParamName,

                                         const nsACString& aFallbackCharset, 

                                         bool aTryLocaleCharset, 

                                         char **aLang, nsAString& aResult)

 {

   return DoGetParameter(aHeaderVal, aParamName, HTTP_FIELD_ENCODING,

                         aFallbackCharset, aTryLocaleCharset, aLang, aResult);

 }

 // XXX : aTryLocaleCharset is not yet effective.

 nsresult 

 nsMIMEHeaderParamImpl::DoGetParameter(const nsACString& aHeaderVal, 

                                       const char *aParamName,

                                       ParamDecoding aDecoding,

                                       const nsACString& aFallbackCharset, 

                                       bool aTryLocaleCharset, 

                                       char **aLang, nsAString& aResult)

 {

     aResult.Truncate();

     nsresult rv;

     // get parameter (decode RFC 2231/5987 when applicable, as specified by

     // aDecoding (5987 being a subset of 2231) and return charset.)

     nsXPIDLCString med;

     nsXPIDLCString charset;

     rv = DoParameterInternal(PromiseFlatCString(aHeaderVal).get(), aParamName, 

                              aDecoding, getter_Copies(charset), aLang, 

                              getter_Copies(med));

     if (NS_FAILED(rv))

         return rv; 

     // convert to UTF-8 after charset conversion and RFC 2047 decoding 

     // if necessary.

     nsAutoCString str1;

     rv = internalDecodeParameter(med, charset.get(), nullptr, false,

                                  // was aDecoding == MIME_FIELD_ENCODING

                                  // see bug 875615

                                  true,

                                  str1);

     NS_ENSURE_SUCCESS(rv, rv);

     if (!aFallbackCharset.IsEmpty())

     {

         nsAutoCString charset;

         EncodingUtils::FindEncodingForLabel(aFallbackCharset, charset);

         nsAutoCString str2;

         nsCOMPtr<nsIUTF8ConverterService> 

           cvtUTF8(do_GetService(NS_UTF8CONVERTERSERVICE_CONTRACTID));

         if (cvtUTF8 &&

             NS_SUCCEEDED(cvtUTF8->ConvertStringToUTF8(str1, 

                 PromiseFlatCString(aFallbackCharset).get(), false,

                                    !charset.EqualsLiteral("UTF-8"),

                                    1, str2))) {

           CopyUTF8toUTF16(str2, aResult);

           return NS_OK;

         }

     }

     if (IsUTF8(str1)) {

       CopyUTF8toUTF16(str1, aResult);

       return NS_OK;

     }

     if (aTryLocaleCharset && !NS_IsNativeUTF8()) 

       return NS_CopyNativeToUnicode(str1, aResult);

     CopyASCIItoUTF16(str1, aResult);

     return NS_OK;

 }

 // remove backslash-encoded sequences from quoted-strings

 // modifies string in place, potentially shortening it

 void RemoveQuotedStringEscapes(char *src)

 {

   char *dst = src;

   for (char *c = src; *c; ++c)

   {

     if (c[0] == '\\' && c[1])

     {

       // skip backslash if not at end

       ++c;

     }

     *dst++ = *c;

   }

   *dst = 0;

 }

 // true is character is a hex digit

 bool IsHexDigit(char aChar)

 {

   char c = aChar;

   return (c >= 'a' && c <= 'f') ||

          (c >= 'A' && c <= 'F') ||

          (c >= '0' && c <= '9');

 }

 // validate that a C String containing %-escapes is syntactically valid

 bool IsValidPercentEscaped(const char *aValue, int32_t len)

 {

   for (int32_t i = 0; i < len; i++) {

     if (aValue[i] == '%') {

       if (!IsHexDigit(aValue[i + 1]) || !IsHexDigit(aValue[i + 2])) {

         return false;

       }

     }

   }

   return true;

 }

 // Support for continuations (RFC 2231, Section 3)

 // only a sane number supported

 #define MAX_CONTINUATIONS 999

 // part of a continuation

 class Continuation {

   public:

     Continuation(const char *aValue, uint32_t aLength,

                  bool aNeedsPercentDecoding, bool aWasQuotedString) {

       value = aValue;

       length = aLength;

       needsPercentDecoding = aNeedsPercentDecoding;

       wasQuotedString = aWasQuotedString;

     }

     Continuation() {

       // empty constructor needed for nsTArray

       value = 0L;

       length = 0;

       needsPercentDecoding = false;

       wasQuotedString = false;

     }

     ~Continuation() {}

     const char *value;

     uint32_t length;

     bool needsPercentDecoding;

     bool wasQuotedString;

 };

 // combine segments into a single string, returning the allocated string

 // (or nullptr) while emptying the list 

 char *combineContinuations(nsTArray<Continuation>& aArray)

 {

   // Sanity check

   if (aArray.Length() == 0)

     return nullptr;

   // Get an upper bound for the length

   uint32_t length = 0;

   for (uint32_t i = 0; i < aArray.Length(); i++) {

     length += aArray[i].length;

   }

   // Allocate

   char *result = (char *) nsMemory::Alloc(length + 1);

   // Concatenate

   if (result) {

     *result = '\0';

     for (uint32_t i = 0; i < aArray.Length(); i++) {

       Continuation cont = aArray[i];

       if (! cont.value) break;

       char *c = result + strlen(result);

       strncat(result, cont.value, cont.length);

       if (cont.needsPercentDecoding) {

         nsUnescape(c);

       }

       if (cont.wasQuotedString) {

         RemoveQuotedStringEscapes(c);

       }

     }

     // return null if empty value

     if (*result == '\0') {

       nsMemory::Free(result);

       result = nullptr;

     }

   } else {

     // Handle OOM

     NS_WARNING("Out of memory\n");

   }

   return result;

 }

 // add a continuation, return false on error if segment already has been seen

 bool addContinuation(nsTArray<Continuation>& aArray, uint32_t aIndex,

                      const char *aValue, uint32_t aLength,

                      bool aNeedsPercentDecoding, bool aWasQuotedString)

 {

   if (aIndex < aArray.Length() && aArray[aIndex].value) {

     NS_WARNING("duplicate RC2231 continuation segment #\n");

     return false;

   }

   if (aIndex > MAX_CONTINUATIONS) {

     NS_WARNING("RC2231 continuation segment # exceeds limit\n");

     return false;

   }

   if (aNeedsPercentDecoding && aWasQuotedString) {

     NS_WARNING("RC2231 continuation segment can't use percent encoding and quoted string form at the same time\n");

     return false;

   }

   Continuation cont(aValue, aLength, aNeedsPercentDecoding, aWasQuotedString);

   if (aArray.Length() <= aIndex) {

     aArray.SetLength(aIndex + 1);

   }

   aArray[aIndex] = cont;

   return true;

 }

 // parse a segment number; return -1 on error

 int32_t parseSegmentNumber(const char *aValue, int32_t aLen)

 {

   if (aLen < 1) {

     NS_WARNING("segment number missing\n");

     return -1;

   }

   if (aLen > 1 && aValue[0] == '0') {

     NS_WARNING("leading '0' not allowed in segment number\n");

     return -1;

   }

   int32_t segmentNumber = 0;

   for (int32_t i = 0; i < aLen; i++) {

     if (! (aValue[i] >= '0' && aValue[i] <= '9')) {

       NS_WARNING("invalid characters in segment number\n");

       return -1;

     }

     segmentNumber *= 10;

     segmentNumber += aValue[i] - '0';

     if (segmentNumber > MAX_CONTINUATIONS) {

       NS_WARNING("Segment number exceeds sane size\n");

       return -1;

     }

   }

   return segmentNumber;

 }

 // validate a given octet sequence for compliance with the specified

 // encoding

 bool IsValidOctetSequenceForCharset(nsACString& aCharset, const char *aOctets)

 {

   nsCOMPtr<nsIUTF8ConverterService> cvtUTF8(do_GetService

     (NS_UTF8CONVERTERSERVICE_CONTRACTID));

   if (!cvtUTF8) {

     NS_WARNING("Can't get UTF8ConverterService\n");

     return false;

   }

   nsAutoCString tmpRaw;

   tmpRaw.Assign(aOctets);

   nsAutoCString tmpDecoded;

   nsresult rv = cvtUTF8->ConvertStringToUTF8(tmpRaw,

                                              PromiseFlatCString(aCharset).get(),

                                              false, false, 1, tmpDecoded);

   if (rv != NS_OK) {

     // we can't decode; charset may be unsupported, or the octet sequence

     // is broken (illegal or incomplete octet sequence contained)

     NS_WARNING("RFC2231/5987 parameter value does not decode according to specified charset\n");

     return false;

   }

   return true;

 }

 // moved almost verbatim from mimehdrs.cpp

 // char *

 // MimeHeaders_get_parameter (const char *header_value, const char *parm_name,

 //                            char **charset, char **language)

 //

 // The format of these header lines  is

 // <token> [ ';' <token> '=' <token-or-quoted-string> ]*

 NS_IMETHODIMP 

 nsMIMEHeaderParamImpl::GetParameterInternal(const char *aHeaderValue, 

                                             const char *aParamName,

                                             char **aCharset,

                                             char **aLang,

                                             char **aResult)

 {

   return DoParameterInternal(aHeaderValue, aParamName, MIME_FIELD_ENCODING,

                              aCharset, aLang, aResult);

 }

 nsresult 

 nsMIMEHeaderParamImpl::DoParameterInternal(const char *aHeaderValue, 

                                            const char *aParamName,

                                            ParamDecoding aDecoding,

                                            char **aCharset,

                                            char **aLang,

                                            char **aResult)

 {

   if (!aHeaderValue ||  !*aHeaderValue || !aResult)

     return NS_ERROR_INVALID_ARG;

   *aResult = nullptr;

   if (aCharset) *aCharset = nullptr;

   if (aLang) *aLang = nullptr;

   nsAutoCString charset;

   // change to (aDecoding != HTTP_FIELD_ENCODING) when we want to disable

   // them for HTTP header fields later on, see bug 776324

   bool acceptContinuations = true;

   const char *str = aHeaderValue;

   // skip leading white space.

   for (; *str &&  nsCRT::IsAsciiSpace(*str); ++str)

     ;

   const char *start = str;

   // aParamName is empty. return the first (possibly) _unnamed_ 'parameter'

   // For instance, return 'inline' in the following case:

   // Content-Disposition: inline; filename=.....

   if (!aParamName || !*aParamName) 

     {

       for (; *str && *str != ';' && !nsCRT::IsAsciiSpace(*str); ++str)

         ;

       if (str == start)

         return NS_ERROR_FIRST_HEADER_FIELD_COMPONENT_EMPTY;

       *aResult = (char *) nsMemory::Clone(start, (str - start) + 1);

       NS_ENSURE_TRUE(*aResult, NS_ERROR_OUT_OF_MEMORY);

       (*aResult)[str - start] = '\0';  // null-terminate

       return NS_OK;

     }

   /* Skip forward to first ';' */

   for (; *str && *str != ';' && *str != ','; ++str)

     ;

   if (*str)

     str++;

   /* Skip over following whitespace */

   for (; *str && nsCRT::IsAsciiSpace(*str); ++str)

     ;

   // Some broken http servers just specify parameters

   // like 'filename' without specifying disposition

   // method. Rewind to the first non-white-space

   // character.

   if (!*str)

     str = start;

   // RFC2231 - The legitimate parm format can be:

   // A. title=ThisIsTitle 

   // B. title*=us-ascii'en-us'This%20is%20wierd.

   // C. title*0*=us-ascii'en'This%20is%20wierd.%20We

   //    title*1*=have%20to%20support%20this.

   //    title*2="Else..."

   // D. title*0="Hey, what you think you are doing?"

   //    title*1="There is no charset and lang info."

   // RFC5987: only A and B

   // collect results for the different algorithms (plain filename,

   // RFC5987/2231-encoded filename, + continuations) separately and decide

   // which to use at the end

   char *caseAResult = nullptr;

   char *caseBResult = nullptr;

   char *caseCDResult = nullptr;

   // collect continuation segments

   nsTArray<Continuation> segments;

   // our copies of the charset parameter, kept separately as they might

   // differ for the two formats

   nsDependentCSubstring charsetB, charsetCD;

   nsDependentCSubstring lang;

   int32_t paramLen = strlen(aParamName);

   while (*str) {

     // find name/value

     const char *nameStart = str;

     const char *nameEnd = nullptr;

     const char *valueStart = str;

     const char *valueEnd = nullptr;

     bool isQuotedString = false;

     NS_ASSERTION(!nsCRT::IsAsciiSpace(*str), "should be after whitespace.");

     // Skip forward to the end of this token. 

     for (; *str && !nsCRT::IsAsciiSpace(*str) && *str != '=' && *str != ';'; str++)

       ;

     nameEnd = str;

     int32_t nameLen = nameEnd - nameStart;

     // Skip over whitespace, '=', and whitespace

     while (nsCRT::IsAsciiSpace(*str)) ++str;

     if (!*str) {

       break;

     }

     if (*str++ != '=') {

       // don't accept parameters without "="

       goto increment_str;

     }

     while (nsCRT::IsAsciiSpace(*str)) ++str;

     if (*str != '"') {

       // The value is a token, not a quoted string.

       valueStart = str;

       for (valueEnd = str;

            *valueEnd && !nsCRT::IsAsciiSpace (*valueEnd) && *valueEnd != ';';

            valueEnd++)

         ;

       str = valueEnd;

     } else {

       isQuotedString = true;

       ++str;

       valueStart = str;

       for (valueEnd = str; *valueEnd; ++valueEnd) {

         if (*valueEnd == '\\' && *(valueEnd + 1))

           ++valueEnd;

         else if (*valueEnd == '"')

           break;

       }

       str = valueEnd;

       // *valueEnd != null means that *valueEnd is quote character.

       if (*valueEnd)

         str++;

     }

     // See if this is the simplest case (case A above),

     // a 'single' line value with no charset and lang.

     // If so, copy it and return.

     if (nameLen == paramLen &&

         !nsCRT::strncasecmp(nameStart, aParamName, paramLen)) {

       if (caseAResult) {

         // we already have one caseA result, ignore subsequent ones

         goto increment_str;

       }

       // if the parameter spans across multiple lines we have to strip out the

       //     line continuation -- jht 4/29/98 

       nsAutoCString tempStr(valueStart, valueEnd - valueStart);

       tempStr.StripChars("\r\n");

       char *res = ToNewCString(tempStr);

       NS_ENSURE_TRUE(res, NS_ERROR_OUT_OF_MEMORY);

       if (isQuotedString)

         RemoveQuotedStringEscapes(res);

       caseAResult = res;

       // keep going, we may find a RFC 2231/5987 encoded alternative

     }

     // case B, C, and D

     else if (nameLen > paramLen &&

              !nsCRT::strncasecmp(nameStart, aParamName, paramLen) &&

              *(nameStart + paramLen) == '*') {

       // 1st char past '*'       

       const char *cp = nameStart + paramLen + 1; 

       // if param name ends in "*" we need do to RFC5987 "ext-value" decoding

       bool needExtDecoding = *(nameEnd - 1) == '*';      

       bool caseB = nameLen == paramLen + 1;

       bool caseCStart = (*cp == '0') && needExtDecoding;

       // parse the segment number

       int32_t segmentNumber = -1;

       if (!caseB) {

         int32_t segLen = (nameEnd - cp) - (needExtDecoding ? 1 : 0);

         segmentNumber = parseSegmentNumber(cp, segLen);

         if (segmentNumber == -1) {

           acceptContinuations = false;

           goto increment_str;

         }

       }

       // CaseB and start of CaseC: requires charset and optional language

       // in quotes (quotes required even if lang is blank)

       if (caseB || (caseCStart && acceptContinuations)) {

         // look for single quotation mark(')

         const char *sQuote1 = PL_strchr(valueStart, 0x27);

         const char *sQuote2 = sQuote1 ? PL_strchr(sQuote1 + 1, 0x27) : nullptr;

         // Two single quotation marks must be present even in

         // absence of charset and lang. 

         if (!sQuote1 || !sQuote2) {

           NS_WARNING("Mandatory two single quotes are missing in header parameter\n");

         }

         const char *charsetStart = nullptr;

         int32_t charsetLength = 0;

         const char *langStart = nullptr;

         int32_t langLength = 0;

         const char *rawValStart = nullptr;

         int32_t rawValLength = 0;

         if (sQuote2 && sQuote1) {

           // both delimiters present: charSet'lang'rawVal

           rawValStart = sQuote2 + 1;

           rawValLength = valueEnd - rawValStart;

           langStart = sQuote1 + 1;

           langLength = sQuote2 - langStart;

           charsetStart = valueStart;

           charsetLength = sQuote1 - charsetStart;

         }

         else if (sQuote1) {

           // one delimiter; assume charset'rawVal

           rawValStart = sQuote1 + 1;

           rawValLength = valueEnd - rawValStart;

           charsetStart = valueStart;

           charsetLength = sQuote1 - valueStart;

         }

         else {

           // no delimiter: just rawVal

           rawValStart = valueStart;

           rawValLength = valueEnd - valueStart;

         }

         if (langLength != 0) {

           lang.Assign(langStart, langLength);

         }

         // keep the charset for later

         if (caseB) {

           charsetB.Assign(charsetStart, charsetLength);

         } else {

           // if caseCorD

           charsetCD.Assign(charsetStart, charsetLength);

         }

         // non-empty value part

         if (rawValLength > 0) {

           if (!caseBResult && caseB) {

             if (!IsValidPercentEscaped(rawValStart, rawValLength)) {

               goto increment_str;

             }

             // allocate buffer for the raw value

             char *tmpResult = (char *) nsMemory::Clone(rawValStart, rawValLength + 1);

             if (!tmpResult) {

               goto increment_str;

             }

             *(tmpResult + rawValLength) = 0;

             nsUnescape(tmpResult);

             caseBResult = tmpResult;

           } else {

             // caseC

             bool added = addContinuation(segments, 0, rawValStart,

                                          rawValLength, needExtDecoding,

                                          isQuotedString);

             if (!added) {

               // continuation not added, stop processing them

               acceptContinuations = false;

             }

           }

         }

       }  // end of if-block :  title*0*=  or  title*= 

       // caseD: a line of multiline param with no need for unescaping : title*[0-9]=

       // or 2nd or later lines of a caseC param : title*[1-9]*= 

       else if (acceptContinuations && segmentNumber != -1) {

         uint32_t valueLength = valueEnd - valueStart;

         bool added = addContinuation(segments, segmentNumber, valueStart,

                                      valueLength, needExtDecoding,

                                      isQuotedString);

         if (!added) {

           // continuation not added, stop processing them

           acceptContinuations = false;

         }

       } // end of if-block :  title*[0-9]= or title*[1-9]*=

     }

     // str now points after the end of the value.

     //   skip over whitespace, ';', whitespace.

 increment_str:      

     while (nsCRT::IsAsciiSpace(*str)) ++str;

     if (*str == ';') {

       ++str;

     } else {

       // stop processing the header field; either we are done or the

       // separator was missing

       break;

     }

     while (nsCRT::IsAsciiSpace(*str)) ++str;

   }

   caseCDResult = combineContinuations(segments);

   if (caseBResult && !charsetB.IsEmpty()) {

     // check that the 2231/5987 result decodes properly given the

     // specified character set

     if (!IsValidOctetSequenceForCharset(charsetB, caseBResult))

       caseBResult = nullptr;

   }

   if (caseCDResult && !charsetCD.IsEmpty()) {

     // check that the 2231/5987 result decodes properly given the

     // specified character set

     if (!IsValidOctetSequenceForCharset(charsetCD, caseCDResult))

       caseCDResult = nullptr;

   }

   if (caseBResult) {

     // prefer simple 5987 format over 2231 with continuations

     *aResult = caseBResult;

     caseBResult = nullptr;

     charset.Assign(charsetB);

   }

   else if (caseCDResult) {

     // prefer 2231/5987 with or without continuations over plain format

     *aResult = caseCDResult;

     caseCDResult = nullptr;

     charset.Assign(charsetCD);

   }

   else if (caseAResult) {

     *aResult = caseAResult;

     caseAResult = nullptr;

   }

   // free unused stuff

   nsMemory::Free(caseAResult);

   nsMemory::Free(caseBResult);

   nsMemory::Free(caseCDResult);

   // if we have a result

   if (*aResult) {

     // then return charset and lang as well

     if (aLang && !lang.IsEmpty()) {

       uint32_t len = lang.Length();

       *aLang = (char *) nsMemory::Clone(lang.BeginReading(), len + 1);

       if (*aLang) {

         *(*aLang + len) = 0;

       }

    }

     if (aCharset && !charset.IsEmpty()) {

       uint32_t len = charset.Length();

       *aCharset = (char *) nsMemory::Clone(charset.BeginReading(), len + 1);

       if (*aCharset) {

         *(*aCharset + len) = 0;

       }

     }

   }

   return *aResult ? NS_OK : NS_ERROR_INVALID_ARG;

 }

 nsresult

 internalDecodeRFC2047Header(const char* aHeaderVal, const char* aDefaultCharset,

                             bool aOverrideCharset, bool aEatContinuations,

                             nsACString& aResult)

 {

   aResult.Truncate();

   if (!aHeaderVal)

     return NS_ERROR_INVALID_ARG;

   if (!*aHeaderVal)

     return NS_OK;

   // If aHeaderVal is RFC 2047 encoded or is not a UTF-8 string  but

   // aDefaultCharset is specified, decodes RFC 2047 encoding and converts

   // to UTF-8. Otherwise, just strips away CRLF. 

   if (PL_strstr(aHeaderVal, "=?") || 

       (aDefaultCharset && (!IsUTF8(nsDependentCString(aHeaderVal)) || 

       Is7bitNonAsciiString(aHeaderVal, strlen(aHeaderVal))))) {

     DecodeRFC2047Str(aHeaderVal, aDefaultCharset, aOverrideCharset, aResult);

   } else if (aEatContinuations && 

              (PL_strchr(aHeaderVal, '\n') || PL_strchr(aHeaderVal, '\r'))) {

     aResult = aHeaderVal;

   } else {

     aEatContinuations = false;

     aResult = aHeaderVal;

   }

   if (aEatContinuations) {

     nsAutoCString temp(aResult);

     temp.ReplaceSubstring("\n\t", " ");

     temp.ReplaceSubstring("\r\t", " ");

     temp.StripChars("\r\n");

     aResult = temp;

   }

   return NS_OK;

 }

 NS_IMETHODIMP

 nsMIMEHeaderParamImpl::DecodeRFC2047Header(const char* aHeaderVal, 

                                            const char* aDefaultCharset, 

                                            bool aOverrideCharset, 

                                            bool aEatContinuations,

                                            nsACString& aResult)

 {

   return internalDecodeRFC2047Header(aHeaderVal, aDefaultCharset,

                                      aOverrideCharset, aEatContinuations,

                                      aResult);

 }

 // true if the character is allowed in a RFC 5987 value

 // see RFC 5987, Section 3.2.1, "attr-char"

 bool IsRFC5987AttrChar(char aChar)

 {

   char c = aChar;

   return (c >= 'a' && c <= 'z') ||

          (c >= 'A' && c <= 'Z') ||

          (c >= '0' && c <= '9') ||

          (c == '!' || c == '#' || c == '$' || c == '&' ||

           c == '+' || c == '-' || c == '.' || c == '^' ||

           c == '_' || c == '`' || c == '|' || c == '~');

 }

 // percent-decode a value

 // returns false on failure

 bool PercentDecode(nsACString& aValue)

 {

   char *c = (char *) nsMemory::Alloc(aValue.Length() + 1);

   if (!c) {

     return false;

   }

   strcpy(c, PromiseFlatCString(aValue).get());

   nsUnescape(c);

   aValue.Assign(c);

   nsMemory::Free(c);

   return true;

 }

 // Decode a parameter value using the encoding defined in RFC 5987

 // 

 // charset  "'" [ language ] "'" value-chars

 NS_IMETHODIMP 

 nsMIMEHeaderParamImpl::DecodeRFC5987Param(const nsACString& aParamVal,

                                           nsACString& aLang,

                                           nsAString& aResult)

 {

   nsAutoCString charset;

   nsAutoCString language;

   nsAutoCString value;

   uint32_t delimiters = 0;

   const char *encoded = PromiseFlatCString(aParamVal).get();

   const char *c = encoded;

   while (*c) {

     char tc = *c++;

     if (tc == '\'') {

       // single quote

       delimiters++;

     } else if (((unsigned char)tc) >= 128) {

       // fail early, not ASCII

       NS_WARNING("non-US-ASCII character in RFC5987-encoded param");

       return NS_ERROR_INVALID_ARG;

     } else {

       if (delimiters == 0) {

         // valid characters are checked later implicitly

         charset.Append(tc);

       } else if (delimiters == 1) {

         // no value checking for now

         language.Append(tc);

       } else if (delimiters == 2) {

         if (IsRFC5987AttrChar(tc)) {

           value.Append(tc);

         } else if (tc == '%') {

           if (!IsHexDigit(c[0]) || !IsHexDigit(c[1])) {

             // we expect two more characters

             NS_WARNING("broken %-escape in RFC5987-encoded param");

             return NS_ERROR_INVALID_ARG;

           }

           value.Append(tc);

           // we consume two more

           value.Append(*c++);

           value.Append(*c++);

         } else {

           // character not allowed here

           NS_WARNING("invalid character in RFC5987-encoded param");

           return NS_ERROR_INVALID_ARG;

         }      

       }

     }

   }

   if (delimiters != 2) {

     NS_WARNING("missing delimiters in RFC5987-encoded param");

     return NS_ERROR_INVALID_ARG;

   }

   // abort early for unsupported encodings

   if (!charset.LowerCaseEqualsLiteral("utf-8")) {

     NS_WARNING("unsupported charset in RFC5987-encoded param");

     return NS_ERROR_INVALID_ARG;

   }

   // percent-decode

   if (!PercentDecode(value)) {

     return NS_ERROR_OUT_OF_MEMORY;

   }

   // return the encoding

   aLang.Assign(language);

   // finally convert octet sequence to UTF-8 and be done

   nsresult rv = NS_OK;

   nsCOMPtr<nsIUTF8ConverterService> cvtUTF8 =

     do_GetService(NS_UTF8CONVERTERSERVICE_CONTRACTID, &rv);

   NS_ENSURE_SUCCESS(rv, rv);

   nsAutoCString utf8;

   rv = cvtUTF8->ConvertStringToUTF8(value, charset.get(), true, false, 1, utf8);

   NS_ENSURE_SUCCESS(rv, rv);

   CopyUTF8toUTF16(utf8, aResult);

   return NS_OK;

 }

 nsresult 

 internalDecodeParameter(const nsACString& aParamValue, const char* aCharset,

                         const char* aDefaultCharset, bool aOverrideCharset,

                         bool aDecode2047, nsACString& aResult)

 {

   aResult.Truncate();

   // If aCharset is given, aParamValue was obtained from RFC2231/5987 

   // encoding and we're pretty sure that it's in aCharset.

   if (aCharset && *aCharset)

   {

     nsCOMPtr<nsIUTF8ConverterService> cvtUTF8(do_GetService(NS_UTF8CONVERTERSERVICE_CONTRACTID));

     if (cvtUTF8)

       return cvtUTF8->ConvertStringToUTF8(aParamValue, aCharset,

           true, true, 1, aResult);

   }

   const nsAFlatCString& param = PromiseFlatCString(aParamValue);

   nsAutoCString unQuoted;

   nsACString::const_iterator s, e;

   param.BeginReading(s);

   param.EndReading(e);

   // strip '\' when used to quote CR, LF, '"' and '\'

   for ( ; s != e; ++s) {

     if ((*s == '\\')) {

       if (++s == e) {

         --s; // '\' is at the end. move back and append '\'.

       }

       else if (*s != nsCRT::CR && *s != nsCRT::LF && *s != '"' && *s != '\\') {

         --s; // '\' is not foll. by CR,LF,'"','\'. move back and append '\'

       }

       // else : skip '\' and append the quoted character.

     }

     unQuoted.Append(*s);

   }

   aResult = unQuoted;

   nsresult rv = NS_OK;

   if (aDecode2047) {

     nsAutoCString decoded;

     // Try RFC 2047 encoding, instead.

     rv = internalDecodeRFC2047Header(unQuoted.get(), aDefaultCharset,

                                      aOverrideCharset, true, decoded);

     if (NS_SUCCEEDED(rv) && !decoded.IsEmpty())

       aResult = decoded;

   }

   return rv;

 }

 NS_IMETHODIMP

 nsMIMEHeaderParamImpl::DecodeParameter(const nsACString& aParamValue,

                                        const char* aCharset,

                                        const char* aDefaultCharset,

                                        bool aOverrideCharset,

                                        nsACString& aResult)

 {

   return internalDecodeParameter(aParamValue, aCharset, aDefaultCharset,

                                  aOverrideCharset, true, aResult);

 }

 #define ISHEXCHAR(c) \

         ((0x30 <= uint8_t(c) && uint8_t(c) <= 0x39)  ||  \

          (0x41 <= uint8_t(c) && uint8_t(c) <= 0x46)  ||  \

          (0x61 <= uint8_t(c) && uint8_t(c) <= 0x66))

 // Decode Q encoding (RFC 2047).

 // static

 char *DecodeQ(const char *in, uint32_t length)

 {

   char *out, *dest = 0;

   out = dest = (char *)PR_Calloc(length + 1, sizeof(char));

   if (dest == nullptr)

     return nullptr;

   while (length > 0) {

     unsigned c = 0;

     switch (*in) {

     case '=':

       // check if |in| in the form of '=hh'  where h is [0-9a-fA-F].

       if (length < 3 || !ISHEXCHAR(in[1]) || !ISHEXCHAR(in[2]))

         goto badsyntax;

       PR_sscanf(in + 1, "%2X", &c);

       *out++ = (char) c;

       in += 3;

       length -= 3;

       break;

     case '_':

       *out++ = ' ';

       in++;

       length--;

       break;

     default:

       if (*in & 0x80) goto badsyntax;

       *out++ = *in++;

       length--;

     }

   }

   *out++ = '\0';

   for (out = dest; *out ; ++out) {

     if (*out == '\t')

       *out = ' ';

   }

   return dest;

  badsyntax:

   PR_Free(dest);

   return nullptr;

 }

 // check if input is HZ (a 7bit encoding for simplified Chinese : RFC 1842)) 

 // or has  ESC which may be an  indication that  it's in one of many ISO 

 // 2022 7bit  encodings (e.g. ISO-2022-JP(-2)/CN : see RFC 1468, 1922, 1554).

 // static

 bool Is7bitNonAsciiString(const char *input, uint32_t len)

 {

   int32_t c;

   enum { hz_initial, // No HZ seen yet

          hz_escaped, // Inside an HZ ~{ escape sequence 

          hz_seen, // Have seen at least one complete HZ sequence 

          hz_notpresent // Have seen something that is not legal HZ

   } hz_state;

   hz_state = hz_initial;

   while (len) {

     c = uint8_t(*input++);

     len--;

     if (c & 0x80) return false;

     if (c == 0x1B) return true;

     if (c == '~') {

       switch (hz_state) {

       case hz_initial:

       case hz_seen:

         if (*input == '{') {

           hz_state = hz_escaped;

         } else if (*input == '~') {

           // ~~ is the HZ encoding of ~.  Skip over second ~ as well

           hz_state = hz_seen;

           input++;

           len--;

         } else {

           hz_state = hz_notpresent;

         }

         break;

       case hz_escaped:

         if (*input == '}') hz_state = hz_seen;

         break;

       default:

         break;

       }

     }

   }

   return hz_state == hz_seen;

 }

 #define REPLACEMENT_CHAR "\357\277\275" // EF BF BD (UTF-8 encoding of U+FFFD)

 // copy 'raw' sequences of octets in aInput to aOutput.

 // If aDefaultCharset is specified, the input is assumed to be in the

 // charset and converted to UTF-8. Otherwise, a blind copy is made.

 // If aDefaultCharset is specified, but the conversion to UTF-8

 // is not successful, each octet is replaced by Unicode replacement

 // chars. *aOutput is advanced by the number of output octets.

 // static

 void CopyRawHeader(const char *aInput, uint32_t aLen, 

                    const char *aDefaultCharset, nsACString &aOutput)

 {

   int32_t c;

   // If aDefaultCharset is not specified, make a blind copy.

   if (!aDefaultCharset || !*aDefaultCharset) {

     aOutput.Append(aInput, aLen);

     return;

   }

   // Copy as long as it's US-ASCII.  An ESC may indicate ISO 2022

   // A ~ may indicate it is HZ

   while (aLen && (c = uint8_t(*aInput++)) != 0x1B && c != '~' && !(c & 0x80)) {

     aOutput.Append(char(c));

     aLen--;

   }

   if (!aLen) {

     return;

   }

   aInput--;

   // skip ASCIIness/UTF8ness test if aInput is supected to be a 7bit non-ascii

   // string and aDefaultCharset is a 7bit non-ascii charset.

   bool skipCheck = (c == 0x1B || c == '~') && 

                      IS_7BIT_NON_ASCII_CHARSET(aDefaultCharset);

   // If not UTF-8, treat as default charset

   nsCOMPtr<nsIUTF8ConverterService> 

     cvtUTF8(do_GetService(NS_UTF8CONVERTERSERVICE_CONTRACTID));

   nsAutoCString utf8Text;

   if (cvtUTF8 &&

       NS_SUCCEEDED(

       cvtUTF8->ConvertStringToUTF8(Substring(aInput, aInput + aLen), 

                                    aDefaultCharset, skipCheck, true, 1,

                                    utf8Text))) {

     aOutput.Append(utf8Text);

   } else { // replace each octet with Unicode replacement char in UTF-8.

     for (uint32_t i = 0; i < aLen; i++) {

       c = uint8_t(*aInput++);

       if (c & 0x80)

         aOutput.Append(REPLACEMENT_CHAR);

       else

         aOutput.Append(char(c));

     }

   }

 }

 nsresult DecodeQOrBase64Str(const char *aEncoded, size_t aLen, char aQOrBase64,

                             const char *aCharset, nsACString &aResult)

 {

   char *decodedText;

   NS_ASSERTION(aQOrBase64 == 'Q' || aQOrBase64 == 'B', "Should be 'Q' or 'B'");

   if(aQOrBase64 == 'Q')

     decodedText = DecodeQ(aEncoded, aLen);

   else if (aQOrBase64 == 'B') {

     decodedText = PL_Base64Decode(aEncoded, aLen, nullptr);

   } else {

     return NS_ERROR_INVALID_ARG;

   }

   if (!decodedText) {

     return NS_ERROR_INVALID_ARG;

   }

   nsresult rv;

   nsCOMPtr<nsIUTF8ConverterService>

     cvtUTF8(do_GetService(NS_UTF8CONVERTERSERVICE_CONTRACTID, &rv));

   nsAutoCString utf8Text;

   if (NS_SUCCEEDED(rv)) {

     // skip ASCIIness/UTF8ness test if aCharset is 7bit non-ascii charset.

     rv = cvtUTF8->ConvertStringToUTF8(nsDependentCString(decodedText),

                                       aCharset,

                                       IS_7BIT_NON_ASCII_CHARSET(aCharset),

                                       true, 1, utf8Text);

   }

   PR_Free(decodedText);

   if (NS_FAILED(rv)) {

     return rv;

   }

   aResult.Append(utf8Text);

   return NS_OK;

 }

 static const char especials[] = "()<>@,;:\\\"/[]?.=";

 // |decode_mime_part2_str| taken from comi18n.c

 // Decode RFC2047-encoded words in the input and convert the result to UTF-8.

 // If aOverrideCharset is true, charset in RFC2047-encoded words is 

 // ignored and aDefaultCharset is assumed, instead. aDefaultCharset

 // is also used to convert raw octets (without RFC 2047 encoding) to UTF-8.

 //static

 nsresult DecodeRFC2047Str(const char *aHeader, const char *aDefaultCharset, 

                           bool aOverrideCharset, nsACString &aResult)

 {

   const char *p, *q = nullptr, *r;

   const char *begin; // tracking pointer for where we are in the input buffer

   int32_t isLastEncodedWord = 0;

   const char *charsetStart, *charsetEnd;

   nsAutoCString prevCharset, curCharset;

   nsAutoCString encodedText;

   char prevEncoding = '\0', curEncoding;

   nsresult rv;

   begin = aHeader;

   // To avoid buffer realloc, if possible, set capacity in advance. No 

   // matter what,  more than 3x expansion can never happen for all charsets

   // supported by Mozilla. SCSU/BCSU with the sliding window set to a

   // non-BMP block may be exceptions, but Mozilla does not support them. 

   // Neither any known mail/news program use them. Even if there's, we're

   // safe because we don't use a raw *char any more.

   aResult.SetCapacity(3 * strlen(aHeader));

   while ((p = PL_strstr(begin, "=?")) != 0) {

     if (isLastEncodedWord) {

       // See if it's all whitespace.

       for (q = begin; q < p; ++q) {

         if (!PL_strchr(" \t\r\n", *q)) break;

       }

     }

     if (!isLastEncodedWord || q < p) {

       if (!encodedText.IsEmpty()) {

         rv = DecodeQOrBase64Str(encodedText.get(), encodedText.Length(),

                                 prevEncoding, prevCharset.get(), aResult);

         if (NS_FAILED(rv)) {

           aResult.Append(encodedText);

         }

         encodedText.Truncate();

         prevCharset.Truncate();

         prevEncoding = '\0';

       }

       // copy the part before the encoded-word

       CopyRawHeader(begin, p - begin, aDefaultCharset, aResult);

       begin = p;

     }

     p += 2;

     // Get charset info

     charsetStart = p;

     charsetEnd = 0;

     for (q = p; *q != '?'; q++) {

       if (*q <= ' ' || PL_strchr(especials, *q)) {

         goto badsyntax;

       }

       // RFC 2231 section 5

       if (!charsetEnd && *q == '*') {

         charsetEnd = q; 

       }

     }

     if (!charsetEnd) {

       charsetEnd = q;

     }

     q++;

     curEncoding = nsCRT::ToUpper(*q);

     if (curEncoding != 'Q' && curEncoding != 'B')

       goto badsyntax;

     if (q[1] != '?')

       goto badsyntax;

     r = q;

     for (r = q + 2; *r != '?'; r++) {

       if (*r < ' ') goto badsyntax;

     }

     if (r[1] != '=')

         goto badsyntax;

     else if (r == q + 2) {

         // it's empty, skip

         begin = r + 2;

         isLastEncodedWord = 1;

         continue;

     }

     curCharset.Assign(charsetStart, charsetEnd - charsetStart);

     // Override charset if requested.  Never override labeled UTF-8.

     // Use default charset instead of UNKNOWN-8BIT

     if ((aOverrideCharset && 0 != nsCRT::strcasecmp(curCharset.get(), "UTF-8"))

     || (aDefaultCharset && 0 == nsCRT::strcasecmp(curCharset.get(), "UNKNOWN-8BIT"))

     ) {

       curCharset = aDefaultCharset;

     }

     const char *R;

     R = r;

     if (curEncoding == 'B') {

       // bug 227290. ignore an extraneous '=' at the end.

       // (# of characters in B-encoded part has to be a multiple of 4)

       int32_t n = r - (q + 2);

       R -= (n % 4 == 1 && !PL_strncmp(r - 3, "===", 3)) ? 1 : 0;

     }

     // Bug 493544. Don't decode the encoded text until it ends

     if (R[-1] != '='

       && (prevCharset.IsEmpty()

         || (curCharset == prevCharset && curEncoding == prevEncoding))

     ) {

       encodedText.Append(q + 2, R - (q + 2));

       prevCharset = curCharset;

       prevEncoding = curEncoding;

       begin = r + 2;

       isLastEncodedWord = 1;

       continue;

     }

     bool bDecoded; // If the current line has been decoded.

     bDecoded = false;

     if (!encodedText.IsEmpty()) {

       if (curCharset == prevCharset && curEncoding == prevEncoding) {

         encodedText.Append(q + 2, R - (q + 2));

         bDecoded = true;

       }

       rv = DecodeQOrBase64Str(encodedText.get(), encodedText.Length(),

                               prevEncoding, prevCharset.get(), aResult);

       if (NS_FAILED(rv)) {

         aResult.Append(encodedText);

       }

       encodedText.Truncate();

       prevCharset.Truncate();

       prevEncoding = '\0';

     }

     if (!bDecoded) {

       rv = DecodeQOrBase64Str(q + 2, R - (q + 2), curEncoding,

                               curCharset.get(), aResult);

       if (NS_FAILED(rv)) {

         aResult.Append(encodedText);

       }

     }

     begin = r + 2;

     isLastEncodedWord = 1;

     continue;

   badsyntax:

     if (!encodedText.IsEmpty()) {

       rv = DecodeQOrBase64Str(encodedText.get(), encodedText.Length(),

                               prevEncoding, prevCharset.get(), aResult);

       if (NS_FAILED(rv)) {

         aResult.Append(encodedText);

       }

       encodedText.Truncate();

       prevCharset.Truncate();

     }

     // copy the part before the encoded-word

     aResult.Append(begin, p - begin);

     begin = p;

     isLastEncodedWord = 0;

   }

   if (!encodedText.IsEmpty()) {

     rv = DecodeQOrBase64Str(encodedText.get(), encodedText.Length(),

                             prevEncoding, prevCharset.get(), aResult);

     if (NS_FAILED(rv)) {

       aResult.Append(encodedText);

     }

   }

   // put the tail back

   CopyRawHeader(begin, strlen(begin), aDefaultCharset, aResult);

   nsAutoCString tempStr(aResult);

   tempStr.ReplaceChar('\t', ' ');

   aResult = tempStr;

   return NS_OK;

 }