exiv2/exiv2-CVE-2021-32617.patch
Jan Grulich 99c067b851 CVE-2021-29623 exiv2: a read of uninitialized memory may lead to information leak
Resolves: bz#1964183

CVE-2021-32617 exiv2: DoS due to quadratic complexity in ProcessUTF8Portion
Resolves: bz#1964189
2021-05-25 12:13:08 +02:00

126 lines
4.7 KiB
Diff

From c261fbaa2567687eec6a595d3016212fd6ae648d Mon Sep 17 00:00:00 2001
From: Kevin Backhouse <kevinbackhouse@github.com>
Date: Sun, 16 May 2021 15:05:08 +0100
Subject: [PATCH] Fix quadratic complexity performance bug.
---
xmpsdk/src/XMPMeta-Parse.cpp | 57 +++++++++++++++++++++++-------------
1 file changed, 36 insertions(+), 21 deletions(-)
diff --git a/xmpsdk/src/XMPMeta-Parse.cpp b/xmpsdk/src/XMPMeta-Parse.cpp
index 9f66fe8..f9c37d7 100644
--- a/xmpsdk/src/XMPMeta-Parse.cpp
+++ b/xmpsdk/src/XMPMeta-Parse.cpp
@@ -976,12 +976,26 @@ ProcessUTF8Portion ( XMLParserAdapter * xmlParser,
{
const XMP_Uns8 * bufEnd = buffer + length;
- const XMP_Uns8 * spanStart = buffer;
const XMP_Uns8 * spanEnd;
-
- for ( spanEnd = spanStart; spanEnd < bufEnd; ++spanEnd ) {
- if ( (0x20 <= *spanEnd) && (*spanEnd <= 0x7E) && (*spanEnd != '&') ) continue; // A regular ASCII character.
+ // `buffer` is copied into this std::string. If `buffer` only
+ // contains valid UTF-8 and no escape characters, then the copy
+ // will be identical to the original, but invalid characters are
+ // replaced - usually with a space character. This std::string was
+ // added as a performance fix for:
+ // https://github.com/Exiv2/exiv2/security/advisories/GHSA-w8mv-g8qq-36mj
+ // Previously, the code was repeatedly calling
+ // `xmlParser->ParseBuffer()`, which turned out to have quadratic
+ // complexity, because expat kept reparsing the entire string from
+ // the beginning.
+ std::string copy;
+
+ for ( spanEnd = buffer; spanEnd < bufEnd; ++spanEnd ) {
+
+ if ( (0x20 <= *spanEnd) && (*spanEnd <= 0x7E) && (*spanEnd != '&') ) {
+ copy.push_back(*spanEnd);
+ continue; // A regular ASCII character.
+ }
if ( *spanEnd >= 0x80 ) {
@@ -992,21 +1006,20 @@ ProcessUTF8Portion ( XMLParserAdapter * xmlParser,
if ( uniLen > 0 ) {
// A valid UTF-8 character, keep it as-is.
+ copy.append((const char*)spanEnd, uniLen);
spanEnd += uniLen - 1; // ! The loop increment will put back the +1.
} else if ( (uniLen < 0) && (! last) ) {
// Have a partial UTF-8 character at the end of the buffer and more input coming.
- xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
+ xmlParser->ParseBuffer ( copy.c_str(), copy.size(), false );
return (spanEnd - buffer);
} else {
// Not a valid UTF-8 sequence. Replace the first byte with the Latin-1 equivalent.
- xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
const char * replacement = kReplaceLatin1 [ *spanEnd - 0x80 ];
- xmlParser->ParseBuffer ( replacement, strlen ( replacement ), false );
- spanStart = spanEnd + 1; // ! The loop increment will do "spanEnd = spanStart".
+ copy.append ( replacement );
}
@@ -1014,11 +1027,12 @@ ProcessUTF8Portion ( XMLParserAdapter * xmlParser,
// Replace ASCII controls other than tab, LF, and CR with a space.
- if ( (*spanEnd == kTab) || (*spanEnd == kLF) || (*spanEnd == kCR) ) continue;
+ if ( (*spanEnd == kTab) || (*spanEnd == kLF) || (*spanEnd == kCR) ) {
+ copy.push_back(*spanEnd);
+ continue;
+ }
- xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
- xmlParser->ParseBuffer ( " ", 1, false );
- spanStart = spanEnd + 1; // ! The loop increment will do "spanEnd = spanStart".
+ copy.push_back(' ');
} else {
@@ -1030,18 +1044,21 @@ ProcessUTF8Portion ( XMLParserAdapter * xmlParser,
if ( escLen < 0 ) {
// Have a partial numeric escape in this buffer, wait for more input.
- if ( last ) continue; // No more buffers, not an escape, absorb as normal input.
- xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
+ if ( last ) {
+ copy.push_back('&');
+ continue; // No more buffers, not an escape, absorb as normal input.
+ }
+ xmlParser->ParseBuffer ( copy.c_str(), copy.size(), false );
return (spanEnd - buffer);
} else if ( escLen > 0 ) {
// Have a complete numeric escape to replace.
- xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
- xmlParser->ParseBuffer ( " ", 1, false );
- spanStart = spanEnd + escLen;
- spanEnd = spanStart - 1; // ! The loop continuation will increment spanEnd!
+ copy.push_back(' ');
+ spanEnd = spanEnd + escLen - 1; // ! The loop continuation will increment spanEnd!
+ } else {
+ copy.push_back('&');
}
}
@@ -1050,8 +1067,8 @@ ProcessUTF8Portion ( XMLParserAdapter * xmlParser,
XMP_Assert ( spanEnd == bufEnd );
- if ( spanStart < bufEnd ) xmlParser->ParseBuffer ( spanStart, (spanEnd - spanStart), false );
- if ( last ) xmlParser->ParseBuffer ( " ", 1, true );
+ copy.push_back(' ');
+ xmlParser->ParseBuffer ( copy.c_str(), copy.size(), true );
return length;