Improve fix for CVE-2022-25236
Related: CVE-2022-25236
This commit is contained in:
Tomas Korbar
parent
6c4005223e
commit
f23fd2fa9c
@ -1,17 +1,14 @@
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From 6881a4fc8596307ab9ff2e85e605afa2e413ab71 Mon Sep 17 00:00:00 2001
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From: Sebastian Pipping <sebastian@pipping.org>
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Date: Sat, 12 Feb 2022 00:19:13 +0100
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Subject: [PATCH 1/4] lib: Fix (harmless) use of uninitialized memory
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commit 5c47ae80738d0985babf06a023b3845169682064
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Author: Tomas Korbar <tkorbar@redhat.com>
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Date: Mon Mar 14 10:22:37 2022 +0100
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---
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expat/lib/xmlparse.c | 6 ++----
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1 file changed, 2 insertions(+), 4 deletions(-)
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Protect against malicious namespace declarations
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diff --git a/lib/xmlparse.c b/lib/xmlparse.c
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index 902895d5..c768f856 100644
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index 5c3f573..901abbf 100644
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--- a/lib/xmlparse.c
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+++ b/lib/xmlparse.c
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@@ -718,8 +718,7 @@ XML_ParserCreate(const XML_Char *encodingName) {
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@@ -638,8 +638,7 @@ XML_ParserCreate(const XML_Char *encodingName) {
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XML_Parser XMLCALL
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XML_ParserCreateNS(const XML_Char *encodingName, XML_Char nsSep) {
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@ -21,7 +18,7 @@ index 902895d5..c768f856 100644
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return XML_ParserCreate_MM(encodingName, NULL, tmp);
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}
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@@ -1344,8 +1343,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser, const XML_Char *context,
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@@ -1253,8 +1252,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser, const XML_Char *context,
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would be otherwise.
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*/
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if (parser->m_ns) {
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@ -31,54 +28,159 @@ index 902895d5..c768f856 100644
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parser = parserCreate(encodingName, &parser->m_mem, tmp, newDtd);
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} else {
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parser = parserCreate(encodingName, &parser->m_mem, NULL, newDtd);
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From a2fe525e660badd64b6c557c2b1ec26ddc07f6e4 Mon Sep 17 00:00:00 2001
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From: Sebastian Pipping <sebastian@pipping.org>
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Date: Sat, 12 Feb 2022 01:09:29 +0100
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Subject: [PATCH 2/4] lib: Protect against malicious namespace declarations
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(CVE-2022-25236)
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---
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expat/lib/xmlparse.c | 11 +++++++++++
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1 file changed, 11 insertions(+)
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diff --git a/lib/xmlparse.c b/lib/xmlparse.c
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index c768f856..a3aef88c 100644
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--- a/lib/xmlparse.c
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+++ b/lib/xmlparse.c
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@@ -3754,6 +3754,17 @@ addBinding(XML_Parser parser, PREFIX *prefix, const ATTRIBUTE_ID *attId,
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@@ -3526,6 +3524,117 @@ storeAtts(XML_Parser parser, const ENCODING *enc, const char *attStr,
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return XML_ERROR_NONE;
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}
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+static XML_Bool
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+is_rfc3986_uri_char(XML_Char candidate) {
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+ // For the RFC 3986 ANBF grammar see
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+ // https://datatracker.ietf.org/doc/html/rfc3986#appendix-A
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+
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+ switch (candidate) {
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+ // From rule "ALPHA" (uppercase half)
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+ case 'A':
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+ case 'B':
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+ case 'C':
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+ case 'D':
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+ case 'E':
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+ case 'F':
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+ case 'G':
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+ case 'H':
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+ case 'I':
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+ case 'J':
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+ case 'K':
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+ case 'L':
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+ case 'M':
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+ case 'N':
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+ case 'O':
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+ case 'P':
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+ case 'Q':
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+ case 'R':
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+ case 'S':
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+ case 'T':
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+ case 'U':
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+ case 'V':
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+ case 'W':
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+ case 'X':
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+ case 'Y':
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+ case 'Z':
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+
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+ // From rule "ALPHA" (lowercase half)
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+ case 'a':
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+ case 'b':
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+ case 'c':
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+ case 'd':
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+ case 'e':
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+ case 'f':
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+ case 'g':
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+ case 'h':
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+ case 'i':
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+ case 'j':
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+ case 'k':
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+ case 'l':
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+ case 'm':
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+ case 'n':
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+ case 'o':
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+ case 'p':
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+ case 'q':
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+ case 'r':
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+ case 's':
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+ case 't':
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+ case 'u':
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+ case 'v':
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+ case 'w':
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+ case 'x':
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+ case 'y':
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+ case 'z':
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+
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+ // From rule "DIGIT"
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+ case '0':
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+ case '1':
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+ case '2':
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+ case '3':
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+ case '4':
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+ case '5':
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+ case '6':
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+ case '7':
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+ case '8':
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+ case '9':
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+
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+ // From rule "pct-encoded"
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+ case '%':
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+
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+ // From rule "unreserved"
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+ case '-':
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+ case '.':
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+ case '_':
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+ case '~':
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+
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+ // From rule "gen-delims"
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+ case ':':
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+ case '/':
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+ case '?':
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+ case '#':
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+ case '[':
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+ case ']':
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+ case '@':
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+
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+ // From rule "sub-delims"
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+ case '!':
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+ case '$':
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+ case '&':
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+ case '\'':
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+ case '(':
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+ case ')':
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+ case '*':
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+ case '+':
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+ case ',':
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+ case ';':
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+ case '=':
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+ return XML_TRUE;
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+
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+ default:
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+ return XML_FALSE;
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+ }
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+}
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+
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/* addBinding() overwrites the value of prefix->binding without checking.
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Therefore one must keep track of the old value outside of addBinding().
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*/
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@@ -3581,6 +3690,29 @@ addBinding(XML_Parser parser, PREFIX *prefix, const ATTRIBUTE_ID *attId,
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if (! mustBeXML && isXMLNS
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&& (len > xmlnsLen || uri[len] != xmlnsNamespace[len]))
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isXMLNS = XML_FALSE;
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+
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+ // NOTE: While Expat does not validate namespace URIs against RFC 3986,
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+ // we have to at least make sure that the XML processor on top of
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+ // Expat (that is splitting tag names by namespace separator into
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+ // 2- or 3-tuples (uri-local or uri-local-prefix)) cannot be confused
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+ // by an attacker putting additional namespace separator characters
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+ // into namespace declarations. That would be ambiguous and not to
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+ // be expected.
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+ if (parser->m_ns && (uri[len] == parser->m_namespaceSeparator)) {
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+ // NOTE: While Expat does not validate namespace URIs against RFC 3986
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+ // today (and is not REQUIRED to do so with regard to the XML 1.0
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+ // namespaces specification) we have to at least make sure, that
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+ // the application on top of Expat (that is likely splitting expanded
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+ // element names ("qualified names") of form
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+ // "[uri sep] local [sep prefix] '\0'" back into 1, 2 or 3 pieces
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+ // in its element handler code) cannot be confused by an attacker
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+ // putting additional namespace separator characters into namespace
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+ // declarations. That would be ambiguous and not to be expected.
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+ //
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+ // While the HTML API docs of function XML_ParserCreateNS have been
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+ // advising against use of a namespace separator character that can
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+ // appear in a URI for >20 years now, some widespread applications
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+ // are using URI characters (':' (colon) in particular) for a
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+ // namespace separator, in practice. To keep these applications
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+ // functional, we only reject namespaces URIs containing the
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+ // application-chosen namespace separator if the chosen separator
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+ // is a non-URI character with regard to RFC 3986.
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+ if (parser->m_ns && (uri[len] == parser->m_namespaceSeparator)
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+ && ! is_rfc3986_uri_char(uri[len])) {
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+ return XML_ERROR_SYNTAX;
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+ }
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}
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isXML = isXML && len == xmlLen;
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isXMLNS = isXMLNS && len == xmlnsLen;
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From 2de077423fb22750ebea599677d523b53cb93b1d Mon Sep 17 00:00:00 2001
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From: Sebastian Pipping <sebastian@pipping.org>
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Date: Sat, 12 Feb 2022 00:51:43 +0100
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Subject: [PATCH 3/4] tests: Cover CVE-2022-25236
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---
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expat/tests/runtests.c | 30 ++++++++++++++++++++++++++++++
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1 file changed, 30 insertions(+)
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diff --git a/tests/runtests.c b/tests/runtests.c
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index d07203f2..bc5344b1 100644
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index f03e008..40172d2 100644
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--- a/tests/runtests.c
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+++ b/tests/runtests.c
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@@ -7220,6 +7220,35 @@ START_TEST(test_ns_double_colon_doctype) {
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@@ -7233,6 +7233,37 @@ START_TEST(test_ns_double_colon_doctype) {
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}
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END_TEST
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@ -86,16 +188,18 @@ index d07203f2..bc5344b1 100644
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+ struct test_case {
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+ enum XML_Status expectedStatus;
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+ const char *doc;
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+ XML_Char namesep;
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+ };
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+ struct test_case cases[] = {
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+ {XML_STATUS_OK, "<doc xmlns='one_two' />"},
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+ {XML_STATUS_ERROR, "<doc xmlns='one
two' />"},
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+ {XML_STATUS_OK, "<doc xmlns='one_two' />", XCS('\n')},
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+ {XML_STATUS_ERROR, "<doc xmlns='one
two' />", XCS('\n')},
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+ {XML_STATUS_OK, "<doc xmlns='one:two' />", XCS(':')},
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+ };
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+
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+ size_t i = 0;
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+ size_t failCount = 0;
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+ for (; i < sizeof(cases) / sizeof(cases[0]); i++) {
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+ XML_Parser parser = XML_ParserCreateNS(NULL, '\n');
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+ XML_Parser parser = XML_ParserCreateNS(NULL, cases[i].namesep);
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+ XML_SetElementHandler(parser, dummy_start_element, dummy_end_element);
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+ if (XML_Parse(parser, cases[i].doc, (int)strlen(cases[i].doc),
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+ /*isFinal*/ XML_TRUE)
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@ -114,7 +218,7 @@ index d07203f2..bc5344b1 100644
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/* Control variable; the number of times duff_allocator() will successfully
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* allocate */
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#define ALLOC_ALWAYS_SUCCEED (-1)
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@@ -11905,6 +11934,7 @@ make_suite(void) {
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@@ -11527,6 +11558,7 @@ make_suite(void) {
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tcase_add_test(tc_namespace, test_ns_utf16_doctype);
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tcase_add_test(tc_namespace, test_ns_invalid_doctype);
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tcase_add_test(tc_namespace, test_ns_double_colon_doctype);
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@ -122,4 +226,3 @@ index d07203f2..bc5344b1 100644
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suite_add_tcase(s, tc_misc);
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tcase_add_checked_fixture(tc_misc, NULL, basic_teardown);
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@ -3,7 +3,7 @@
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Summary: An XML parser library
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Name: expat
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Version: %(echo %{unversion} | sed 's/_/./g')
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Release: 10%{?dist}
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Release: 11%{?dist}
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Source: https://github.com/libexpat/libexpat/archive/R_%{unversion}.tar.gz#/expat-%{version}.tar.gz
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URL: https://libexpat.github.io/
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License: MIT
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@ -89,6 +89,10 @@ make check
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%{_libdir}/lib*.a
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%changelog
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* Mon Mar 14 2022 Tomas Korbar <tkorbar@redhat.com> - 2.2.10-11
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- Improve fix for CVE-2022-25236
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- Related: CVE-2022-25236
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* Mon Feb 28 2022 Tomas Korbar <tkorbar@redhat.com> - 2.2.10-10
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- Fix multiple CVEs
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- CVE-2022-25236 expat: namespace-separator characters in "xmlns[:prefix]" attribute values can lead to arbitrary code execution
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