From 1699293a7011797895c284d6ad664c66badba426 Mon Sep 17 00:00:00 2001
From: Steve Sakoman <steve@sakoman.com>
Date: Wed, 21 Jul 2021 07:12:14 -1000
Subject: [PATCH] libxml2: fix CVE-2021-3541

A flaw was found in libxml2. Exponential entity expansion attack
is possible bypassing all existing protection mechanisms and leading
to denial of service.

https://nvd.nist.gov/vuln/detail/CVE-2021-3541
CVE: 2021-3541

Signed-off-by: Steve Sakoman <steve@sakoman.com>
---
 .../libxml/libxml2/CVE-2021-3541.patch        | 73 +++++++++++++++++++
 meta/recipes-core/libxml/libxml2_2.9.10.bb    |  1 +
 2 files changed, 74 insertions(+)
 create mode 100644 meta/recipes-core/libxml/libxml2/CVE-2021-3541.patch

diff --git a/meta/recipes-core/libxml/libxml2/CVE-2021-3541.patch b/meta/recipes-core/libxml/libxml2/CVE-2021-3541.patch
new file mode 100644
index 0000000000..1f392b4cd7
--- /dev/null
+++ b/meta/recipes-core/libxml/libxml2/CVE-2021-3541.patch
@@ -0,0 +1,73 @@
+From 8598060bacada41a0eb09d95c97744ff4e428f8e Mon Sep 17 00:00:00 2001
+From: Daniel Veillard <veillard@redhat.com>
+Date: Thu, 13 May 2021 14:55:12 +0200
+Subject: [PATCH] Patch for security issue CVE-2021-3541
+
+This is relapted to parameter entities expansion and following
+the line of the billion laugh attack. Somehow in that path the
+counting of parameters was missed and the normal algorithm based
+on entities "density" was useless.
+
+Upstream-Status: Backport
+[https://gitlab.gnome.org/GNOME/libxml2/-/commit/8598060bacada41a0eb09d95c97744ff4e428f8e]
+CVE: CVE-2021-3541
+Signed-off-by: Steve Sakoman <steve@sakoman.com>
+
+---
+ parser.c | 26 ++++++++++++++++++++++++++
+ 1 file changed, 26 insertions(+)
+
+diff --git a/parser.c b/parser.c
+index f5e5e169..c9312fa4 100644
+--- a/parser.c
++++ b/parser.c
+@@ -140,6 +140,7 @@ xmlParserEntityCheck(xmlParserCtxtPtr ctxt, size_t size,
+                      xmlEntityPtr ent, size_t replacement)
+ {
+     size_t consumed = 0;
++    int i;
+ 
+     if ((ctxt == NULL) || (ctxt->options & XML_PARSE_HUGE))
+         return (0);
+@@ -177,6 +178,28 @@ xmlParserEntityCheck(xmlParserCtxtPtr ctxt, size_t size,
+ 	    rep = NULL;
+ 	}
+     }
++
++    /*
++     * Prevent entity exponential check, not just replacement while
++     * parsing the DTD
++     * The check is potentially costly so do that only once in a thousand
++     */
++    if ((ctxt->instate == XML_PARSER_DTD) && (ctxt->nbentities > 10000) &&
++        (ctxt->nbentities % 1024 == 0)) {
++	for (i = 0;i < ctxt->inputNr;i++) {
++	    consumed += ctxt->inputTab[i]->consumed +
++	               (ctxt->inputTab[i]->cur - ctxt->inputTab[i]->base);
++	}
++	if (ctxt->nbentities > consumed * XML_PARSER_NON_LINEAR) {
++	    xmlFatalErr(ctxt, XML_ERR_ENTITY_LOOP, NULL);
++	    ctxt->instate = XML_PARSER_EOF;
++	    return (1);
++	}
++	consumed = 0;
++    }
++
++
++
+     if (replacement != 0) {
+ 	if (replacement < XML_MAX_TEXT_LENGTH)
+ 	    return(0);
+@@ -7963,6 +7986,9 @@ xmlParsePEReference(xmlParserCtxtPtr ctxt)
+             xmlChar start[4];
+             xmlCharEncoding enc;
+ 
++	    if (xmlParserEntityCheck(ctxt, 0, entity, 0))
++	        return;
++
+ 	    if ((entity->etype == XML_EXTERNAL_PARAMETER_ENTITY) &&
+ 	        ((ctxt->options & XML_PARSE_NOENT) == 0) &&
+ 		((ctxt->options & XML_PARSE_DTDVALID) == 0) &&
+-- 
+GitLab
+
diff --git a/meta/recipes-core/libxml/libxml2_2.9.10.bb b/meta/recipes-core/libxml/libxml2_2.9.10.bb
index b5fb3e6315..60dc71f38d 100644
--- a/meta/recipes-core/libxml/libxml2_2.9.10.bb
+++ b/meta/recipes-core/libxml/libxml2_2.9.10.bb
@@ -26,6 +26,7 @@ SRC_URI = "http://www.xmlsoft.org/sources/libxml2-${PV}.tar.gz;name=libtar \
            file://CVE-2021-3517.patch \
            file://CVE-2021-3537.patch \
            file://CVE-2021-3518.patch \
+           file://CVE-2021-3541.patch \
            "
 
 SRC_URI[libtar.md5sum] = "10942a1dc23137a8aa07f0639cbfece5"
-- 
2.40.1