commit f9ba0addb8e60cb72f8a8524fb4379d741cd4e7d
Author: Tomas Korbar <tkorbar@redhat.com>
Date: Mon Mar 21 12:42:50 2022 +0100
Protect against malicious namespace declarations
diff --git a/lib/xmlparse.c b/lib/xmlparse.c
index 87d1a98..4bfb860 100644
--- a/lib/xmlparse.c
+++ b/lib/xmlparse.c
@@ -679,8 +679,7 @@ XML_ParserCreate(const XML_Char *encodingName)
XML_Parser XMLCALL
XML_ParserCreateNS(const XML_Char *encodingName, XML_Char nsSep)
{
- XML_Char tmp[2];
- *tmp = nsSep;
+ XML_Char tmp[2] = {nsSep, 0};
return XML_ParserCreate_MM(encodingName, NULL, tmp);
}
@@ -1044,8 +1043,7 @@ XML_ExternalEntityParserCreate(XML_Parser oldParser,
would be otherwise.
*/
if (ns) {
- XML_Char tmp[2];
- *tmp = namespaceSeparator;
+ XML_Char tmp[2] = {parser->m_namespaceSeparator, 0};
parser = parserCreate(encodingName, &parser->m_mem, tmp, newDtd);
}
else {
@@ -3173,6 +3171,117 @@ storeAtts(XML_Parser parser, const ENCODING *enc,
return XML_ERROR_NONE;
}
+static XML_Bool
+is_rfc3986_uri_char(XML_Char candidate) {
+ // For the RFC 3986 ANBF grammar see
+ // https://datatracker.ietf.org/doc/html/rfc3986#appendix-A
+
+ switch (candidate) {
+ // From rule "ALPHA" (uppercase half)
+ case 'A':
+ case 'B':
+ case 'C':
+ case 'D':
+ case 'E':
+ case 'F':
+ case 'G':
+ case 'H':
+ case 'I':
+ case 'J':
+ case 'K':
+ case 'L':
+ case 'M':
+ case 'N':
+ case 'O':
+ case 'P':
+ case 'Q':
+ case 'R':
+ case 'S':
+ case 'T':
+ case 'U':
+ case 'V':
+ case 'W':
+ case 'X':
+ case 'Y':
+ case 'Z':
+
+ // From rule "ALPHA" (lowercase half)
+ case 'a':
+ case 'b':
+ case 'c':
+ case 'd':
+ case 'e':
+ case 'f':
+ case 'g':
+ case 'h':
+ case 'i':
+ case 'j':
+ case 'k':
+ case 'l':
+ case 'm':
+ case 'n':
+ case 'o':
+ case 'p':
+ case 'q':
+ case 'r':
+ case 's':
+ case 't':
+ case 'u':
+ case 'v':
+ case 'w':
+ case 'x':
+ case 'y':
+ case 'z':
+
+ // From rule "DIGIT"
+ case '0':
+ case '1':
+ case '2':
+ case '3':
+ case '4':
+ case '5':
+ case '6':
+ case '7':
+ case '8':
+ case '9':
+
+ // From rule "pct-encoded"
+ case '%':
+
+ // From rule "unreserved"
+ case '-':
+ case '.':
+ case '_':
+ case '~':
+
+ // From rule "gen-delims"
+ case ':':
+ case '/':
+ case '?':
+ case '#':
+ case '[':
+ case ']':
+ case '@':
+
+ // From rule "sub-delims"
+ case '!':
+ case '$':
+ case '&':
+ case '\'':
+ case '(':
+ case ')':
+ case '*':
+ case '+':
+ case ',':
+ case ';':
+ case '=':
+ return XML_TRUE;
+
+ default:
+ return XML_FALSE;
+ }
+}
+
/* addBinding() overwrites the value of prefix->binding without checking.
Therefore one must keep track of the old value outside of addBinding().
*/
@@ -3233,6 +3342,29 @@ addBinding(XML_Parser parser, PREFIX *prefix, const ATTRIBUTE_ID *attId,
if (!mustBeXML && isXMLNS
&& (len > xmlnsLen || uri[len] != xmlnsNamespace[len]))
isXMLNS = XML_FALSE;
+
+ // NOTE: While Expat does not validate namespace URIs against RFC 3986
+ // today (and is not REQUIRED to do so with regard to the XML 1.0
+ // namespaces specification) we have to at least make sure, that
+ // the application on top of Expat (that is likely splitting expanded
+ // element names ("qualified names") of form
+ // "[uri sep] local [sep prefix] '\0'" back into 1, 2 or 3 pieces
+ // in its element handler code) cannot be confused by an attacker
+ // putting additional namespace separator characters into namespace
+ // declarations. That would be ambiguous and not to be expected.
+ //
+ // While the HTML API docs of function XML_ParserCreateNS have been
+ // advising against use of a namespace separator character that can
+ // appear in a URI for >20 years now, some widespread applications
+ // are using URI characters (':' (colon) in particular) for a
+ // namespace separator, in practice. To keep these applications
+ // functional, we only reject namespaces URIs containing the
+ // application-chosen namespace separator if the chosen separator
+ // is a non-URI character with regard to RFC 3986.
+ if (parser->m_ns && (uri[len] == parser->m_namespaceSeparator)
+ && ! is_rfc3986_uri_char(uri[len])) {
+ return XML_ERROR_SYNTAX;
+ }
}
isXML = isXML && len == xmlLen;
isXMLNS = isXMLNS && len == xmlnsLen;
diff --git a/tests/runtests.c b/tests/runtests.c
index b99e375..86f8b18 100644
--- a/tests/runtests.c
+++ b/tests/runtests.c
@@ -31,6 +31,13 @@
static XML_Parser parser;
+#ifndef UNUSED_P
+# ifdef __GNUC__
+# define UNUSED_P(p) UNUSED_ ## p __attribute__((__unused__))
+# else
+# define UNUSED_P(p) UNUSED_ ## p
+# endif
+#endif
static void
basic_setup(void)
@@ -40,6 +47,10 @@ basic_setup(void)
fail("Parser not created.");
}
+static void
+dummy_end_element(void *UNUSED_P(userData), const XML_Char *UNUSED_P(name))
+{}
+
static void
basic_teardown(void)
{
@@ -1499,6 +1510,138 @@ START_TEST(test_ns_unbound_prefix_on_element)
}
END_TEST
+START_TEST(test_ns_separator_in_uri) {
+ struct test_case {
+ enum XML_Status expectedStatus;
+ const char *doc;
+ XML_Char namesep;
+ };
+ struct test_case cases[] = {
+ {XML_STATUS_OK, "<doc xmlns='one_two' />", '\n'},
+ {XML_STATUS_ERROR, "<doc xmlns='one
two' />", '\n'},
+ {XML_STATUS_OK, "<doc xmlns='one:two' />", ':'},
+ };
+
+ size_t i = 0;
+ size_t failCount = 0;
+ for (; i < sizeof(cases) / sizeof(cases[0]); i++) {
+ XML_Parser parser = XML_ParserCreateNS(NULL, cases[i].namesep);
+ XML_SetElementHandler(parser, dummy_start_element, dummy_end_element);
+ if (XML_Parse(parser, cases[i].doc, (int)strlen(cases[i].doc),
+ /*isFinal*/ XML_TRUE)
+ != cases[i].expectedStatus) {
+ failCount++;
+ }
+ XML_ParserFree(parser);
+ }
+
+ if (failCount) {
+ fail("Namespace separator handling is broken");
+ }
+}
+END_TEST
+
+
+START_TEST(test_utf8_in_start_tags) {
+ struct test_case {
+ bool goodName;
+ bool goodNameStart;
+ const char *tagName;
+ };
+
+ // The idea with the tests below is this:
+ // We want to cover 1-, 2- and 3-byte sequences, 4-byte sequences
+ // go to isNever and are hence not a concern.
+ //
+ // We start with a character that is a valid name character
+ // (or even name-start character, see XML 1.0r4 spec) and then we flip
+ // single bits at places where (1) the result leaves the UTF-8 encoding space
+ // and (2) we stay in the same n-byte sequence family.
+ //
+ // The flipped bits are highlighted in angle brackets in comments,
+ // e.g. "[<1>011 1001]" means we had [0011 1001] but we now flipped
+ // the most significant bit to 1 to leave UTF-8 encoding space.
+ struct test_case cases[] = {
+ // 1-byte UTF-8: [0xxx xxxx]
+ {true, true, "\x3A"}, // [0011 1010] = ASCII colon ':'
+ {false, false, "\xBA"}, // [<1>011 1010]
+ {true, false, "\x39"}, // [0011 1001] = ASCII nine '9'
+ {false, false, "\xB9"}, // [<1>011 1001]
+
+ // 2-byte UTF-8: [110x xxxx] [10xx xxxx]
+ {true, true, "\xDB\xA5"}, // [1101 1011] [1010 0101] =
+ // Arabic small waw U+06E5
+ {false, false, "\x9B\xA5"}, // [1<0>01 1011] [1010 0101]
+ {false, false, "\xDB\x25"}, // [1101 1011] [<0>010 0101]
+ {false, false, "\xDB\xE5"}, // [1101 1011] [1<1>10 0101]
+ {true, false, "\xCC\x81"}, // [1100 1100] [1000 0001] =
+ // combining char U+0301
+ {false, false, "\x8C\x81"}, // [1<0>00 1100] [1000 0001]
+ {false, false, "\xCC\x01"}, // [1100 1100] [<0>000 0001]
+ {false, false, "\xCC\xC1"}, // [1100 1100] [1<1>00 0001]
+
+ // 3-byte UTF-8: [1110 xxxx] [10xx xxxx] [10xxxxxx]
+ {true, true, "\xE0\xA4\x85"}, // [1110 0000] [1010 0100] [1000 0101] =
+ // Devanagari Letter A U+0905
+ {false, false, "\xA0\xA4\x85"}, // [1<0>10 0000] [1010 0100] [1000 0101]
+ {false, false, "\xE0\x24\x85"}, // [1110 0000] [<0>010 0100] [1000 0101]
+ {false, false, "\xE0\xE4\x85"}, // [1110 0000] [1<1>10 0100] [1000 0101]
+ {false, false, "\xE0\xA4\x05"}, // [1110 0000] [1010 0100] [<0>000 0101]
+ {false, false, "\xE0\xA4\xC5"}, // [1110 0000] [1010 0100] [1<1>00 0101]
+ {true, false, "\xE0\xA4\x81"}, // [1110 0000] [1010 0100] [1000 0001] =
+ // combining char U+0901
+ {false, false, "\xA0\xA4\x81"}, // [1<0>10 0000] [1010 0100] [1000 0001]
+ {false, false, "\xE0\x24\x81"}, // [1110 0000] [<0>010 0100] [1000 0001]
+ {false, false, "\xE0\xE4\x81"}, // [1110 0000] [1<1>10 0100] [1000 0001]
+ {false, false, "\xE0\xA4\x01"}, // [1110 0000] [1010 0100] [<0>000 0001]
+ {false, false, "\xE0\xA4\xC1"}, // [1110 0000] [1010 0100] [1<1>00 0001]
+ };
+ const bool atNameStart[] = {true, false};
+
+ size_t i = 0;
+ char doc[1024];
+ size_t failCount = 0;
+
+ for (; i < sizeof(cases) / sizeof(cases[0]); i++) {
+ size_t j = 0;
+ for (; j < sizeof(atNameStart) / sizeof(atNameStart[0]); j++) {
+ const bool expectedSuccess
+ = atNameStart[j] ? cases[i].goodNameStart : cases[i].goodName;
+ sprintf(doc, "<%s%s><!--", atNameStart[j] ? "" : "a", cases[i].tagName);
+ XML_Parser parser = XML_ParserCreate(NULL);
+
+ const enum XML_Status status
+ = XML_Parse(parser, doc, (int)strlen(doc), /*isFinal=*/XML_FALSE);
+
+ bool success = true;
+ if ((status == XML_STATUS_OK) != expectedSuccess) {
+ success = false;
+ }
+ if ((status == XML_STATUS_ERROR)
+ && (XML_GetErrorCode(parser) != XML_ERROR_INVALID_TOKEN)) {
+ success = false;
+ }
+
+ if (! success) {
+ fprintf(
+ stderr,
+ "FAIL case %2u (%sat name start, %u-byte sequence, error code %d)\n",
+ (unsigned)i + 1u, atNameStart[j] ? " " : "not ",
+ (unsigned)strlen(cases[i].tagName), XML_GetErrorCode(parser));
+ failCount++;
+ }
+
+ XML_ParserFree(parser);
+
+ }
+
+ if (failCount > 0) {
+ fail("UTF-8 regression detected");
+ }
+}
+}
+END_TEST
+
static Suite *
make_suite(void)
{
@@ -1569,6 +1712,7 @@ make_suite(void)
tcase_add_test(tc_namespace, test_ns_duplicate_attrs_diff_prefixes);
tcase_add_test(tc_namespace, test_ns_unbound_prefix_on_attribute);
tcase_add_test(tc_namespace, test_ns_unbound_prefix_on_element);
+ tcase_add_test(tc_namespace, test_ns_separator_in_uri);
#ifdef XML_DTD
tcase_add_test(tc_basic,