Update 'archive_mstring_update_utf8' to attempt UTF8->WCS conversion …

…on Windows if MBS conversion fails (#1978)

Currently, functions like `archive_entry_pathname_w` etc. fail on
Windows for .rar files that contain entries with Unicode filenames that
cannot be represented by the active codepage. This is because
`archive_mstring_update_utf8` first attempts to perform a UTF8->MBS
conversion before doing an MBS->WCS conversion. The first conversion (to
MBS) fails, which short-circuits to return failure. Later when we try
and read the string, `archive_mstring_get_wcs` will fail because it
_also_ tries to do a UTF8->MBS followed by an MBS->WCS conversion. The
conversion to MBS will of course fail again.

One possible workaround is to call `setlocale` with something like
`"en_US.utf8"`, however this is not feasible for some consumers.

This change fixes this issue by adding a "fallback" in
'archive_mstring_update_utf8' which will attempt to do a UTF8->WCS
conversion on Windows if the MBS conversion failed. This is not too
dissimilar from the implementation of `archive_mstring_copy_mbs_len_l`
which most - if not all - other archive formats seem to take, which will
by default call `archive_wstring_append_from_mbs_in_codepage` if the
passed in `archive_string_conv` object is non-null

Fixes #1971

libarchive/archive_string.c

@@ -4226,6 +4226,17 @@ archive_mstring_update_utf8(struct archive *a, struct archive_mstring *aes,
 	if (sc == NULL)
 		return (-1);/* Couldn't allocate memory for sc. */
 	r = archive_strcpy_l(&(aes->aes_mbs), utf8, sc);
+
+#if defined(_WIN32) && !defined(__CYGWIN__)
+	/* On failure, make an effort to convert UTF8 to WCS as the active code page
+	 * may not be able to represent all characters in the string */
+	if (r != 0) {
+		if (archive_wstring_append_from_mbs_in_codepage(&(aes->aes_wcs),
+			aes->aes_utf8.s, aes->aes_utf8.length, sc) == 0)
+			aes->aes_set = AES_SET_UTF8 | AES_SET_WCS;
+	}
+#endif
+
 	if (a == NULL)
 		free_sconv_object(sc);
 	if (r != 0)

libarchive/test/test_read_format_rar5.c

@@ -806,6 +806,36 @@ DEFINE_TEST(test_read_format_rar5_extract_win32)
 	EPILOGUE();
 }
 
+DEFINE_TEST(test_read_format_rar5_unicode)
+{
+#if !defined(WIN32) || defined(__CYGWIN__)
+	skipping("Skipping test on non-Windows");
+	return;
+#else
+	/* Corresponds to the names:
+	 * 👋🌎.txt
+	 * 𝒮𝓎𝓂𝒷𝑜𝓁𝒾𝒸 𝐿𝒾𝓃𝓀.txt
+	 * Ⓗⓐⓡⓓ Ⓛⓘⓝⓚ.txt */
+	const wchar_t* emoji_name = L"\U0001f44b\U0001f30e.txt";
+	const wchar_t* italic_name = L"\U0001d4ae\U0001d4ce\U0001d4c2\U0001d4b7\U0001d45c\U0001d4c1\U0001d4be\U0001d4b8 \U0001d43f\U0001d4be\U0001d4c3\U0001d4c0.txt";
+	const wchar_t* circle_name = L"\u24bd\u24d0\u24e1\u24d3 \u24c1\u24d8\u24dd\u24da.txt";
+
+	PROLOGUE("test_read_format_rar5_unicode.rar");
+	assertA(0 == archive_read_next_header(a, &ae));
+	assertEqualWString(emoji_name, archive_entry_pathname_w(ae));
+	assertEqualInt(archive_entry_mode(ae), AE_IFREG | 0644);
+	assertA(0 == archive_read_next_header(a, &ae));
+	assertEqualWString(circle_name, archive_entry_pathname_w(ae));
+	assertEqualInt(archive_entry_mode(ae), AE_IFREG | 0644);
+	assertEqualWString(emoji_name, archive_entry_hardlink_w(ae));
+	assertA(0 == archive_read_next_header(a, &ae));
+	assertEqualWString(italic_name, archive_entry_pathname_w(ae));
+	assertEqualInt(archive_entry_mode(ae), AE_IFLNK | 0644);
+	assertEqualWString(emoji_name, archive_entry_symlink_w(ae));
+	EPILOGUE();
+#endif
+}
+
 DEFINE_TEST(test_read_format_rar5_block_by_block)
 {
 	/* This test uses strange buffer sizes intentionally. */

libarchive/test/test_read_format_rar5_unicode.rar.uu

@@ -0,0 +1,9 @@
+begin 0744 test_read_format_rar5_unicode.rar
+M4F%R(1H'`0#SX8+K"P$%!P`&`0&`@(``//TR$"@"`PN-``2-`"#FQN;K@```
+M#/"?D8OPGXR.+G1X=`H#`D:)>%;RZ]D!2&5L;&\L('=O<FQD(2/9BPA(`@,<
+M``0-(`````"````=XI*]XI.0XI.AXI.3(.*3@>*3F.*3G>*3FBYT>'0*`P)&
+MB7A6\NO9`1`%!``,\)^1B_"?C(XN='ATD-'.1V$"`QP`!`"@"`````"````U
+M\)V2KO"=DX[PG9."\)V2M_"=D9SPG9.!\)V2OO"=DK@@\)V0O_"=DK[PG9.#
+L\)V3@"YT>'0*`P(>7'J>!.S9`1`%`@`,\)^1B_"?C(XN='AT'7=640,%!```
+`
+end