55 lines
2.0 KiB
Diff
55 lines
2.0 KiB
Diff
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From aa3c16bd709ef9b9c8c785af48f368e08f70c74b Mon Sep 17 00:00:00 2001
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From: Karl Williamson <khw@cpan.org>
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Date: Tue, 17 Jul 2018 13:57:54 -0600
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Subject: [PATCH] Make utf8_to_uvchr() safer
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This function is deprecated because the API doesn't allow it to
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determine the end of the input string, so it can read off the far end.
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But I just realized that since many strings are NUL-terminated, so we
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can forbid it from reading past the next NUL, and hence make it safe in
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many cases.
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Signed-off-by: Petr Písař <ppisar@redhat.com>
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---
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utf8.c | 21 ++++++++++++++++++++-
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1 file changed, 20 insertions(+), 1 deletion(-)
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diff --git a/utf8.c b/utf8.c
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index dec8aa1252..51039aed4f 100644
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--- a/utf8.c
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+++ b/utf8.c
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@@ -6345,7 +6345,26 @@ Perl_utf8_to_uvchr(pTHX_ const U8 *s, STRLEN *retlen)
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{
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PERL_ARGS_ASSERT_UTF8_TO_UVCHR;
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- return utf8_to_uvchr_buf(s, s + UTF8_MAXBYTES, retlen);
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+ /* This function is unsafe if malformed UTF-8 input is given it, which is
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+ * why the function is deprecated. If the first byte of the input
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+ * indicates that there are more bytes remaining in the sequence that forms
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+ * the character than there are in the input buffer, it can read past the
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+ * end. But we can make it safe if the input string happens to be
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+ * NUL-terminated, as many strings in Perl are, by refusing to read past a
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+ * NUL. A NUL indicates the start of the next character anyway. If the
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+ * input isn't NUL-terminated, the function remains unsafe, as it always
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+ * has been.
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+ *
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+ * An initial NUL has to be handled separately, but all ASCIIs can be
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+ * handled the same way, speeding up this common case */
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+
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+ if (UTF8_IS_INVARIANT(*s)) { /* Assumes 's' contains at least 1 byte */
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+ return (UV) *s;
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+ }
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+
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+ return utf8_to_uvchr_buf(s,
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+ s + strnlen((char *) s, UTF8_MAXBYTES),
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+ retlen);
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}
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/*
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--
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2.14.4
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