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From d5a522c0bb738efdd7cc1e762840b579fc9ea3de Mon Sep 17 00:00:00 2001
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From: Laszlo Ersek <lersek@redhat.com>
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Date: Fri, 10 Sep 2021 01:06:17 +0200
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Subject: [PATCH] lib: write: improve key collation compatibility with Windows
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There are multiple problems with using strcasecmp() for ordering registry
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keys:
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(1) strcasecmp() is influenced by LC_CTYPE.
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(2) strcasecmp() cannot implement case conversion for multibyte UTF-8
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sequences.
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(3) Even with LC_CTYPE=POSIX and key names consisting solely of ASCII
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characters, strcasecmp() converts characters to lowercase, for
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comparison. But on Windows, the CompareStringOrdinal() function
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converts characters to uppercase. This makes a difference when
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comparing a letter to one of the characters that fall between 'Z'
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(0x5A) and 'a' (0x61), namely {'[', '\\', ']', '^', '_', '`'}. For
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example,
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'c' (0x63) > '_' (0x5F)
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'C' (0x43) < '_' (0x5F)
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Compare key names byte for byte, eliminating problems (1) and (3).
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1648520
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Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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Message-Id: <20210909230617.31256-1-lersek@redhat.com>
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Acked-by: Richard W.M. Jones <rjones@redhat.com>
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---
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lib/write.c | 32 +++++++++++++++++++++++++++++++-
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1 file changed, 31 insertions(+), 1 deletion(-)
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diff --git a/lib/write.c b/lib/write.c
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index 70105c9d9907..d9a13a3c18b6 100644
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--- a/lib/write.c
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+++ b/lib/write.c
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@@ -462,7 +462,37 @@ compare_name_with_nk_name (hive_h *h, const char *name, hive_node_h nk_offs)
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return 0;
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}
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- int r = strcasecmp (name, nname);
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+ /* Perform a limited case-insensitive comparison. ASCII letters will be
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+ * *upper-cased*. Multibyte sequences will produce nonsensical orderings.
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+ */
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+ int r = 0;
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+ const char *s1 = name;
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+ const char *s2 = nname;
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+
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+ for (;;) {
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+ unsigned char c1 = *(s1++);
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+ unsigned char c2 = *(s2++);
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+
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+ if (c1 >= 'a' && c1 <= 'z')
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+ c1 = 'A' + (c1 - 'a');
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+ if (c2 >= 'a' && c2 <= 'z')
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+ c2 = 'A' + (c2 - 'a');
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+ if (c1 < c2) {
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+ /* Also covers the case when "name" is a prefix of "nname". */
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+ r = -1;
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+ break;
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+ }
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+ if (c1 > c2) {
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+ /* Also covers the case when "nname" is a prefix of "name". */
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+ r = 1;
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+ break;
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+ }
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+ if (c1 == '\0') {
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+ /* Both strings end. */
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+ break;
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+ }
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+ }
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+
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free (nname);
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return r;
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--
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2.19.1.3.g30247aa5d201
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