145 lines
4.3 KiB
Diff
145 lines
4.3 KiB
Diff
From 84998f4d717de484c510594e00fd0a6f07babf1c Mon Sep 17 00:00:00 2001
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From: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
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Date: Wed, 3 Mar 2021 19:17:36 +1300
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Subject: [PATCH 002/284] CVE-2020-25718 ldb_match: trailing chunk must match
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Conflict: NA
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Reference: https://git.samba.org/samba.git/?p=samba.git;a=patch;h=84998f4d717de484c510594e00fd0a6f07babf1c
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end of string
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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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A wildcard search is divided into chunks by the asterisks. While most
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chunks match the first suitable string, the last chunk matches the
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last possible string (unless there is a trailing asterisk, in which
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case this distinction is moot).
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We always knew this in our hearts, but we tried to do it in a funny
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complicated way that stepped through the string, comparing here and
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there, leading to CVE-2019-3824 and missed matches (bug 14044).
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With this patch, we just jump to the end of the string and compare it.
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As well as being correct, this should also improve performance, as the
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previous algorithm involved a quadratic loop of erroneous memmem()s.
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See https://tools.ietf.org/html/rfc4517
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BUG: https://bugzilla.samba.org/show_bug.cgi?id=14044
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Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
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Reviewed-by: Bj枚rn Jacke <bjacke@samba.org>
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Reviewed-by: Andrew Bartlett <abartlet@samba.org>
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BUG: https://bugzilla.samba.org/show_bug.cgi?id=14558
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(cherry picked from commit cc098f1cad04b2cfec4ddd6b2511cd5a600f31c6)
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---
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lib/ldb/common/ldb_match.c | 80 +++++++++++++++++---------------------
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1 file changed, 35 insertions(+), 45 deletions(-)
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diff --git a/lib/ldb/common/ldb_match.c b/lib/ldb/common/ldb_match.c
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index 829afa77e716..da595615bd94 100644
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--- a/lib/ldb/common/ldb_match.c
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+++ b/lib/ldb/common/ldb_match.c
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@@ -295,8 +295,9 @@ static int ldb_wildcard_compare(struct ldb_context *ldb,
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uint8_t *p;
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chunk = tree->u.substring.chunks[c];
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- if(a->syntax->canonicalise_fn(ldb, ldb, chunk, &cnk) != 0) goto mismatch;
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-
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+ if(a->syntax->canonicalise_fn(ldb, ldb, chunk, &cnk) != 0) {
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+ goto mismatch;
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+ }
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/*
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* Empty strings are returned as length 0. Ensure
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* we can cope with this.
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@@ -304,52 +305,41 @@ static int ldb_wildcard_compare(struct ldb_context *ldb,
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if (cnk.length == 0) {
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goto mismatch;
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}
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- /*
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- * Values might be binary blobs. Don't use string
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- * search, but memory search instead.
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- */
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- p = memmem((const void *)val.data,val.length,
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- (const void *)cnk.data, cnk.length);
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- if (p == NULL) goto mismatch;
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-
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- /*
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- * At this point we know cnk.length <= val.length as
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- * otherwise there could be no match
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- */
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+ if (cnk.length > val.length) {
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+ goto mismatch;
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+ }
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- if ( (! tree->u.substring.chunks[c + 1]) && (! tree->u.substring.end_with_wildcard) ) {
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- uint8_t *g;
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- uint8_t *end = val.data + val.length;
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- do { /* greedy */
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-
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- /*
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- * haystack is a valid pointer in val
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- * because the memmem() can only
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- * succeed if the needle (cnk.length)
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- * is <= haystacklen
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- *
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- * p will be a pointer at least
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- * cnk.length from the end of haystack
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- */
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- uint8_t *haystack
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- = p + cnk.length;
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- size_t haystacklen
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- = end - (haystack);
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-
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- g = memmem(haystack,
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- haystacklen,
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- (const uint8_t *)cnk.data,
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- cnk.length);
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- if (g) {
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- p = g;
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- }
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- } while(g);
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+ if ( (tree->u.substring.chunks[c + 1]) == NULL &&
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+ (! tree->u.substring.end_with_wildcard) ) {
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+ /*
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+ * The last bit, after all the asterisks, must match
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+ * exactly the last bit of the string.
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+ */
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+ int cmp;
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+ p = val.data + val.length - cnk.length;
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+ cmp = memcmp(p,
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+ cnk.data,
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+ cnk.length);
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+ if (cmp != 0) {
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+ goto mismatch;
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+ }
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+ } else {
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+ /*
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+ * Values might be binary blobs. Don't use string
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+ * search, but memory search instead.
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+ */
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+ p = memmem((const void *)val.data, val.length,
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+ (const void *)cnk.data, cnk.length);
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+ if (p == NULL) {
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+ goto mismatch;
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+ }
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+ /* move val to the end of the match */
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+ p += cnk.length;
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+ val.length -= (p - val.data);
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+ val.data = p;
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}
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- val.length = val.length - (p - (uint8_t *)(val.data)) - cnk.length;
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- val.data = (uint8_t *)(p + cnk.length);
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c++;
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- talloc_free(cnk.data);
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- cnk.data = NULL;
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+ TALLOC_FREE(cnk.data);
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}
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/* last chunk may not have reached end of string */
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--
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2.25.1
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