181 lines
5.7 KiB
Diff
181 lines
5.7 KiB
Diff
From d1a83b6767f68b3cb5b4b4ea2617254acd040c82 Mon Sep 17 00:00:00 2001
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From: Arjun Shankar <arjun@redhat.com>
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Date: Mon, 15 Jan 2024 17:44:43 +0100
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Subject: [PATCH] syslog: Fix heap buffer overflow in __vsyslog_internal
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(CVE-2023-6246)
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__vsyslog_internal did not handle a case where printing a SYSLOG_HEADER
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containing a long program name failed to update the required buffer
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size, leading to the allocation and overflow of a too-small buffer on
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the heap. This commit fixes that. It also adds a new regression test
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that uses glibc.malloc.check.
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Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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Tested-by: Carlos O'Donell <carlos@redhat.com>
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(cherry picked from commit 6bd0e4efcc78f3c0115e5ea9739a1642807450da)
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---
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misc/Makefile | 8 ++-
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misc/syslog.c | 50 +++++++++++++------
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misc/tst-syslog-long-progname.c | 39 +++++++++++++++
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.../postclean.req | 0
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4 files changed, 82 insertions(+), 15 deletions(-)
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create mode 100644 misc/tst-syslog-long-progname.c
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create mode 100644 misc/tst-syslog-long-progname.root/postclean.req
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diff --git a/misc/Makefile b/misc/Makefile
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index ba8232a0e9..66e9ded8f9 100644
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--- a/misc/Makefile
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+++ b/misc/Makefile
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@@ -115,7 +115,10 @@ tests-special += $(objpfx)tst-error1-mem.out \
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$(objpfx)tst-allocate_once-mem.out
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endif
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-tests-container := tst-syslog
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+tests-container := \
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+ tst-syslog \
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+ tst-syslog-long-progname \
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+ # tests-container
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CFLAGS-select.c += -fexceptions -fasynchronous-unwind-tables
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CFLAGS-tsearch.c += $(uses-callbacks)
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@@ -175,6 +178,9 @@ $(objpfx)tst-allocate_once-mem.out: $(objpfx)tst-allocate_once.out
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$(common-objpfx)malloc/mtrace $(objpfx)tst-allocate_once.mtrace > $@; \
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$(evaluate-test)
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+tst-syslog-long-progname-ENV = GLIBC_TUNABLES=glibc.malloc.check=3 \
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+ LD_PRELOAD=libc_malloc_debug.so.0
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+
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$(objpfx)tst-select: $(librt)
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$(objpfx)tst-select-time64: $(librt)
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$(objpfx)tst-pselect: $(librt)
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diff --git a/misc/syslog.c b/misc/syslog.c
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index f67d4b58a4..fe1daf988b 100644
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--- a/misc/syslog.c
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+++ b/misc/syslog.c
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@@ -122,8 +122,9 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
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{
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/* Try to use a static buffer as an optimization. */
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char bufs[1024];
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- char *buf = NULL;
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- size_t bufsize = 0;
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+ char *buf = bufs;
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+ size_t bufsize;
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+
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int msgoff;
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int saved_errno = errno;
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@@ -175,29 +176,50 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
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#define SYSLOG_HEADER_WITHOUT_TS(__pri, __msgoff) \
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"<%d>: %n", __pri, __msgoff
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- int l;
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+ int l, vl;
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if (has_ts)
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l = __snprintf (bufs, sizeof bufs,
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SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
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else
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l = __snprintf (bufs, sizeof bufs,
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SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
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+
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+ char *pos;
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+ size_t len;
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+
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if (0 <= l && l < sizeof bufs)
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{
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- va_list apc;
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- va_copy (apc, ap);
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+ /* At this point, there is still a chance that we can print the
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+ remaining part of the log into bufs and use that. */
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+ pos = bufs + l;
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+ len = sizeof (bufs) - l;
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+ }
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+ else
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+ {
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+ buf = NULL;
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+ /* We already know that bufs is too small to use for this log message.
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+ The next vsnprintf into bufs is used only to calculate the total
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+ required buffer length. We will discard bufs contents and allocate
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+ an appropriately sized buffer later instead. */
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+ pos = bufs;
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+ len = sizeof (bufs);
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+ }
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- /* Restore errno for %m format. */
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- __set_errno (saved_errno);
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+ {
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+ va_list apc;
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+ va_copy (apc, ap);
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- int vl = __vsnprintf_internal (bufs + l, sizeof bufs - l, fmt, apc,
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- mode_flags);
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- if (0 <= vl && vl < sizeof bufs - l)
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- buf = bufs;
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- bufsize = l + vl;
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+ /* Restore errno for %m format. */
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+ __set_errno (saved_errno);
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- va_end (apc);
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- }
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+ vl = __vsnprintf_internal (pos, len, fmt, apc, mode_flags);
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+
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+ if (!(0 <= vl && vl < len))
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+ buf = NULL;
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+
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+ bufsize = l + vl;
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+ va_end (apc);
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+ }
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if (buf == NULL)
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{
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diff --git a/misc/tst-syslog-long-progname.c b/misc/tst-syslog-long-progname.c
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new file mode 100644
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index 0000000000..88f37a8a00
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--- /dev/null
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+++ b/misc/tst-syslog-long-progname.c
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@@ -0,0 +1,39 @@
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+/* Test heap buffer overflow in syslog with long __progname (CVE-2023-6246)
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+ Copyright (C) 2023 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <syslog.h>
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+#include <string.h>
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+
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+extern char * __progname;
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+
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+static int
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+do_test (void)
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+{
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+ char long_progname[2048];
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+
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+ memset (long_progname, 'X', sizeof (long_progname) - 1);
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+ long_progname[sizeof (long_progname) - 1] = '\0';
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+
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+ __progname = long_progname;
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+
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+ syslog (LOG_INFO, "Hello, World!");
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+
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+ return 0;
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+}
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+
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+#include <support/test-driver.c>
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diff --git a/misc/tst-syslog-long-progname.root/postclean.req b/misc/tst-syslog-long-progname.root/postclean.req
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new file mode 100644
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index 0000000000..e69de29bb2
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--
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2.39.3
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