118 lines
4.4 KiB
Diff
118 lines
4.4 KiB
Diff
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From 068862767ef95ebc54977e1df49ab700c20ae347 Mon Sep 17 00:00:00 2001
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From: Peter Hutterer <peter.hutterer@who-t.net>
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Date: Tue, 20 Dec 2022 10:42:03 +1000
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Subject: [PATCH xserver 3/3] Disallow byte-swapped clients by default
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The X server swapping code is a huge attack surface, much of this code
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is untested and prone to security issues. The use-case of byte-swapped
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clients is very niche, so let's disable this by default and allow it
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only when the respective config option or commandline flag is given.
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For Xorg, this adds the ServerFlag "AllowByteSwappedClients" "on".
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For all DDX, this adds the commandline options +byteswappedclients and
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-byteswappedclients to enable or disable, respectively.
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Fixes #1201
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https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1029
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Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
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(cherry picked from commit 412777664a20dd3561b936c02c96571a756fe9b2)
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---
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dix/dispatch.c | 4 +++-
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hw/xwayland/xwayland.pc.in | 1 +
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include/opaque.h | 2 ++
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man/Xserver.man | 6 ++++++
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os/utils.c | 9 +++++++++
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5 files changed, 21 insertions(+), 1 deletion(-)
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diff --git a/dix/dispatch.c b/dix/dispatch.c
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index 2efa2dcf1..0570ec07c 100644
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--- a/dix/dispatch.c
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+++ b/dix/dispatch.c
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@@ -3777,7 +3777,9 @@ ProcEstablishConnection(ClientPtr client)
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prefix = (xConnClientPrefix *) ((char *) stuff + sz_xReq);
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- if ((client->req_len << 2) != sz_xReq + sz_xConnClientPrefix +
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+ if (client->swapped && !AllowByteSwappedClients) {
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+ reason = "Prohibited client endianess, see the Xserver man page ";
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+ } else if ((client->req_len << 2) != sz_xReq + sz_xConnClientPrefix +
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pad_to_int32(prefix->nbytesAuthProto) +
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pad_to_int32(prefix->nbytesAuthString))
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reason = "Bad length";
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diff --git a/hw/xwayland/xwayland.pc.in b/hw/xwayland/xwayland.pc.in
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index 9d727b002..e920d7608 100644
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--- a/hw/xwayland/xwayland.pc.in
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+++ b/hw/xwayland/xwayland.pc.in
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@@ -12,3 +12,4 @@ have_listenfd=true
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have_verbose=true
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have_terminate_delay=true
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have_no_touch_pointer_emulation=true
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+have_byteswappedclients=true
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diff --git a/include/opaque.h b/include/opaque.h
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index 256261c2a..398d4b4e5 100644
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--- a/include/opaque.h
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+++ b/include/opaque.h
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@@ -74,4 +74,6 @@ extern _X_EXPORT Bool bgNoneRoot;
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extern _X_EXPORT Bool CoreDump;
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extern _X_EXPORT Bool NoListenAll;
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+extern _X_EXPORT Bool AllowByteSwappedClients;
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+
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#endif /* OPAQUE_H */
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diff --git a/man/Xserver.man b/man/Xserver.man
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index 764bd1d90..e7adf9eb3 100644
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--- a/man/Xserver.man
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+++ b/man/Xserver.man
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@@ -114,6 +114,12 @@ pattern. This is the default unless -retro or -wr is specified.
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.B \-bs
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disables backing store support on all screens.
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.TP 8
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+.B \+byteswappedclients
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+Allow connections from clients with an endianess different to that of the server.
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+.TP 8
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+.B \-byteswappedclients
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+Prohibit connections from clients with an endianess different to that of the server.
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+.TP 8
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.B \-c
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turns off key-click.
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.TP 8
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diff --git a/os/utils.c b/os/utils.c
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index c9a8e7367..6f5e64cee 100644
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--- a/os/utils.c
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+++ b/os/utils.c
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@@ -189,6 +189,8 @@ Bool CoreDump;
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Bool enableIndirectGLX = FALSE;
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+Bool AllowByteSwappedClients = FALSE;
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+
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#ifdef PANORAMIX
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Bool PanoramiXExtensionDisabledHack = FALSE;
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#endif
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@@ -523,6 +525,8 @@ UseMsg(void)
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ErrorF("-br create root window with black background\n");
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ErrorF("+bs enable any backing store support\n");
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ErrorF("-bs disable any backing store support\n");
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+ ErrorF("+byteswappedclients Allow clients with endianess different to that of the server\n");
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+ ErrorF("-byteswappedclients Prohibit clients with endianess different to that of the server\n");
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ErrorF("-c turns off key-click\n");
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ErrorF("c # key-click volume (0-100)\n");
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ErrorF("-cc int default color visual class\n");
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@@ -720,6 +724,11 @@ ProcessCommandLine(int argc, char *argv[])
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else
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UseMsg();
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}
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+ else if (strcmp(argv[i], "-byteswappedclients") == 0) {
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+ AllowByteSwappedClients = FALSE;
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+ } else if (strcmp(argv[i], "+byteswappedclients") == 0) {
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+ AllowByteSwappedClients = TRUE;
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+ }
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else if (strcmp(argv[i], "-br") == 0); /* default */
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else if (strcmp(argv[i], "+bs") == 0)
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enableBackingStore = TRUE;
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--
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2.39.0
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