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package/screen: add security fix for CVE-2021-26937

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encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a
denial of service (invalid write access and application crash) or possibly
have unspecified other impact via a crafted UTF-8 character sequence.

For more details, see the oss-security discussion:
https://www.openwall.com/lists/oss-security/2021/02/09/3

So far no fix has been added to upstream git, and a number of early proposed
fixes caused regressions, so pull the security fix from the screen 4.8.0-5
Debian package.

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
This commit is contained in:
Peter Korsgaard 2021-02-27 00:22:55 +01:00 committed by Yann E. MORIN
parent 42c80b515a
commit 6ca1a7c277
2 changed files with 71 additions and 0 deletions
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68
package/screen/0008_CVE-2021-26937.patch Normal file
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@ -0,0 +1,68 @@
Description: [CVE-2021-26937] Fix out of bounds array access
Author: Michael Schröder <mls@suse.de>
Bug-Debian: https://bugs.debian.org/982435
Bug: https://savannah.gnu.org/bugs/?60030
Bug: https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00000.html
Bug-OSS-Security: https://www.openwall.com/lists/oss-security/2021/02/09/3
Origin: https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00010.html
Downloaded from Debian:
https://sources.debian.org/data/main/s/screen/4.8.0-5/debian/patches/99_CVE-2021-26937.patch
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
--- a/encoding.c
+++ b/encoding.c
@@ -43,7 +43,7 @@
# ifdef UTF8
static int recode_char __P((int, int, int));
static int recode_char_to_encoding __P((int, int));
-static void comb_tofront __P((int, int));
+static void comb_tofront __P((int));
# ifdef DW_CHARS
static int recode_char_dw __P((int, int *, int, int));
static int recode_char_dw_to_encoding __P((int, int *, int));
@@ -1263,6 +1263,8 @@
{0x30000, 0x3FFFD},
};
+ if (c >= 0xdf00 && c <= 0xdfff)
+ return 1; /* dw combining sequence */
return ((bisearch(c, wide, sizeof(wide) / sizeof(struct interval) - 1)) ||
(cjkwidth &&
bisearch(c, ambiguous,
@@ -1330,11 +1332,12 @@
}
static void
-comb_tofront(root, i)
-int root, i;
+comb_tofront(i)
+int i;
{
for (;;)
{
+ int root = i >= 0x700 ? 0x801 : 0x800;
debug1("bring to front: %x\n", i);
combchars[combchars[i]->prev]->next = combchars[i]->next;
combchars[combchars[i]->next]->prev = combchars[i]->prev;
@@ -1396,9 +1399,9 @@
{
/* full, recycle old entry */
if (c1 >= 0xd800 && c1 < 0xe000)
- comb_tofront(root, c1 - 0xd800);
+ comb_tofront(c1 - 0xd800);
i = combchars[root]->prev;
- if (c1 == i + 0xd800)
+ if (i == 0x800 || i == 0x801 || c1 == i + 0xd800)
{
/* completely full, can't recycle */
debug("utf8_handle_comp: completely full!\n");
@@ -1422,7 +1425,7 @@
mc->font = (i >> 8) + 0xd8;
mc->fontx = 0;
debug3("combinig char %x %x -> %x\n", c1, c, i + 0xd800);
- comb_tofront(root, i);
+ comb_tofront(i);
}
#else /* !UTF8 */

3
package/screen/screen.mk
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@ -15,6 +15,9 @@ SCREEN_CONF_ENV = CFLAGS="$(TARGET_CFLAGS)"
SCREEN_CONF_OPTS = --enable-colors256
SCREEN_INSTALL_TARGET_OPTS = DESTDIR=$(TARGET_DIR) SCREEN=screen install_bin
# 0008_CVE-2021-26937.patch
SCREEN_IGNORE_CVES += CVE-2021-26937
ifeq ($(BR2_PACKAGE_LINUX_PAM),y)
SCREEN_DEPENDENCIES += linux-pam
SCREEN_CONF_OPTS += --enable-pam