* Bash 5 change in behavior and SELinux
@ 2019-02-24 16:59 Dominick Grift
2019-02-24 17:39 ` Dominick Grift
0 siblings, 1 reply; 6+ messages in thread
From: Dominick Grift @ 2019-02-24 16:59 UTC (permalink / raw)
To: selinux
Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
[kcinimod@brutus ~]$ touch mytest1.test
[kcinimod@brutus ~]$ rm ~/*.test
rm: cannot remove '/home/kcinimod/*.test': No such file or directory
[kcinimod@brutus ~]$ rm ~/mytest1.test
[kcinimod@brutus ~]$ echo $?
0
After running `semodule -DB` the following AVC denials surfaced:
avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
So I took to #bash and they told me:
17:43 <_abc_> grift: that is exactly what you see on android and is
a direct result of the missing x bit equivalent in
the selinux policy
17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
set
17:44 <_abc_> (it's equivalent in selinux policy)
So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
Scripts break everywhere because of this
Here is an strace:
execve("/usr/bin/rm", ["rm", "/home/kcinimod/*.test"], 0x7ffd4a604e68 /* 33 vars */) = 0
brk(NULL) = 0x55fd172f2000
arch_prctl(0x3001 /* ARCH_??? */, 0x7ffd55284d40) = -1 EINVAL (Invalid argument)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=73196, ...}) = 0
mmap(NULL, 73196, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f2000
close(3) = 0
openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@@\2\0\0\0\0\0"..., 832) = 832
lseek(3, 792, SEEK_SET) = 792
read(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0's\373BN\237-\352\fHBW\214\275t\225"..., 68) = 68
fstat(3, {st_mode=S_IFREG|0755, st_size=5591560, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce3e2f0000
lseek(3, 792, SEEK_SET) = 792
read(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0's\373BN\237-\352\fHBW\214\275t\225"..., 68) = 68
lseek(3, 864, SEEK_SET) = 864
read(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32) = 32
mmap(NULL, 1857568, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fce3e12a000
mprotect(0x7fce3e14c000, 1679360, PROT_NONE) = 0
mmap(0x7fce3e14c000, 1363968, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fce3e14c000
mmap(0x7fce3e299000, 311296, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16f000) = 0x7fce3e299000
mmap(0x7fce3e2e6000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1bb000) = 0x7fce3e2e6000
mmap(0x7fce3e2ec000, 14368, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fce3e2ec000
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7fce3e2f1580) = 0
mprotect(0x7fce3e2e6000, 16384, PROT_READ) = 0
mprotect(0x55fd17129000, 4096, PROT_READ) = 0
mprotect(0x7fce3e32e000, 4096, PROT_READ) = 0
munmap(0x7fce3e2f2000, 73196) = 0
brk(NULL) = 0x55fd172f2000
brk(0x55fd17313000) = 0x55fd17313000
brk(NULL) = 0x55fd17313000
openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2997, ...}) = 0
read(3, "# Locale name alias data base.\n#"..., 4096) = 2997
read(3, "", 4096) = 0
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_IDENTIFICATION", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_IDENTIFICATION", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=368, ...}) = 0
mmap(NULL, 368, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e32d000
close(3) = 0
openat(AT_FDCWD, "/usr/lib64/gconv/gconv-modules.cache", O_RDONLY) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=26398, ...}) = 0
mmap(NULL, 26398, PROT_READ, MAP_SHARED, 3, 0) = 0x7fce3e2fd000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MEASUREMENT", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MEASUREMENT", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=23, ...}) = 0
mmap(NULL, 23, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fc000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TELEPHONE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TELEPHONE", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=59, ...}) = 0
mmap(NULL, 59, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fb000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_ADDRESS", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_ADDRESS", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=167, ...}) = 0
mmap(NULL, 167, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fa000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NAME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NAME", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=77, ...}) = 0
mmap(NULL, 77, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f9000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_PAPER", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_PAPER", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=34, ...}) = 0
mmap(NULL, 34, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f8000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MESSAGES", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MESSAGES", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MESSAGES/SYS_LC_MESSAGES", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=57, ...}) = 0
mmap(NULL, 57, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f7000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=286, ...}) = 0
mmap(NULL, 286, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f6000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_COLLATE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_COLLATE", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=2586242, ...}) = 0
mmap(NULL, 2586242, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3deb2000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TIME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TIME", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=3284, ...}) = 0
mmap(NULL, 3284, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f5000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=54, ...}) = 0
mmap(NULL, 54, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f4000
close(3) = 0
openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=337024, ...}) = 0
mmap(NULL, 337024, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3de5f000
close(3) = 0
ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
newfstatat(AT_FDCWD, "/home/kcinimod/*.test", 0x55fd172f88e8, AT_SYMLINK_NOFOLLOW) = -1 ENOENT (No such file or directory)
geteuid() = 1000
newfstatat(AT_FDCWD, "/home/kcinimod/*.test", 0x7ffd55284a60, AT_SYMLINK_NOFOLLOW) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, "rm: ", 4rm: ) = 4
write(2, "cannot remove '/home/kcinimod/*."..., 37cannot remove '/home/kcinimod/*.test') = 37
openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
write(2, ": No such file or directory", 27: No such file or directory) = 27
write(2, "\n", 1
) = 1
lseek(0, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
close(0) = 0
close(1) = 0
close(2) = 0
exit_group(1) = ?
+++ exited with 1 +++
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Bash 5 change in behavior and SELinux
2019-02-24 16:59 Bash 5 change in behavior and SELinux Dominick Grift
@ 2019-02-24 17:39 ` Dominick Grift
2019-02-24 18:17 ` Nicolas Iooss
0 siblings, 1 reply; 6+ messages in thread
From: Dominick Grift @ 2019-02-24 17:39 UTC (permalink / raw)
To: selinux
On Sun, Feb 24, 2019 at 05:59:19PM +0100, Dominick Grift wrote:
> Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
I suppose this is just a "feature" or a "bug" in Bash-5 and that i will just have to deal with it. Just seems a bit unnecessary access to me.
>
> [kcinimod@brutus ~]$ touch mytest1.test
> [kcinimod@brutus ~]$ rm ~/*.test
> rm: cannot remove '/home/kcinimod/*.test': No such file or directory
> [kcinimod@brutus ~]$ rm ~/mytest1.test
> [kcinimod@brutus ~]$ echo $?
> 0
>
> After running `semodule -DB` the following AVC denials surfaced:
>
> avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
> avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
>
> So I took to #bash and they told me:
>
> 17:43 <_abc_> grift: that is exactly what you see on android and is
> a direct result of the missing x bit equivalent in
> the selinux policy
>
> 17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
> set
> 17:44 <_abc_> (it's equivalent in selinux policy)
>
> So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
>
> Scripts break everywhere because of this
>
> Here is an strace:
>
> execve("/usr/bin/rm", ["rm", "/home/kcinimod/*.test"], 0x7ffd4a604e68 /* 33 vars */) = 0
> brk(NULL) = 0x55fd172f2000
> arch_prctl(0x3001 /* ARCH_??? */, 0x7ffd55284d40) = -1 EINVAL (Invalid argument)
> access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=73196, ...}) = 0
> mmap(NULL, 73196, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f2000
> close(3) = 0
> openat(AT_FDCWD, "/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
> read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0@@\2\0\0\0\0\0"..., 832) = 832
> lseek(3, 792, SEEK_SET) = 792
> read(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0's\373BN\237-\352\fHBW\214\275t\225"..., 68) = 68
> fstat(3, {st_mode=S_IFREG|0755, st_size=5591560, ...}) = 0
> mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fce3e2f0000
> lseek(3, 792, SEEK_SET) = 792
> read(3, "\4\0\0\0\24\0\0\0\3\0\0\0GNU\0's\373BN\237-\352\fHBW\214\275t\225"..., 68) = 68
> lseek(3, 864, SEEK_SET) = 864
> read(3, "\4\0\0\0\20\0\0\0\5\0\0\0GNU\0\2\0\0\300\4\0\0\0\3\0\0\0\0\0\0\0", 32) = 32
> mmap(NULL, 1857568, PROT_READ, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fce3e12a000
> mprotect(0x7fce3e14c000, 1679360, PROT_NONE) = 0
> mmap(0x7fce3e14c000, 1363968, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x22000) = 0x7fce3e14c000
> mmap(0x7fce3e299000, 311296, PROT_READ, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x16f000) = 0x7fce3e299000
> mmap(0x7fce3e2e6000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1bb000) = 0x7fce3e2e6000
> mmap(0x7fce3e2ec000, 14368, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fce3e2ec000
> close(3) = 0
> arch_prctl(ARCH_SET_FS, 0x7fce3e2f1580) = 0
> mprotect(0x7fce3e2e6000, 16384, PROT_READ) = 0
> mprotect(0x55fd17129000, 4096, PROT_READ) = 0
> mprotect(0x7fce3e32e000, 4096, PROT_READ) = 0
> munmap(0x7fce3e2f2000, 73196) = 0
> brk(NULL) = 0x55fd172f2000
> brk(0x55fd17313000) = 0x55fd17313000
> brk(NULL) = 0x55fd17313000
> openat(AT_FDCWD, "/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/locale.alias", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=2997, ...}) = 0
> read(3, "# Locale name alias data base.\n#"..., 4096) = 2997
> read(3, "", 4096) = 0
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_IDENTIFICATION", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_IDENTIFICATION", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=368, ...}) = 0
> mmap(NULL, 368, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e32d000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib64/gconv/gconv-modules.cache", O_RDONLY) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=26398, ...}) = 0
> mmap(NULL, 26398, PROT_READ, MAP_SHARED, 3, 0) = 0x7fce3e2fd000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MEASUREMENT", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MEASUREMENT", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=23, ...}) = 0
> mmap(NULL, 23, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fc000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TELEPHONE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TELEPHONE", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=59, ...}) = 0
> mmap(NULL, 59, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fb000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_ADDRESS", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_ADDRESS", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=167, ...}) = 0
> mmap(NULL, 167, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2fa000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NAME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NAME", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=77, ...}) = 0
> mmap(NULL, 77, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f9000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_PAPER", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_PAPER", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=34, ...}) = 0
> mmap(NULL, 34, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f8000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MESSAGES", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MESSAGES", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MESSAGES/SYS_LC_MESSAGES", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=57, ...}) = 0
> mmap(NULL, 57, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f7000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_MONETARY", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=286, ...}) = 0
> mmap(NULL, 286, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f6000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_COLLATE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_COLLATE", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=2586242, ...}) = 0
> mmap(NULL, 2586242, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3deb2000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_TIME", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_TIME", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=3284, ...}) = 0
> mmap(NULL, 3284, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f5000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_NUMERIC", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=54, ...}) = 0
> mmap(NULL, 54, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3e2f4000
> close(3) = 0
> openat(AT_FDCWD, "/usr/lib/locale/en_US.UTF-8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/lib/locale/en_US.utf8/LC_CTYPE", O_RDONLY|O_CLOEXEC) = 3
> fstat(3, {st_mode=S_IFREG|0644, st_size=337024, ...}) = 0
> mmap(NULL, 337024, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fce3de5f000
> close(3) = 0
> ioctl(0, TCGETS, {B38400 opost isig icanon echo ...}) = 0
> newfstatat(AT_FDCWD, "/home/kcinimod/*.test", 0x55fd172f88e8, AT_SYMLINK_NOFOLLOW) = -1 ENOENT (No such file or directory)
> geteuid() = 1000
> newfstatat(AT_FDCWD, "/home/kcinimod/*.test", 0x7ffd55284a60, AT_SYMLINK_NOFOLLOW) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/coreutils.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> write(2, "rm: ", 4rm: ) = 4
> write(2, "cannot remove '/home/kcinimod/*."..., 37cannot remove '/home/kcinimod/*.test') = 37
> openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en_US.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en_US/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en.utf8/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> openat(AT_FDCWD, "/usr/share/locale/en/LC_MESSAGES/libc.mo", O_RDONLY) = -1 ENOENT (No such file or directory)
> write(2, ": No such file or directory", 27: No such file or directory) = 27
> write(2, "\n", 1
> ) = 1
> lseek(0, 0, SEEK_CUR) = -1 ESPIPE (Illegal seek)
> close(0) = 0
> close(1) = 0
> close(2) = 0
> exit_group(1) = ?
> +++ exited with 1 +++
>
> --
> Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
> https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
> Dominick Grift
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Bash 5 change in behavior and SELinux
2019-02-24 17:39 ` Dominick Grift
@ 2019-02-24 18:17 ` Nicolas Iooss
2019-02-24 18:37 ` Dominick Grift
0 siblings, 1 reply; 6+ messages in thread
From: Nicolas Iooss @ 2019-02-24 18:17 UTC (permalink / raw)
To: Dominick Grift; +Cc: selinux
On Sun, Feb 24, 2019 at 6:39 PM Dominick Grift
<dominick.grift@defensec.nl> wrote:
>
> On Sun, Feb 24, 2019 at 05:59:19PM +0100, Dominick Grift wrote:
> > Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
>
> I suppose this is just a "feature" or a "bug" in Bash-5 and that i will just have to deal with it. Just seems a bit unnecessary access to me.
>
> >
> > [kcinimod@brutus ~]$ touch mytest1.test
> > [kcinimod@brutus ~]$ rm ~/*.test
> > rm: cannot remove '/home/kcinimod/*.test': No such file or directory
> > [kcinimod@brutus ~]$ rm ~/mytest1.test
> > [kcinimod@brutus ~]$ echo $?
> > 0
> >
> > After running `semodule -DB` the following AVC denials surfaced:
> >
> > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
> > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
[For other readers: these are the labels of /home and /, the parent
directories of /home/kcinimod/]
> > So I took to #bash and they told me:
> >
> > 17:43 <_abc_> grift: that is exactly what you see on android and is
> > a direct result of the missing x bit equivalent in
> > the selinux policy
> >
> > 17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
> > set
> > 17:44 <_abc_> (it's equivalent in selinux policy)
> >
> > So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
> >
> > Scripts break everywhere because of this
What is the syscall associated with the avc entries? This would help
finding in bash's source what triggered this behavior.
I tried to reproduce your commands in Arch Linux (bash package
5.0.0-1) or Fedora 30 (bash package 5.0.2-1.fc30 for x86_64) by using
strace on bash and watching the syscalls, but nothing stood out: I see
an "openat(AT_FDCWD, "/home/kcinimod/",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3" followed by calls to
"getdents64(3, ...)", which are like expected. This could be due to
several things:
* The bash version you are using is not 5.0.2-1.fc30. Which one are you using?
* It might come from a kernel bug (which would open the parent
directories with read access). That would be really strange, but only
to be sure: is bash 4 working fine when you downgrade bash package
while keeping the same kernel?
* Or it might come from a bash dependency (like readline).
> >
> > Here is an strace:
> >
> > execve("/usr/bin/rm", ["rm", "/home/kcinimod/*.test"], 0x7ffd4a604e68 /* 33 vars */) = 0
By the way, using strace on rm was not useful because it only showed
that it was been called with the raw (unexpanded) parameter. Could you
run the same commands of your test-case in a "strace -s1024 -o
strace-bash.log bash" and share the resulting strace-bash.log file?
Thanks,
Nicolas
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Bash 5 change in behavior and SELinux
2019-02-24 18:17 ` Nicolas Iooss
@ 2019-02-24 18:37 ` Dominick Grift
2019-02-24 20:32 ` Nicolas Iooss
0 siblings, 1 reply; 6+ messages in thread
From: Dominick Grift @ 2019-02-24 18:37 UTC (permalink / raw)
To: Nicolas Iooss; +Cc: selinux
On Sun, Feb 24, 2019 at 07:17:33PM +0100, Nicolas Iooss wrote:
> On Sun, Feb 24, 2019 at 6:39 PM Dominick Grift
> <dominick.grift@defensec.nl> wrote:
> >
> > On Sun, Feb 24, 2019 at 05:59:19PM +0100, Dominick Grift wrote:
> > > Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
> >
> > I suppose this is just a "feature" or a "bug" in Bash-5 and that i will just have to deal with it. Just seems a bit unnecessary access to me.
> >
> > >
> > > [kcinimod@brutus ~]$ touch mytest1.test
> > > [kcinimod@brutus ~]$ rm ~/*.test
> > > rm: cannot remove '/home/kcinimod/*.test': No such file or directory
> > > [kcinimod@brutus ~]$ rm ~/mytest1.test
> > > [kcinimod@brutus ~]$ echo $?
> > > 0
> > >
> > > After running `semodule -DB` the following AVC denials surfaced:
> > >
> > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
> > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
>
> [For other readers: these are the labels of /home and /, the parent
> directories of /home/kcinimod/]
>
> > > So I took to #bash and they told me:
> > >
> > > 17:43 <_abc_> grift: that is exactly what you see on android and is
> > > a direct result of the missing x bit equivalent in
> > > the selinux policy
> > >
> > > 17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
> > > set
> > > 17:44 <_abc_> (it's equivalent in selinux policy)
> > >
> > > So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
> > >
> > > Scripts break everywhere because of this
>
> What is the syscall associated with the avc entries? This would help
> finding in bash's source what triggered this behavior.
> I tried to reproduce your commands in Arch Linux (bash package
> 5.0.0-1) or Fedora 30 (bash package 5.0.2-1.fc30 for x86_64) by using
> strace on bash and watching the syscalls, but nothing stood out: I see
> an "openat(AT_FDCWD, "/home/kcinimod/",
> O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3" followed by calls to
> "getdents64(3, ...)", which are like expected. This could be due to
> several things:
type=SYSCALL msg=audit(02/24/2019 19:33:13.924:18121) : arch=x86_64 syscall=openat success=yes exit=3 a0=0xffffff9c a1=0x561168c81e40 a2=O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC a3=0x0 items=1 ppid=2270 pid=27900 auid=kcinimod uid=kcinimod gid=kcinimod euid=kcinimod suid=kcinimod fsuid=
>
> * The bash version you are using is not 5.0.2-1.fc30. Which one are you using?
it is 5.0.2-1, downgrading to 4.4.23-7 fixes it
> * It might come from a kernel bug (which would open the parent
> directories with read access). That would be really strange, but only
> to be sure: is bash 4 working fine when you downgrade bash package
> while keeping the same kernel?
Yes 4 is fine
> * Or it might come from a bash dependency (like readline).
Does not look like it: just downgrading "bash" fixes it
>
> > >
> > > Here is an strace:
> > >
> > > execve("/usr/bin/rm", ["rm", "/home/kcinimod/*.test"], 0x7ffd4a604e68 /* 33 vars */) = 0
>
> By the way, using strace on rm was not useful because it only showed
> that it was been called with the raw (unexpanded) parameter. Could you
> run the same commands of your test-case in a "strace -s1024 -o
> strace-bash.log bash" and share the resulting strace-bash.log file?
>
> Thanks,
> Nicolas
>
--
Key fingerprint = 5F4D 3CDB D3F8 3652 FBD8 02D5 3B6C 5F1D 2C7B 6B02
https://sks-keyservers.net/pks/lookup?op=get&search=0x3B6C5F1D2C7B6B02
Dominick Grift
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Bash 5 change in behavior and SELinux
2019-02-24 18:37 ` Dominick Grift
@ 2019-02-24 20:32 ` Nicolas Iooss
2019-02-25 7:35 ` Dominick Grift
0 siblings, 1 reply; 6+ messages in thread
From: Nicolas Iooss @ 2019-02-24 20:32 UTC (permalink / raw)
To: Dominick Grift; +Cc: selinux
On Sun, Feb 24, 2019 at 7:37 PM Dominick Grift
<dominick.grift@defensec.nl> wrote:
>
> On Sun, Feb 24, 2019 at 07:17:33PM +0100, Nicolas Iooss wrote:
> > On Sun, Feb 24, 2019 at 6:39 PM Dominick Grift
> > <dominick.grift@defensec.nl> wrote:
> > >
> > > On Sun, Feb 24, 2019 at 05:59:19PM +0100, Dominick Grift wrote:
> > > > Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
> > >
> > > I suppose this is just a "feature" or a "bug" in Bash-5 and that i will just have to deal with it. Just seems a bit unnecessary access to me.
> > >
> > > >
> > > > [kcinimod@brutus ~]$ touch mytest1.test
> > > > [kcinimod@brutus ~]$ rm ~/*.test
> > > > rm: cannot remove '/home/kcinimod/*.test': No such file or directory
> > > > [kcinimod@brutus ~]$ rm ~/mytest1.test
> > > > [kcinimod@brutus ~]$ echo $?
> > > > 0
> > > >
> > > > After running `semodule -DB` the following AVC denials surfaced:
> > > >
> > > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
> > > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
> >
> > [For other readers: these are the labels of /home and /, the parent
> > directories of /home/kcinimod/]
> >
> > > > So I took to #bash and they told me:
> > > >
> > > > 17:43 <_abc_> grift: that is exactly what you see on android and is
> > > > a direct result of the missing x bit equivalent in
> > > > the selinux policy
> > > >
> > > > 17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
> > > > set
> > > > 17:44 <_abc_> (it's equivalent in selinux policy)
> > > >
> > > > So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
> > > >
> > > > Scripts break everywhere because of this
> >
> > What is the syscall associated with the avc entries? This would help
> > finding in bash's source what triggered this behavior.
> > I tried to reproduce your commands in Arch Linux (bash package
> > 5.0.0-1) or Fedora 30 (bash package 5.0.2-1.fc30 for x86_64) by using
> > strace on bash and watching the syscalls, but nothing stood out: I see
> > an "openat(AT_FDCWD, "/home/kcinimod/",
> > O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3" followed by calls to
> > "getdents64(3, ...)", which are like expected. This could be due to
> > several things:
>
> type=SYSCALL msg=audit(02/24/2019 19:33:13.924:18121) : arch=x86_64 syscall=openat success=yes exit=3 a0=0xffffff9c a1=0x561168c81e40 a2=O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC a3=0x0 items=1 ppid=2270 pid=27900 auid=kcinimod uid=kcinimod gid=kcinimod euid=kcinimod suid=kcinimod fsuid=
>
> >
> > * The bash version you are using is not 5.0.2-1.fc30. Which one are you using?
>
> it is 5.0.2-1, downgrading to 4.4.23-7 fixes it
>
> > * It might come from a kernel bug (which would open the parent
> > directories with read access). That would be really strange, but only
> > to be sure: is bash 4 working fine when you downgrade bash package
> > while keeping the same kernel?
>
> Yes 4 is fine
>
> > * Or it might come from a bash dependency (like readline).
>
> Does not look like it: just downgrading "bash" fixes it
I managed to reproduce the issue. Here are the steps I followed:
* Download a Fedora 30 (Rawhide) live CD from
https://dl.fedoraproject.org/pub/fedora/linux/development/rawhide/Workstation/x86_64/iso/
and boot it in a QEMU virtual machine.
* Audit accesses to listing / from the live user: echo '(auditallow
unconfined_t root_t (dir (read)))' > auditallow_custom.cil && semodule
-i auditallow_custom.cil
* Executing "rm ~/*.test" leads to the following log: type=AVC
msg=audit(1551039100.144:488): avc: granted { read } for pid=5225
comm="bash" name="/" dev="dm-0" ino=2
scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
tcontext=system_u:object_r:root_t:s0 tclass=dir
* Executing "rm ./*.test" or anything else without the tilde does NOT
produce the AVC.
* Here is a gdb session with an interesting backtrace (once debug
symbols are installed using "sudo dnf debuginfo-install bash glibc"):
$ gdb -q --args bash -c 'rm ~/*.test'
(gdb) catch syscall openat
Catchpoint 1 (syscall 'openat' [257])
(gdb) commands
Type commands for breakpoint(s) 1, one per line.
End with a line saying just "end".
>p (char*)$rsi
>end
(gdb) r
Starting program: /usr/bin/bash -c rm\ \~/\*.test
[... enter "c" quite some times...]
Catchpoint 1 (call to syscall openat), __GI___open64_nocancel
(file=file@entry=0x55555568bb50 "/", oflag=oflag@entry=591872) at
../sysdeps/unix/sysv/linux/open64_nocancel.c:45
45 return INLINE_SYSCALL_CALL (openat, AT_FDCWD, file, oflag |
EXTRA_OPEN_FLAGS,
$17 = 0x55555568bb50 "/"
(gdb) bt
#0 __GI___open64_nocancel (file=file@entry=0x55555568bb50 "/",
oflag=oflag@entry=591872) at
../sysdeps/unix/sysv/linux/open64_nocancel.c:45
#1 0x00007ffff7e7d0b9 in __opendir (name=name@entry=0x55555568bb50
"/") at ../sysdeps/posix/opendir.c:92
#2 0x00005555555fe699 in glob_vector (pat=pat@entry=0x5555556a1b81
"\\h\\o\\m\\e", dir=dir@entry=0x55555568bb50 "/", flags=flags@entry=0)
at glob.c:717
#3 0x00005555555ff53e in glob_filename (pathname=<optimized out>,
flags=0) at glob.c:1385
#4 0x00005555555ff442 in glob_filename (pathname=<optimized out>,
flags=0) at glob.c:1178
#5 0x00005555555ff442 in glob_filename
(pathname=pathname@entry=0x55555569cc40
"/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test", flags=0) at
glob.c:1178
#6 0x00005555555cc953 in shell_glob_filename (pathname=<optimized
out>) at pathexp.c:434
#7 0x00005555555c77de in glob_expand_word_list (eflags=<optimized
out>, tlist=0x5555556a0450) at subst.c:11035
#8 expand_word_list_internal (list=<optimized out>,
eflags=eflags@entry=31) at subst.c:11472
#9 0x00005555555c7a0e in expand_words (list=<optimized out>) at subst.c:10984
#10 0x000055555559bda5 in execute_simple_command
(fds_to_close=0xffffffff, async=0, pipe_out=-1, pipe_in=-1,
simple_command=<optimized out>) at execute_cmd.c:4317
#11 execute_command_internal (command=<optimized out>,
asynchronous=asynchronous@entry=0, pipe_in=pipe_in@entry=-1,
pipe_out=pipe_out@entry=-1,
fds_to_close=fds_to_close@entry=0x5555556a27c0) at execute_cmd.c:854
#12 0x00005555555eb877 in parse_and_execute (string=<optimized out>,
from_file=0x55555563208d "-c", flags=4) at evalstring.c:436
#13 0x0000555555584adb in run_one_command (command=<optimized out>) at
/usr/include/bits/string_fortified.h:90
#14 0x0000555555583711 in main (argc=3, argv=0x7fffffffd9a8,
env=0x7fffffffd9c8) at shell.c:745
(gdb)
Here is what happens, as far I as understand:
* bash runs execute_simple_command(), which expands the command arguments.
* It expands the ~ in expand_word_internal()
(https://git.savannah.gnu.org/cgit/bash.git/tree/subst.c?h=bash-5.0#n9959)
* glob_expand_word_list() calls
shell_glob_filename(pathname="\001/\001h\001o\001m\001e\001/\001l\001i\001v\001e\001u\001s\001e\001r/*.test")
(frame #6 in the debug backtrace)
* shell_glob_filename() starts by calling quote_string_for_globbing()
(https://git.savannah.gnu.org/cgit/bash.git/tree/pathexp.c?h=bash-5.0#n385).
This function replaces CTLESC (=\001) with backslashes and returns
"/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test".
* shell_glob_filename() calls
glob_filename(pathname="/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test",
flags=0) (frame #5)
* This function calls itself with the directory,
glob_filename(pathname="/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r",
flags=0) (frame #4)
* This function calls itself with the directory,
glob_filename(pathname="/\\h\\o\\m\\e", flags=0) (frame #3)
* This function calls glob_vector(pat="\\h\\o\\m\\e", dir="/",
flags=0) (frame #2), implemented in
https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob.c?h=bash-5.0#n577
* This function checks whether pat is a pattern, by calling
glob_pattern_p(pat). As variable pat contains backslashes, the answer
is yes (cf. https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob_loop.c?h=bash-5.0#n56).
* glob_vector opens / in order to expand the pattern
(https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob.c?h=bash-5.0#n709).
* The kernel asks SELinux whether it can list the content of /.
In my humble opinion, bash could be fixed in order not to escape
letters in paths when expanding ~. Could you please forward this
analysis to bash's developers in order to ask them whether they
consider this as a bug?
Cheers,
Nicolas
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Bash 5 change in behavior and SELinux
2019-02-24 20:32 ` Nicolas Iooss
@ 2019-02-25 7:35 ` Dominick Grift
0 siblings, 0 replies; 6+ messages in thread
From: Dominick Grift @ 2019-02-25 7:35 UTC (permalink / raw)
To: Nicolas Iooss; +Cc: selinux
On Sun, Feb 24, 2019 at 09:32:13PM +0100, Nicolas Iooss wrote:
> On Sun, Feb 24, 2019 at 7:37 PM Dominick Grift
> <dominick.grift@defensec.nl> wrote:
> >
> > On Sun, Feb 24, 2019 at 07:17:33PM +0100, Nicolas Iooss wrote:
> > > On Sun, Feb 24, 2019 at 6:39 PM Dominick Grift
> > > <dominick.grift@defensec.nl> wrote:
> > > >
> > > > On Sun, Feb 24, 2019 at 05:59:19PM +0100, Dominick Grift wrote:
> > > > > Recently Bash-5 appeared in the Fedora repositories and i instantly noticed an inpleasant change (for the record: this did not happen before):
> > > >
> > > > I suppose this is just a "feature" or a "bug" in Bash-5 and that i will just have to deal with it. Just seems a bit unnecessary access to me.
> > > >
> > > > >
> > > > > [kcinimod@brutus ~]$ touch mytest1.test
> > > > > [kcinimod@brutus ~]$ rm ~/*.test
> > > > > rm: cannot remove '/home/kcinimod/*.test': No such file or directory
> > > > > [kcinimod@brutus ~]$ rm ~/mytest1.test
> > > > > [kcinimod@brutus ~]$ echo $?
> > > > > 0
> > > > >
> > > > > After running `semodule -DB` the following AVC denials surfaced:
> > > > >
> > > > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-3" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:files.home.file:s0 tclass=dir permissive=1
> > > > > avc: denied { read } for pid=2178 comm="bash" name="/" dev="dm-1" ino=2 scontext=wheel.id:wheel.role:wheel.subj:s0 tcontext=sys.id:sys.role:fs.rootfs.fs:s0 tclass=dir permissive=1
> > >
> > > [For other readers: these are the labels of /home and /, the parent
> > > directories of /home/kcinimod/]
> > >
> > > > > So I took to #bash and they told me:
> > > > >
> > > > > 17:43 <_abc_> grift: that is exactly what you see on android and is
> > > > > a direct result of the missing x bit equivalent in
> > > > > the selinux policy
> > > > >
> > > > > 17:44 <_abc_> grift: rephrased: globbing the * requires the x bit
> > > > > set
> > > > > 17:44 <_abc_> (it's equivalent in selinux policy)
> > > > >
> > > > > So why does this show up as a "read"? Its allowed to "search" "/" and "/home", but since Bash 5 this no longer is enough.
> > > > >
> > > > > Scripts break everywhere because of this
> > >
> > > What is the syscall associated with the avc entries? This would help
> > > finding in bash's source what triggered this behavior.
> > > I tried to reproduce your commands in Arch Linux (bash package
> > > 5.0.0-1) or Fedora 30 (bash package 5.0.2-1.fc30 for x86_64) by using
> > > strace on bash and watching the syscalls, but nothing stood out: I see
> > > an "openat(AT_FDCWD, "/home/kcinimod/",
> > > O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3" followed by calls to
> > > "getdents64(3, ...)", which are like expected. This could be due to
> > > several things:
> >
> > type=SYSCALL msg=audit(02/24/2019 19:33:13.924:18121) : arch=x86_64 syscall=openat success=yes exit=3 a0=0xffffff9c a1=0x561168c81e40 a2=O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC a3=0x0 items=1 ppid=2270 pid=27900 auid=kcinimod uid=kcinimod gid=kcinimod euid=kcinimod suid=kcinimod fsuid=
> >
> > >
> > > * The bash version you are using is not 5.0.2-1.fc30. Which one are you using?
> >
> > it is 5.0.2-1, downgrading to 4.4.23-7 fixes it
> >
> > > * It might come from a kernel bug (which would open the parent
> > > directories with read access). That would be really strange, but only
> > > to be sure: is bash 4 working fine when you downgrade bash package
> > > while keeping the same kernel?
> >
> > Yes 4 is fine
> >
> > > * Or it might come from a bash dependency (like readline).
> >
> > Does not look like it: just downgrading "bash" fixes it
>
> I managed to reproduce the issue. Here are the steps I followed:
> * Download a Fedora 30 (Rawhide) live CD from
> https://dl.fedoraproject.org/pub/fedora/linux/development/rawhide/Workstation/x86_64/iso/
> and boot it in a QEMU virtual machine.
> * Audit accesses to listing / from the live user: echo '(auditallow
> unconfined_t root_t (dir (read)))' > auditallow_custom.cil && semodule
> -i auditallow_custom.cil
> * Executing "rm ~/*.test" leads to the following log: type=AVC
> msg=audit(1551039100.144:488): avc: granted { read } for pid=5225
> comm="bash" name="/" dev="dm-0" ino=2
> scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
> tcontext=system_u:object_r:root_t:s0 tclass=dir
> * Executing "rm ./*.test" or anything else without the tilde does NOT
> produce the AVC.
> * Here is a gdb session with an interesting backtrace (once debug
> symbols are installed using "sudo dnf debuginfo-install bash glibc"):
>
> $ gdb -q --args bash -c 'rm ~/*.test'
> (gdb) catch syscall openat
> Catchpoint 1 (syscall 'openat' [257])
> (gdb) commands
> Type commands for breakpoint(s) 1, one per line.
> End with a line saying just "end".
> >p (char*)$rsi
> >end
> (gdb) r
> Starting program: /usr/bin/bash -c rm\ \~/\*.test
>
> [... enter "c" quite some times...]
>
> Catchpoint 1 (call to syscall openat), __GI___open64_nocancel
> (file=file@entry=0x55555568bb50 "/", oflag=oflag@entry=591872) at
> ../sysdeps/unix/sysv/linux/open64_nocancel.c:45
> 45 return INLINE_SYSCALL_CALL (openat, AT_FDCWD, file, oflag |
> EXTRA_OPEN_FLAGS,
> $17 = 0x55555568bb50 "/"
> (gdb) bt
> #0 __GI___open64_nocancel (file=file@entry=0x55555568bb50 "/",
> oflag=oflag@entry=591872) at
> ../sysdeps/unix/sysv/linux/open64_nocancel.c:45
> #1 0x00007ffff7e7d0b9 in __opendir (name=name@entry=0x55555568bb50
> "/") at ../sysdeps/posix/opendir.c:92
> #2 0x00005555555fe699 in glob_vector (pat=pat@entry=0x5555556a1b81
> "\\h\\o\\m\\e", dir=dir@entry=0x55555568bb50 "/", flags=flags@entry=0)
> at glob.c:717
> #3 0x00005555555ff53e in glob_filename (pathname=<optimized out>,
> flags=0) at glob.c:1385
> #4 0x00005555555ff442 in glob_filename (pathname=<optimized out>,
> flags=0) at glob.c:1178
> #5 0x00005555555ff442 in glob_filename
> (pathname=pathname@entry=0x55555569cc40
> "/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test", flags=0) at
> glob.c:1178
> #6 0x00005555555cc953 in shell_glob_filename (pathname=<optimized
> out>) at pathexp.c:434
> #7 0x00005555555c77de in glob_expand_word_list (eflags=<optimized
> out>, tlist=0x5555556a0450) at subst.c:11035
> #8 expand_word_list_internal (list=<optimized out>,
> eflags=eflags@entry=31) at subst.c:11472
> #9 0x00005555555c7a0e in expand_words (list=<optimized out>) at subst.c:10984
> #10 0x000055555559bda5 in execute_simple_command
> (fds_to_close=0xffffffff, async=0, pipe_out=-1, pipe_in=-1,
> simple_command=<optimized out>) at execute_cmd.c:4317
> #11 execute_command_internal (command=<optimized out>,
> asynchronous=asynchronous@entry=0, pipe_in=pipe_in@entry=-1,
> pipe_out=pipe_out@entry=-1,
> fds_to_close=fds_to_close@entry=0x5555556a27c0) at execute_cmd.c:854
> #12 0x00005555555eb877 in parse_and_execute (string=<optimized out>,
> from_file=0x55555563208d "-c", flags=4) at evalstring.c:436
> #13 0x0000555555584adb in run_one_command (command=<optimized out>) at
> /usr/include/bits/string_fortified.h:90
> #14 0x0000555555583711 in main (argc=3, argv=0x7fffffffd9a8,
> env=0x7fffffffd9c8) at shell.c:745
> (gdb)
>
> Here is what happens, as far I as understand:
> * bash runs execute_simple_command(), which expands the command arguments.
> * It expands the ~ in expand_word_internal()
> (https://git.savannah.gnu.org/cgit/bash.git/tree/subst.c?h=bash-5.0#n9959)
> * glob_expand_word_list() calls
> shell_glob_filename(pathname="\001/\001h\001o\001m\001e\001/\001l\001i\001v\001e\001u\001s\001e\001r/*.test")
> (frame #6 in the debug backtrace)
> * shell_glob_filename() starts by calling quote_string_for_globbing()
> (https://git.savannah.gnu.org/cgit/bash.git/tree/pathexp.c?h=bash-5.0#n385).
> This function replaces CTLESC (=\001) with backslashes and returns
> "/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test".
> * shell_glob_filename() calls
> glob_filename(pathname="/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r/*.test",
> flags=0) (frame #5)
> * This function calls itself with the directory,
> glob_filename(pathname="/\\h\\o\\m\\e/\\l\\i\\v\\e\\u\\s\\e\\r",
> flags=0) (frame #4)
> * This function calls itself with the directory,
> glob_filename(pathname="/\\h\\o\\m\\e", flags=0) (frame #3)
> * This function calls glob_vector(pat="\\h\\o\\m\\e", dir="/",
> flags=0) (frame #2), implemented in
> https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob.c?h=bash-5.0#n577
> * This function checks whether pat is a pattern, by calling
> glob_pattern_p(pat). As variable pat contains backslashes, the answer
> is yes (cf. https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob_loop.c?h=bash-5.0#n56).
> * glob_vector opens / in order to expand the pattern
> (https://git.savannah.gnu.org/cgit/bash.git/tree/lib/glob/glob.c?h=bash-5.0#n709).
> * The kernel asks SELinux whether it can list the content of /.
>
> In my humble opinion, bash could be fixed in order not to escape
> letters in paths when expanding ~. Could you please forward this
> analysis to bash's developers in order to ask them whether they
> consider this as a bug?
Thanks. Turns out that this bug was already reported, and that there is a fix in the development branch.
>
> Cheers,
> Nicolas
>
--
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Dominick Grift
^ permalink raw reply [flat|nested] 6+ messages in thread
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2019-02-24 16:59 Bash 5 change in behavior and SELinux Dominick Grift
2019-02-24 17:39 ` Dominick Grift
2019-02-24 18:17 ` Nicolas Iooss
2019-02-24 18:37 ` Dominick Grift
2019-02-24 20:32 ` Nicolas Iooss
2019-02-25 7:35 ` Dominick Grift
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