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Diffstat (limited to '')
| -rw-r--r-- | debian/patches/0001-gpasswd-1-Fix-password-leak.patch | 137 |
1 files changed, 0 insertions, 137 deletions
diff --git a/debian/patches/0001-gpasswd-1-Fix-password-leak.patch b/debian/patches/0001-gpasswd-1-Fix-password-leak.patch deleted file mode 100644 index 1596b2d..0000000 --- a/debian/patches/0001-gpasswd-1-Fix-password-leak.patch +++ /dev/null @@ -1,137 +0,0 @@ -From 65c88a43a23c2391dcc90c0abda3e839e9c57904 Mon Sep 17 00:00:00 2001 -From: Alejandro Colomar <alx@kernel.org> -Date: Sat, 10 Jun 2023 16:20:05 +0200 -Subject: [PATCH] gpasswd(1): Fix password leak - -How to trigger this password leak? -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -When gpasswd(1) asks for the new password, it asks twice (as is usual -for confirming the new password). Each of those 2 password prompts -uses agetpass() to get the password. If the second agetpass() fails, -the first password, which has been copied into the 'static' buffer -'pass' via STRFCPY(), wasn't being zeroed. - -agetpass() is defined in <./libmisc/agetpass.c> (around line 91), and -can fail for any of the following reasons: - -- malloc(3) or readpassphrase(3) failure. - - These are going to be difficult to trigger. Maybe getting the system - to the limits of memory utilization at that exact point, so that the - next malloc(3) gets ENOMEM, and possibly even the OOM is triggered. - About readpassphrase(3), ENFILE and EINTR seem the only plausible - ones, and EINTR probably requires privilege or being the same user; - but I wouldn't discard ENFILE so easily, if a process starts opening - files. - -- The password is longer than PASS_MAX. - - The is plausible with physical access. However, at that point, a - keylogger will be a much simpler attack. - -And, the attacker must be able to know when the second password is being -introduced, which is not going to be easy. - -How to read the password after the leak? -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Provoking the leak yourself at the right point by entering a very long -password is easy, and inspecting the process stack at that point should -be doable. Try to find some consistent patterns. - -Then, search for those patterns in free memory, right after the victim -leaks their password. - -Once you get the leak, a program should read all the free memory -searching for patterns that gpasswd(1) leaves nearby the leaked -password. - -On 6/10/23 03:14, Seth Arnold wrote: -> An attacker process wouldn't be able to use malloc(3) for this task. -> There's a handful of tools available for userspace to allocate memory: -> -> - brk / sbrk -> - mmap MAP_ANONYMOUS -> - mmap /dev/zero -> - mmap some other file -> - shm_open -> - shmget -> -> Most of these return only pages of zeros to a process. Using mmap of an -> existing file, you can get some of the contents of the file demand-loaded -> into the memory space on the first use. -> -> The MAP_UNINITIALIZED flag only works if the kernel was compiled with -> CONFIG_MMAP_ALLOW_UNINITIALIZED. This is rare. -> -> malloc(3) doesn't zero memory, to our collective frustration, but all the -> garbage in the allocations is from previous allocations in the current -> process. It isn't leftover from other processes. -> -> The avenues available for reading the memory: -> - /dev/mem and /dev/kmem (requires root, not available with Secure Boot) -> - /proc/pid/mem (requires ptrace privileges, mediated by YAMA) -> - ptrace (requires ptrace privileges, mediated by YAMA) -> - causing memory to be swapped to disk, and then inspecting the swap -> -> These all require a certain amount of privileges. - -How to fix it? -~~~~~~~~~~~~~~ - -memzero(), which internally calls explicit_bzero(3), or whatever -alternative the system provides with a slightly different name, will -make sure that the buffer is zeroed in memory, and optimizations are not -allowed to impede this zeroing. - -This is not really 100% effective, since compilers may place copies of -the string somewhere hidden in the stack. Those copies won't get zeroed -by explicit_bzero(3). However, that's arguably a compiler bug, since -compilers should make everything possible to avoid optimizing strings -that are later passed to explicit_bzero(3). But we all know that -sometimes it's impossible to have perfect knowledge in the compiler, so -this is plausible. Nevertheless, there's nothing we can do against such -issues, except minimizing the time such passwords are stored in plain -text. - -Security concerns -~~~~~~~~~~~~~~~~~ - -We believe this isn't easy to exploit. Nevertheless, and since the fix -is trivial, this fix should probably be applied soon, and backported to -all supported distributions, to prevent someone else having more -imagination than us to find a way. - -Affected versions -~~~~~~~~~~~~~~~~~ - -All. Bug introduced in shadow 19990709. That's the second commit in -the git history. - -Fixes: 45c6603cc86c ("[svn-upgrade] Integrating new upstream version, shadow (19990709)") -Reported-by: Alejandro Colomar <alx@kernel.org> -Cc: Serge Hallyn <serge@hallyn.com> -Cc: Iker Pedrosa <ipedrosa@redhat.com> -Cc: Seth Arnold <seth.arnold@canonical.com> -Cc: Christian Brauner <christian@brauner.io> -Cc: Balint Reczey <rbalint@debian.org> -Cc: Sam James <sam@gentoo.org> -Cc: David Runge <dvzrv@archlinux.org> -Cc: Andreas Jaeger <aj@suse.de> -Cc: <~hallyn/shadow@lists.sr.ht> -Signed-off-by: Alejandro Colomar <alx@kernel.org> ---- - src/gpasswd.c | 1 + - 1 file changed, 1 insertion(+) - ---- a/src/gpasswd.c -+++ b/src/gpasswd.c -@@ -896,6 +896,7 @@ - strzero (cp); - cp = getpass (_("Re-enter new password: ")); - if (NULL == cp) { -+ memzero (pass, sizeof pass); - exit (1); - } - |