Re: Zenbleed

[Jung-uk Kim]

On 23. 7. 27., Jung-uk Kim wrote:

On 23. 7. 27., mike tancsa wrote:

On 7/26/2023 5:46 PM, Shawn Webb wrote:

On Wed, Jul 26, 2023 at 08:34:56PM +0000, 0x1eef wrote:

Hello,

I was curious if there are plans to apply the "chicken bit"
workaround for the Ryzen line of processors. A firmware
update is not scheduled to be released until Nov or Dec
at the earliest. Thanks.

For those that would like to test if their systems are affected, this
proof-of-concept was reported to work on at least one system:

https://git.hardenedbsd.org/shawn.webb/zenbleed/-/tree/shawn.webb/bsd/main

Building it depends on gmake and nasm. You'll want to be on the
shawn.webb/bsd/main branch.

% gmake
cc -O0 -ggdb3 -march=znver2   -c -o pattern.o pattern.c
pattern.c:15:10: fatal error: 'sys/sysinfo.h' file not found
#include <sys/sysinfo.h>
          ^~~~~~~~~~~~~~~
1 error generated.
gmake: *** [<builtin>: pattern.o] Error 1

Thanks for that. Is there a way to compile on RELENG_12 or is it 13 only ?

https://lock.cmpxchg8b.com/files/zenbleed-v5.tar.gz

I guess you checked out a wrong branch.  Please see the attached minimal patch I made for FreeBSD.  I think it will work on any supported FreeBSD branches.  Note the original exploit is available from here:

With the forgotten attachment.

Jung-uk Kim

--- zenbleed/pattern.c.orig	2023-07-23 10:45:32.000000000 -0400
+++ zenbleed/pattern.c	2023-07-27 12:26:28.324346000 -0400
@@ -6,13 +6,14 @@
 #include <stdbool.h>
 #include <x86intrin.h>
 #include <sched.h>
+#ifdef __linux__
 #include <syscall.h>
+#endif
 #include <err.h>
 #include <pthread.h>
 #include <assert.h>
 #include <ctype.h>
 #include <signal.h>
-#include <sys/sysinfo.h>
 
 #include "zenbleed.h"
 
@@ -82,7 +83,7 @@ void * pattern_leak_consumer(void *param)
             }
         }
 
-        fprintf(stdout, "%.*s", matchlen, matchptr);
+        fprintf(stdout, "%.*s", (int)matchlen, matchptr);
 
         // If the match is bigger than our pattern size, we skip to the end of it.
         if (matchlen > patlen) {
--- zenbleed/util.c.orig	2023-07-23 10:45:32.000000000 -0400
+++ zenbleed/util.c	2023-07-27 13:26:09.509588000 -0400
@@ -46,6 +46,9 @@ bool num_inrange(char *range, int num)
 bool num_inrange(char *range, int num)
 {
     char *r, *s, *e;
+#ifndef __linux__
+    size_t len;
+#endif
 
     // Example:
     // 1,2,3,4-8,2
@@ -53,7 +56,14 @@ bool num_inrange(char *range, int num)
     if (range == NULL)
         return false;
 
-    s = strtok_r(strdupa(range), ",", &r);
+#ifndef __linux__
+    len = strlen(range) + 1;
+    s = alloca(len);
+    memcpy(s, range, len);
+#else
+    s = strdupa(range);
+#endif
+    s = strtok_r(s, ",", &r);
 
     while (s) {
         int start;
--- zenbleed/zenbleed.c.orig	2023-07-23 10:45:32.000000000 -0400
+++ zenbleed/zenbleed.c	2023-07-27 13:07:27.502780000 -0400
@@ -6,13 +6,16 @@
 #include <stdbool.h>
 #include <x86intrin.h>
 #include <sched.h>
+#ifdef __FreeBSD__
+#include <pthread_np.h>
+#else
 #include <syscall.h>
+#endif
 #include <err.h>
 #include <pthread.h>
 #include <assert.h>
 #include <ctype.h>
 #include <signal.h>
-#include <sys/sysinfo.h>
 
 #include "zenbleed.h"
 
@@ -298,7 +301,7 @@ int main(int argc, char **argv) {
     }
 
     // We spawn a thread on every evailable core and start leaking to see what we get.
-    ncpus   = get_nprocs();
+    ncpus = sysconf(_SC_NPROCESSORS_ONLN);
     thread_arg_t* args = calloc(sizeof(thread_arg_t), ncpus);
     threads = calloc(sizeof(pthread_t), ncpus);
 

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