Peter S. Mazinger writes:

Hello Erik!

I have made some cosmetical changes to the files, removed the added
SCRT=-fPIC option from building the crt0.S file (but it is a requirement
to build them with -fPIC), and changed some comments. I have left the
ldso.c patch with PIE_SUPPORT ifdefs, but consider applying it w/o them
(see some earlier comment from PaX Team on this issue, as it is considered
a bug). To have it work correctly, you'll also need removing
COMPLETELY_PIC.
One thing is missing: PIE_SUPPORT should be usable only for i386 (for
now).

Also added the support for propolice protection (that works for me and
catches memcpy/strcpy attacks (but needs a special gcc version).

Thanks, Peter

4 files changed, 133 insertions, 2 deletions

diff --git a/libc/sysdeps/linux/common/Makefile b/libc/sysdeps/linux/common/Makefile
index cfd95300f..5b5034095 100644
--- a/libc/sysdeps/linux/common/Makefile
+++ b/libc/sysdeps/linux/common/Makefile
@@ -33,6 +33,9 @@ endif
 ifeq ($(strip $(UCLIBC_PROFILING)),y)
 CSRC+=gmon.c
 endif
+ifeq ($(strip $(UCLIBC_PROPOLICE)),y)
+CSRC+=ssp.c
+endif
 COBJS=$(patsubst %.c,%.o, $(CSRC))
 
 MSRC=syscalls.c
diff --git a/libc/sysdeps/linux/common/ssp.c b/libc/sysdeps/linux/common/ssp.c
new file mode 100644
index 000000000..135892c37
--- /dev/null
+++ b/libc/sysdeps/linux/common/ssp.c
@@ -0,0 +1,97 @@
+#include <stdio.h>
+#include <string.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#ifdef _POSIX_SOURCE
+#include <signal.h>
+#endif
+
+#if defined(HAVE_SYSLOG)
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <sys/syslog.h>
+#ifndef _PATH_LOG
+#define _PATH_LOG "/dev/log"
+#endif
+#endif
+
+long __guard[8] = {0, 0, 0, 0, 0, 0, 0, 0};
+
+void __guard_setup (void)
+{
+  int fd;
+  if (__guard[0]!=0) return;
+  fd = open ("/dev/urandom", 0);
+  if (fd != -1) {
+    ssize_t size = read (fd, (char*)&__guard, sizeof(__guard));
+    close (fd) ;
+    if (size == sizeof(__guard)) return;
+  }
+  /* If a random generator can't be used, the protector switches the guard
+     to the "terminator canary" */
+  ((char*)__guard)[0] = 0; ((char*)__guard)[1] = 0;
+  ((char*)__guard)[2] = '\n'; ((char*)__guard)[3] = 255;
+}
+
+void __stack_smash_handler (char func[], int damaged)
+{
+#if defined (__GNU_LIBRARY__)
+  extern char * __progname;
+#endif
+  const char message[] = ": stack smashing attack in function ";
+  int bufsz = 512, len;
+  char buf[bufsz];
+#if defined(HAVE_SYSLOG)
+  int LogFile;
+  struct sockaddr_un SyslogAddr;  /* AF_UNIX address of local logger */
+#endif
+#ifdef _POSIX_SOURCE
+  {
+    sigset_t mask;
+    sigfillset(&mask);
+    sigdelset(&mask, SIGABRT);  /* Block all signal handlers */
+    sigprocmask(SIG_BLOCK, &mask, NULL); /* except SIGABRT */
+  }
+#endif
+
+  strcpy(buf, "<2>"); len=3;    /* send LOG_CRIT */
+#if defined (__GNU_LIBRARY__)
+  strncat(buf, __progname, bufsz-len-1); len = strlen(buf);
+#endif
+  if (bufsz>len) {strncat(buf, message, bufsz-len-1); len = strlen(buf);}
+  if (bufsz>len) {strncat(buf, func, bufsz-len-1); len = strlen(buf);}
+  /* print error message */
+  write (STDERR_FILENO, buf+3, len-3);
+#if defined(HAVE_SYSLOG)
+  if ((LogFile = socket(AF_UNIX, SOCK_DGRAM, 0)) != -1) {
+                                                                                                                     
+    /*                                                                                                               
+     * Send "found" message to the "/dev/log" path
+     */
+    SyslogAddr.sun_family = AF_UNIX;
+    (void)strncpy(SyslogAddr.sun_path, _PATH_LOG,
+          sizeof(SyslogAddr.sun_path) - 1);
+    SyslogAddr.sun_path[sizeof(SyslogAddr.sun_path) - 1] = '\0';
+    sendto(LogFile, buf, len, 0, (struct sockaddr *)&SyslogAddr,
+       sizeof(SyslogAddr));
+  }
+#endif
+
+#ifdef _POSIX_SOURCE
+  { /* Make sure the default handler is associated with SIGABRT */
+    struct sigaction sa;
+
+    memset(&sa, 0, sizeof(struct sigaction));
+    sigfillset(&sa.sa_mask);    /* Block all signals */
+    sa.sa_flags = 0;
+    sa.sa_handler = SIG_DFL;
+    sigaction(SIGABRT, &sa, NULL);
+    (void)kill(getpid(), SIGABRT);
+  }
+#endif
+  _exit(127);
+}
+
diff --git a/libc/sysdeps/linux/i386/Makefile b/libc/sysdeps/linux/i386/Makefile
index 9ba60f59e..c7f88b681 100644
--- a/libc/sysdeps/linux/i386/Makefile
+++ b/libc/sysdeps/linux/i386/Makefile
@@ -22,6 +22,9 @@ ASFLAGS=$(CFLAGS)
 
 CRT0_SRC = crt0.S
 CRT0_OBJ = crt0.o crt1.o gcrt1.o
+ifeq ($(strip $(UCLIBC_PIE_SUPPORT)),y)
+CRT0_OBJ += Scrt0.o Scrt1.o
+endif
 CRT0_DEPS=gmon-start.S
 CTOR_TARGETS=$(TOPDIR)lib/crti.o $(TOPDIR)lib/crtn.o
 
@@ -44,6 +47,13 @@ $(LIBC): ar-target
 ar-target: $(OBJS) $(CRT0_OBJ) $(CTOR_TARGETS)
 	$(AR) $(ARFLAGS) $(LIBC) $(OBJS)
 	cp $(CRT0_OBJ) $(TOPDIR)lib/
+ifeq ($(strip $(UCLIBC_PIE_SUPPORT)),y)
+ifeq ($(strip $(UCLIBC_CTOR_DTOR)),y)
+	$(RM) $(TOPDIR)lib/Scrt0.o
+else
+	mv $(TOPDIR)lib/Scrt0.o $(TOPDIR)lib/Scrt1.o
+endif
+endif
 
 $(CRT0_OBJ): $(CRT0_SRC)
 	$(CC) $(CFLAGS) -DL_$* $< -c -o $*.o
diff --git a/libc/sysdeps/linux/i386/crt0.S b/libc/sysdeps/linux/i386/crt0.S
index a488d6508..e7df6992b 100644
--- a/libc/sysdeps/linux/i386/crt0.S
+++ b/libc/sysdeps/linux/i386/crt0.S
@@ -18,6 +18,7 @@ Cambridge, MA 02139, USA.  */
 
 
 /*  Based on the code from GNU libc, but hacked up by John Beppu and Erik Andersen */
+/*  adapted by PaX Team for ET_DYN/PIE binaries */
 
 /*
     When we enter this piece of code, the program stack looks like this:
@@ -37,7 +38,7 @@ Cambridge, MA 02139, USA.  */
 
 	.global	_start
 	.type	_start,%function
-#if defined L_crt0 || ! defined __UCLIBC_CTOR_DTOR__
+#if defined L_crt0 || defined L_Scrt0 || ! defined __UCLIBC_CTOR_DTOR__
 	.type	__uClibc_main,%function
 #else
 	.weak	_init
@@ -74,10 +75,22 @@ _start:
 	pushl %ebp      /* callers %ebp (frame pointer) */
 	movl %esp,%ebp  /* mark callers stack frame as invalid */
 
-#if (defined L_crt1 || defined L_gcrt1 ) && defined __UCLIBC_CTOR_DTOR__
+#if defined L_Scrt0 || defined L_Scrt1
+	call .L0
+.L0:
+	pop %edx
+	addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%edx
+#endif
+
+#if (defined L_crt1 || defined L_Scrt1 || defined L_gcrt1 ) && defined __UCLIBC_CTOR_DTOR__
 	/* Push .init and .fini arguments to __uClibc_start_main() on the stack */
+#ifdef L_Scrt1
+	pushl _fini@GOT(%edx)
+	pushl _init@GOT(%edx)
+#else
 	pushl $_fini
 	pushl $_init
+#endif
 
 	/* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */ 
 	pushl %eax	/* Environment pointer */
@@ -85,15 +98,23 @@ _start:
 	pushl %ecx	/* And the argument count */
 
 	/* Ok, now run uClibc's main() -- shouldn't return */
+#ifdef L_Scrt1
+	call *__uClibc_start_main@GOT(%edx)
+#else
 	call __uClibc_start_main
+#endif
 #else
 	/* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */ 
 	pushl %eax	/* Environment pointer */
 	pushl %ebx	/* Argument pointer */
 	pushl %ecx	/* And the argument count */
 
+#ifdef L_Scrt0
+	call *__uClibc_main@GOT(%edx)
+#else
 	call __uClibc_main
 #endif
+#endif
 
 	/* Crash if somehow `exit' returns anyways.  */
 	hlt