Commit 125c8e54 authored by Nick Mathewson's avatar Nick Mathewson 🤹
Browse files

Merge remote-tracking branch 'public/bug11465'

parents 03e0c7e3 bd83d0ed

changes/bug11465

0 → 100644
+9 −0
Original line number Diff line number Diff line 
  o Minor features:

    - When the Linux syscall sandbox finds an illegal system call, it

      now tries to log a stack trace before exiting. Resolves ticket

      11465.



  o Minor bugfixes:

    - Using the Linux syscall sandbox no longer prevents stack-trace

      logging on crashes or errors. Fixes part 11465; bugfix on

      0.2.5.1-alpha.

src/common/backtrace.c

+16 −2
Original line number Diff line number Diff line
@@ -5,7 +5,6 @@ 
#define _GNU_SOURCE 1



#include "orconfig.h"

#include "backtrace.h"

#include "compat.h"

#include "util.h"

#include "torlog.h"
@@ -31,6 +30,9 @@ 
#include <ucontext.h>

#endif



#define EXPOSE_CLEAN_BACKTRACE

#include "backtrace.h"



#if defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && \

  defined(HAVE_BACKTRACE_SYMBOLS_FD) && defined(HAVE_SIGACTION)

#define USE_BACKTRACE
@@ -59,7 +61,7 @@ static tor_mutex_t cb_buf_mutex; 
 * onto the stack.  Fortunately, we usually have the program counter in the

 * ucontext_t structure.

 */

static void

void

clean_backtrace(void **stack, int depth, const ucontext_t *ctx)

{

#ifdef PC_FROM_UCONTEXT
@@ -165,6 +167,18 @@ install_bt_handler(void) 
      rv = -1;

    }

  }



  {

    /* Now, generate (but do not log) a backtrace.  This ensures that

     * libc has pre-loaded the symbols we need to dump things, so that later

     * reads won't be denied by the sandbox code */

    char **symbols;

    int depth = backtrace(cb_buf, MAX_DEPTH);

    symbols = backtrace_symbols(cb_buf, depth);

    if (symbols)

      free(symbols);

  }



  return rv;

}

src/common/backtrace.h

+6 −0
Original line number Diff line number Diff line
@@ -4,9 +4,15 @@ 
#ifndef TOR_BACKTRACE_H

#define TOR_BACKTRACE_H



#include "orconfig.h"



void log_backtrace(int severity, int domain, const char *msg);

int configure_backtrace_handler(const char *tor_version);

void clean_up_backtrace_handler(void);



#ifdef EXPOSE_CLEAN_BACKTRACE

void clean_backtrace(void **stack, int depth, const ucontext_t *ctx);

#endif



#endif

src/common/sandbox.c

+36 −0
Original line number Diff line number Diff line
@@ -56,6 +56,17 @@ 
#include <time.h>

#include <poll.h>



#if defined(HAVE_EXECINFO_H) && defined(HAVE_BACKTRACE) && \

  defined(HAVE_BACKTRACE_SYMBOLS_FD) && defined(HAVE_SIGACTION)

#define USE_BACKTRACE

#define EXPOSE_CLEAN_BACKTRACE

#include "backtrace.h"

#endif



#ifdef USE_BACKTRACE

#include <execinfo.h>

#endif



/**Determines if at least one sandbox is active.*/

static int sandbox_active = 0;

/** Holds the parameter list configuration for the sandbox.*/
@@ -119,6 +130,7 @@ static int filter_nopar_gen[] = { 
    SCMP_SYS(stat),

    SCMP_SYS(uname),

    SCMP_SYS(write),

    SCMP_SYS(writev),

    SCMP_SYS(exit_group),

    SCMP_SYS(exit),
@@ -1307,6 +1319,11 @@ install_syscall_filter(sandbox_cfg_t* cfg) 
  return (rc < 0 ? -rc : rc);

}



#ifdef USE_BACKTRACE

#define MAX_DEPTH 256

static void *syscall_cb_buf[MAX_DEPTH];

#endif



/**

 * Function called when a SIGSYS is caught by the application. It notifies the

 * user that an error has occurred and either terminates or allows the
@@ -1318,6 +1335,12 @@ sigsys_debugging(int nr, siginfo_t *info, void *void_context) 
  ucontext_t *ctx = (ucontext_t *) (void_context);

  char number[32];

  int syscall;

#ifdef USE_BACKTRACE

  int depth;

  int n_fds, i;

  const int *fds = NULL;

#endif



  (void) nr;



  if (info->si_code != SYS_SECCOMP)
@@ -1328,12 +1351,25 @@ sigsys_debugging(int nr, siginfo_t *info, void *void_context) 


  syscall = (int) ctx->uc_mcontext.gregs[REG_SYSCALL];



#ifdef USE_BACKTRACE

  depth = backtrace(syscall_cb_buf, MAX_DEPTH);

  /* Clean up the top stack frame so we get the real function

   * name for the most recently failing function. */

  clean_backtrace(syscall_cb_buf, depth, ctx);

#endif



  format_dec_number_sigsafe(syscall, number, sizeof(number));

  tor_log_err_sigsafe("(Sandbox) Caught a bad syscall attempt (syscall ",

                      number,

                      ")\n",

                      NULL);



#ifdef USE_BACKTRACE

  n_fds = tor_log_get_sigsafe_err_fds(&fds);

  for (i=0; i < n_fds; ++i)

    backtrace_symbols_fd(syscall_cb_buf, depth, fds[i]);

#endif



#if defined(DEBUGGING_CLOSE)

  _exit(1);

#endif // DEBUGGING_CLOSE