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Diffstat (limited to 'gcc-4.9/libvtv/vtv_fail.cc')
| -rw-r--r-- | gcc-4.9/libvtv/vtv_fail.cc | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/gcc-4.9/libvtv/vtv_fail.cc b/gcc-4.9/libvtv/vtv_fail.cc new file mode 100644 index 000000000..4f183d8ca --- /dev/null +++ b/gcc-4.9/libvtv/vtv_fail.cc @@ -0,0 +1,233 @@ +/* Copyright (C) 2012-2013 + Free Software Foundation + + This file is part of GCC. + + GCC is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3, or (at your option) + any later version. + + GCC is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + Under Section 7 of GPL version 3, you are granted additional + permissions described in the GCC Runtime Library Exception, version + 3.1, as published by the Free Software Foundation. + + You should have received a copy of the GNU General Public License and + a copy of the GCC Runtime Library Exception along with this program; + see the files COPYING3 and COPYING.RUNTIME respectively. If not, see + <http://www.gnu.org/licenses/>. */ + +/* This file is part of the vtable security feature implementation. + The vtable security feature is designed to detect when a virtual + call is about to be made through an invalid vtable pointer + (possibly due to data corruption or malicious attacks). + + This file also contains the failure functions that get called when + a vtable pointer is not found in the data set. Two particularly + important functions are __vtv_verify_fail and __vtv_really_fail. + They are both externally visible. __vtv_verify_fail is defined in + such a way that it can be replaced by a programmer, if desired. It + is the function that __VLTVerifyVtablePointer calls if it can't + find the pointer in the data set. Allowing the programmer to + overwrite this function means that he/she can do some alternate + verification, including NOT failing in certain specific cases, if + desired. This may be the case if the programmer has to deal wtih + unverified third party software, for example. __vtv_really_fail is + available for the programmer to call from his version of + __vtv_verify_fail, if he decides the failure is real. + +*/ + +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <execinfo.h> +#include <unistd.h> + +#include "vtv_utils.h" +#include "vtv_fail.h" + +/* This is used to disable aborts for debugging purposes. */ +bool vtv_no_abort = false; + + +extern "C" { + + /* __fortify_fail is a function in glibc that calls __libc_message, + causing it to print out a program termination error message + (including the name of the binary being terminated), a stack + trace where the error occurred, and a memory map dump. Ideally + we would have called __libc_message directly, but that function + does not appear to be accessible to functions outside glibc, + whereas __fortify_fail is. We call __fortify_fail from + __vtv_really_fail. We looked at calling __libc_fatal, which is + externally accessible, but it does not do the back trace and + memory dump. */ + + extern void __fortify_fail (const char *) __attribute__((noreturn)); + +} /* extern "C" */ + +const unsigned long SET_HANDLE_HANDLE_BIT = 0x2; + +/* Instantiate the template classes (in vtv_set.h) for our particular + hash table needs. */ +typedef void * vtv_set_handle; +typedef vtv_set_handle * vtv_set_handle_handle; + +static int vtv_failures_log_fd = -1; + +/* Open error logging file, if not already open, and write vtable + verification failure messages (LOG_MSG) to the log file. Also + generate a backtrace in the log file, if GENERATE_BACKTRACE is + set. */ + +static void +log_error_message (const char *log_msg, bool generate_backtrace) +{ + if (vtv_failures_log_fd == -1) + vtv_failures_log_fd = vtv_open_log ("vtable_verification_failures.log"); + + if (vtv_failures_log_fd == -1) + return; + + vtv_add_to_log (vtv_failures_log_fd, "%s", log_msg); + + if (generate_backtrace) + { +#define STACK_DEPTH 20 + void *callers[STACK_DEPTH]; + int actual_depth = backtrace (callers, STACK_DEPTH); + backtrace_symbols_fd (callers, actual_depth, vtv_failures_log_fd); + } +} + +/* In the case where a vtable map variable is the only instance of the + variable we have seen, it points directly to the set of valid + vtable pointers. All subsequent instances of the 'same' vtable map + variable point to the first vtable map variable. This function, + given a vtable map variable PTR, checks a bit to see whether it's + pointing directly to the data set or to the first vtable map + variable. */ + +static inline bool +is_set_handle_handle (void * ptr) +{ + return ((unsigned long) ptr & SET_HANDLE_HANDLE_BIT) + == SET_HANDLE_HANDLE_BIT; +} + +/* Returns the actual pointer value of a vtable map variable, PTR (see + comments for is_set_handle_handle for more details). */ + +static inline vtv_set_handle * +ptr_from_set_handle_handle (void * ptr) +{ + return (vtv_set_handle *) ((unsigned long) ptr & ~SET_HANDLE_HANDLE_BIT); +} + +/* Given a vtable map variable, PTR, this function sets the bit that + says this is the second (or later) instance of a vtable map + variable. */ + +static inline vtv_set_handle_handle +set_handle_handle (vtv_set_handle * ptr) +{ + return (vtv_set_handle_handle) ((unsigned long) ptr | SET_HANDLE_HANDLE_BIT); +} + +/* This function is called from __VLTVerifyVtablePointerDebug; it + sends as much debugging information as it can to the error log + file, then calls __vtv_verify_fail. SET_HANDLE_PTR is the pointer + to the set of valid vtable pointers, VTBL_PTR is the pointer that + was not found in the set, and DEBUG_MSG is the message to be + written to the log file before failing. n */ + +void +__vtv_verify_fail_debug (void **set_handle_ptr, const void *vtbl_ptr, + const char *debug_msg) +{ + log_error_message (debug_msg, false); + + /* Call the public interface in case it has been overwritten by + user. */ + __vtv_verify_fail (set_handle_ptr, vtbl_ptr); + + log_error_message ("Returned from __vtv_verify_fail." + " Secondary verification succeeded.\n", false); +} + +/* This function calls __fortify_fail with a FAILURE_MSG and then + calls abort. */ + +void +__vtv_really_fail (const char *failure_msg) +{ + __fortify_fail (failure_msg); + + /* We should never get this far; __fortify_fail calls __libc_message + which prints out a back trace and a memory dump and then is + supposed to call abort, but let's play it safe anyway and call abort + ourselves. */ + abort (); +} + +/* This function takes an error MSG, a vtable map variable + (DATA_SET_PTR) and a vtable pointer (VTBL_PTR). It is called when + an attempt to verify VTBL_PTR with the set pointed to by + DATA_SET_PTR failed. It outputs a failure message with the + addresses involved, and calls __vtv_really_fail. */ + +static void +vtv_fail (const char *msg, void **data_set_ptr, const void *vtbl_ptr) +{ + char buffer[128]; + int buf_len; + const char *format_str = + "*** Unable to verify vtable pointer (%p) in set (%p) *** \n"; + + snprintf (buffer, sizeof (buffer), format_str, vtbl_ptr, + is_set_handle_handle(*data_set_ptr) ? + ptr_from_set_handle_handle (*data_set_ptr) : + *data_set_ptr); + buf_len = strlen (buffer); + /* Send this to to stderr. */ + write (2, buffer, buf_len); + + if (!vtv_no_abort) + __vtv_really_fail (msg); +} + +/* Send information about what we were trying to do when verification + failed to the error log, then call vtv_fail. This function can be + overwritten/replaced by the user, to implement a secondary + verification function instead. DATA_SET_PTR is the vtable map + variable used for the failed verification, and VTBL_PTR is the + vtable pointer that was not found in the set. */ + +void +__vtv_verify_fail (void **data_set_ptr, const void *vtbl_ptr) +{ + char log_msg[256]; + snprintf (log_msg, sizeof (log_msg), "Looking for vtable %p in set %p.\n", + vtbl_ptr, + is_set_handle_handle (*data_set_ptr) ? + ptr_from_set_handle_handle (*data_set_ptr) : + *data_set_ptr); + log_error_message (log_msg, false); + + const char *format_str = + "*** Unable to verify vtable pointer (%p) in set (%p) *** \n"; + snprintf (log_msg, sizeof (log_msg), format_str, vtbl_ptr, *data_set_ptr); + log_error_message (log_msg, false); + log_error_message (" Backtrace: \n", true); + + const char *fail_msg = "Potential vtable pointer corruption detected!!\n"; + vtv_fail (fail_msg, data_set_ptr, vtbl_ptr); +} + |