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Merged
merged 1 commit into from
Mar 4, 2018
Merged

Bounds checks in fgets, read #1772

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2 changes: 1 addition & 1 deletion regression/cbmc/fgets1/test.desc
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,6 @@ main.c
^SIGNAL=0$
^VERIFICATION FAILED$
\[main.assertion.3\] assertion p\[1\]=='b': FAILURE
\*\* 1 of \d+ failed
\*\* 2 of \d+ failed
--
^warning: ignoring
19 changes: 19 additions & 0 deletions regression/cbmc/read1/main.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,19 @@
#ifdef _WIN32
#include <io.h>
#else
#include <unistd.h>
#endif

#include <stdio.h>

int main()
{
char data[20];

if(read(0, data, 100) < 0)
printf("An error has occurred");
else
printf("Read occurred");

return 0;
}
10 changes: 10 additions & 0 deletions regression/cbmc/read1/test.desc
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
CORE
main.c
--bounds-check --pointer-check --unwind 100
^EXIT=10$
^SIGNAL=0$
^VERIFICATION FAILED$
\[.*] dereference failure: pointer outside object bounds in .*: FAILURE
\*\* 1 of .* failed \(.*\)
--
^warning: ignoring
3 changes: 3 additions & 0 deletions src/ansi-c/library/stdio.c
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Expand Up @@ -247,6 +247,9 @@ char *fgets(char *str, int size, FILE *stream)
{
int str_length=__VERIFIER_nondet_int();
__CPROVER_assume(str_length>=0 && str_length<size);
// check that the memory is accessible
(void)*(char *)str;
(void)*(((const char *)str) + str_length - 1);
char contents_nondet[str_length];
__CPROVER_array_replace(str, contents_nondet);
if(!error)
Expand Down
65 changes: 43 additions & 22 deletions src/ansi-c/library/unistd.c
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Expand Up @@ -122,27 +122,30 @@ inline int _close(int fildes)
// write to _write; this is covered by the explicit definition of
// _write below
#ifdef _MSC_VER
#define ssize_t signed long
#define ret_type int
#define size_type unsigned
#else
#ifndef __CPROVER_SYS_TYPES_H_INCLUDED
#include <sys/types.h>
#define __CPROVER_SYS_TYPES_H_INCLUDED
#endif
#define ret_type ssize_t
#define size_type size_t
#endif

extern struct __CPROVER_pipet __CPROVER_pipes[];
// offset to make sure we don't collide with other fds
extern const int __CPROVER_pipe_offset;

ssize_t __VERIFIER_nondet_ssize_t();
ret_type __VERIFIER_nondet_ret_type();

ssize_t write(int fildes, const void *buf, size_t nbyte)
ret_type write(int fildes, const void *buf, size_type nbyte)
{
__CPROVER_HIDE:;
if((fildes>=0 && fildes<=2) || fildes < __CPROVER_pipe_offset)
{
ssize_t retval=__VERIFIER_nondet_ssize_t();
__CPROVER_assume(retval>=-1 && retval<=(ssize_t)nbyte);
ret_type retval=__VERIFIER_nondet_ret_type();
__CPROVER_assume(retval>=-1 && retval<=(ret_type)nbyte);
return retval;
}

Expand All @@ -155,7 +158,7 @@ ssize_t write(int fildes, const void *buf, size_t nbyte)
sizeof(__CPROVER_pipes[fildes].data) >=
__CPROVER_pipes[fildes].next_avail+nbyte)
{
for(size_t i=0; i<nbyte; ++i)
for(size_type i=0; i<nbyte; ++i)
__CPROVER_pipes[fildes].data[i+__CPROVER_pipes[fildes].next_avail]=
((char*)buf)[i];
__CPROVER_pipes[fildes].next_avail+=nbyte;
Expand All @@ -168,17 +171,20 @@ ssize_t write(int fildes, const void *buf, size_t nbyte)
/* FUNCTION: _write */

#ifdef _MSC_VER
#define ssize_t signed long
#define ret_type int
#define size_type unsigned
#else
#ifndef __CPROVER_SYS_TYPES_H_INCLUDED
#include <sys/types.h>
#define __CPROVER_SYS_TYPES_H_INCLUDED
#endif
#define ret_type ssize_t
#define size_type size_t
#endif

ssize_t write(int fildes, const void *buf, size_t nbyte);
ret_type write(int fildes, const void *buf, size_type nbyte);

inline ssize_t _write(int fildes, const void *buf, size_t nbyte)
inline ret_type _write(int fildes, const void *buf, size_type nbyte)
{
__CPROVER_HIDE:;
return write(fildes, buf, nbyte);
Expand All @@ -190,42 +196,54 @@ inline ssize_t _write(int fildes, const void *buf, size_t nbyte)
// read to _read; this is covered by the explicit definition of _read
// below
#ifdef _MSC_VER
#define ssize_t signed long
#define ret_type int
#define size_type unsigned
#else
#ifndef __CPROVER_SYS_TYPES_H_INCLUDED
#include <sys/types.h>
#define __CPROVER_SYS_TYPES_H_INCLUDED
#endif
#define ret_type ssize_t
#define size_type size_t
#endif

extern struct __CPROVER_pipet __CPROVER_pipes[];
// offset to make sure we don't collide with other fds
extern const int __CPROVER_pipe_offset;

__CPROVER_bool __VERIFIER_nondet___CPROVER_bool();
ssize_t __VERIFIER_nondet_ssize_t();
ret_type __VERIFIER_nondet_ret_type();
size_type __VERIFIER_nondet_size_type();

ssize_t read(int fildes, void *buf, size_t nbyte)
ret_type read(int fildes, void *buf, size_type nbyte)
{
__CPROVER_HIDE:;
if((fildes>=0 && fildes<=2) || fildes < __CPROVER_pipe_offset)
{
ssize_t nread=__VERIFIER_nondet_ssize_t();
__CPROVER_assume(0<=nread && (size_t)nread<=nbyte);
ret_type nread=__VERIFIER_nondet_ret_type();
__CPROVER_assume(0<=nread && (size_type)nread<=nbyte);

__CPROVER_bool error=__VERIFIER_nondet___CPROVER_bool();
#if 0
size_t i;
size_type i;
for(i=0; i<nbyte; i++)
{
char nondet_char;
((char *)buf)[i]=nondet_char;
}
#else
char nondet_bytes[nbyte];
__CPROVER_array_replace((char*)buf, nondet_bytes);
if(nbyte>0)
{
size_type str_length=__VERIFIER_nondet_size_type();
__CPROVER_assume(error ? str_length<=nbyte : str_length==nbyte);
// check that the memory is accessible
(void)*(char *)buf;
(void)*(((const char *)buf) + str_length - 1);
char contents_nondet[str_length];
__CPROVER_array_replace((char*)buf, contents_nondet);
}
#endif

__CPROVER_bool error=__VERIFIER_nondet___CPROVER_bool();
return error ? -1 : nread;
}

Expand All @@ -236,7 +254,7 @@ ssize_t read(int fildes, void *buf, size_t nbyte)
__CPROVER_atomic_begin();
if(!__CPROVER_pipes[fildes].widowed)
{
for(size_t i=0; i<nbyte &&
for(size_type i=0; i<nbyte &&
__CPROVER_pipes[fildes].next_unread <
__CPROVER_pipes[fildes].next_avail;
++i)
Expand All @@ -257,17 +275,20 @@ ssize_t read(int fildes, void *buf, size_t nbyte)
/* FUNCTION: _read */

#ifdef _MSC_VER
#define ssize_t signed long
#define ret_type int
#define size_type unsigned
#else
#ifndef __CPROVER_SYS_TYPES_H_INCLUDED
#include <sys/types.h>
#define __CPROVER_SYS_TYPES_H_INCLUDED
#endif
#define ret_type ssize_t
#define size_type size_t
#endif

ssize_t read(int fildes, void *buf, size_t nbyte);
ret_type read(int fildes, void *buf, size_type nbyte);

inline ssize_t _read(int fildes, void *buf, size_t nbyte)
inline ret_type _read(int fildes, void *buf, size_type nbyte)
{
__CPROVER_HIDE:;
return read(fildes, buf, nbyte);
Expand Down