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| CodeSonar® 9.2p0 | CONFIDENTIAL | CodeSecure Inc |
An attempt to write through a FILE* to a file that was opened as read-only.
| Class Name | Write to Read Only File | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Significance | reliability | ||||||||||||
| Mnemonic | IO.WRITERO | ||||||||||||
| Categories |
|
||||||||||||
| Availability | Available for C and C++. |
||||||||||||
| Enabling | Checks for this warning class are
disabled by default. To enable them, add the following WARNING_FILTER
rule to the project configuration file.
WARNING_FILTER += allow class="Write to Read Only File" |
CodeSonar keeps track of files that have been opened as read-only, then triggers a warning if there is an attempt to write to one of these files.
CodeSonar ships with library models that allow it to recognize a number of functions that take a FILE* argument and write to that file. Some examples are shown in the table below. If one of these functions is called with a pointer to a read-only file in the FILE* parameter position, a warning will be issued.
If you have created a custom library model for some function f() in terms of one of these existing models, calls to f() will also be capable of triggering Write to Read Only File warnings.
| Functions that can trigger warnings include... | |
|---|---|
| gcc Builtins | __builtin___fprintf_chk(), __builtin_fputc() |
| libc | fprintf(), putc(), write() |
| Win32 | fprintf_s(), _fputc_nolock() _fwrite_nolock() |
CodeSonar ships with library models that allow it to recognize functions such as libc fopen() and Win32 fopen_s() as opening files as read-only when called with string "r" or "rb" as the mode argument.
If you have created a custom library model for some function f() in terms of one of these existing models, calls to f() will also be recognized as opening files as read-only in the same circumstances.
Japanese (ja)
#include <stdlib.h>
#include <stdio.h>
int writero(void){
FILE* f;
char* str = "r";
int w;
f = fopen("A.txt","r");
if (!f){return -1;}
w = fputc('A', f); /* 'Write to Read Only File' warning issued here */
fclose(f);
if (w==EOF){return -1;}
f = fopen("B.txt","rb");
if (!f){return -1;}
w = fputc('B', f); /* 'Write to Read Only File' warning issued here */
fclose(f);
if (w==EOF){return -1;}
f = fopen("C.txt","r+");
if (!f){return -1;}
w = fputc('C', f); /* f not opened as read-only */
fclose(f);
if (w==EOF){return -1;}
f = fopen("D.txt","w+");
if (!f){return -1;}
w = fputc('D', f); /* f not opened as read-only */
fclose(f);
if (w==EOF){return -1;}
f = fopen("E.txt", str);
if (!f){return -1;}
w = fputc('E', f); /* 'Write to Read Only File' warning issued here */
fclose(f);
if (w==EOF){return -1;}
return 1;
}
The following configuration file parameters affect checks for this warning class.
To report problems with this documentation, please visit https://support.codesecure.com/.