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It is important to remember to cleanup in order to allow filenames and other resources such as secondary storage to be recycled. In the case of abnormal termination, there is no sure method that can guarantee the removal of orphaned files. For this reason tmp cleaner utilities are widely used. These tmp cleaners are invoked manually by a system administrator or run as a cron daemon to sweep temporary directories and remove old files. These tmp cleaners are themselves vulnerable to file-based exploits, and often require the use of shared directories (see : FIO15-A. Do not create temporary files in shared directories). However, during normal operation, it is the responsibility of the program to ensure that temporary files are either removed explicitly, or through the use of library routines such as tmpfile_s which guarantee their removal upon program termination.
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The C99 tmpfile() function creates a temporary binary file that is different from any other existing file and that is automatically removed when it is closed or at program termination.
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It should be possible to open at least {{TMP_MAX}} temporary files during the lifetime of the program (this limit may be shared with {{tmpfile()}}) |
TMP_MAX is only required to be 25 by the C99 standard. C99 Section 7.19.4.4 allows for the value of the macro {{TMP_MAX}} to be at little as 25 \[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\]. |
Most historic implementations provide only a limited number of possible temporary filenames (usually 26) before filenames are recycled.
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Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
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FIO43-C | 3 ( high ) | 2 ( probable ) | 1 ( high ) | P6 | L2 |
Related Vulnerabilities
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\[[ISO/IEC 9899-1999|AA. C References#ISO/IEC 9899-1999]\] Sections 7.19.4.4, "The {{tmpnam}} function," 7.19.4.3, "The {{tmpfile}} function," and 7.19.5.3, "The {{fopen}} function"
\[[ISO/IEC PDTR 24772|AA. C References#ISO/IEC PDTR 24772]\] "EWR Path Traversal"
\[[ISO/IEC TR 24731-1-2007|AA. C References#ISO/IEC TR 24731-1-2007]\] Sections 6.5.1.2, "The {{tmpnam_s}} function," 6.5.1.1, "The {{tmpfile_s}} function," and 6.5.2.1, "The {{fopen_s}} function"
\[[Open Group 04|AA. C References#Open Group 04]\] [{{mktemp()}}|http://www.opengroup.org/onlinepubs/000095399/functions/mktemp.html], [{{mkstemp()}}|http://www.opengroup.org/onlinepubs/009695399/functions/mkstemp.html], [{{open()}}|http://www.opengroup.org/onlinepubs/009695399/functions/open.html]
\[[Seacord 05a|AA. C References#Seacord 05a]\] Chapter 3, "File I/O", Chapter 7
\[[Wheeler 03|AA. C References#Wheeler 03]\] [Chapter 7, "Structure Program Internals and Approach"|http://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/avoid-race.html#TEMPORARY-FILES]
\[[Viega 03|AA. C References#Viega 03]\] Section 2.1, "Creating Files for Temporary Use"
\[[Kennaway 00|AA. C References#Kennaway 00]\]
\[[HP 03|AA. C References#HP 03]\] |
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