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In the following noncompliant code, unsafe characters are used as part of a file name.
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#include <fcntl.h>
#include <sys/stat.h>
int main(void) {
char *file_name = "»£???«";
mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
int fd = open(file_name, O_CREAT | O_EXCL | O_WRONLY, mode);
if (fd == -1) {
/* Handle Error */
}
}
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Use a descriptive file name, containing only the subset of ASCII previously described.
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#include <fcntl.h>
#include <sys/stat.h>
int main(void) {
char *file_name = "name.ext";
mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
int fd = open(file_name, O_CREAT | O_EXCL | O_WRONLY, mode);
if (fd == -1) {
/* Handle Error */
}
}
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This noncompliant code example is derived from rule FIO30-C. Exclude user input from format strings, except that a newline is removed on the assumption that fgets() will include it.
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char myFilename[1000]; const char elimNewLn[] = "\n"; fgets(myFilename, sizeof(myFilename)-1, stdin); myFilename[sizeof(myFilename)-1] = '\0'; myFilename[strcspn(myFilename, elimNewLn)] = '\0'; |
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In this compliant solution, the program rejects file names that violate the guidelines for selecting safe characters.
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char myFilename[1000];
const char elimNewln[] = "\n";
const char badChars[] = "-\n\r ,;'\\<\"";
do {
fgets(myFilename, sizeof(myFilename)-1, stdin);
myFilename[sizeof(myFilename)-1] ='\0';
myFilename[strcspn(myFilename, elimNewln)]='\0';
} while ( (strcspn(myFilename, badChars))
< (strlen(myFilename)));
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