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EDA263/lab1/pwent.c

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2022-01-29 10:32:11 +01:00
/* $Header: https://svn.ita.chalmers.se/repos/security/edu/course/computer_security/trunk/lab/login_linux/pwent.c 584 2013-01-19 10:30:22Z pk@CHALMERS.SE $ */
/*
A simple library for password databases. Tobias Gedell 2007
*/
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "pwent.h"
#define LINE_BUFFER_LENGTH 1000
/*
Return pointer to password entry for specified user.
Upon error, or if the user couldn't be found, NULL is returned.
Note: The returned pointer points to static data.
*/
mypwent *mygetpwnam(char *name) {
FILE *file;
char buffer[LINE_BUFFER_LENGTH];
static char pwname[LINE_BUFFER_LENGTH], passwd[LINE_BUFFER_LENGTH],
passwd_salt[LINE_BUFFER_LENGTH];
static mypwent ent = { pwname, 0, passwd, passwd_salt, 0, 0 };
/* Open file, return NULL if it failed. */
if ((file = fopen(MYPWENT_FILENAME, "rb")) == NULL)
return NULL;
/* Read each line, looking for the right entry. */
while (fgets(buffer, sizeof(buffer), file) != NULL) {
if (sscanf(buffer, "%[^:]:%d:%[^:]:%[^:]:%d:%d", ent.pwname, &ent.uid,
ent.passwd, ent.passwd_salt, &ent.pwfailed, &ent.pwage) != 6)
break;
if (strcmp(pwname, name) == 0) {
fclose(file);
return &ent;
}
}
fclose(file);
return NULL;
}
/*
Update password entry for user.
Upon error, or if the user couldn't be found, -1 is returned,
otherwise 0.
*/
int mysetpwent(char *name, mypwent *pw) {
FILE *file;
FILE *newfile;
char buffer[LINE_BUFFER_LENGTH];
char pwname[LINE_BUFFER_LENGTH];
int status = -1;
if ((file = fopen(MYPWENT_FILENAME, "rb")) == NULL)
return -1;
if ((newfile = fopen(MYPWENT_TMP_FILENAME, "wb")) == NULL) {
fclose(file);
return -1;
}
/* Read each line, looking for the right entry. */
while (fgets(buffer, sizeof(buffer), file) != NULL) {
if (sscanf(buffer, "%[^:]", pwname) != 1) {
status = -1;
break;
}
/* See if we found the entry to be updated. */
if (strcmp(pwname, name) == 0) {
if (snprintf(buffer, sizeof(buffer), "%s:%d:%s:%s:%d:%d\n",
pw->pwname, pw->uid, pw->passwd, pw->passwd_salt,
pw->pwfailed, pw->pwage) >= sizeof(buffer)) {
status = -1;
break;
}
status = 0;
}
if (fputs(buffer, newfile) < 0) {
status = -1;
break;
}
}
fclose(newfile);
fclose(file);
/* Swap files if user successfully updated. */
if (status == 0) {
if (rename(MYPWENT_TMP_FILENAME, MYPWENT_FILENAME) != 0)
status = -1;
} else
unlink(MYPWENT_TMP_FILENAME);
return status;
}