109 lines
2.4 KiB
C
109 lines
2.4 KiB
C
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/* $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 $ */
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/*
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A simple library for password databases. Tobias Gedell 2007
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*/
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include "pwent.h"
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#define LINE_BUFFER_LENGTH 1000
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/*
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Return pointer to password entry for specified user.
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Upon error, or if the user couldn't be found, NULL is returned.
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Note: The returned pointer points to static data.
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*/
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mypwent *mygetpwnam(char *name) {
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FILE *file;
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char buffer[LINE_BUFFER_LENGTH];
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static char pwname[LINE_BUFFER_LENGTH], passwd[LINE_BUFFER_LENGTH],
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passwd_salt[LINE_BUFFER_LENGTH];
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static mypwent ent = { pwname, 0, passwd, passwd_salt, 0, 0 };
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/* Open file, return NULL if it failed. */
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if ((file = fopen(MYPWENT_FILENAME, "rb")) == NULL)
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return NULL;
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/* Read each line, looking for the right entry. */
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while (fgets(buffer, sizeof(buffer), file) != NULL) {
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if (sscanf(buffer, "%[^:]:%d:%[^:]:%[^:]:%d:%d", ent.pwname, &ent.uid,
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ent.passwd, ent.passwd_salt, &ent.pwfailed, &ent.pwage) != 6)
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break;
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if (strcmp(pwname, name) == 0) {
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fclose(file);
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return &ent;
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}
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}
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fclose(file);
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return NULL;
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}
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/*
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Update password entry for user.
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Upon error, or if the user couldn't be found, -1 is returned,
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otherwise 0.
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*/
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int mysetpwent(char *name, mypwent *pw) {
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FILE *file;
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FILE *newfile;
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char buffer[LINE_BUFFER_LENGTH];
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char pwname[LINE_BUFFER_LENGTH];
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int status = -1;
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if ((file = fopen(MYPWENT_FILENAME, "rb")) == NULL)
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return -1;
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if ((newfile = fopen(MYPWENT_TMP_FILENAME, "wb")) == NULL) {
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fclose(file);
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return -1;
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}
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/* Read each line, looking for the right entry. */
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while (fgets(buffer, sizeof(buffer), file) != NULL) {
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if (sscanf(buffer, "%[^:]", pwname) != 1) {
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status = -1;
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break;
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}
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/* See if we found the entry to be updated. */
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if (strcmp(pwname, name) == 0) {
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if (snprintf(buffer, sizeof(buffer), "%s:%d:%s:%s:%d:%d\n",
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pw->pwname, pw->uid, pw->passwd, pw->passwd_salt,
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pw->pwfailed, pw->pwage) >= sizeof(buffer)) {
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status = -1;
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break;
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}
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status = 0;
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}
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if (fputs(buffer, newfile) < 0) {
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status = -1;
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break;
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}
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}
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fclose(newfile);
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fclose(file);
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/* Swap files if user successfully updated. */
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if (status == 0) {
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if (rename(MYPWENT_TMP_FILENAME, MYPWENT_FILENAME) != 0)
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status = -1;
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} else
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unlink(MYPWENT_TMP_FILENAME);
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return status;
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}
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