Merge pull request #44 from fischerling/add-shadow-file

move passwords from /etc/passwd to /etc/shadow

files/etc/passwd

@@ -1,2 +1,2 @@
-root:root:0:0:Root User:/root:/bin/shell
-user:user:1000:1000:Normal User:/home/user:/bin/shell
+root:x:0:0:Root User:/root:/bin/shell
+user:x:1000:1000:Normal User:/home/user:/bin/shell

files/etc/shadow

@@ -0,0 +1,2 @@
+root:root:::::::
+user:user:::::::

libc/CMakeLists.txt

@@ -5,6 +5,7 @@
 # Add the library.
 add_library(
     libc
+    ${CMAKE_SOURCE_DIR}/libc/src/shadow.c
     ${CMAKE_SOURCE_DIR}/libc/src/unistd/dup.c
     ${CMAKE_SOURCE_DIR}/libc/src/stdio.c
     ${CMAKE_SOURCE_DIR}/libc/src/ctype.c

libc/inc/shadow.h

@@ -0,0 +1,22 @@
+// @file shadow.h
+/// @brief Secret password file routines
+#pragma once
+
+#include "stddef.h"
+
+#define SHADOW "/etc/shadow"
+
+struct spwd {
+	char *sp_namp;
+	char *sp_pwdp;
+	long sp_lstchg;
+	long sp_min;
+	long sp_max;
+	long sp_warn;
+	long sp_inact;
+	long sp_expire;
+	unsigned long sp_flag;
+};
+
+struct spwd *getspnam(const char *);
+int getspnam_r(const char *, struct spwd *, char *, size_t, struct spwd **);

libc/src/shadow.c

@@ -0,0 +1,114 @@
+/// @file shadow.c
+/// @brief
+/// @copyright (c) 2005-2020 Rich Felker, et al.
+/// This file is based on the code from libmusl.
+#include <shadow.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/errno.h>
+#include <sys/unistd.h>
+#include <sys/stat.h>
+#include <ctype.h>
+
+static long xatol(char **s)
+{
+	long x;
+	if (**s == ':' || **s == '\n') return -1;
+	for (x=0; **s-'0'<10U; ++*s) x=10*x+(**s-'0');
+	return x;
+}
+
+int __parsespent(char *s, struct spwd *sp)
+{
+	sp->sp_namp = s;
+	if (!(s = strchr(s, ':'))) return -1;
+	*s = 0;
+
+	sp->sp_pwdp = ++s;
+	if (!(s = strchr(s, ':'))) return -1;
+	*s = 0;
+
+	s++; sp->sp_lstchg = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_min = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_max = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_warn = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_inact = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_expire = xatol(&s);
+	if (*s != ':') return -1;
+
+	s++; sp->sp_flag = xatol(&s);
+	if (*s != '\n') return -1;
+	return 0;
+}
+
+int getspnam_r(const char *name, struct spwd *sp, char *buf, size_t size, struct spwd **res)
+{
+	char path[20+NAME_MAX];
+	int rv = 0;
+	int fd;
+	size_t k, l = strlen(name);
+	int skip = 0;
+	int cs;
+	int orig_errno = errno;
+
+	*res = 0;
+
+	/* Disallow potentially-malicious user names */
+	if (*name=='.' || strchr(name, '/') || !l)
+		return errno = EINVAL;
+
+	/* Buffer size must at least be able to hold name, plus some.. */
+	if (size < l+100)
+		return errno = ERANGE;
+
+	fd = open(SHADOW, O_RDONLY, 0);
+	if (fd < 0) {
+		return errno;
+	}
+
+	while (fgets(buf, size, fd) && (k=strlen(buf))>0) {
+		if (skip || strncmp(name, buf, l) || buf[l]!=':') {
+			skip = buf[k-1] != '\n';
+			continue;
+		}
+		if (buf[k-1] != '\n') {
+			rv = ERANGE;
+			break;
+		}
+
+		if (__parsespent(buf, sp) < 0) continue;
+		*res = sp;
+		break;
+	}
+	errno = rv ? rv : orig_errno;
+	return rv;
+}
+
+#define LINE_LIM 256
+
+struct spwd *getspnam(const char *name)
+{
+	static struct spwd sp;
+	static char *line;
+	struct spwd *res;
+	int e;
+	int orig_errno = errno;
+
+	if (!line) line = malloc(LINE_LIM);
+	if (!line) return 0;
+	e = getspnam_r(name, &sp, line, LINE_LIM, &res);
+	errno = e ? e : orig_errno;
+	return res;
+}

programs/login.c

@@ -12,6 +12,7 @@
 #include <termios.h>
 #include <bits/ioctls.h>
 #include <pwd.h>
+#include <shadow.h>
 #include <strerror.h>
 #include <stdlib.h>
 #include <io/debug.h>
@@ -196,8 +197,14 @@ int main(int argc, char **argv)
             continue;
         }
 
+        struct spwd *spwd;
+        if ((spwd = getspnam(username)) == NULL) {
+            printf("Could not retrieve the secret password of %s:%s\n", username, strerror(errno));
+            continue;
+        }
+
         // Check if the password is correct.
-        if (strcmp(pwd->pw_passwd, password) != 0) {
+        if (strcmp(spwd->sp_pwdp, password) != 0) {
             printf("Wrong password.\n");
             continue;
         }