passwd: Use a random salt when encrypting passwords - ubase - suckless linux base utils
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---
DIR commit fae9ca81a2eaf3534299b7ca3033b1e6605f9ab2
DIR parent 3a5939e81018a05d710d0f3c8cea8794dd8a1637
HTML Author: Michael Forney <mforney@mforney.org>
Date: Sun, 23 Oct 2016 20:59:51 -0700
passwd: Use a random salt when encrypting passwords
Diffstat:
M passwd.c | 39 ++++++++++++++++++++++++++-----
1 file changed, 33 insertions(+), 6 deletions(-)
---
DIR diff --git a/passwd.c b/passwd.c
@@ -2,12 +2,14 @@
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
+#include <sys/syscall.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <pwd.h>
#include <shadow.h>
+#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@@ -127,6 +129,27 @@ cleanup:
return r;
}
+/* generates a random base64-encoded salt string of length 16 */
+static void
+gensalt(char *s)
+{
+ static const char b64[] = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+ uint8_t buf[12];
+ uint32_t n;
+ int i;
+
+ if (syscall(SYS_getrandom, buf, sizeof(buf), 0) < 0)
+ eprintf("getrandom:");
+ for (i = 0; i < 12; i += 3) {
+ n = buf[i] << 16 | buf[i+1] << 8 | buf[i+2];
+ *s++ = b64[n%64]; n /= 64;
+ *s++ = b64[n%64]; n /= 64;
+ *s++ = b64[n%64]; n /= 64;
+ *s++ = b64[n];
+ }
+ *s++ = '\0';
+}
+
static void
usage(void)
{
@@ -137,7 +160,7 @@ int
main(int argc, char *argv[])
{
char *cryptpass1 = NULL, *cryptpass2 = NULL, *cryptpass3 = NULL;
- char *inpass, *p, *salt = PW_CIPHER, *prevhash = NULL;
+ char *inpass, *p, *prevhash = NULL, salt[sizeof(PW_CIPHER) + 16] = PW_CIPHER;
struct passwd *pw;
struct spwd *spw = NULL;
FILE *fp = NULL;
@@ -188,9 +211,9 @@ main(int argc, char *argv[])
goto newpass;
}
if (pw->pw_passwd[0] == 'x')
- prevhash = salt = spw->sp_pwdp;
+ prevhash = spw->sp_pwdp;
else
- prevhash = salt = pw->pw_passwd;
+ prevhash = pw->pw_passwd;
}
printf("Changing password for %s\n", pw->pw_name);
@@ -199,7 +222,7 @@ main(int argc, char *argv[])
eprintf("getpass:");
if (inpass[0] == '\0')
eprintf("no password supplied\n");
- p = crypt(inpass, salt);
+ p = crypt(inpass, prevhash);
if (!p)
eprintf("crypt:");
cryptpass1 = estrdup(p);
@@ -212,12 +235,16 @@ newpass:
eprintf("getpass:");
if (inpass[0] == '\0')
eprintf("no password supplied\n");
+ p = crypt(inpass, prevhash);
+ if (!p)
+ eprintf("crypt:");
+ if (cryptpass1 && strcmp(cryptpass1, p) == 0)
+ eprintf("password left unchanged\n");
+ gensalt(salt + strlen(salt));
p = crypt(inpass, salt);
if (!p)
eprintf("crypt:");
cryptpass2 = estrdup(p);
- if (cryptpass1 && strcmp(cryptpass1, cryptpass2) == 0)
- eprintf("password left unchanged\n");
/* Flush pending input */
ioctl(0, TCFLSH, (void *)0);