Use arc4random_uniform() to avoid "modulo bias"

[pw-darwin.git] / pw / pw_user.c

diff --git a/pw/pw_user.c b/pw/pw_user.c
index 7da16f8773a0e240933864d78bee4e6176df60b9..4c62fe83c6324a3ed1969b9082269849d3f1f5a1 100644 (file)
--- a/pw/pw_user.c
+++ b/pw/pw_user.c
@@ -43,9 +43,6 @@ static const char rcsid[] =
 #include <unistd.h>
 #include <utmp.h>
 #include <login_cap.h>
-#if defined(USE_MD5RAND)
-#include <md5.h>
-#endif
 #include "pw.h"
 #include "bitmap.h"
 
@@ -1045,74 +1042,24 @@ pw_pwcrypt(char *password)
         * Calculate a salt value
         */
        for (i = 0; i < SALTSIZE; i++)
-               salt[i] = chars[arc4random() % (sizeof(chars) - 1)];
+               salt[i] = chars[arc4random_uniform(sizeof(chars) - 1)];
        salt[SALTSIZE] = '\0';
 
        return strcpy(buf, crypt(password, salt));
 }
 
-#if defined(USE_MD5RAND)
-u_char *
-pw_getrand(u_char *buf, int len)       /* cryptographically secure rng */
-{
-       int i;
-       for (i=0;i<len;i+=16) {
-               u_char ubuf[16];
-
-               MD5_CTX md5_ctx;
-               struct timeval tv, tvo;
-               struct rusage ru;
-               int n=0;
-               int t;
-
-               MD5Init (&md5_ctx);
-               t=getpid();
-               MD5Update (&md5_ctx, (u_char*)&t, sizeof t);
-               t=getppid();
-               MD5Update (&md5_ctx, (u_char*)&t, sizeof t);
-               gettimeofday (&tvo, NULL);
-               do {
-                       getrusage (RUSAGE_SELF, &ru);
-                       MD5Update (&md5_ctx, (u_char*)&ru, sizeof ru);
-                       gettimeofday (&tv, NULL);
-                       MD5Update (&md5_ctx, (u_char*)&tv, sizeof tv);
-               } while (n++<20 || tv.tv_usec-tvo.tv_usec<100*1000);
-               MD5Final (ubuf, &md5_ctx);
-               memcpy(buf+i, ubuf, MIN(16, len-i));
-       }
-       return buf;
-}
-
-#else  /* Portable version */
-
-static u_char *
-pw_getrand(u_char *buf, int len)
-{
-       int i;
-
-       for (i = 0; i < len; i++) {
-               unsigned long val = arc4random();
-               /* Use all bits in the random value */
-               buf[i]=(u_char)((val >> 24) ^ (val >> 16) ^ (val >> 8) ^ val);
-       }
-       return buf;
-}
-
-#endif
 
 static char    *
 pw_password(struct userconf * cnf, struct cargs * args, char const * user)
 {
        int             i, l;
        char            pwbuf[32];
-       u_char          rndbuf[sizeof pwbuf];
 
        switch (cnf->default_password) {
        case -1:                /* Random password */
                l = (arc4random() % 8 + 8);     /* 8 - 16 chars */
-               pw_getrand(rndbuf, l);
                for (i = 0; i < l; i++)
-                       pwbuf[i] = chars[rndbuf[i] % (sizeof(chars)-1)];
+                       pwbuf[i] = chars[arc4random_uniform(sizeof(chars)-1)];
                pwbuf[i] = '\0';
 
                /*