passwd: initialize pointers correctly

Fix for running passwd as root (or sudo passwd $USER).
Crashed on call to free(orig) during cleanup.

Fix regression from commit 17058a06c4333fc0c492c168c8a971ebd0fd5a5a
Root user never changes the orig pointer, so when cleaning up, passwd tried to
free orig=(char*)""
Example: sudo passwd $USER
Changing password for xxx
New password:
Bad password: too short
Retype password:
Passwords don't match
free(): invalid pointer
Aborted

function                                             old     new   delta
passwd_main                                          958     961      +3

Signed-off-by: Einar Jón <tolvupostur@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/loginutils/passwd.c b/loginutils/passwd.c
index 59f47fc7b6b450e3456e84033cd46c3e40962385..30e096460d02b9925968455fce5149125794be59 100644 (file)
--- a/loginutils/passwd.c
+++ b/loginutils/passwd.c
@@ -43,7 +43,7 @@
 static char* new_password(const struct passwd *pw, uid_t myuid, const char *algo)
 {
        char salt[MAX_PW_SALT_LEN];
-       char *orig = (char*)"";
+       char *orig = NULL;
        char *newp = NULL;
        char *cp = NULL;
        char *ret = NULL; /* failure so far */
@@ -51,7 +51,7 @@ static char* new_password(const struct passwd *pw, uid_t myuid, const char *algo
        if (myuid != 0 && pw->pw_passwd[0]) {
                char *encrypted;
 
-               orig = bb_ask_noecho_stdin("Old password: "); /* returns ptr to static */
+               orig = bb_ask_noecho_stdin("Old password: "); /* returns malloced str */
                if (!orig)
                        goto err_ret;
                encrypted = pw_encrypt(orig, pw->pw_passwd, 1); /* returns malloced str */
@@ -64,11 +64,11 @@ static char* new_password(const struct passwd *pw, uid_t myuid, const char *algo
                if (ENABLE_FEATURE_CLEAN_UP)
                        free(encrypted);
        }
-       newp = bb_ask_noecho_stdin("New password: "); /* returns ptr to static */
+       newp = bb_ask_noecho_stdin("New password: "); /* returns malloced str */
        if (!newp)
                goto err_ret;
        if (ENABLE_FEATURE_PASSWD_WEAK_CHECK
-        && obscure(orig, newp, pw)
+        && obscure(orig, newp, pw) /* NB: passing NULL orig is ok */
         && myuid != 0
        ) {
                goto err_ret; /* non-root is not allowed to have weak passwd */