Fix srp app missing NULL termination with password callback

The password_callback() function does not necessarily NULL terminate
the password buffer, the caller must use the returned length but the
srp app uses this function as if it was doing NULL termination.

This made the -passin and -passout options of "openssl srp"
fail inexpicably and randomly or even crash.

Fixed by enlarging the buffer by one, so that the maximum password length
remains unchanged, and adding NULL termination upon return.

[Rearrange code for coding style compliance in process.]
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3475)

apps/srp.c

@@ -119,32 +119,35 @@ static char *srp_verify_user(const char *user, const char *srp_verifier,
                              char *srp_usersalt, const char *g, const char *N,
                              const char *passin, int verbose)
 {
-    char password[1024];
+    char password[1025];
     PW_CB_DATA cb_tmp;
     char *verifier = NULL;
     char *gNid = NULL;
+    int len;
 
     cb_tmp.prompt_info = user;
     cb_tmp.password = passin;
 
-    if (password_callback(password, sizeof(password), 0, &cb_tmp) > 0) {
+    len = password_callback(password, sizeof(password)-1, 0, &cb_tmp);
+    if (len > 0) {
+        password[len] = 0;
         if (verbose)
             BIO_printf(bio_err,
                        "Validating\n   user=\"%s\"\n srp_verifier=\"%s\"\n srp_usersalt=\"%s\"\n g=\"%s\"\n N=\"%s\"\n",
                        user, srp_verifier, srp_usersalt, g, N);
-        BIO_printf(bio_err, "Pass %s\n", password);
+        if (verbose > 1)
+            BIO_printf(bio_err, "Pass %s\n", password);
 
         OPENSSL_assert(srp_usersalt != NULL);
-        if (!
-            (gNid =
-             SRP_create_verifier(user, password, &srp_usersalt, &verifier, N,
-                                 g))) {
+        if (!(gNid = SRP_create_verifier(user, password, &srp_usersalt,
+                                         &verifier, N, g)) ) {
             BIO_printf(bio_err, "Internal error validating SRP verifier\n");
         } else {
             if (strcmp(verifier, srp_verifier))
                 gNid = NULL;
             OPENSSL_free(verifier);
         }
+        OPENSSL_cleanse(password, len);
     }
     return gNid;
 }
@@ -153,27 +156,30 @@ static char *srp_create_user(char *user, char **srp_verifier,
                              char **srp_usersalt, char *g, char *N,
                              char *passout, int verbose)
 {
-    char password[1024];
+    char password[1025];
     PW_CB_DATA cb_tmp;
     char *gNid = NULL;
     char *salt = NULL;
+    int len;
     cb_tmp.prompt_info = user;
     cb_tmp.password = passout;
 
-    if (password_callback(password, sizeof(password), 1, &cb_tmp) > 0) {
+    len = password_callback(password, sizeof(password)-1, 1, &cb_tmp);
+    if (len > 0) {
+        password[len] = 0;
         if (verbose)
             BIO_printf(bio_err, "Creating\n user=\"%s\"\n g=\"%s\"\n N=\"%s\"\n",
                        user, g, N);
-        if (!
-            (gNid =
-             SRP_create_verifier(user, password, &salt, srp_verifier, N,
-                                 g))) {
+        if (!(gNid = SRP_create_verifier(user, password, &salt,
+                                         srp_verifier, N, g)) ) {
             BIO_printf(bio_err, "Internal error creating SRP verifier\n");
-        } else
+        } else {
             *srp_usersalt = salt;
+        }
+        OPENSSL_cleanse(password, len);
         if (verbose > 1)
-            BIO_printf(bio_err, "gNid=%s salt =\"%s\"\n verifier =\"%s\"\n", gNid,
-                       salt, *srp_verifier);
+            BIO_printf(bio_err, "gNid=%s salt =\"%s\"\n verifier =\"%s\"\n",
+                       gNid, salt, *srp_verifier);
 
     }
     return gNid;
@@ -251,7 +257,7 @@ int srp_main(int argc, char **argv)
         case OPT_LIST:
             if (mode != OPT_ERR) {
                 BIO_printf(bio_err,
-                           "%s: Only one of -add/delete-modify/-list\n",
+                           "%s: Only one of -add/-delete/-modify/-list\n",
                            prog);
                 goto opthelp;
             }
@@ -293,7 +299,7 @@ int srp_main(int argc, char **argv)
                    "Need at least one user for options -add, -delete, -modify. \n");
         goto opthelp;
     }
-    if ((passin || passout) && argc != 1) {
+    if ((passinarg || passoutarg) && argc != 1) {
         BIO_printf(bio_err,
                    "-passin, -passout arguments only valid with one user.\n");
         goto opthelp;