login: add commented-out PAM double password avoidance from BZ 4003

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 43 insertions, 0 deletions

diff --git a/loginutils/login.c b/loginutils/login.c
index 67fe82e86..4ebc18502 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -78,6 +78,49 @@
  * Apparently they like to confuse people. */
 # include <security/pam_appl.h>
 # include <security/pam_misc.h>
+
+# if 0
+/* This supposedly can be used to avoid double password prompt,
+ * if used instead of standard misc_conv():
+ *
+ * "When we want to authenticate first with local method and then with tacacs for example,
+ *  the password is asked for local method and if not good is asked a second time for tacacs.
+ *  So if we want to authenticate a user with tacacs, and the user exists localy, the password is
+ *  asked two times before authentication is accepted."
+ *
+ * However, code looks shaky. For example, why misc_conv() return value is ignored?
+ * Are msg[i] and resp[i] indexes handled correctly?
+ */
+static char *passwd = NULL;
+static int my_conv(int num_msg, const struct pam_message **msg,
+                struct pam_response **resp, void *data)
+{
+        int i;
+        for (i = 0; i < num_msg; i++) {
+                switch (msg[i]->msg_style) {
+                case PAM_PROMPT_ECHO_OFF:
+                        if (passwd == NULL) {
+                                misc_conv(num_msg, msg, resp, data);
+                                passwd = xstrdup(resp[i]->resp);
+                                return PAM_SUCCESS;
+                        }
+
+                        resp[0] = xzalloc(sizeof(struct pam_response));
+                        resp[0]->resp = passwd;
+                        passwd = NULL;
+                        resp[0]->resp_retcode = PAM_SUCCESS;
+                        resp[1] = NULL;
+                        return PAM_SUCCESS;
+
+                default:
+                        break;
+                }
+        }
+
+        return PAM_SUCCESS;
+}
+# endif
+
 static const struct pam_conv conv = {
         misc_conv,
         NULL