Avoid logging complaints about abandoned connections when using PAM.

For a long time (since commit aed378e8d) we have had a policy to log
nothing about a connection if the client disconnects when challenged
for a password.  This is because libpq-using clients will typically
do that, and then come back for a new connection attempt once they've
collected a password from their user, so that logging the abandoned
connection attempt will just result in log spam.  However, this did
not work well for PAM authentication: the bottom-level function
pam_passwd_conv_proc() was on board with it, but we logged messages
at higher levels anyway, for lack of any reporting mechanism.
Add a flag and tweak the logic so that the case is silent, as it is
for other password-using auth mechanisms.

Per complaint from Yoann La Cancellera.  It's been like this for awhile,
so back-patch to all supported branches.

Discussion: https://postgr.es/m/CACP=ajbrFFYUrLyJBLV8=q+eNCapa1xDEyvXhMoYrNphs-xqPw@mail.gmail.com

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index d28271c1d87ba8bb76a9e547d3b8d49b8585cf9b..5bc42a6726486d9ede27c073103300ca23870f84 100644 (file)
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -110,6 +110,7 @@ static const char *pam_passwd = NULL;   /* Workaround for Solaris 2.6
                                         * brokenness */
 static Port *pam_port_cludge;  /* Workaround for passing "Port *port" into
                                 * pam_passwd_conv_proc */
+static bool pam_no_password;   /* For detecting no-password-given */
 #endif                         /* USE_PAM */
 
 
@@ -2099,8 +2100,10 @@ pam_passwd_conv_proc(int num_msg, const struct pam_message **msg,
                    {
                        /*
                         * Client didn't want to send password.  We
-                        * intentionally do not log anything about this.
+                        * intentionally do not log anything about this,
+                        * either here or at higher levels.
                         */
+                       pam_no_password = true;
                        goto fail;
                    }
                }
@@ -2159,6 +2162,7 @@ CheckPAMAuth(Port *port, const char *user, const char *password)
     */
    pam_passwd = password;
    pam_port_cludge = port;
+   pam_no_password = false;
 
    /*
     * Set the application data portion of the conversation struct.  This is
@@ -2244,22 +2248,26 @@ CheckPAMAuth(Port *port, const char *user, const char *password)
 
    if (retval != PAM_SUCCESS)
    {
-       ereport(LOG,
-               (errmsg("pam_authenticate failed: %s",
-                       pam_strerror(pamh, retval))));
+       /* If pam_passwd_conv_proc saw EOF, don't log anything */
+       if (!pam_no_password)
+           ereport(LOG,
+                   (errmsg("pam_authenticate failed: %s",
+                           pam_strerror(pamh, retval))));
        pam_passwd = NULL;      /* Unset pam_passwd */
-       return STATUS_ERROR;
+       return pam_no_password ? STATUS_EOF : STATUS_ERROR;
    }
 
    retval = pam_acct_mgmt(pamh, 0);
 
    if (retval != PAM_SUCCESS)
    {
-       ereport(LOG,
-               (errmsg("pam_acct_mgmt failed: %s",
-                       pam_strerror(pamh, retval))));
+       /* If pam_passwd_conv_proc saw EOF, don't log anything */
+       if (!pam_no_password)
+           ereport(LOG,
+                   (errmsg("pam_acct_mgmt failed: %s",
+                           pam_strerror(pamh, retval))));
        pam_passwd = NULL;      /* Unset pam_passwd */
-       return STATUS_ERROR;
+       return pam_no_password ? STATUS_EOF : STATUS_ERROR;
    }
 
    retval = pam_end(pamh, retval);