Fix incorrect error message reported for non-existent users

Previously, lookups of non-existent user names could return "Success";
it will now return "User does not exist" by resetting errno.  This also
centralizes the user name lookup code in libpgport.

Report and analysis by Nicolas Marchildon;  patch by me

2 files changed, 8 insertions, 44 deletions

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 2dbf7e53a12..6d11e576a4b 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -1771,7 +1771,8 @@ auth_peer(hbaPort *port)
 	char		ident_user[IDENT_USERNAME_MAX + 1];
 	uid_t		uid;
 	gid_t		gid;
-	struct passwd *pass;
+	const char *user_name;
+	char	   *errstr;
 
 	errno = 0;
 	if (getpeereid(port->sock, &uid, &gid) != 0)
@@ -1788,17 +1789,15 @@ auth_peer(hbaPort *port)
 		return STATUS_ERROR;
 	}
 
-	pass = getpwuid(uid);
-
-	if (pass == NULL)
+	user_name = get_user_name(&errstr);
+	if (!user_name)
 	{
-		ereport(LOG,
-				(errmsg("local user with ID %d does not exist",
-						(int) uid)));
+		ereport(LOG, (errmsg_internal("%s", errstr)));
+		pfree(errstr);
 		return STATUS_ERROR;
 	}
 
-	strlcpy(ident_user, pass->pw_name, IDENT_USERNAME_MAX + 1);
+	strlcpy(ident_user, user_name, IDENT_USERNAME_MAX + 1);
 
 	return check_usermap(port->hba->usermap, port->user_name, ident_user, false);
 }
diff --git a/src/backend/main/main.c b/src/backend/main/main.c
index d71885dba9d..376aa39a985 100644
--- a/src/backend/main/main.c
+++ b/src/backend/main/main.c
@@ -20,7 +20,6 @@
  */
 #include "postgres.h"
 
-#include <pwd.h>
 #include <unistd.h>
 
 #if defined(__alpha) && defined(__osf__)		/* no __alpha__ ? */
@@ -49,7 +48,6 @@ const char *progname;
 static void startup_hacks(const char *progname);
 static void help(const char *progname);
 static void check_root(const char *progname);
-static char *get_current_username(const char *progname);
 
 
 /*
@@ -191,7 +189,7 @@ main(int argc, char *argv[])
 	else if (argc > 1 && strcmp(argv[1], "--single") == 0)
 		PostgresMain(argc, argv,
 					 NULL,		/* no dbname */
-					 get_current_username(progname));	/* does not return */
+					 strdup(get_user_name_or_exit(progname)));	/* does not return */
 	else
 		PostmasterMain(argc, argv);		/* does not return */
 	abort();					/* should not get here */
@@ -372,36 +370,3 @@ check_root(const char *progname)
 	}
 #endif   /* WIN32 */
 }
-
-
-
-static char *
-get_current_username(const char *progname)
-{
-#ifndef WIN32
-	struct passwd *pw;
-
-	pw = getpwuid(geteuid());
-	if (pw == NULL)
-	{
-		write_stderr("%s: invalid effective UID: %d\n",
-					 progname, (int) geteuid());
-		exit(1);
-	}
-	/* Allocate new memory because later getpwuid() calls can overwrite it. */
-	return strdup(pw->pw_name);
-#else
-	unsigned long namesize = 256 /* UNLEN */ + 1;
-	char	   *name;
-
-	name = malloc(namesize);
-	if (!GetUserName(name, &namesize))
-	{
-		write_stderr("%s: could not determine user name (GetUserName failed)\n",
-					 progname);
-		exit(1);
-	}
-
-	return name;
-#endif
-}