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

Author: bmomjian

contrib/pg_upgrade/util.c

@@ -203,32 +203,25 @@ quote_identifier(const char *s)
 
 /*
  * get_user_info()
- * (copied from initdb.c) find the current user
  */
 int
 get_user_info(char **user_name)
 {
 	int			user_id;
+	char	   *errstr;
 
 #ifndef WIN32
-	struct passwd *pw = getpwuid(geteuid());
-
 	user_id = geteuid();
-#else							/* the windows code */
-	struct passwd_win32
-	{
-		int			pw_uid;
-		char		pw_name[128];
-	}			pass_win32;
-	struct passwd_win32 *pw = &pass_win32;
-	DWORD		pwname_size = sizeof(pass_win32.pw_name) - 1;
-
-	GetUserName(pw->pw_name, &pwname_size);
-
+#else
 	user_id = 1;
 #endif
 
-	*user_name = pg_strdup(pw->pw_name);
+	*user_name = get_user_name(&errstr);
+	if (!*user_name)
+		pg_fatal("%s\n", errstr);
+
+	/* make a copy */
+	*user_name = pg_strdup(*user_name);
 
 	return user_id;
 }

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);
 }

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
-}

src/bin/initdb/initdb.c

@@ -770,15 +770,14 @@ exit_nicely(void)
 /*
  * find the current user
  *
- * on unix make sure it isn't really root
+ * on unix make sure it isn't root
  */
 static char *
 get_id(void)
 {
-#ifndef WIN32
-
-	struct passwd *pw;
+	const char	   *username;
 
+#ifndef WIN32
 	if (geteuid() == 0)			/* 0 is root's uid */
 	{
 		fprintf(stderr,
@@ -789,35 +788,11 @@ get_id(void)
 				progname);
 		exit(1);
 	}
-
-	pw = getpwuid(geteuid());
-	if (!pw)
-	{
-		fprintf(stderr,
-			  _("%s: could not obtain information about current user: %s\n"),
-				progname, strerror(errno));
-		exit(1);
-	}
-#else							/* the windows code */
-
-	struct passwd_win32
-	{
-		int			pw_uid;
-		char		pw_name[128];
-	}			pass_win32;
-	struct passwd_win32 *pw = &pass_win32;
-	DWORD		pwname_size = sizeof(pass_win32.pw_name) - 1;
-
-	pw->pw_uid = 1;
-	if (!GetUserName(pw->pw_name, &pwname_size))
-	{
-		fprintf(stderr, _("%s: could not get current user name: %s\n"),
-				progname, strerror(errno));
-		exit(1);
-	}
 #endif
 
-	return pg_strdup(pw->pw_name);
+	username = get_user_name_or_exit(progname);
+
+	return pg_strdup(username);
 }
 
 static char *

src/bin/psql/command.c

@@ -265,10 +265,13 @@ exec_command(const char *cmd,
 #ifndef WIN32
 			struct passwd *pw;
 
+			errno = 0;	/* clear errno before call */
 			pw = getpwuid(geteuid());
 			if (!pw)
 			{
-				psql_error("could not get home directory: %s\n", strerror(errno));
+				psql_error("could not get home directory for user id %d: %s\n",
+						   (int) geteuid(), errno ?
+						   strerror(errno) : "user does not exist");
 				exit(EXIT_FAILURE);
 			}
 			dir = pw->pw_dir;

src/bin/psql/help.c

@@ -8,9 +8,6 @@
 #include "postgres_fe.h"
 
 #ifndef WIN32
-#ifdef HAVE_PWD_H
-#include <pwd.h>				/* for getpwuid() */
-#endif
 #include <sys/types.h>			/* (ditto) */
 #include <unistd.h>				/* for geteuid() */
 #else
@@ -52,31 +49,18 @@ usage(void)
 {
 	const char *env;
 	const char *user;
-
-#ifndef WIN32
-	struct passwd *pw = NULL;
-#endif
+	char	   *errstr;
 
 	/* Find default user, in case we need it. */
 	user = getenv("PGUSER");
 	if (!user)
 	{
-#if !defined(WIN32) && !defined(__OS2__)
-		pw = getpwuid(geteuid());
-		if (pw)
-			user = pw->pw_name;
-		else
+		user = get_user_name(&errstr);
+		if (!user)
 		{
-			psql_error("could not get current user name: %s\n", strerror(errno));
+			psql_error("%s\n", errstr);
 			exit(EXIT_FAILURE);
 		}
-#else							/* WIN32 */
-		char		buf[128];
-		DWORD		bufsize = sizeof(buf) - 1;
-
-		if (GetUserName(buf, &bufsize))
-			user = buf;
-#endif   /* WIN32 */
 	}
 
 	printf(_("psql is the PostgreSQL interactive terminal.\n\n"));

src/bin/scripts/clusterdb.c

@@ -160,7 +160,7 @@ main(int argc, char *argv[])
 			else if (getenv("PGUSER"))
 				dbname = getenv("PGUSER");
 			else
-				dbname = get_user_name(progname);
+				dbname = get_user_name_or_exit(progname);
 		}
 
 		if (tables.head != NULL)

src/bin/scripts/common.c

@@ -14,7 +14,6 @@
 
 #include "postgres_fe.h"
 
-#include <pwd.h>
 #include <signal.h>
 #include <unistd.h>
 
@@ -29,38 +28,6 @@ static PGcancel *volatile cancelConn = NULL;
 static CRITICAL_SECTION cancelConnLock;
 #endif
 
-/*
- * Returns the current user name.
- */
-const char *
-get_user_name(const char *progname)
-{
-#ifndef WIN32
-	struct passwd *pw;
-
-	pw = getpwuid(geteuid());
-	if (!pw)
-	{
-		fprintf(stderr, _("%s: could not obtain information about current user: %s\n"),
-				progname, strerror(errno));
-		exit(1);
-	}
-	return pw->pw_name;
-#else
-	static char username[128];	/* remains after function exit */
-	DWORD		len = sizeof(username) - 1;
-
-	if (!GetUserName(username, &len))
-	{
-		fprintf(stderr, _("%s: could not get current user name: %s\n"),
-				progname, strerror(errno));
-		exit(1);
-	}
-	return username;
-#endif
-}
-
-
 /*
  * Provide strictly harmonized handling of --help and --version
  * options.

src/bin/scripts/common.h

@@ -22,8 +22,6 @@ enum trivalue
 
 typedef void (*help_handler) (const char *progname);
 
-extern const char *get_user_name(const char *progname);
-
 extern void handle_help_version_opts(int argc, char *argv[],
 						 const char *fixed_progname,
 						 help_handler hlp);

src/bin/scripts/createdb.c

@@ -174,7 +174,7 @@ main(int argc, char *argv[])
 		else if (getenv("PGUSER"))
 			dbname = getenv("PGUSER");
 		else
-			dbname = get_user_name(progname);
+			dbname = get_user_name_or_exit(progname);
 	}
 
 	initPQExpBuffer(&sql);