More use of getpwuid_r() directly

Remove src/port/user.c, call getpwuid_r() directly.  This reduces some
complexity and allows better control of the error behavior.  For
example, the old code would in some circumstances silently truncate
the result string, or produce error message strings that the caller
wouldn't use.

src/port/user.c used to be called src/port/thread.c and contained
various portability complications to support thread-safety.  These are
all obsolete, and all but the user-lookup functions have already been
removed.  This patch completes this by also removing the user-lookup
functions.

Also convert src/backend/libpq/auth.c to use getpwuid_r() for
thread-safety.

Originally, I tried to be overly correct by using
sysconf(_SC_GETPW_R_SIZE_MAX) to get the buffer size for getpwuid_r(),
but that doesn't work on FreeBSD.  All the OS where I could find the
source code internally use 1024 as the suggested buffer size, so I
just ended up hardcoding that.  The previous code used BUFSIZ, which
is an unrelated constant from stdio.h, so its use seemed
inappropriate.

Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://www.postgresql.org/message-id/flat/5f293da9-ceb4-4937-8e52-82c25db8e4d3%40eisentraut.org

src/interfaces/libpq/fe-auth.c

@@ -28,6 +28,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <pwd.h>
 #include <sys/param.h>			/* for MAXHOSTNAMELEN on most */
 #include <sys/socket.h>
 #ifdef HAVE_SYS_UCRED_H
@@ -1203,7 +1204,10 @@ pg_fe_getusername(uid_t user_id, PQExpBuffer errorMessage)
 	char		username[256 + 1];
 	DWORD		namesize = sizeof(username);
 #else
-	char		pwdbuf[BUFSIZ];
+	struct passwd pwbuf;
+	struct passwd *pw;
+	char		buf[1024];
+	int			rc;
 #endif
 
 #ifdef WIN32
@@ -1214,10 +1218,19 @@ pg_fe_getusername(uid_t user_id, PQExpBuffer errorMessage)
 						   "user name lookup failure: error code %lu",
 						   GetLastError());
 #else
-	if (pg_get_user_name(user_id, pwdbuf, sizeof(pwdbuf)))
-		name = pwdbuf;
-	else if (errorMessage)
-		appendPQExpBuffer(errorMessage, "%s\n", pwdbuf);
+	rc = getpwuid_r(user_id, &pwbuf, buf, sizeof buf, &pw);
+	if (rc != 0)
+	{
+		errno = rc;
+		if (errorMessage)
+			libpq_append_error(errorMessage, "could not look up local user ID %ld: %m", (long) user_id);
+	}
+	else if (!pw)
+	{
+		if (errorMessage)
+			libpq_append_error(errorMessage, "local user with ID %ld does not exist", (long) user_id);
+	}
+	name = pw->pw_name;
 #endif
 
 	if (name)

src/interfaces/libpq/fe-connect.c

@@ -50,6 +50,7 @@
 #include <netdb.h>
 #include <netinet/in.h>
 #include <netinet/tcp.h>
+#include <pwd.h>
 #endif
 
 #ifdef WIN32
@@ -7702,10 +7703,24 @@ pqGetHomeDirectory(char *buf, int bufsize)
 	const char *home;
 
 	home = getenv("HOME");
-	if (home == NULL || home[0] == '\0')
-		return pg_get_user_home_dir(geteuid(), buf, bufsize);
-	strlcpy(buf, home, bufsize);
-	return true;
+	if (home && home[0])
+	{
+		strlcpy(buf, home, bufsize);
+		return true;
+	}
+	else
+	{
+		struct passwd pwbuf;
+		struct passwd *pw;
+		char		tmpbuf[1024];
+		int			rc;
+
+		rc = getpwuid_r(geteuid(), &pwbuf, tmpbuf, sizeof tmpbuf, &pw);
+		if (rc != 0 || !pw)
+			return false;
+		strlcpy(buf, pw->pw_dir, bufsize);
+		return true;
+	}
 #else
 	char		tmppath[MAX_PATH];
 

src/interfaces/libpq/nls.mk

@@ -13,8 +13,7 @@ GETTEXT_FILES    = fe-auth.c \
                    fe-secure-common.c \
                    fe-secure-gssapi.c \
                    fe-secure-openssl.c \
-                   win32.c \
-                   ../../port/user.c
+                   win32.c
 GETTEXT_TRIGGERS = libpq_append_conn_error:2 \
                    libpq_append_error:2 \
                    libpq_gettext \