From 2764d5dcfa84d240c901c20ec6e194f72d82b78a Mon Sep 17 00:00:00 2001
From: Peter Eisentraut
Date: Mon, 2 Apr 2018 11:34:52 -0400
Subject: Make be-secure-common.c more consistent for future SSL
 implementations

Recent commit 8a3d9425 has introduced be-secure-common.c, which is aimed
at including backend-side APIs that can be used by any SSL
implementation.  The purpose is similar to fe-secure-common.c for the
frontend-side APIs.

However, this has forgotten to include check_ssl_key_file_permissions()
in the move, which causes a double dependency between be-secure.c and
be-secure-openssl.c.

Refactor the code in a more logical way.  This also puts into light an
API which is usable by future SSL implementations for permissions on SSL
key files.

Author: Michael Paquier <michael@paquier.xyz>
---
 src/backend/libpq/be-secure-common.c | 74 ++++++++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

(limited to 'src/backend/libpq/be-secure-common.c')

diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index d1740967f19..46f0b5f4a32 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -19,6 +19,9 @@
 
 #include "postgres.h"
 
+#include <sys/stat.h>
+#include <unistd.h>
+
 #include "libpq/libpq.h"
 #include "storage/fd.h"
 
@@ -118,3 +121,74 @@ error:
 	pfree(command.data);
 	return len;
 }
+
+
+/*
+ * Check permissions for SSL key files.
+ */
+bool
+check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
+{
+	int			loglevel = isServerStart ? FATAL : LOG;
+	struct stat	buf;
+
+	if (stat(ssl_key_file, &buf) != 0)
+	{
+		ereport(loglevel,
+				(errcode_for_file_access(),
+				 errmsg("could not access private key file \"%s\": %m",
+						ssl_key_file)));
+		return false;
+	}
+
+	if (!S_ISREG(buf.st_mode))
+	{
+		ereport(loglevel,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("private key file \"%s\" is not a regular file",
+						ssl_key_file)));
+		return false;
+	}
+
+	/*
+	 * Refuse to load key files owned by users other than us or root.
+	 *
+	 * XXX surely we can check this on Windows somehow, too.
+	 */
+#if !defined(WIN32) && !defined(__CYGWIN__)
+	if (buf.st_uid != geteuid() && buf.st_uid != 0)
+	{
+		ereport(loglevel,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("private key file \"%s\" must be owned by the database user or root",
+						ssl_key_file)));
+		return false;
+	}
+#endif
+
+	/*
+	 * Require no public access to key file. If the file is owned by us,
+	 * require mode 0600 or less. If owned by root, require 0640 or less to
+	 * allow read access through our gid, or a supplementary gid that allows
+	 * to read system-wide certificates.
+	 *
+	 * XXX temporarily suppress check when on Windows, because there may not
+	 * be proper support for Unix-y file permissions.  Need to think of a
+	 * reasonable check to apply on Windows.  (See also the data directory
+	 * permission check in postmaster.c)
+	 */
+#if !defined(WIN32) && !defined(__CYGWIN__)
+	if ((buf.st_uid == geteuid() && buf.st_mode & (S_IRWXG | S_IRWXO)) ||
+		(buf.st_uid == 0 && buf.st_mode & (S_IWGRP | S_IXGRP | S_IRWXO)))
+	{
+		ereport(loglevel,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("private key file \"%s\" has group or world access",
+						ssl_key_file),
+				 errdetail("File must have permissions u=rw (0600) or less if owned by the database user, or permissions u=rw,g=r (0640) or less if owned by root.")));
+		return false;
+	}
+#endif
+
+	return true;
+}
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