From 22a291f703b2511daaa8e0d325ab48523e817558 Mon Sep 17 00:00:00 2001
From: Sebastiaan van Stijn <github@gone.nl>
Date: Tue, 17 Dec 2019 09:36:25 +0100
Subject: [PATCH] config: preserve ownership and permissions on configfile

When running `docker login` or `docker logout`, the CLI updates
the configuration file by creating a temporary file, to replace
the old one (if exists).

When using `sudo`, this caused the file to be created as `root`,
making it inaccessible to the current user.

This patch updates the CLI to fetch permissions and ownership of
the existing configuration file, and applies those permissions
to the new file, so that it has the same permissions as the
existing file (if any).

Currently, only done for "Unix-y" systems (Mac, Linux), but
can be implemented for Windows in future if there's a need.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
---
 cli/config/configfile/file.go         |  3 +++
 cli/config/configfile/file_unix.go    | 35 +++++++++++++++++++++++++++
 cli/config/configfile/file_windows.go |  5 ++++
 3 files changed, 43 insertions(+)
 create mode 100644 cli/config/configfile/file_unix.go
 create mode 100644 cli/config/configfile/file_windows.go

diff --git a/cli/config/configfile/file.go b/cli/config/configfile/file.go
index 388a5d54d6..a4e97a5caa 100644
--- a/cli/config/configfile/file.go
+++ b/cli/config/configfile/file.go
@@ -196,6 +196,9 @@ func (configFile *ConfigFile) Save() error {
 		os.Remove(temp.Name())
 		return err
 	}
+	// Try copying the current config file (if any) ownership and permissions
+	copyFilePermissions(configFile.Filename, temp.Name())
+
 	return os.Rename(temp.Name(), configFile.Filename)
 }
 
diff --git a/cli/config/configfile/file_unix.go b/cli/config/configfile/file_unix.go
new file mode 100644
index 0000000000..3ca65c6140
--- /dev/null
+++ b/cli/config/configfile/file_unix.go
@@ -0,0 +1,35 @@
+// +build !windows
+
+package configfile
+
+import (
+	"os"
+	"syscall"
+)
+
+// copyFilePermissions copies file ownership and permissions from "src" to "dst",
+// ignoring any error during the process.
+func copyFilePermissions(src, dst string) {
+	var (
+		mode     os.FileMode = 0600
+		uid, gid int
+	)
+
+	fi, err := os.Stat(src)
+	if err != nil {
+		return
+	}
+	if fi.Mode().IsRegular() {
+		mode = fi.Mode()
+	}
+	if err := os.Chmod(dst, mode); err != nil {
+		return
+	}
+
+	uid = int(fi.Sys().(*syscall.Stat_t).Uid)
+	gid = int(fi.Sys().(*syscall.Stat_t).Gid)
+
+	if uid > 0 && gid > 0 {
+		_ = os.Chown(dst, uid, gid)
+	}
+}
diff --git a/cli/config/configfile/file_windows.go b/cli/config/configfile/file_windows.go
new file mode 100644
index 0000000000..42fffc39ad
--- /dev/null
+++ b/cli/config/configfile/file_windows.go
@@ -0,0 +1,5 @@
+package configfile
+
+func copyFilePermissions(src, dst string) {
+	// TODO implement for Windows
+}