From ccd5bd8d5754d8924905b05a67dc8ca11c280baf Mon Sep 17 00:00:00 2001
From: Alano Terblanche <18033717+Benehiko@users.noreply.github.com>
Date: Fri, 4 Jul 2025 14:05:11 +0200
Subject: [PATCH] registry: warn of DOCKER_AUTH_CONFIG usage in login and
 logout

Signed-off-by: Alano Terblanche <18033717+Benehiko@users.noreply.github.com>
---
 cli/command/registry/login.go   |  3 +++
 cli/command/registry/logout.go  |  2 ++
 cli/command/registry/warning.go | 18 ++++++++++++++++++
 3 files changed, 23 insertions(+)
 create mode 100644 cli/command/registry/warning.go

diff --git a/cli/command/registry/login.go b/cli/command/registry/login.go
index ce5e584859..3679e51edd 100644
--- a/cli/command/registry/login.go
+++ b/cli/command/registry/login.go
@@ -110,6 +110,9 @@ func runLogin(ctx context.Context, dockerCLI command.Cli, opts loginOptions) err
 	if err := verifyLoginOptions(dockerCLI, &opts); err != nil {
 		return err
 	}
+
+	maybePrintEnvAuthWarning(dockerCLI)
+
 	var (
 		serverAddress string
 		msg           string
diff --git a/cli/command/registry/logout.go b/cli/command/registry/logout.go
index 6dc75dc585..2af2cdad3f 100644
--- a/cli/command/registry/logout.go
+++ b/cli/command/registry/logout.go
@@ -36,6 +36,8 @@ func NewLogoutCommand(dockerCli command.Cli) *cobra.Command {
 }
 
 func runLogout(ctx context.Context, dockerCLI command.Cli, serverAddress string) error {
+	maybePrintEnvAuthWarning(dockerCLI)
+
 	var isDefaultRegistry bool
 
 	if serverAddress == "" {
diff --git a/cli/command/registry/warning.go b/cli/command/registry/warning.go
new file mode 100644
index 0000000000..22a8c8655b
--- /dev/null
+++ b/cli/command/registry/warning.go
@@ -0,0 +1,18 @@
+package registry
+
+import (
+	"os"
+
+	"github.com/docker/cli/cli/command"
+	"github.com/docker/cli/cli/config/configfile"
+	"github.com/docker/cli/internal/tui"
+)
+
+// maybePrintEnvAuthWarning if the `DOCKER_AUTH_CONFIG` environment variable is
+// set this function will output a warning to stdErr
+func maybePrintEnvAuthWarning(out command.Streams) {
+	if os.Getenv(configfile.DockerEnvConfigKey) != "" {
+		tui.NewOutput(out.Err()).
+			PrintWarning("%[1]s is set and takes precedence.\nUnset %[1]s to restore the CLI auth behaviour.\n", configfile.DockerEnvConfigKey)
+	}
+}