Fix podman keep-id mapping for numeric and named users - fixes #1284

CHANGELOG.md

@@ -6,6 +6,7 @@ Notable changes.
 
 ### [0.88.0]
 - Add WSLc support (https://github.com/devcontainers/cli/pull/1249)
+- Derive the `--userns=keep-id` mapping from the remote user's actual UID/GID when using Podman, so the container user is mapped to the host user even when their UIDs differ (e.g. high UIDs from AD/SSSD). (https://github.com/devcontainers/cli/issues/1284)
 
 ## May 2026
 

src/spec-node/singleContainer.ts

@@ -410,7 +410,7 @@ while sleep 1 & wait $!; do :; done`, '-']; // `wait $!` allows for the `trap` t
 		...getLabels(labels),
 		...containerEnv,
 		...containerUserArgs,
-		...await getPodmanArgs(params, config, mergedConfig, imageDetails),
+		...await getPodmanArgs(params, config, mergedConfig, imageName, imageDetails),
 		...(config.runArgs || []),
 		...(await extraRunArgs(common, params, config) || []),
 		...featureArgs,
@@ -435,21 +435,65 @@ while sleep 1 & wait $!; do :; done`, '-']; // `wait $!` allows for the `trap` t
 	common.output.stop(text, start);
 }
 
-async function getPodmanArgs(params: DockerResolverParameters, config: DevContainerFromDockerfileConfig | DevContainerFromImageConfig, mergedConfig: MergedDevContainerConfig, imageDetails: () => Promise<ImageDetails>): Promise<string[]> {
+async function getPodmanArgs(params: DockerResolverParameters, config: DevContainerFromDockerfileConfig | DevContainerFromImageConfig, mergedConfig: MergedDevContainerConfig, imageName: string, imageDetails: () => Promise<ImageDetails>): Promise<string[]> {
 	if (params.cliVariant === CLIVariant.Podman && params.common.cliHost.platform === 'linux') {
 		const args = ['--security-opt', 'label=disable'];
 		const hasIdMapping = (config.runArgs || []).some(arg => /--[ug]idmap(=|$)/.test(arg));
 		if (!hasIdMapping) {
 			const remoteUser = mergedConfig.remoteUser || findUserArg(config.runArgs) || (await imageDetails()).Config.User || 'root';
 			if (remoteUser !== 'root' && remoteUser !== '0') {
-				args.push('--userns=keep-id');
+				// Prefer parsing a numeric user spec directly from config; only fall back to
+				// running a throwaway container when the user is a name that must be resolved
+				// from the image's /etc/passwd and /etc/group.
+				const uidGid = parseNumericUidGid(remoteUser) ?? await resolveRemoteUserUidGid(params, imageName, remoteUser);
+				args.push(...getKeepIdArgs(uidGid));
 			}
 		}
 		return args;
 	}
 	return [];
 }
 
+// Parses a user spec (e.g. "1000", "1000:1000", "vscode", "vscode:1000") and returns
+// numeric uid/gid only when both parts are numeric. When no group is given, the gid
+// defaults to the uid. Returns undefined when the user is a name, in which case the
+// caller must resolve the mapping from the image (e.g. via a throwaway container).
+export function parseNumericUidGid(remoteUser: string): { uid: string; gid: string } | undefined {
+	const [user, group] = remoteUser.split(':');
+	if (!user || !/^\d+$/.test(user)) {
+		return undefined;
+	}
+	const gid = group ?? user;
+	if (!/^\d+$/.test(gid)) {
+		return undefined;
+	}
+	return { uid: user, gid };
+}
+
+// Resolves the remote user's UID and GID inside the image by running a throwaway container.
+// Returns undefined if the resolution fails, in which case the caller falls back to plain --userns=keep-id.
+export async function resolveRemoteUserUidGid(params: DockerResolverParameters, imageName: string, remoteUser: string): Promise<{ uid: string; gid: string } | undefined> {
+	try {
+		const infoParams = { ...toExecParameters(params), output: makeLog(params.common.output, LogLevel.Info) };
+		const result = await dockerCLI(infoParams, 'run', '--rm', '--entrypoint', '/bin/sh', imageName, '-c', `id -u ${remoteUser}; id -g ${remoteUser}`);
+		const [uid, gid] = result.stdout.toString().trim().split(/\r?\n/);
+		if (uid && gid && /^\d+$/.test(uid) && /^\d+$/.test(gid)) {
+			return { uid, gid };
+		}
+	} catch {
+		// Fall through to plain --userns=keep-id.
+	}
+	return undefined;
+}
+
+// Builds the --userns=keep-id argument, using the explicit uid/gid mapping when available.
+export function getKeepIdArgs(uidGid: { uid: string; gid: string } | undefined): string[] {
+	if (uidGid) {
+		return [`--userns=keep-id:uid=${uidGid.uid},gid=${uidGid.gid}`];
+	}
+	return ['--userns=keep-id'];
+}
+
 // Convert a --mount string (e.g., "type=bind,source=/a,target=/b,consistency=cached") to -v syntax for wslc.
 function convertMountToVolume(mountStr: string): string[] {
 	const parts = new Map(mountStr.split(',').map(p => {

src/test/cli.podman.test.ts

@@ -40,5 +40,46 @@ describe('Dev Containers CLI using Podman', function () {
 			assert.ok(containerId, 'Container id not found.');
 			await shellExec(`podman rm -f ${containerId}`);
 		});
+
+		it('should map the remote user uid/gid with an explicit --userns=keep-id mapping', async () => {
+			const testFolder = `${__dirname}/configs/podman-keep-id`;
+			const res = await shellExec(`${cli} up --docker-path podman --workspace-folder ${testFolder}`);
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'success');
+			const containerId: string = response.containerId;
+			assert.ok(containerId, 'Container id not found.');
+
+			// The container user 'foo' is baked to uid 1234 / gid 4321. With an explicit
+			// keep-id mapping, files the remote user creates in the bind-mounted workspace
+			// must be owned by the host user (not by host uid 1234).
+			const marker = `keepidtest_${Date.now()}`;
+			await shellExec(`podman exec ${containerId} sh -c "touch /workspaces/cli/${marker}"`);
+			const hostStat = await shellExec(`stat -c '%u:%g' ${path.join(__dirname, '..', '..', marker)}`);
+			assert.strictEqual(hostStat.stdout.trim(), `${process.getuid!()}:${process.getgid!()}`);
+			await shellExec(`rm -f ${path.join(__dirname, '..', '..', marker)}`);
+
+			await shellExec(`podman rm -f ${containerId}`);
+		});
+
+		it('should map a numeric remote user uid/gid without resolving from the image', async () => {
+			const testFolder = `${__dirname}/configs/podman-keep-id-numeric`;
+			const res = await shellExec(`${cli} up --docker-path podman --workspace-folder ${testFolder}`);
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'success');
+			const containerId: string = response.containerId;
+			assert.ok(containerId, 'Container id not found.');
+
+			// The remote user is specified numerically (1234), so the CLI must derive the
+			// keep-id mapping directly from config rather than running a throwaway container.
+			// Files the remote user creates in the bind-mounted workspace must be owned by
+			// the host user (not by host uid 1234).
+			const marker = `keepidtest_${Date.now()}`;
+			await shellExec(`podman exec ${containerId} sh -c "touch /workspaces/cli/${marker}"`);
+			const hostStat = await shellExec(`stat -c '%u:%g' ${path.join(__dirname, '..', '..', marker)}`);
+			assert.strictEqual(hostStat.stdout.trim(), `${process.getuid!()}:${process.getgid!()}`);
+			await shellExec(`rm -f ${path.join(__dirname, '..', '..', marker)}`);
+
+			await shellExec(`podman rm -f ${containerId}`);
+		});
 	});
 });

src/test/configs/podman-keep-id-numeric/.devcontainer.json

@@ -0,0 +1,7 @@
+{
+	"build": {
+		"dockerfile": "Dockerfile"
+	},
+	"remoteUser": "1234",
+	"updateRemoteUserUID": false
+}

src/test/configs/podman-keep-id-numeric/Dockerfile

@@ -0,0 +1,4 @@
+FROM debian:latest
+
+RUN groupadd -g 4321 foo
+RUN useradd -m -u 1234 -g 4321 foo

src/test/configs/podman-keep-id/.devcontainer.json

@@ -0,0 +1,7 @@
+{
+	"build": {
+		"dockerfile": "Dockerfile"
+	},
+	"remoteUser": "foo",
+	"updateRemoteUserUID": false
+}

src/test/configs/podman-keep-id/Dockerfile

@@ -0,0 +1,4 @@
+FROM debian:latest
+
+RUN groupadd -g 4321 foo
+RUN useradd -m -u 1234 -g 4321 foo

src/test/keepIdArgs.test.ts

@@ -0,0 +1,54 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as assert from 'assert';
+import { getKeepIdArgs, parseNumericUidGid } from '../spec-node/singleContainer';
+
+describe('parseNumericUidGid', function () {
+	it('should parse a plain numeric uid, defaulting gid to the uid', () => {
+		assert.deepStrictEqual(parseNumericUidGid('1000'), { uid: '1000', gid: '1000' });
+	});
+
+	it('should parse a numeric uid:gid pair', () => {
+		assert.deepStrictEqual(parseNumericUidGid('1000:1001'), { uid: '1000', gid: '1001' });
+	});
+
+	it('should return undefined for a named user', () => {
+		assert.strictEqual(parseNumericUidGid('vscode'), undefined);
+	});
+
+	it('should return undefined for a named user with numeric group', () => {
+		assert.strictEqual(parseNumericUidGid('vscode:1000'), undefined);
+	});
+
+	it('should return undefined for a numeric user with named group', () => {
+		assert.strictEqual(parseNumericUidGid('1000:vscode'), undefined);
+	});
+
+	it('should return undefined for an empty or malformed spec', () => {
+		assert.strictEqual(parseNumericUidGid(''), undefined);
+		assert.strictEqual(parseNumericUidGid(':1000'), undefined);
+	});
+});
+
+describe('getKeepIdArgs', function () {
+	it('should return plain --userns=keep-id when uid/gid are not resolved', () => {
+		assert.deepStrictEqual(getKeepIdArgs(undefined), ['--userns=keep-id']);
+	});
+
+	it('should return explicit uid/gid mapping when resolved', () => {
+		assert.deepStrictEqual(
+			getKeepIdArgs({ uid: '1000', gid: '1000' }),
+			['--userns=keep-id:uid=1000,gid=1000']
+		);
+	});
+
+	it('should return explicit mapping for a high (non-bakeable) uid', () => {
+		assert.deepStrictEqual(
+			getKeepIdArgs({ uid: '1400601103', gid: '1400600513' }),
+			['--userns=keep-id:uid=1400601103,gid=1400600513']
+		);
+	});
+});