implement preserving env from host into vm in shell command

cmd/limactl/shell.go

@@ -19,6 +19,7 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 
+	"github.com/lima-vm/lima/v2/pkg/envutil"
 	"github.com/lima-vm/lima/v2/pkg/instance"
 	"github.com/lima-vm/lima/v2/pkg/ioutilx"
 	"github.com/lima-vm/lima/v2/pkg/limayaml"
@@ -54,6 +55,7 @@ func newShellCommand() *cobra.Command {
 	shellCmd.Flags().String("shell", "", "Shell interpreter, e.g. /bin/bash")
 	shellCmd.Flags().String("workdir", "", "Working directory")
 	shellCmd.Flags().Bool("reconnect", false, "Reconnect to the SSH session")
+	shellCmd.Flags().Bool("preserve-env", false, "Propagate environment variables to the shell")
 	return shellCmd
 }
 
@@ -178,7 +180,23 @@ func shellAction(cmd *cobra.Command, args []string) error {
 	} else {
 		shell = shellescape.Quote(shell)
 	}
-	script := fmt.Sprintf("%s ; exec %s --login", changeDirCmd, shell)
+	// Handle environment variable propagation
+	var envPrefix string
+	preserveEnv, err := cmd.Flags().GetBool("preserve-env")
+	if err != nil {
+		return err
+	}
+	if preserveEnv {
+		filteredEnv := envutil.FilterEnvironment()
+		if len(filteredEnv) > 0 {
+			envPrefix = "env "
+			for _, envVar := range filteredEnv {
+				envPrefix += shellescape.Quote(envVar) + " "
+			}
+		}
+	}
+
+	script := fmt.Sprintf("%s ; exec %s%s --login", changeDirCmd, envPrefix, shell)
 	if len(args) > 1 {
 		quotedArgs := make([]string, len(args[1:]))
 		parsingEnv := true

cmd/nerdctl.lima

@@ -1,3 +1,3 @@
 #!/bin/sh
 set -eu
-exec lima nerdctl "$@"
+exec limactl shell --preserve-env default nerdctl "$@"

pkg/envutil/envutil.go

@@ -0,0 +1,135 @@
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package envutil
+
+import (
+	"os"
+	"slices"
+	"strings"
+
+	"github.com/sirupsen/logrus"
+)
+
+// defaultBlockList contains environment variables that should not be propagated by default.
+var defaultBlockList = []string{
+	"BASH*",
+	"DISPLAY",
+	"DYLD_*",
+	"EUID",
+	"FPATH",
+	"GID",
+	"GROUP",
+	"HOME",
+	"HOSTNAME",
+	"LD_*",
+	"LOGNAME",
+	"OLDPWD",
+	"PATH",
+	"PWD",
+	"SHELL",
+	"SHLVL",
+	"SSH_*",
+	"TERM",
+	"TERMINFO",
+	"TMPDIR",
+	"UID",
+	"USER",
+	"XAUTHORITY",
+	"XDG_*",
+	"ZDOTDIR",
+	"ZSH*",
+	"_*", // Variables starting with underscore are typically internal
+}
+
+func getBlockList() []string {
+	blockEnv := os.Getenv("LIMA_SHELLENV_BLOCK")
+	if blockEnv == "" {
+		return defaultBlockList
+	}
+	after, found := strings.CutPrefix(blockEnv, "+")
+	if !found {
+		return parseEnvList(blockEnv)
+	}
+	return slices.Concat(defaultBlockList, parseEnvList(after))
+}
+
+func getAllowList() []string {
+	if allowEnv := os.Getenv("LIMA_SHELLENV_ALLOW"); allowEnv != "" {
+		return parseEnvList(allowEnv)
+	}
+	return nil
+}
+
+func parseEnvList(envList string) []string {
+	parts := strings.Split(envList, ",")
+	result := make([]string, 0, len(parts))
+	for _, part := range parts {
+		if trimmed := strings.TrimSpace(part); trimmed != "" {
+			result = append(result, trimmed)
+		}
+	}
+
+	return result
+}
+
+func matchesPattern(name, pattern string) bool {
+	if pattern == name {
+		return true
+	}
+
+	prefix, found := strings.CutSuffix(pattern, "*")
+	return found && strings.HasPrefix(name, prefix)
+}
+
+func matchesAnyPattern(name string, patterns []string) bool {
+	return slices.ContainsFunc(patterns, func(pattern string) bool {
+		return matchesPattern(name, pattern)
+	})
+}
+
+// FilterEnvironment filters environment variables based on configuration from environment variables.
+// It returns a slice of environment variables that are not blocked by the current configuration.
+// The filtering is controlled by LIMA_SHELLENV_BLOCK and LIMA_SHELLENV_ALLOW environment variables.
+func FilterEnvironment() []string {
+	return filterEnvironmentWithLists(
+		os.Environ(),
+		getAllowList(),
+		getBlockList(),
+	)
+}
+
+func filterEnvironmentWithLists(env, allowList, blockList []string) []string {
+	var filtered []string
+
+	for _, envVar := range env {
+		parts := strings.SplitN(envVar, "=", 2)
+		if len(parts) != 2 {
+			continue
+		}
+
+		name := parts[0]
+
+		if len(allowList) > 0 {
+			if !matchesAnyPattern(name, allowList) {
+				continue
+			}
+			filtered = append(filtered, envVar)
+			continue
+		}
+
+		if matchesAnyPattern(name, blockList) {
+			logrus.Debugf("Blocked env variable %q", name)
+			continue
+		}
+
+		filtered = append(filtered, envVar)
+	}
+
+	return filtered
+}
+
+// GetDefaultBlockList returns a copy of the default block list.
+func GetDefaultBlockList() []string {
+	return slices.Clone(defaultBlockList)
+}

pkg/envutil/envutil_test.go

@@ -0,0 +1,210 @@
+// SPDX-FileCopyrightText: Copyright The Lima Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package envutil
+
+import (
+	"os"
+	"slices"
+	"strings"
+	"testing"
+
+	"gotest.tools/v3/assert"
+)
+
+func isUsingDefaultBlockList() bool {
+	blockEnv := os.Getenv("LIMA_SHELLENV_BLOCK")
+	return blockEnv == "" || strings.HasPrefix(blockEnv, "+")
+}
+
+func TestMatchesPattern(t *testing.T) {
+	tests := []struct {
+		name     string
+		pattern  string
+		expected bool
+	}{
+		{"PATH", "PATH", true},
+		{"PATH", "HOME", false},
+		{"SSH_AUTH_SOCK", "SSH_*", true},
+		{"SSH_AGENT_PID", "SSH_*", true},
+		{"HOME", "SSH_*", false},
+		{"XDG_CONFIG_HOME", "XDG_*", true},
+		{"_LIMA_TEST", "_*", true},
+		{"LIMA_HOME", "_*", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name+"_matches_"+tt.pattern, func(t *testing.T) {
+			result := matchesPattern(tt.name, tt.pattern)
+			assert.Equal(t, result, tt.expected)
+		})
+	}
+}
+
+func TestMatchesAnyPattern(t *testing.T) {
+	patterns := []string{"PATH", "SSH_*", "XDG_*"}
+
+	tests := []struct {
+		name     string
+		expected bool
+	}{
+		{"PATH", true},
+		{"HOME", false},
+		{"SSH_AUTH_SOCK", true},
+		{"XDG_CONFIG_HOME", true},
+		{"USER", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := matchesAnyPattern(tt.name, patterns)
+			assert.Equal(t, result, tt.expected)
+		})
+	}
+}
+
+func TestParseEnvList(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected []string
+	}{
+		{"", []string{}},
+		{"PATH", []string{"PATH"}},
+		{"PATH,HOME", []string{"PATH", "HOME"}},
+		{"PATH, HOME , USER", []string{"PATH", "HOME", "USER"}},
+		{" , , ", []string{}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.input, func(t *testing.T) {
+			result := parseEnvList(tt.input)
+			assert.DeepEqual(t, result, tt.expected)
+		})
+	}
+}
+
+func TestGetBlockAndAllowLists(t *testing.T) {
+	t.Run("default config", func(t *testing.T) {
+		t.Setenv("LIMA_SHELLENV_BLOCK", "")
+		t.Setenv("LIMA_SHELLENV_ALLOW", "")
+
+		blockList := getBlockList()
+		allowList := getAllowList()
+
+		assert.Assert(t, isUsingDefaultBlockList())
+		assert.DeepEqual(t, blockList, defaultBlockList)
+		assert.Equal(t, len(allowList), 0)
+	})
+
+	t.Run("custom blocklist", func(t *testing.T) {
+		t.Setenv("LIMA_SHELLENV_BLOCK", "PATH,HOME")
+
+		blockList := getBlockList()
+		assert.Assert(t, !isUsingDefaultBlockList())
+		expected := []string{"PATH", "HOME"}
+		assert.DeepEqual(t, blockList, expected)
+	})
+
+	t.Run("additive blocklist", func(t *testing.T) {
+		t.Setenv("LIMA_SHELLENV_BLOCK", "+CUSTOM_VAR")
+
+		blockList := getBlockList()
+		assert.Assert(t, isUsingDefaultBlockList())
+		expected := slices.Concat(GetDefaultBlockList(), []string{"CUSTOM_VAR"})
+		assert.DeepEqual(t, blockList, expected)
+	})
+
+	t.Run("allowlist", func(t *testing.T) {
+		t.Setenv("LIMA_SHELLENV_ALLOW", "FOO,BAR")
+
+		allowList := getAllowList()
+		expected := []string{"FOO", "BAR"}
+		assert.DeepEqual(t, allowList, expected)
+	})
+}
+
+func TestFilterEnvironment(t *testing.T) {
+	testEnv := []string{
+		"PATH=/usr/bin",
+		"HOME=/home/user",
+		"USER=testuser",
+		"FOO=bar",
+		"SSH_AUTH_SOCK=/tmp/ssh",
+		"XDG_CONFIG_HOME=/config",
+		"BASH_VERSION=5.0",
+		"_INTERNAL=secret",
+		"CUSTOM_VAR=value",
+	}
+
+	t.Run("default blocklist", func(t *testing.T) {
+		result := filterEnvironmentWithLists(testEnv, nil, defaultBlockList)
+
+		expected := []string{"FOO=bar", "CUSTOM_VAR=value"}
+		assert.Assert(t, containsAll(result, expected))
+
+		blockedPrefixes := []string{
+			"PATH=",
+			"HOME=",
+			"SSH_AUTH_SOCK=",
+			"XDG_CONFIG_HOME=",
+			"BASH_VERSION=",
+			"_INTERNAL=",
+		}
+		for _, prefix := range blockedPrefixes {
+			for _, envVar := range result {
+				assert.Assert(t, !strings.HasPrefix(envVar, prefix), "Expected result to not contain variable with prefix %q, but found %q", prefix, envVar)
+			}
+		}
+	})
+
+	t.Run("custom blocklist", func(t *testing.T) {
+		result := filterEnvironmentWithLists(testEnv, nil, []string{"FOO"})
+
+		assert.Assert(t, !slices.Contains(result, "FOO=bar"))
+
+		expected := []string{"PATH=/usr/bin", "HOME=/home/user", "USER=testuser"}
+		assert.Assert(t, containsAll(result, expected))
+	})
+
+	t.Run("allowlist", func(t *testing.T) {
+		result := filterEnvironmentWithLists(testEnv, []string{"FOO", "USER"}, nil)
+
+		expected := []string{"FOO=bar", "USER=testuser"}
+		assert.Equal(t, len(result), len(expected))
+		assert.Assert(t, containsAll(result, expected))
+	})
+
+	t.Run("allowlist takes precedence over blocklist", func(t *testing.T) {
+		result := filterEnvironmentWithLists(testEnv, []string{"FOO", "CUSTOM_VAR"}, []string{"FOO", "USER"})
+
+		expected := []string{"FOO=bar", "CUSTOM_VAR=value"}
+		assert.Assert(t, containsAll(result, expected))
+
+		assert.Assert(t, !slices.Contains(result, "USER=testuser"))
+	})
+}
+
+func containsAll(slice, items []string) bool {
+	for _, item := range items {
+		if !slices.Contains(slice, item) {
+			return false
+		}
+	}
+	return true
+}
+
+func TestGetDefaultBlockList(t *testing.T) {
+	blocklist := GetDefaultBlockList()
+
+	if &blocklist[0] == &defaultBlockList[0] {
+		t.Error("GetDefaultBlockList should return a copy, not the original slice")
+	}
+
+	assert.DeepEqual(t, blocklist, defaultBlockList)
+
+	expectedItems := []string{"PATH", "HOME", "SSH_*"}
+	for _, item := range expectedItems {
+		found := slices.Contains(blocklist, item)
+		assert.Assert(t, found, "Expected builtin blocklist to contain %q", item)
+	}
+}