snap: support "command: foo $ENV_STRING"

cmd/snap-exec/main.go

@@ -141,16 +141,34 @@ func snapExecApp(snapApp, revision, command string, args []string) error {
 	if err != nil {
 		return err
 	}
-	// strings.Split() is ok here because we validate all app fields
-	// and the whitelist is pretty strict (see
-	// snap/validate.go:appContentWhitelist)
-	cmdArgv := strings.Split(cmdAndArgs, " ")
-	cmd := cmdArgv[0]
-	cmdArgs := cmdArgv[1:]
 
 	// build the environment from the yaml
 	env := append(os.Environ(), osutil.SubstituteEnv(app.Env())...)
 
+	// strings.Split() is ok here because we validate all app fields
+	// and the whitelist is pretty strict (see
+	// snap/validate.go:appContentWhitelist)
+	tmpCmdArgv := strings.Split(cmdAndArgs, " ")
+	cmd := tmpCmdArgv[0]
+
+	cmdArgs := make([]string, 0, len(tmpCmdArgv[1:]))
+	for _, arg := range tmpCmdArgv[1:] {
+		maybeExpanded := os.Expand(arg, func(k string) string {
+			for _, kv := range env {
+				l := strings.SplitN(kv, "=", 2)
+				if len(l) == 2 {
+					if k == l[0] {
+						return l[1]
+					}
+				}
+			}
+			return ""
+		})
+		if maybeExpanded != "" {
+			cmdArgs = append(cmdArgs, maybeExpanded)
+		}
+	}
+
 	// run the command
 	fullCmd := filepath.Join(app.Snap.MountDir(), cmd)
 	switch command {

cmd/snap-exec/main_test.go

@@ -58,7 +58,7 @@ var mockYaml = []byte(`name: snapname
 version: 1.0
 apps:
  app:
-  command: run-app cmd-arg1
+  command: run-app cmd-arg1 $SNAP_DATA
   stop-command: stop-app
   post-stop-command: post-stop-app
   environment:
@@ -104,7 +104,7 @@ func (s *snapExecSuite) TestFindCommand(c *C) {
 		cmd      string
 		expected string
 	}{
-		{cmd: "", expected: `run-app cmd-arg1`},
+		{cmd: "", expected: `run-app cmd-arg1 $SNAP_DATA`},
 		{cmd: "stop", expected: "stop-app"},
 		{cmd: "post-stop", expected: "post-stop-app"},
 	} {
@@ -313,3 +313,33 @@ func (s *snapExecSuite) TestSnapExecShellIntegration(c *C) {
 	c.Check(execArgs, DeepEquals, []string{execArgv0, "-c", "echo foo"})
 	c.Check(execEnv, testutil.Contains, "LD_LIBRARY_PATH=/some/path/lib")
 }
+
+func (s *snapExecSuite) TestSnapExecAppIntegrationWithVars(c *C) {
+	dirs.SetRootDir(c.MkDir())
+	snaptest.MockSnap(c, string(mockYaml), string(mockContents), &snap.SideInfo{
+		Revision: snap.R("42"),
+	})
+
+	execArgv0 := ""
+	execArgs := []string{}
+	execEnv := []string{}
+	syscallExec = func(argv0 string, argv []string, env []string) error {
+		execArgv0 = argv0
+		execArgs = argv
+		execEnv = env
+		return nil
+	}
+
+	// setup env
+	os.Setenv("SNAP_DATA", "/var/snap/snapname/42")
+	defer os.Unsetenv("SNAP_DATA")
+
+	// launch and verify its run the right way
+	err := snapExecApp("snapname.app", "42", "", []string{"user-arg1"})
+	c.Assert(err, IsNil)
+	c.Check(execArgv0, Equals, fmt.Sprintf("%s/snapname/42/run-app", dirs.SnapMountDir))
+	c.Check(execArgs, DeepEquals, []string{execArgv0, "cmd-arg1", "/var/snap/snapname/42", "user-arg1"})
+	c.Check(execEnv, testutil.Contains, "BASE_PATH=/some/path")
+	c.Check(execEnv, testutil.Contains, "LD_LIBRARY_PATH=/some/path/lib")
+	c.Check(execEnv, testutil.Contains, fmt.Sprintf("MY_PATH=%s", os.Getenv("PATH")))
+}

snap/validate.go

@@ -165,7 +165,7 @@ func validateField(name, cont string, whitelist *regexp.Regexp) error {
 
 // appContentWhitelist is the whitelist of legal chars in the "apps"
 // section of snap.yaml
-var appContentWhitelist = regexp.MustCompile(`^[A-Za-z0-9/. _#:-]*$`)
+var appContentWhitelist = regexp.MustCompile(`^[A-Za-z0-9/. _#:$-]*$`)
 var validAppName = regexp.MustCompile("^[a-zA-Z0-9](?:-?[a-zA-Z0-9])*$")
 
 // ValidateApp verifies the content in the app info.

snap/validate_test.go

@@ -155,6 +155,12 @@ func (s *ValidateSuite) TestAppWhitelistSimple(c *C) {
 	c.Check(ValidateApp(&AppInfo{Name: "foo", PostStopCommand: "foo"}), IsNil)
 }
 
+func (s *ValidateSuite) TestAppWhitelistWithVars(c *C) {
+	c.Check(ValidateApp(&AppInfo{Name: "foo", Command: "foo $SNAP_DATA"}), IsNil)
+	c.Check(ValidateApp(&AppInfo{Name: "foo", StopCommand: "foo $SNAP_DATA"}), IsNil)
+	c.Check(ValidateApp(&AppInfo{Name: "foo", PostStopCommand: "foo $SNAP_DATA"}), IsNil)
+}
+
 func (s *ValidateSuite) TestAppWhitelistIllegal(c *C) {
 	c.Check(ValidateApp(&AppInfo{Name: "x\n"}), NotNil)
 	c.Check(ValidateApp(&AppInfo{Name: "test!me"}), NotNil)
@@ -190,7 +196,7 @@ func (s *ValidateSuite) TestAppDaemonValue(c *C) {
 func (s *ValidateSuite) TestAppWhitelistError(c *C) {
 	err := ValidateApp(&AppInfo{Name: "foo", Command: "x\n"})
 	c.Assert(err, NotNil)
-	c.Check(err.Error(), Equals, `app description field 'command' contains illegal "x\n" (legal: '^[A-Za-z0-9/. _#:-]*$')`)
+	c.Check(err.Error(), Equals, `app description field 'command' contains illegal "x\n" (legal: '^[A-Za-z0-9/. _#:$-]*$')`)
 }
 
 // Validate

tests/lib/snaps/basic-run/meta/snap.yaml

@@ -0,0 +1,6 @@
+name: basic-run
+version: 1.0
+apps:
+ echo-data:
+  command: echo $SNAP_DATA
+

tests/main/snap-run-hook/task.yaml

@@ -15,9 +15,6 @@ prepare: |
 restore: |
     rm basic-hooks_1.0_all.snap
 
-restore: |
-    rm basic-hooks_1.0_all.snap
-
 execute: |
     # Note that `snap run` doesn't exit non-zero if the hook is missing, so we
     # check the output instead.

tests/main/snap-run/task.yaml

@@ -0,0 +1,12 @@
+summary: Check that `snap run` runs
+
+prepare: |
+    . $TESTSLIB/snaps.sh
+    install_local "$TESTSLIB/snaps/basic-run"
+
+restore: |
+    rm basic-run_1.0_all.snap
+
+execute: |
+    echo "Test that snap run use environments"
+    basic-run.echo | MATCH ^/var/snap