Fix golangci-lint errors

Fixes golangci-lint errors introduced by containers#258

If `gosec` linting is enabled for the return statement in `Cmd`, an
error will be returned: `G204: Subprocess launched with a potential tainted
input or cmd arguments (gosec)`. This error tries to make sure a
user cannot provide a binary that could cause harm to the system. However,
since the binary path is sanitized and the arguments are generated by
gvproxy, this should be safe to ignore.

Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

pkg/types/command.go

@@ -1,8 +1,10 @@
 package types
 
 import (
+	"errors"
 	"fmt"
 	"os/exec"
+	"strings"
 )
 
 type Command struct {
@@ -85,11 +87,7 @@ func (c *Command) AddVfkitSocket(socket string) {
 }
 
 func (c *Command) addForwardInfo(flag, value string) {
-	if _, ok := c.forwardInfo[flag]; ok {
-		c.forwardInfo[flag] = append(c.forwardInfo[flag], value)
-	} else {
-		c.forwardInfo[flag] = []string{value}
-	}
+	c.forwardInfo[flag] = append(c.forwardInfo[flag], value)
 }
 
 func (c *Command) AddForwardSock(socket string) {
@@ -186,8 +184,26 @@ func (c *Command) ToCmdline() []string {
 	return args
 }
 
+// validateGvproxyPath ensures the path provided by the user points to a gvproxy
+// binary
+func validateGvproxyPath(path string) error {
+	if !strings.ContainsAny(path, "/") && path == "gvproxy" {
+		return nil
+	}
+
+	lastSlashIndex := strings.LastIndex(path, "/")
+	if path[lastSlashIndex+1:] == "gvproxy" {
+		return nil
+	}
+
+	return errors.New("Invalid gvproxy binary path: " + path)
+}
+
 // Cmd converts Command to a commandline format and returns an exec.Cmd which
 // can be executed by os/exec
-func (c *Command) Cmd(gvproxyPath string) *exec.Cmd {
-	return exec.Command(gvproxyPath, c.ToCmdline()...)
+func (c *Command) Cmd(gvproxyPath string) (*exec.Cmd, error) {
+	if err := validateGvproxyPath(gvproxyPath); err != nil {
+		return nil, err
+	}
+	return exec.Command(gvproxyPath, c.ToCmdline()...), nil // nolint:gosec
 }

test/basic_test.go

@@ -217,4 +217,17 @@ var _ = Describe("command-line format", func() {
 			"-pid-file ~/gv-pidfile.txt",
 		}))
 	})
+
+	It("invalid gvproxy path", func() {
+		command := types.NewCommand()
+		_, err := command.Cmd("/usr/bin/gvproxy-wrong")
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(Equal("Invalid gvproxy binary path: /usr/bin/gvproxy-wrong"))
+	})
+
+	It("valid gvproxy path", func() {
+		command := types.NewCommand()
+		_, err := command.Cmd("/usr/bin/gvproxy")
+		Expect(err).ToNot(HaveOccurred())
+	})
 })