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Change workdir for gomplate (#3684)
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Workaround to run gomplate from a non-root directory in distroless images, because gomplate tries to access CWD on start.
See: hairyhenderson/gomplate#2202

Signed-off-by: m.nabokikh <[email protected]>
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@nabokihms
nabokihms committed Aug 7, 2024
1 parent 54fb570 commit 43956db
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Showing 2 changed files with 62 additions and 63 deletions.
46 changes: 27 additions & 19 deletions cmd/docker-entrypoint/main.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,20 +22,13 @@ func main() {
os.Exit(1)
}

if err := run(args, realExec, realWhich); err != nil {
if err := run(args, realExec, realWhich, realGomplate); err != nil {
fmt.Println("error:", err.Error())
os.Exit(1)
}
}

func realExec(fork bool, args ...string) error {
if fork {
if output, err := exec.Command(args[0], args[1:]...).CombinedOutput(); err != nil {
return fmt.Errorf("cannot fork/exec command %s: %w (output: %q)", args, err, string(output))
}
return nil
}

func realExec(args ...string) error {
argv0, err := exec.LookPath(args[0])
if err != nil {
return fmt.Errorf("cannot lookup path for command %s: %w", args[0], err)
Expand All @@ -56,34 +49,49 @@ func realWhich(path string) string {
return fullPath
}

func run(args []string, execFunc func(bool, ...string) error, whichFunc func(string) string) error {
func realGomplate(path string) (string, error) {
tmpFile, err := os.CreateTemp("/tmp", "dex.config.yaml-*")
if err != nil {
return "", fmt.Errorf("cannot create temp file: %w", err)
}

cmd := exec.Command("gomplate", "-f", path, "-o", tmpFile.Name())
// TODO(nabokihms): Workaround to run gomplate from a non-root directory in distroless images
// gomplate tries to access CWD on start, see: https://github.com/hairyhenderson/gomplate/pull/2202
cmd.Dir = "/etc/dex"

output, err := cmd.CombinedOutput()
if err != nil {
return "", fmt.Errorf("error executing gomplate: %w, (output: %q)", err, string(output))
}

return tmpFile.Name(), nil
}

func run(args []string, execFunc func(...string) error, whichFunc func(string) string, gomplateFunc func(string) (string, error)) error {
if args[0] != "dex" && args[0] != whichFunc("dex") {
return execFunc(false, args...)
return execFunc(args...)
}

if args[1] != "serve" {
return execFunc(false, args...)
return execFunc(args...)
}

newArgs := []string{}
for _, tplCandidate := range args {
if hasSuffixes(tplCandidate, ".tpl", ".tmpl", ".yaml") {
tmpFile, err := os.CreateTemp("/tmp", "dex.config.yaml-*")
fileName, err := gomplateFunc(tplCandidate)
if err != nil {
return fmt.Errorf("cannot create temp file: %w", err)
}

if err := execFunc(true, "gomplate", "-f", tplCandidate, "-o", tmpFile.Name()); err != nil {
return err
}

newArgs = append(newArgs, tmpFile.Name())
newArgs = append(newArgs, fileName)
} else {
newArgs = append(newArgs, tplCandidate)
}
}

return execFunc(false, newArgs...)
return execFunc(newArgs...)
}

func hasSuffixes(s string, suffixes ...string) bool {
Expand Down
79 changes: 35 additions & 44 deletions cmd/docker-entrypoint/main_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ import (
)

type execArgs struct {
fork bool
gomplate bool
argPrefixes []string
}

Expand All @@ -16,98 +16,89 @@ func TestRun(t *testing.T) {
args []string
execReturns error
whichReturns string
wantExecArgs []execArgs
wantExecArgs execArgs
wantErr error
}{
{
name: "executable not dex",
args: []string{"tuna", "fish"},
wantExecArgs: []execArgs{{fork: false, argPrefixes: []string{"tuna", "fish"}}},
wantExecArgs: execArgs{gomplate: false, argPrefixes: []string{"tuna", "fish"}},
},
{
name: "executable is full path to dex",
args: []string{"/usr/local/bin/dex", "marshmallow", "zelda"},
whichReturns: "/usr/local/bin/dex",
wantExecArgs: []execArgs{{fork: false, argPrefixes: []string{"/usr/local/bin/dex", "marshmallow", "zelda"}}},
wantExecArgs: execArgs{gomplate: false, argPrefixes: []string{"/usr/local/bin/dex", "marshmallow", "zelda"}},
},
{
name: "command is not serve",
args: []string{"dex", "marshmallow", "zelda"},
wantExecArgs: []execArgs{{fork: false, argPrefixes: []string{"dex", "marshmallow", "zelda"}}},
wantExecArgs: execArgs{gomplate: false, argPrefixes: []string{"dex", "marshmallow", "zelda"}},
},
{
name: "no templates",
args: []string{"dex", "serve", "config.yaml.not-a-template"},
wantExecArgs: []execArgs{{fork: false, argPrefixes: []string{"dex", "serve", "config.yaml.not-a-template"}}},
wantExecArgs: execArgs{gomplate: false, argPrefixes: []string{"dex", "serve", "config.yaml.not-a-template"}},
},
{
name: "no templates",
args: []string{"dex", "serve", "config.yaml.not-a-template"},
wantExecArgs: []execArgs{{fork: false, argPrefixes: []string{"dex", "serve", "config.yaml.not-a-template"}}},
wantExecArgs: execArgs{gomplate: false, argPrefixes: []string{"dex", "serve", "config.yaml.not-a-template"}},
},
{
name: ".tpl template",
args: []string{"dex", "serve", "config.tpl"},
wantExecArgs: []execArgs{
{fork: true, argPrefixes: []string{"gomplate", "-f", "config.tpl", "-o", "/tmp/dex.config.yaml-"}},
{fork: false, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
name: ".tpl template",
args: []string{"dex", "serve", "config.tpl"},
wantExecArgs: execArgs{gomplate: true, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
{
name: ".tmpl template",
args: []string{"dex", "serve", "config.tmpl"},
wantExecArgs: []execArgs{
{fork: true, argPrefixes: []string{"gomplate", "-f", "config.tmpl", "-o", "/tmp/dex.config.yaml-"}},
{fork: false, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
name: ".tmpl template",
args: []string{"dex", "serve", "config.tmpl"},
wantExecArgs: execArgs{gomplate: true, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
{
name: ".yaml template",
args: []string{"dex", "serve", "some/path/config.yaml"},
wantExecArgs: []execArgs{
{fork: true, argPrefixes: []string{"gomplate", "-f", "some/path/config.yaml", "-o", "/tmp/dex.config.yaml-"}},
{fork: false, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
name: ".yaml template",
args: []string{"dex", "serve", "some/path/config.yaml"},
wantExecArgs: execArgs{gomplate: true, argPrefixes: []string{"dex", "serve", "/tmp/dex.config.yaml-"}},
},
}
for _, test := range tests {
t.Run(test.name, func(t *testing.T) {
var gotExecForks []bool
var gotExecArgs [][]string
fakeExec := func(fork bool, args ...string) error {
gotExecForks = append(gotExecForks, fork)
gotExecArgs = append(gotExecArgs, args)
var gotExecArgs []string
var runsGomplate bool

fakeExec := func(args ...string) error {
gotExecArgs = append(args, gotExecArgs...)
return test.execReturns
}

fakeWhich := func(_ string) string { return test.whichReturns }

gotErr := run(test.args, fakeExec, fakeWhich)
fakeGomplate := func(file string) (string, error) {
runsGomplate = true
return "/tmp/dex.config.yaml-", nil
}

gotErr := run(test.args, fakeExec, fakeWhich, fakeGomplate)
if (test.wantErr == nil) != (gotErr == nil) {
t.Errorf("wanted error %s, got %s", test.wantErr, gotErr)
}
if !execArgsMatch(test.wantExecArgs, gotExecForks, gotExecArgs) {
t.Errorf("wanted exec args %+v, got %+v %+v", test.wantExecArgs, gotExecForks, gotExecArgs)

if !execArgsMatch(test.wantExecArgs, runsGomplate, gotExecArgs) {
t.Errorf("wanted exec args %+v (running gomplate: %+v), got %+v (running gomplate: %+v)",
test.wantExecArgs.argPrefixes, test.wantExecArgs.gomplate, gotExecArgs, runsGomplate)
}
})
}
}

func execArgsMatch(wantExecArgs []execArgs, gotForks []bool, gotExecArgs [][]string) bool {
if len(wantExecArgs) != len(gotForks) {
func execArgsMatch(wantExecArgs execArgs, gomplate bool, gotExecArgs []string) bool {
if wantExecArgs.gomplate != gomplate {
return false
}

for i := range wantExecArgs {
if wantExecArgs[i].fork != gotForks[i] {
for i := range wantExecArgs.argPrefixes {
if !strings.HasPrefix(gotExecArgs[i], wantExecArgs.argPrefixes[i]) {
return false
}
for j := range wantExecArgs[i].argPrefixes {
if !strings.HasPrefix(gotExecArgs[i][j], wantExecArgs[i].argPrefixes[j]) {
return false
}
}
}

return true
}

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