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program_resolver.go
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program_resolver.go
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package command
import (
"bytes"
"fmt"
"io"
"slices"
"strings"
"sync"
"github.com/pkg/errors"
"mvdan.cc/sh/v3/syntax"
)
type ProgramResolverMode uint8
const (
// ProgramResolverModeAuto is a default which prompts for all unresolved variables.
ProgramResolverModeAuto ProgramResolverMode = iota
// ProgramResolverModePromptAll always prompts even if variables are resolved.
ProgramResolverModePromptAll
// ProgramResolverModeSkipAll does not prompt even if variables are unresolved.
// All variables will be marked as resolved.
ProgramResolverModeSkipAll
)
type ProgramResolverSource func() []string
func ProgramResolverSourceFunc(env []string) ProgramResolverSource {
return func() []string {
return env
}
}
// ProgramResolver uses a list of ProgramResolverSource to resolve environment variables
// found in a shell program.
type ProgramResolver struct {
mode ProgramResolverMode
sources []ProgramResolverSource
sensitiveEnvNames []string
envCache *sync.Map
astPrinter *syntax.Printer
}
func NewProgramResolver(mode ProgramResolverMode, sensitiveEnvNames []string, sources ...ProgramResolverSource) *ProgramResolver {
return &ProgramResolver{
mode: mode,
sensitiveEnvNames: sensitiveEnvNames,
sources: sources,
astPrinter: syntax.NewPrinter(),
}
}
type ProgramResolverStatus uint8
const (
// ProgramResolverStatusUnresolved indicates a variable is unresolved.
ProgramResolverStatusUnresolved ProgramResolverStatus = iota
// ProgramResolverStatusUnresolvedWithMessage indicates a variable is unresolved but it has a message.
// It typically means that the variable is of form `export FOO=this is a message`.
ProgramResolverStatusUnresolvedWithMessage
// ProgramResolverStatusUnresolvedWithPlaceholder indicates a variable is unresolved but it has a placeholder.
// It typically means that the variable is of form `export FOO="this is a placeholder"`.
ProgramResolverStatusUnresolvedWithPlaceholder
// ProgramResolverStatusUnresolvedWithSecret indicates a variable is unresolved and needs to be treated with sensitivity.
// It typically means that the variable is a password, certificate, or access key.
ProgramResolverStatusUnresolvedWithSecret
// ProgramResolverStatusResolved indicates a variable is resolved.
ProgramResolverStatusResolved
)
type ProgramResolverResult struct {
Variables []ProgramResolverVarResult
ModifiedProgram bool
}
type ProgramResolverVarResult struct {
// Status indicates the status of the result.
Status ProgramResolverStatus
// Name is the name of the variable.
// It is set always.
Name string
// OriginalValue is the original value of the variable.
// It's either a placeholder (`export FOO="this is a placeholder"`) or
// a message (`export FOO=this is a message`).
OriginalValue string
// Value is the resolved value of the variable.
// It is set only if Status is ProgramResolverStatusResolved.
Value string
}
// Resolve resolves the environment variables found in a shell program.
// It might modify the program and write it provided writer.
func (r *ProgramResolver) Resolve(reader io.Reader, writer io.Writer) (*ProgramResolverResult, error) {
f, err := syntax.NewParser().Parse(reader, "")
if err != nil {
return nil, errors.WithStack(err)
}
decls, modified, err := r.walk(f)
if err != nil {
return nil, err
}
result := ProgramResolverResult{
ModifiedProgram: modified,
}
for _, decl := range decls {
if len(decl.Args) < 1 {
continue
}
name := decl.Args[0].Name.Value
originalValue, isPlaceholder := r.findOriginalValue(decl)
resolvedValue, hasResolvedValue := r.findEnvValue(name)
isSensitive := r.IsEnvSensitive(name)
varResult := ProgramResolverVarResult{
Status: ProgramResolverStatusUnresolved,
Name: name,
OriginalValue: originalValue,
Value: resolvedValue,
}
switch r.mode {
case ProgramResolverModePromptAll:
if isSensitive {
varResult.Status = ProgramResolverStatusUnresolvedWithSecret
varResult.Value = ""
break
}
if hasResolvedValue {
varResult.Status = ProgramResolverStatusUnresolvedWithPlaceholder
break
}
if isPlaceholder {
varResult.Status = ProgramResolverStatusUnresolvedWithPlaceholder
} else {
varResult.Status = ProgramResolverStatusUnresolvedWithMessage
}
case ProgramResolverModeSkipAll:
// For ProgramResolverModeSkip the status is awalys ProgramResolverStatusResolved.
varResult.Status = ProgramResolverStatusResolved
if !hasResolvedValue {
varResult.Value = originalValue
}
default:
if hasResolvedValue {
varResult.Status = ProgramResolverStatusResolved
} else if isSensitive {
varResult.Status = ProgramResolverStatusUnresolvedWithSecret
} else if isPlaceholder {
varResult.Status = ProgramResolverStatusUnresolvedWithPlaceholder
} else if originalValue != "" {
varResult.Status = ProgramResolverStatusUnresolvedWithMessage
} else {
varResult.Status = ProgramResolverStatusUnresolved
}
}
result.Variables = append(result.Variables, varResult)
}
slices.SortStableFunc(result.Variables, func(a, b ProgramResolverVarResult) int {
aResolved, bResolved := a.Status == ProgramResolverStatusResolved, b.Status == ProgramResolverStatusResolved
if aResolved && bResolved {
return strings.Compare(a.Name, b.Name)
}
if aResolved {
return -1
}
return 1
})
err = syntax.NewPrinter().Print(writer, f)
if err != nil {
return nil, err
}
return &result, nil
}
// findOriginalValue walks the AST to find the original value of the variable.
// This method is called only for the value of "export" statement.
func (r *ProgramResolver) findOriginalValue(decl *syntax.DeclClause) (string, bool) {
if len(decl.Args) < 1 || decl.Args[0].Value == nil {
return "", false
}
var fragments []string
isPlaceholder := false
processingVarName := false
syntax.Walk(decl, func(node syntax.Node) bool {
switch node := node.(type) {
// Skip variable name.
case *syntax.Assign:
if node.Name != nil && !node.Naked {
processingVarName = true
}
return true
// export FOO=bar
case *syntax.Lit:
if processingVarName {
processingVarName = false
return false
}
fragments = append(fragments, node.Value)
return true
// export FOO="bar"
case *syntax.DblQuoted:
if len(node.Parts) == 1 {
p, ok := node.Parts[0].(*syntax.Lit)
// Break for quoted stmt, ie non-literal, e.g. export FOO="$( echo 'this is a test' )"
if !ok {
break
}
if p.Value != "" {
isPlaceholder = true
fragments = append(fragments, p.Value)
}
return false
}
// export FOO='bar'
case *syntax.SglQuoted:
if node.Value != "" {
isPlaceholder = true
fragments = append(fragments, node.Value)
}
return false
// export FOO=${FOO:-bar}
case *syntax.ParamExp:
if node.Exp.Op == syntax.DefaultUnsetOrNull {
fragments = append(fragments, node.Exp.Word.Lit())
return true
}
}
return true
})
return strings.Join(fragments, " "), isPlaceholder
}
func (r *ProgramResolver) findEnvValue(name string) (string, bool) {
r.collectEnvFromSources()
val, ok := r.envCache.Load(name)
if ok {
return val.(string), ok
}
return "", ok
}
func (r *ProgramResolver) IsEnvSensitive(name string) bool {
for _, key := range r.sensitiveEnvNames {
if key == name {
return true
}
}
return false
}
func (r *ProgramResolver) collectEnvFromSources() {
if r.envCache != nil {
return
}
r.envCache = &sync.Map{}
for _, source := range r.sources {
env := source()
for _, e := range env {
parts := strings.SplitN(e, "=", 2)
if len(parts) == 2 {
r.envCache.Store(parts[0], parts[1])
}
}
}
}
func (r *ProgramResolver) walk(f *syntax.File) (result []*syntax.DeclClause, modified bool, err error) {
syntax.Walk(f, func(node syntax.Node) bool {
if err != nil {
return false
}
switch node := node.(type) {
case *syntax.File:
return true
case *syntax.Stmt:
decl, ok := r.isStmtSupportedDecl(node)
if !ok {
return false
}
err = r.modifyStmt(node, decl)
if err != nil {
return false
}
// TODO(adamb): does not make sense
modified = true
result = append(result, decl)
return false
default:
// noop
}
// Unless stmt is at top level bail;
// we don't want to go deeper.
return false
})
return
}
func (r *ProgramResolver) isStmtSupportedDecl(stmt *syntax.Stmt) (*syntax.DeclClause, bool) {
decl, ok := stmt.Cmd.(*syntax.DeclClause)
if !ok {
return nil, false
}
isSupported := decl.Variant.Value == "export" && !r.hasExpr(decl.Args[0])
if !isSupported {
return nil, false
}
return decl, true
}
func (r *ProgramResolver) modifyStmt(stmt *syntax.Stmt, decl *syntax.DeclClause) error {
exportStmt := bytes.NewBuffer(nil)
if err := r.astPrinter.Print(exportStmt, decl); err != nil {
return errors.WithStack(err)
}
stmt.Comments = append(stmt.Comments,
syntax.Comment{Text: "\n"},
syntax.Comment{Text: fmt.Sprintf(" %s set in smart env store", decl.Args[0].Name.Value)},
syntax.Comment{Text: fmt.Sprintf(" %q", exportStmt.String())},
)
stmt.Cmd = nil
return nil
}
// hasExpr walks the AST to check for nested expressions.
func (r *ProgramResolver) hasExpr(node syntax.Node) (found bool) {
syntax.Walk(node, func(node syntax.Node) bool {
switch node.(type) {
case *syntax.CmdSubst, *syntax.Subshell, *syntax.ParamExp, *syntax.ArithmExp, *syntax.ProcSubst, *syntax.ExtGlob, *syntax.BraceExp:
found = true
return false
default:
return !found
}
})
return
}