| 1 | // Package rootaws keeps root's AWS clients away from executable shared profiles. |
| 2 | package rootaws |
| 3 | |
| 4 | import ( |
| 5 | "context" |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "log" |
| 9 | "os" |
| 10 | |
| 11 | "github.com/aws/aws-sdk-go-v2/aws" |
| 12 | awsconfig "github.com/aws/aws-sdk-go-v2/config" |
| 13 | "github.com/aws/aws-sdk-go-v2/credentials" |
| 14 | ) |
| 15 | |
| 16 | const credentialsPath = "/etc/carlos/credentials" |
| 17 | |
| 18 | // OffcloudCredentials returns the validated root file credentials only when |
| 19 | // complete environment keys do not take precedence. It never contacts IMDS. |
| 20 | func OffcloudCredentials() (aws.Credentials, error) { |
| 21 | return offcloudCredentials(credentialsPath) |
| 22 | } |
| 23 | |
| 24 | func offcloudCredentials(path string) (aws.Credentials, error) { |
| 25 | if envAccessKey() != "" && envSecretKey() != "" { |
| 26 | return aws.Credentials{}, nil |
| 27 | } |
| 28 | creds, err := readStaticCredentials(path) |
| 29 | if errors.Is(err, os.ErrNotExist) { |
| 30 | return aws.Credentials{}, nil |
| 31 | } |
| 32 | return creds, err |
| 33 | } |
| 34 | |
| 35 | // LoadDefaultConfig preserves the SDK chain for non-root callers. Root disables |
| 36 | // both shared-file lists, including paths selected through HOME or AWS_* vars. |
| 37 | func LoadDefaultConfig(ctx context.Context, opts ...func(*awsconfig.LoadOptions) error) (aws.Config, error) { |
| 38 | if os.Geteuid() != 0 { |
| 39 | return awsconfig.LoadDefaultConfig(ctx, opts...) |
| 40 | } |
| 41 | return loadRootConfig(ctx, credentialsPath, opts...) |
| 42 | } |
| 43 | |
| 44 | func loadRootConfig(ctx context.Context, path string, opts ...func(*awsconfig.LoadOptions) error) (aws.Config, error) { |
| 45 | // The SDK cannot ignore an environment profile per call. Refuse it rather |
| 46 | // than mutate process-wide environment while other goroutines may read it. |
| 47 | if os.Getenv("AWS_PROFILE") != "" || os.Getenv("AWS_DEFAULT_PROFILE") != "" { |
| 48 | err := fmt.Errorf("root AWS clients do not support AWS_PROFILE or AWS_DEFAULT_PROFILE") |
| 49 | log.Printf("ALERT: %v", err) |
| 50 | return aws.Config{}, err |
| 51 | } |
| 52 | // Complete environment keys are used as given and the fallback file is not |
| 53 | // opened, so a file nobody uses cannot make loading fail. |
| 54 | access, secret := envAccessKey(), envSecretKey() |
| 55 | envKeys := access != "" && secret != "" |
| 56 | var static aws.Credentials |
| 57 | var refused error |
| 58 | if !envKeys { |
| 59 | var err error |
| 60 | static, err = readStaticCredentials(path) |
| 61 | if err != nil && !errors.Is(err, os.ErrNotExist) { |
| 62 | log.Printf("ALERT: refusing unsafe offcloud credentials %s: %v", path, err) |
| 63 | refused = fmt.Errorf("root AWS credentials: %w", err) |
| 64 | } |
| 65 | if err != nil { |
| 66 | static = aws.Credentials{} |
| 67 | } |
| 68 | } |
| 69 | // Append last so callers cannot restore file loading or select a profile. |
| 70 | opts = append(opts, awsconfig.WithSharedConfigFiles([]string{}), |
| 71 | awsconfig.WithSharedCredentialsFiles([]string{}), awsconfig.WithSharedConfigProfile("")) |
| 72 | switch { |
| 73 | case refused != nil: |
| 74 | // Opening a store must not abort adoption before it uses AWS. Refuse |
| 75 | // retrieval instead, without falling through to another identity. |
| 76 | opts = append(opts, awsconfig.WithCredentialsProvider(aws.CredentialsProviderFunc( |
| 77 | func(context.Context) (aws.Credentials, error) { return aws.Credentials{}, refused }))) |
| 78 | case envKeys: |
| 79 | opts = append(opts, awsconfig.WithCredentialsProvider(credentials.NewStaticCredentialsProvider( |
| 80 | access, secret, os.Getenv("AWS_SESSION_TOKEN")))) |
| 81 | case static.AccessKeyID != "": |
| 82 | opts = append(opts, awsconfig.WithCredentialsProvider(credentials.NewStaticCredentialsProvider( |
| 83 | static.AccessKeyID, static.SecretAccessKey, static.SessionToken))) |
| 84 | } |
| 85 | return awsconfig.LoadDefaultConfig(ctx, opts...) |
| 86 | } |
| 87 | |
| 88 | func envAccessKey() string { |
| 89 | if v := os.Getenv("AWS_ACCESS_KEY_ID"); v != "" { |
| 90 | return v |
| 91 | } |
| 92 | return os.Getenv("AWS_ACCESS_KEY") |
| 93 | } |
| 94 | |
| 95 | func envSecretKey() string { |
| 96 | if v := os.Getenv("AWS_SECRET_ACCESS_KEY"); v != "" { |
| 97 | return v |
| 98 | } |
| 99 | return os.Getenv("AWS_SECRET_KEY") |
| 100 | } |
| 101 | |
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