| 1 | package hostfence |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "encoding/json" |
| 6 | "errors" |
| 7 | "io" |
| 8 | "os" |
| 9 | "regexp" |
| 10 | |
| 11 | "github.com/aws/aws-sdk-go-v2/aws" |
| 12 | "github.com/aws/aws-sdk-go-v2/credentials" |
| 13 | "github.com/aws/aws-sdk-go-v2/credentials/stscreds" |
| 14 | "github.com/aws/aws-sdk-go-v2/service/s3" |
| 15 | "github.com/aws/aws-sdk-go-v2/service/sts" |
| 16 | "github.com/carlosframework/platform/internal/hostfloor" |
| 17 | "github.com/carlosframework/platform/internal/release" |
| 18 | ) |
| 19 | |
| 20 | type fenceCredentials struct { |
| 21 | Role string `json:"role"` |
| 22 | Region string `json:"region"` |
| 23 | Bucket string `json:"bucket"` |
| 24 | AccessKey string `json:"access_key"` |
| 25 | SecretKey string `json:"secret_key"` |
| 26 | } |
| 27 | |
| 28 | // OpenRootFenceStore uses only the dedicated root bootstrap identity. AWS |
| 29 | // environment credentials, IMDS and shared profiles are never consulted. |
| 30 | func OpenRootFenceStore(ctx context.Context, bucket string) (release.Store, error) { |
| 31 | if os.Geteuid() != 0 { |
| 32 | return nil, os.ErrPermission |
| 33 | } |
| 34 | if err := ctx.Err(); err != nil { |
| 35 | return nil, err |
| 36 | } |
| 37 | f, err := hostfloor.OpenProtected("/etc/carlos/fence-writer/credentials.json") |
| 38 | if err != nil { |
| 39 | return nil, err |
| 40 | } |
| 41 | defer f.Close() |
| 42 | st, err := f.Stat() |
| 43 | if err != nil { |
| 44 | return nil, err |
| 45 | } |
| 46 | if st.Mode().Perm() != 0400 && st.Mode().Perm() != 0600 { |
| 47 | return nil, os.ErrPermission |
| 48 | } |
| 49 | var reader io.Reader = f |
| 50 | if st.Mode().Perm() == 0600 { |
| 51 | reader, err = activationCredentialReader(f) |
| 52 | if err != nil { |
| 53 | return nil, err |
| 54 | } |
| 55 | } |
| 56 | c, err := decodeFenceCredentials(reader, bucket) |
| 57 | if err != nil { |
| 58 | return nil, err |
| 59 | } |
| 60 | cfg := aws.Config{Region: c.Region, Credentials: aws.NewCredentialsCache(credentials.NewStaticCredentialsProvider(c.AccessKey, c.SecretKey, ""))} |
| 61 | provider := stscreds.NewAssumeRoleProvider(sts.NewFromConfig(cfg), c.Role, func(o *stscreds.AssumeRoleOptions) { o.RoleSessionName = "carlos-root-fence" }) |
| 62 | cfg.Credentials = aws.NewCredentialsCache(provider) |
| 63 | return &release.S3Store{Client: s3.NewFromConfig(cfg), Bucket: c.Bucket}, nil |
| 64 | } |
| 65 | func decodeFenceCredentials(r io.Reader, bucket string) (fenceCredentials, error) { |
| 66 | var c fenceCredentials |
| 67 | d := json.NewDecoder(io.LimitReader(r, 16385)) |
| 68 | d.DisallowUnknownFields() |
| 69 | if err := d.Decode(&c); err != nil { |
| 70 | return c, err |
| 71 | } |
| 72 | var extra any |
| 73 | if err := d.Decode(&extra); err != io.EOF { |
| 74 | return c, errors.New("host fences: invalid credential file") |
| 75 | } |
| 76 | if c.Bucket != bucket || bucket == "" || c.Region == "" || c.AccessKey == "" || c.SecretKey == "" || !regexp.MustCompile(`^arn:aws:iam::[0-9]{12}:role/[A-Za-z0-9+=,.@_/-]+$`).MatchString(c.Role) { |
| 77 | return c, errors.New("host fences: incomplete dedicated credential scope") |
| 78 | } |
| 79 | return c, nil |
| 80 | } |
| 81 | |
amadan