|
| 1 | +package logincreds |
| 2 | + |
| 3 | +import ( |
| 4 | + "context" |
| 5 | + "crypto/ecdsa" |
| 6 | + cryptorand "crypto/rand" |
| 7 | + "crypto/sha256" |
| 8 | + "crypto/x509" |
| 9 | + "encoding/base64" |
| 10 | + "encoding/json" |
| 11 | + "encoding/pem" |
| 12 | + "fmt" |
| 13 | + |
| 14 | + "github.com/aws/aws-sdk-go-v2/internal/sdk" |
| 15 | + "github.com/aws/aws-sdk-go-v2/service/signin" |
| 16 | + "github.com/aws/smithy-go/middleware" |
| 17 | + smithyrand "github.com/aws/smithy-go/rand" |
| 18 | + smithyhttp "github.com/aws/smithy-go/transport/http" |
| 19 | +) |
| 20 | + |
| 21 | +// AWS signin DPOP always uses the P256 curve |
| 22 | +const curvelen = 256 / 8 // bytes |
| 23 | + |
| 24 | +// https://datatracker.ietf.org/doc/html/rfc9449 |
| 25 | +func mkdpop(token *loginToken, htu string) (string, error) { |
| 26 | + key, err := parseKey(token.DPOPKey) |
| 27 | + if err != nil { |
| 28 | + return "", fmt.Errorf("parse key: %w", err) |
| 29 | + } |
| 30 | + |
| 31 | + header, err := jsonb64(&dpopHeader{ |
| 32 | + Typ: "dpop+jwt", |
| 33 | + Alg: "ES256", |
| 34 | + Jwk: &dpopHeaderJwk{ |
| 35 | + Kty: "EC", |
| 36 | + X: base64.RawURLEncoding.EncodeToString(key.X.Bytes()), |
| 37 | + Y: base64.RawURLEncoding.EncodeToString(key.Y.Bytes()), |
| 38 | + Crv: "P-256", |
| 39 | + }, |
| 40 | + }) |
| 41 | + if err != nil { |
| 42 | + return "", fmt.Errorf("marshal header: %w", err) |
| 43 | + } |
| 44 | + |
| 45 | + uuid, err := smithyrand.NewUUID(cryptorand.Reader).GetUUID() |
| 46 | + if err != nil { |
| 47 | + return "", fmt.Errorf("uuid: %w", err) |
| 48 | + } |
| 49 | + |
| 50 | + payload, err := jsonb64(&dpopPayload{ |
| 51 | + Jti: uuid, |
| 52 | + Htm: "POST", |
| 53 | + Htu: htu, |
| 54 | + Iat: sdk.NowTime().Unix(), |
| 55 | + }) |
| 56 | + if err != nil { |
| 57 | + return "", fmt.Errorf("marshal payload: %w", err) |
| 58 | + } |
| 59 | + |
| 60 | + msg := fmt.Sprintf("%s.%s", header, payload) |
| 61 | + |
| 62 | + h := sha256.New() |
| 63 | + h.Write([]byte(msg)) |
| 64 | + |
| 65 | + r, s, err := ecdsa.Sign(cryptorand.Reader, key, h.Sum(nil)) |
| 66 | + if err != nil { |
| 67 | + return "", fmt.Errorf("sign: %w", err) |
| 68 | + } |
| 69 | + |
| 70 | + // DPOP signatures are formatted in RAW r || s form (with each value padded |
| 71 | + // to fit in curve size which in our case is always the 256 bits) - rather |
| 72 | + // than encoded in something like asn.1 |
| 73 | + sig := make([]byte, curvelen*2) |
| 74 | + r.FillBytes(sig[0:curvelen]) |
| 75 | + s.FillBytes(sig[curvelen:]) |
| 76 | + |
| 77 | + dpop := fmt.Sprintf("%s.%s", msg, base64.RawURLEncoding.EncodeToString(sig)) |
| 78 | + return dpop, nil |
| 79 | +} |
| 80 | + |
| 81 | +func parseKey(pemBlock string) (*ecdsa.PrivateKey, error) { |
| 82 | + block, _ := pem.Decode([]byte(pemBlock)) |
| 83 | + priv, err := x509.ParseECPrivateKey(block.Bytes) |
| 84 | + if err != nil { |
| 85 | + return nil, fmt.Errorf("parse ec private key: %w", err) |
| 86 | + } |
| 87 | + |
| 88 | + return priv, nil |
| 89 | +} |
| 90 | + |
| 91 | +func jsonb64(v any) (string, error) { |
| 92 | + j, err := json.MarshalIndent(v, "", " ") |
| 93 | + if err != nil { |
| 94 | + return "", err |
| 95 | + } |
| 96 | + |
| 97 | + return base64.RawURLEncoding.EncodeToString(j), nil |
| 98 | +} |
| 99 | + |
| 100 | +type dpopHeader struct { |
| 101 | + Typ string `json:"typ"` |
| 102 | + Alg string `json:"alg"` |
| 103 | + Jwk *dpopHeaderJwk `json:"jwk"` |
| 104 | +} |
| 105 | + |
| 106 | +type dpopHeaderJwk struct { |
| 107 | + Kty string `json:"kty"` |
| 108 | + X string `json:"x"` |
| 109 | + Y string `json:"y"` |
| 110 | + Crv string `json:"crv"` |
| 111 | +} |
| 112 | + |
| 113 | +type dpopPayload struct { |
| 114 | + Jti string `json:"jti"` |
| 115 | + Htm string `json:"htm"` |
| 116 | + Htu string `json:"htu"` |
| 117 | + Iat int64 `json:"iat"` |
| 118 | +} |
| 119 | + |
| 120 | +type signDPOP struct { |
| 121 | + Token *loginToken |
| 122 | +} |
| 123 | + |
| 124 | +func addSignDPOP(token *loginToken) func(o *signin.Options) { |
| 125 | + return signin.WithAPIOptions(func(stack *middleware.Stack) error { |
| 126 | + return stack.Finalize.Add(&signDPOP{token}, middleware.After) |
| 127 | + }) |
| 128 | +} |
| 129 | + |
| 130 | +func (*signDPOP) ID() string { |
| 131 | + return "signDPOP" |
| 132 | +} |
| 133 | + |
| 134 | +func (m *signDPOP) HandleFinalize( |
| 135 | + ctx context.Context, in middleware.FinalizeInput, next middleware.FinalizeHandler) ( |
| 136 | + out middleware.FinalizeOutput, md middleware.Metadata, err error, |
| 137 | +) { |
| 138 | + req, ok := in.Request.(*smithyhttp.Request) |
| 139 | + if !ok { |
| 140 | + return out, md, fmt.Errorf("unexpected transport type %T", req) |
| 141 | + } |
| 142 | + |
| 143 | + dpop, err := mkdpop(m.Token, req.URL.String()) |
| 144 | + if err != nil { |
| 145 | + return out, md, fmt.Errorf("sign dpop: %w", err) |
| 146 | + } |
| 147 | + |
| 148 | + req.Header.Set("DPoP", dpop) |
| 149 | + return next.HandleFinalize(ctx, in) |
| 150 | +} |
0 commit comments