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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,156 @@ | ||
| /* | ||
| Copyright © 2025 Acronis International GmbH. | ||
| Released under MIT license. | ||
| */ | ||
|
|
||
| // Package jwk provides JSON Web Key (JWK) structure and methods to decode it to public and private keys. | ||
| package jwk | ||
|
|
||
| import ( | ||
| "crypto" | ||
| "crypto/rsa" | ||
| "encoding/base64" | ||
| "encoding/binary" | ||
| "errors" | ||
| "fmt" | ||
| "math/big" | ||
| ) | ||
|
|
||
| const typeRSA = "RSA" | ||
|
|
||
| var supportedKeyTypes = map[string]struct{}{ | ||
| typeRSA: {}, | ||
| } | ||
|
|
||
| // Key defines JSON Web Key structure. | ||
| type Key struct { | ||
| Alg string `json:"alg"` // algorithm | ||
| Crv string `json:"crv,omitempty"` // curve - for EC keys | ||
| D string `json:"d"` // private exponent | ||
| DP string `json:"dp"` // d mod (p-1) | ||
| DQ string `json:"dq"` // d mod (p-1) | ||
| E string `json:"e"` // public exponent | ||
| K string `json:"k,omitempty"` // symmetric key | ||
| Kid string `json:"kid"` // Key ID | ||
| Kty string `json:"kty"` // Key Type | ||
| N string `json:"n"` // modulus | ||
| P string `json:"p"` // prime factor 1 | ||
| Q string `json:"q"` // prime factor 2 | ||
| QI string `json:"qi"` // q^(-1) mod p | ||
| Use string `json:"use"` | ||
| X string `json:"x,omitempty"` // x coordinate - for EC keys | ||
| Y string `json:"y,omitempty"` // y coordinate - for EC keys | ||
| } | ||
|
|
||
| // DecodePublicKey decodes Key to public key. | ||
| func (j *Key) DecodePublicKey() (crypto.PublicKey, error) { | ||
| if _, ok := supportedKeyTypes[j.Kty]; !ok { | ||
| return nil, fmt.Errorf("unsupported key type %s", j.Kty) | ||
| } | ||
|
|
||
| var result interface{} | ||
|
|
||
| if j.Kty == typeRSA { | ||
| if j.N == "" || j.E == "" { | ||
| return nil, errors.New("malformed JWK RSA key: missing N or E") | ||
| } | ||
|
|
||
| e, err := decodeBase64URLToBigInt(j.E) | ||
| if err != nil { | ||
| return nil, errors.New("malformed JWK RSA key") | ||
| } | ||
| eBytes := e.Bytes() | ||
| if len(eBytes) < 4 { | ||
| ndata := make([]byte, 4) | ||
| copy(ndata[4-len(eBytes):], eBytes) | ||
| eBytes = ndata | ||
| } | ||
|
|
||
| pubKey := &rsa.PublicKey{ | ||
| N: &big.Int{}, | ||
| E: int(binary.BigEndian.Uint32(eBytes)), | ||
| } | ||
|
|
||
| n, err := decodeBase64URLToBigInt(j.N) | ||
| if err != nil { | ||
| return nil, errors.New("malformed JWK RSA key") | ||
| } | ||
| pubKey.N = n | ||
|
|
||
| result = pubKey | ||
| } | ||
|
|
||
| return result, nil | ||
| } | ||
|
|
||
| // DecodePrivateKey decodes Key to private key. | ||
| func (j *Key) DecodePrivateKey() (crypto.PrivateKey, error) { | ||
| if _, ok := supportedKeyTypes[j.Kty]; !ok { | ||
| return nil, fmt.Errorf("unsupported key type %s", j.Kty) | ||
| } | ||
|
|
||
| var result interface{} | ||
| var err error | ||
|
|
||
| if j.Kty == typeRSA { | ||
| if j.D == "" { | ||
| return nil, errors.New("malformed JWK RSA private exponent") | ||
| } | ||
|
|
||
| // Decode base64url-encoded Key components | ||
| components := []string{j.N, j.E, j.D, j.P, j.Q, j.DP, j.DQ, j.QI} | ||
| decodedComponents := make([]*big.Int, len(components)) | ||
|
|
||
| for i, component := range components { | ||
| decodedComponents[i], err = decodeBase64URLToBigInt(component) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("malformed Key RSA component: %w", err) | ||
| } | ||
| } | ||
|
|
||
| n := decodedComponents[0] | ||
| e := decodedComponents[1] | ||
| d := decodedComponents[2] | ||
| p := decodedComponents[3] | ||
| q := decodedComponents[4] | ||
| dp := decodedComponents[5] | ||
| dq := decodedComponents[6] | ||
| qi := decodedComponents[7] | ||
|
|
||
| // Convert Key to *rsa.PrivateKey. | ||
| rsaPrivateKey := &rsa.PrivateKey{ | ||
| PublicKey: rsa.PublicKey{ | ||
| N: n, | ||
| E: int(e.Int64()), | ||
| }, | ||
| D: d, | ||
| Primes: []*big.Int{p, q}, | ||
| Precomputed: rsa.PrecomputedValues{ | ||
| Dp: dp, | ||
| Dq: dq, | ||
| Qinv: qi, | ||
| }, | ||
| } | ||
|
|
||
| rsaPrivateKey.Precompute() | ||
|
|
||
| err = rsaPrivateKey.Validate() | ||
| if err != nil { | ||
| return nil, fmt.Errorf("invalid RSA private key: %w", err) | ||
| } | ||
|
|
||
| result = rsaPrivateKey | ||
| } | ||
|
|
||
| return result, err | ||
| } | ||
|
|
||
| // decodeBase64URLToBigInt is a helper function to decode base64url without padding. | ||
| func decodeBase64URLToBigInt(encoded string) (*big.Int, error) { | ||
| data, err := base64.RawURLEncoding.DecodeString(encoded) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to decode base64url: %w", err) | ||
| } | ||
| return new(big.Int).SetBytes(data), nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,177 @@ | ||
| package jwk_test | ||
|
|
||
| import ( | ||
| "crypto/rsa" | ||
| "encoding/base64" | ||
| "math/big" | ||
| "testing" | ||
|
|
||
| "github.com/stretchr/testify/require" | ||
|
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| "github.com/acronis/go-authkit/internal/jwk" | ||
| ) | ||
|
|
||
| func encodeBigIntToBase64URL(n *big.Int) string { | ||
| return base64.RawURLEncoding.EncodeToString(n.Bytes()) | ||
| } | ||
|
|
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| func TestDecodePublicKey(t *testing.T) { | ||
| // Define meaningful primes | ||
| p := big.NewInt(61) | ||
| q := big.NewInt(53) | ||
|
|
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| // Compute modulus n = p * q | ||
| n := new(big.Int).Mul(p, q) // n = 61 × 53 = 3233 | ||
| e := big.NewInt(65537) // common public exponent | ||
|
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| key := &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: encodeBigIntToBase64URL(n), | ||
| E: encodeBigIntToBase64URL(e), | ||
| } | ||
|
|
||
| pubKey, err := key.DecodePublicKey() | ||
| require.NoError(t, err) | ||
| require.NotNil(t, pubKey) | ||
| require.IsType(t, &rsa.PublicKey{}, pubKey) | ||
| require.Equal(t, n, pubKey.(*rsa.PublicKey).N) | ||
| require.Equal(t, int(e.Int64()), pubKey.(*rsa.PublicKey).E) | ||
| } | ||
|
|
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| func TestDecodePublicKeyFails(t *testing.T) { | ||
| key := &jwk.Key{ | ||
| Kty: "MEOW", | ||
| N: "invalid", | ||
| E: "invalid", | ||
| } | ||
|
|
||
| pubKey, err := key.DecodePublicKey() | ||
| require.Error(t, err) | ||
| require.ErrorContains(t, err, "unsupported key type") | ||
| require.Nil(t, pubKey) | ||
|
|
||
| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| } | ||
|
|
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| pubKey, err = key.DecodePublicKey() | ||
| require.Error(t, err, "N and E are missing") | ||
| require.ErrorContains(t, err, "malformed JWK RSA key") | ||
| require.Nil(t, pubKey) | ||
|
|
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| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: "invalid", | ||
| E: "!!invalid!!", | ||
| } | ||
|
|
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| pubKey, err = key.DecodePublicKey() | ||
| require.Error(t, err, "E is invalid") | ||
| require.ErrorContains(t, err, "malformed JWK RSA key") | ||
| require.Nil(t, pubKey) | ||
|
|
||
| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: "!!invalid!!", | ||
| E: "invalid", | ||
| } | ||
|
|
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| pubKey, err = key.DecodePublicKey() | ||
| require.Error(t, err, "N is invalid") | ||
| require.ErrorContains(t, err, "malformed JWK RSA key") | ||
| require.Nil(t, pubKey) | ||
| } | ||
|
|
||
| func TestDecodePrivateKey(t *testing.T) { | ||
| p := big.NewInt(11) | ||
| q := big.NewInt(13) | ||
| n := new(big.Int).Mul(p, q) // modulus calc: n = p * q | ||
|
|
||
| e := big.NewInt(65537) // Common public exponent | ||
| phi := new(big.Int).Mul( | ||
| new(big.Int).Sub(p, big.NewInt(1)), | ||
| new(big.Int).Sub(q, big.NewInt(1)), | ||
| ) // phi(n) | ||
|
|
||
| d := new(big.Int).ModInverse(e, phi) // Compute private exponent | ||
| if d == nil { | ||
| t.Fatal("Failed to compute modular inverse for d") | ||
| } | ||
|
|
||
| dp := new(big.Int).Mod(d, new(big.Int).Sub(p, big.NewInt(1))) // dp = d mod (p-1) | ||
| dq := new(big.Int).Mod(d, new(big.Int).Sub(q, big.NewInt(1))) // dq = d mod (q-1) | ||
| qi := new(big.Int).ModInverse(q, p) // qi = q^(-1) mod p | ||
| if qi == nil { | ||
| t.Fatal("Failed to compute modular inverse for qi") | ||
| } | ||
|
|
||
| key := &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: base64.RawURLEncoding.EncodeToString(n.Bytes()), | ||
| E: encodeBigIntToBase64URL(e), | ||
| D: encodeBigIntToBase64URL(d), | ||
| P: base64.RawURLEncoding.EncodeToString(p.Bytes()), | ||
| Q: base64.RawURLEncoding.EncodeToString(q.Bytes()), | ||
| DP: encodeBigIntToBase64URL(dp), | ||
| DQ: encodeBigIntToBase64URL(dq), | ||
| QI: encodeBigIntToBase64URL(qi), | ||
| } | ||
|
|
||
| privKey, err := key.DecodePrivateKey() | ||
| require.NoError(t, err) | ||
| require.NotNil(t, privKey) | ||
| require.IsType(t, &rsa.PrivateKey{}, privKey) | ||
| require.Equal(t, n, privKey.(*rsa.PrivateKey).PublicKey.N) | ||
| require.Equal(t, int(e.Int64()), privKey.(*rsa.PrivateKey).PublicKey.E) | ||
| } | ||
|
|
||
| func TestDecodePrivateKeyFails(t *testing.T) { | ||
| key := &jwk.Key{ | ||
| Kty: "MEOW", | ||
| } | ||
|
|
||
| privKey, err := key.DecodePrivateKey() | ||
| require.Error(t, err, "unsupported key type") | ||
| require.ErrorContains(t, err, "unsupported key type") | ||
| require.Nil(t, privKey) | ||
|
|
||
| n := big.NewInt(111) // bad modulus, not a mul of p and q | ||
|
|
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| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: base64.RawURLEncoding.EncodeToString(n.Bytes()), | ||
| P: base64.RawURLEncoding.EncodeToString(big.NewInt(11).Bytes()), | ||
| Q: base64.RawURLEncoding.EncodeToString(big.NewInt(13).Bytes()), | ||
| } | ||
|
|
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| privKey, err = key.DecodePrivateKey() | ||
| require.Error(t, err, "bad modulus triggers crypto error") | ||
| require.ErrorContains(t, err, "malformed JWK RSA private exponent") | ||
| require.Nil(t, privKey) | ||
|
|
||
| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: base64.RawURLEncoding.EncodeToString(n.Bytes()), | ||
| P: base64.RawURLEncoding.EncodeToString(big.NewInt(11).Bytes()), | ||
| Q: base64.RawURLEncoding.EncodeToString(big.NewInt(13).Bytes()), | ||
| D: "!!invalid!!", | ||
| } | ||
|
|
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| privKey, err = key.DecodePrivateKey() | ||
| require.Error(t, err, "malformed D") | ||
| require.ErrorContains(t, err, "malformed Key RSA component") | ||
| require.Nil(t, privKey) | ||
|
|
||
| key = &jwk.Key{ | ||
| Kty: "RSA", | ||
| N: base64.RawURLEncoding.EncodeToString(n.Bytes()), | ||
| P: base64.RawURLEncoding.EncodeToString(big.NewInt(11).Bytes()), | ||
| Q: base64.RawURLEncoding.EncodeToString(big.NewInt(13).Bytes()), | ||
| D: "asdasd", | ||
| } | ||
|
|
||
| privKey, err = key.DecodePrivateKey() | ||
| require.Error(t, err, "exported D is not a valid base64url") | ||
| require.ErrorContains(t, err, "public exponent too small") | ||
| require.Nil(t, privKey) | ||
| } |
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