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jwt.go
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jwt.go
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package lib
import (
"encoding/json"
"fmt"
"strings"
"time"
"github.com/dgrijalva/jwt-go/v4"
"github.com/hashicorp/hcl/v2"
"github.com/zclconf/go-cty/cty"
"github.com/zclconf/go-cty/cty/function"
"github.com/zclconf/go-cty/cty/function/stdlib"
acjwt "github.com/avenga/couper/accesscontrol/jwt"
"github.com/avenga/couper/config"
"github.com/avenga/couper/config/reader"
"github.com/avenga/couper/internal/seetie"
)
const FnJWTSign = "jwt_sign"
type JWTSigningConfig struct {
Claims config.Claims
Headers hcl.Expression
Key interface{}
Name string
SignatureAlgorithm string
TTL time.Duration
}
func checkData(ttl, signatureAlgorithm string) (time.Duration, acjwt.Algorithm, error) {
var (
dur time.Duration
parseErr error
)
alg := acjwt.NewAlgorithm(signatureAlgorithm)
if alg == acjwt.AlgorithmUnknown {
return dur, alg, fmt.Errorf("algorithm is not supported")
}
if ttl != "0" {
dur, parseErr = time.ParseDuration(ttl)
if parseErr != nil {
return dur, alg, parseErr
}
}
return dur, alg, nil
}
func getKey(keyBytes []byte, signatureAlgorithm string) (interface{}, error) {
var (
key interface{}
parseErr error
)
key = keyBytes
if strings.HasPrefix(signatureAlgorithm, "RS") {
key, parseErr = jwt.ParseRSAPrivateKeyFromPEM(keyBytes)
if parseErr != nil {
return nil, parseErr
}
}
return key, nil
}
func NewJWTSigningConfigFromJWTSigningProfile(j *config.JWTSigningProfile) (*JWTSigningConfig, error) {
ttl, _, err := checkData(j.TTL, j.SignatureAlgorithm)
if err != nil {
return nil, err
}
key, err := getKey(j.KeyBytes, j.SignatureAlgorithm)
if err != nil {
return nil, err
}
c := &JWTSigningConfig{
Claims: j.Claims,
Headers: j.Headers,
Key: key,
Name: j.Name,
SignatureAlgorithm: j.SignatureAlgorithm,
TTL: ttl,
}
return c, nil
}
func NewJWTSigningConfigFromJWT(j *config.JWT) (*JWTSigningConfig, error) {
if j.SigningTTL == "" {
return nil, nil
}
ttl, alg, err := checkData(j.SigningTTL, j.SignatureAlgorithm)
if err != nil {
return nil, err
}
var signingKey, signingKeyFile string
if alg.IsHMAC() {
signingKey = j.Key
signingKeyFile = j.KeyFile
} else {
signingKey = j.SigningKey
signingKeyFile = j.SigningKeyFile
}
keyBytes, err := reader.ReadFromAttrFile("jwt signing key", signingKey, signingKeyFile)
if err != nil {
return nil, err
}
key, err := getKey(keyBytes, j.SignatureAlgorithm)
if err != nil {
return nil, err
}
c := &JWTSigningConfig{
Claims: j.Claims,
Key: key,
Name: j.Name,
SignatureAlgorithm: j.SignatureAlgorithm,
TTL: ttl,
}
return c, nil
}
func NewJwtSignFunction(ctx *hcl.EvalContext, jwtSigningConfigs map[string]*JWTSigningConfig,
evalFn func(*hcl.EvalContext, hcl.Expression) (cty.Value, error)) function.Function {
return function.New(&function.Spec{
Params: []function.Parameter{
{
Name: "jwt_signing_profile_label",
Type: cty.String,
},
{
Name: "claims",
Type: cty.DynamicPseudoType,
},
},
Type: function.StaticReturnType(cty.String),
Impl: func(args []cty.Value, _ cty.Type) (ret cty.Value, err error) {
if len(jwtSigningConfigs) == 0 {
return cty.StringVal(""), fmt.Errorf("missing jwt_signing_profile or jwt (with signing_ttl) definitions")
}
label := args[0].AsString()
signingConfig := jwtSigningConfigs[label]
if signingConfig == nil {
return cty.StringVal(""), fmt.Errorf("missing jwt_signing_profile or jwt (with signing_ttl) for given label %q", label)
}
mapClaims := jwt.MapClaims{}
var defaultClaims, argumentClaims, headers map[string]interface{}
if signingConfig.Headers != nil {
h, diags := evalFn(ctx, signingConfig.Headers)
if diags != nil {
return cty.StringVal(""), diags
}
headers = seetie.ValueToMap(h)
}
// get claims from signing profile
if signingConfig.Claims != nil {
v, diags := evalFn(ctx, signingConfig.Claims)
if diags != nil {
return cty.StringVal(""), err
}
defaultClaims = seetie.ValueToMap(v)
}
for k, v := range defaultClaims {
mapClaims[k] = v
}
if signingConfig.TTL != 0 {
mapClaims["exp"] = time.Now().Unix() + int64(signingConfig.TTL.Seconds())
}
// get claims from function argument
jsonClaims, err := stdlib.JSONEncode(args[1])
if err != nil {
return cty.StringVal(""), err
}
err = json.Unmarshal([]byte(jsonClaims.AsString()), &argumentClaims)
if err != nil {
return cty.StringVal(""), err
}
for k, v := range argumentClaims {
mapClaims[k] = v
}
tokenString, err := CreateJWT(signingConfig.SignatureAlgorithm, signingConfig.Key, mapClaims, headers)
if err != nil {
return cty.StringVal(""), err
}
return cty.StringVal(tokenString), nil
},
})
}
func CreateJWT(signatureAlgorithm string, key interface{}, mapClaims jwt.MapClaims, headers map[string]interface{}) (string, error) {
signingMethod := jwt.GetSigningMethod(signatureAlgorithm)
if signingMethod == nil {
return "", fmt.Errorf("no signing method for given algorithm: %s", signatureAlgorithm)
}
if headers == nil {
headers = map[string]interface{}{}
}
headers["typ"] = "JWT"
headers["alg"] = signingMethod.Alg()
// create token
token := &jwt.Token{Header: headers, Claims: mapClaims, Method: signingMethod}
// sign token
return token.SignedString(key)
}