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fix: [#630] Use the correct algorithm for at_hash and c_hash #659

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merged 4 commits into from
Apr 16, 2022
Merged

fix: [#630] Use the correct algorithm for at_hash and c_hash #659

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53fec39
feat: [#630] Use the correct algorithm for at_hash and c_hash
vivshankar Mar 26, 2022
914c09f
style: Condensed the hashSize allocation
vivshankar Apr 10, 2022
03b0441
review: Remove hashSize and simplify the code
vivshankar Apr 12, 2022
5c83196
fix: Added a len check and tests
vivshankar Apr 16, 2022
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9 changes: 4 additions & 5 deletions handler/openid/flow_hybrid.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@ package openid

import (
"context"
"encoding/base64"
"time"

"github.com/ory/x/errorsx"
Expand Down Expand Up @@ -122,11 +121,11 @@ func (c *OpenIDConnectHybridHandler) HandleAuthorizeEndpointRequest(ctx context.
resp.AddParameter("code", code)
ar.SetResponseTypeHandled("code")

hash, err := c.Enigma.Hash(ctx, []byte(resp.GetParameters().Get("code")))
hash, err := c.IDTokenHandleHelper.ComputeHash(ctx, sess, resp.GetParameters().Get("code"))
if err != nil {
return err
}
claims.CodeHash = base64.RawURLEncoding.EncodeToString([]byte(hash[:c.Enigma.GetSigningMethodLength()/2]))
claims.CodeHash = hash

if ar.GetGrantedScopes().Has("openid") {
if err := c.OpenIDConnectRequestStorage.CreateOpenIDConnectSession(ctx, resp.GetCode(), ar.Sanitize(oidcParameters)); err != nil {
Expand All @@ -143,11 +142,11 @@ func (c *OpenIDConnectHybridHandler) HandleAuthorizeEndpointRequest(ctx context.
}
ar.SetResponseTypeHandled("token")

hash, err := c.Enigma.Hash(ctx, []byte(resp.GetParameters().Get("access_token")))
hash, err := c.IDTokenHandleHelper.ComputeHash(ctx, sess, resp.GetParameters().Get("access_token"))
if err != nil {
return err
}
claims.AccessTokenHash = base64.RawURLEncoding.EncodeToString([]byte(hash[:c.Enigma.GetSigningMethodLength()/2]))
claims.AccessTokenHash = hash
}

if resp.GetParameters().Get("state") == "" {
Expand Down
5 changes: 2 additions & 3 deletions handler/openid/flow_implicit.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,6 @@ package openid

import (
"context"
"encoding/base64"

"github.com/ory/x/errorsx"

Expand Down Expand Up @@ -93,12 +92,12 @@ func (c *OpenIDConnectImplicitHandler) HandleAuthorizeEndpointRequest(ctx contex
}

ar.SetResponseTypeHandled("token")
hash, err := c.RS256JWTStrategy.Hash(ctx, []byte(resp.GetParameters().Get("access_token")))
hash, err := c.ComputeHash(ctx, sess, resp.GetParameters().Get("access_token"))
if err != nil {
return err
}

claims.AccessTokenHash = base64.RawURLEncoding.EncodeToString([]byte(hash[:c.RS256JWTStrategy.GetSigningMethodLength()/2]))
claims.AccessTokenHash = hash
} else {
resp.AddParameter("state", ar.GetState())
}
Expand Down
44 changes: 44 additions & 0 deletions handler/openid/helper.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,10 @@ import (
"bytes"
"context"
"crypto/sha256"
"crypto/sha512"
"encoding/base64"
"hash"
"strconv"

"github.com/ory/fosite"
)
Expand All @@ -36,6 +39,16 @@ type IDTokenHandleHelper struct {

func (i *IDTokenHandleHelper) GetAccessTokenHash(ctx context.Context, requester fosite.AccessRequester, responder fosite.AccessResponder) string {
token := responder.GetAccessToken()
// The session should always be a openid.Session but best to safely cast
if session, ok := requester.GetSession().(Session); ok {
val, err := i.ComputeHash(ctx, session, token)
if err != nil {
// this should never happen
panic(err)
}

return val
}

buffer := bytes.NewBufferString(token)
hash := sha256.New()
Expand Down Expand Up @@ -76,3 +89,34 @@ func (i *IDTokenHandleHelper) IssueExplicitIDToken(ctx context.Context, ar fosit
resp.SetExtra("id_token", token)
return nil
}

// ComputeHash computes the hash using the alg defined in the id_token header
func (i *IDTokenHandleHelper) ComputeHash(ctx context.Context, sess Session, token string) (string, error) {
var err error
hashSize := 256
if alg, ok := sess.IDTokenHeaders().Get("alg").(string); ok {
hashSize, err = strconv.Atoi(alg[2:])
if err != nil {
hashSize = 256
}
}

var hash hash.Hash
if hashSize == 384 {
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I think it would make sense to set hash directly, without the intermediate hashSize variable :)

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Hmm, could you elaborate on this please? The alg may or may not be present in the header, so the first step here is to compute the hash size.

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I guess something along this pseudo-code:

hash := sha256.New()

if alg, ok := sess.IDTokenHeaders().Get("alg").(string); ok {
 		hashSize, _ := strconv.Atoi(alg[2:]) // 0 per default
 		switch hashSize {
 			case 384
				hash = sha512.New()
 			// ...
 		}
 	}

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@aeneasr Made the change.

hash = sha512.New384()
} else if hashSize == 512 {
hash = sha512.New()
} else {
// fallback to 256
hash = sha256.New()
}

buffer := bytes.NewBufferString(token)
_, err = hash.Write(buffer.Bytes())
if err != nil {
return "", err
}
hashBuf := bytes.NewBuffer(hash.Sum([]byte{}))

return base64.RawURLEncoding.EncodeToString(hashBuf.Bytes()[:hashBuf.Len()/2]), nil
}
22 changes: 22 additions & 0 deletions handler/openid/helper_test.go
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Expand Up @@ -130,10 +130,32 @@ func TestGetAccessTokenHash(t *testing.T) {

defer ctrl.Finish()

req.EXPECT().GetSession().Return(nil)
resp.EXPECT().GetAccessToken().Return("7a35f818-9164-48cb-8c8f-e1217f44228431c41102-d410-4ed5-9276-07ba53dfdcd8")

h := &IDTokenHandleHelper{IDTokenStrategy: strat}

hash := h.GetAccessTokenHash(nil, req, resp)
assert.Equal(t, "Zfn_XBitThuDJiETU3OALQ", hash)
}

func TestGetAccessTokenHashWithDifferentKeyLength(t *testing.T) {
ctrl := gomock.NewController(t)
req := internal.NewMockAccessRequester(ctrl)
resp := internal.NewMockAccessResponder(ctrl)

defer ctrl.Finish()

headers := &jwt.Headers{
Extra: map[string]interface{}{
"alg": "RS384",
},
}
req.EXPECT().GetSession().Return(&DefaultSession{Headers: headers})
resp.EXPECT().GetAccessToken().Return("7a35f818-9164-48cb-8c8f-e1217f44228431c41102-d410-4ed5-9276-07ba53dfdcd8")

h := &IDTokenHandleHelper{IDTokenStrategy: strat}

hash := h.GetAccessTokenHash(nil, req, resp)
assert.Equal(t, "VNX38yiOyeqBPheW5jDsWQKa6IjJzK66", hash)
}