Skip to content

fix: harden AUSF auth secret handling #63

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Alonza0314 merged 1 commit into from
Jun 22, 2026
Merged

fix: harden AUSF auth secret handling #63

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 22 additions & 6 deletions internal/sbi/processor/ue_authentication.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,9 +1,9 @@
package processor

import (
"bytes"
"crypto/hmac"
"crypto/sha256"
"crypto/subtle"
"encoding/base64"
"encoding/binary"
"encoding/hex"
Expand Down Expand Up @@ -132,10 +132,10 @@ func (p *Processor) EapAuthComfirmRequestProcedure(
XRES := ausfCurrentContext.XRES
RES := hex.EncodeToString(decodeEapAkaPrimePkt.Attributes[ausf_context.AT_RES_ATTRIBUTE].Value)

if !bytes.Equal(MAC, XMAC) {
if !constantTimeEqual(MAC, XMAC) {
eapOK = false
eapErrStr = "EAP-AKA' integrity check fail"
} else if XRES == RES {
} else if constantTimeHexEqual(XRES, RES) {
logger.AuthELog.Infoln("Correct RES value, EAP-AKA' auth succeed")
eapSession.KSeaf = ausfCurrentContext.Kseaf
eapSession.Supi = currentSupi
Expand Down Expand Up @@ -391,7 +391,6 @@ func (p *Processor) UeAuthPostRequestProcedure(c *gin.Context, updateAuthenticat
}
hxresStarAll := sha256.Sum256(hxresStarBytes)
hxresStar := hex.EncodeToString(hxresStarAll[16:]) // last 128 bits
logger.Auth5gAkaLog.Infof("XresStar = %x\n", authInfoResult.AuthenticationVector.XresStar)

// Derive Kseaf from Kausf
Kausf := authInfoResult.AuthenticationVector.Kausf
Expand Down Expand Up @@ -575,8 +574,7 @@ func (p *Processor) Auth5gAkaComfirmRequestProcedure(c *gin.Context, updateConfi
servingNetworkName := ausfCurrentContext.ServingNetworkName

// Compare the received RES* with the stored XRES*
logger.Auth5gAkaLog.Infof("res*: %x\nXres*: %x\n", updateConfirmationData.ResStar, ausfCurrentContext.XresStar)
if strings.EqualFold(updateConfirmationData.ResStar, ausfCurrentContext.XresStar) {
if constantTimeHexEqual(updateConfirmationData.ResStar, ausfCurrentContext.XresStar) {
ausfCurrentContext.AuthStatus = models.AusfUeAuthenticationAuthResult_SUCCESS
confirmDataRsp.AuthResult = models.AusfUeAuthenticationAuthResult_SUCCESS
success = true
Expand Down Expand Up @@ -605,6 +603,24 @@ func (p *Processor) Auth5gAkaComfirmRequestProcedure(c *gin.Context, updateConfi
c.JSON(http.StatusOK, confirmDataRsp)
}

func constantTimeHexEqual(a, b string) bool {
aBytes, err := hex.DecodeString(a)
if err != nil {
return false
}

bBytes, err := hex.DecodeString(b)
if err != nil {
return false
}

return constantTimeEqual(aBytes, bBytes)
}

func constantTimeEqual(a, b []byte) bool {
return len(a) == len(b) && subtle.ConstantTimeCompare(a, b) == 1
}

func KDF5gAka(param ...string) hash.Hash {
s := param[0]
s += param[1]
Expand Down
Loading