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fix(api-server): register pre-auth interceptors when only GRPC_SERVICE_ACCOUNT is set #1454

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markturansky wants to merge 2 commits into from
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fix(api-server): register pre-auth interceptors when only GRPC_SERVICE_ACCOUNT is set #1454

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922608d
fix(api-server): recognize OIDC service tokens as service callers for…
Apr 23, 2026
0d2c89e
fix(api-server): register pre-auth interceptors when only GRPC_SERVIC…
Apr 24, 2026
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21 changes: 15 additions & 6 deletions components/ambient-api-server/pkg/middleware/bearer_token.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,10 @@ import (
pkgserver "github.com/openshift-online/rh-trex-ai/pkg/server"
)

const ambientAPITokenEnv = "AMBIENT_API_TOKEN"
const (
ambientAPITokenEnv = "AMBIENT_API_TOKEN"
grpcServiceAccountEnv = "GRPC_SERVICE_ACCOUNT"
)

var httpBypassPaths = map[string]bool{
"/healthcheck": true,
Expand All @@ -21,13 +24,19 @@ var httpBypassPaths = map[string]bool{

func init() {
token := os.Getenv(ambientAPITokenEnv)
if token == "" {
glog.Infof("Service token auth disabled: %s not set", ambientAPITokenEnv)
serviceAccount := os.Getenv(grpcServiceAccountEnv)
if token == "" && serviceAccount == "" {
glog.Infof("Service token auth disabled: neither %s nor %s set", ambientAPITokenEnv, grpcServiceAccountEnv)
return
}
glog.Infof("Service token auth enabled via %s (gRPC only)", ambientAPITokenEnv)
pkgserver.RegisterPreAuthGRPCUnaryInterceptor(bearerTokenGRPCUnaryInterceptor(token))
pkgserver.RegisterPreAuthGRPCStreamInterceptor(bearerTokenGRPCStreamInterceptor(token))
if token != "" {
glog.Infof("Service token auth enabled via %s (gRPC only)", ambientAPITokenEnv)
}
if serviceAccount != "" {
glog.Infof("OIDC service account username: %s", serviceAccount)
}
pkgserver.RegisterPreAuthGRPCUnaryInterceptor(bearerTokenGRPCUnaryInterceptor(token, serviceAccount))
pkgserver.RegisterPreAuthGRPCStreamInterceptor(bearerTokenGRPCStreamInterceptor(token, serviceAccount))
}

func extractBearerToken(header string) (string, error) {
Expand Down
10 changes: 8 additions & 2 deletions components/ambient-api-server/pkg/middleware/bearer_token_grpc.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ var grpcBypassMethods = map[string]bool{
"/grpc.reflection.v1alpha.ServerReflection/ServerReflectionInfo": true,
}

func bearerTokenGRPCUnaryInterceptor(expectedToken string) grpc.UnaryServerInterceptor {
func bearerTokenGRPCUnaryInterceptor(expectedToken, serviceAccountUsername string) grpc.UnaryServerInterceptor {
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
if grpcBypassMethods[info.FullMethod] {
return handler(ctx, req)
Expand All @@ -29,6 +29,9 @@ func bearerTokenGRPCUnaryInterceptor(expectedToken string) grpc.UnaryServerInter
return handler(withCallerType(ctx, CallerTypeService), req)
}
if username := usernameFromJWT(token); username != "" {
if serviceAccountUsername != "" && username == serviceAccountUsername {
ctx = withCallerType(ctx, CallerTypeService)
}
Comment on lines +32 to +34
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@coderabbitai coderabbitai Bot Apr 24, 2026

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⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail

echo "1) Where service caller privilege is assigned/checked:"
rg -n -C3 --type=go '\bwithCallerType\s*\(.*CallerTypeService|\bIsServiceCaller\s*\('

echo
echo "2) Which JWT claims are currently inspected for identity/elevation:"
rg -n -C3 --type=go 'preferred_username|username|sub|azp|client_id|clientId|aud|iss|issuer'

Repository: ambient-code/platform

Length of output: 50378

🏁 Script executed:

#!/bin/bash
set -euo pipefail

echo "=== Finding usernameFromJWT implementation ==="
rg -n "func usernameFromJWT" --type=go -A 20

echo ""
echo "=== Finding JWT validation/parsing ==="
rg -n "jwt\.|JWT\." --type=go | head -30

echo ""
echo "=== Checking for JWT library usage ==="
grep -r "jwt" --include="*.go" components/ambient-api-server/pkg/middleware/ | head -20

Repository: ambient-code/platform

Length of output: 5098

🏁 Script executed:

#!/bin/bash
set -euo pipefail

echo "=== Full bearer_token_grpc.go context around lines 25-65 ==="
sed -n '20,70p' components/ambient-api-server/pkg/middleware/bearer_token_grpc.go

echo ""
echo "=== Check if expectedToken is required for username path ==="
sed -n '20,70p' components/ambient-api-server/pkg/middleware/bearer_token_grpc.go | grep -A 5 -B 5 "usernameFromJWT\|serviceAccountUsername"

Repository: ambient-code/platform

Length of output: 3764

Remove unverified JWT claim path for service caller elevation; implement strict signed token validation.

Lines 31–34 and 57–61 elevate to CallerTypeService when an unverified JWT username claim matches serviceAccountUsername. This is a critical vulnerability: usernameFromJWT() (line 80) uses ParseUnverified(), allowing any attacker to forge a JWT with a matching username claim and bypass token signing entirely. Service elevation must require signature validation and strong claims (e.g., issuer, audience, client_id) beyond username matching. The constant-time token path (lines 28–29, 54–55) is secure; the unverified path should be removed or replaced with cryptographic verification.

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@components/ambient-api-server/pkg/middleware/bearer_token_grpc.go` around
lines 32 - 34, The code elevates to CallerTypeService based on an unverified JWT
claim; remove the ParseUnverified-based path and replace it with strict
signature and claims validation: stop using usernameFromJWT()/ParseUnverified(),
instead validate the token signature (e.g., via jwt.ParseWithClaims or
equivalent) and verify required claims (issuer, audience/client_id, expiry)
before matching the validated subject/username to serviceAccountUsername, and
only then call withCallerType(ctx, CallerTypeService); keep the existing
constant-time token comparison path intact and ensure any new validation uses
the configured signing key and fails closed on errors.

return handler(auth.SetUsernameContext(ctx, username), req)
}
}
Expand All @@ -39,7 +42,7 @@ func bearerTokenGRPCUnaryInterceptor(expectedToken string) grpc.UnaryServerInter
}
}

func bearerTokenGRPCStreamInterceptor(expectedToken string) grpc.StreamServerInterceptor {
func bearerTokenGRPCStreamInterceptor(expectedToken, serviceAccountUsername string) grpc.StreamServerInterceptor {
return func(srv interface{}, ss grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
if grpcBypassMethods[info.FullMethod] {
return handler(srv, ss)
Expand All @@ -53,6 +56,9 @@ func bearerTokenGRPCStreamInterceptor(expectedToken string) grpc.StreamServerInt
}
if username := usernameFromJWT(token); username != "" {
ctx := auth.SetUsernameContext(ss.Context(), username)
if serviceAccountUsername != "" && username == serviceAccountUsername {
ctx = withCallerType(ctx, CallerTypeService)
}
return handler(srv, &serviceCallerStream{ServerStream: ss, ctx: ctx})
}
}
Expand Down
6 changes: 6 additions & 0 deletions components/manifests/base/core/ambient-api-server-service.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -93,6 +93,12 @@ spec:
env:
- name: AMBIENT_ENV
value: development
- name: GRPC_SERVICE_ACCOUNT
valueFrom:
secretKeyRef:
name: ambient-api-server
key: clientId
optional: true
ports:
- name: api
containerPort: 8000
Expand Down
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