s3: Attempt to fix auth problems #5468

Revert "s3: remove WebIdentityRoleProvider to fix crash on auth #5255"

This reverts commit e618ea83dd.

backend/s3/s3.go

@@ -26,6 +26,7 @@ import (
 	"github.com/aws/aws-sdk-go/aws/corehandlers"
 	"github.com/aws/aws-sdk-go/aws/credentials"
 	"github.com/aws/aws-sdk-go/aws/credentials/ec2rolecreds"
+	"github.com/aws/aws-sdk-go/aws/credentials/stscreds"
 	"github.com/aws/aws-sdk-go/aws/defaults"
 	"github.com/aws/aws-sdk-go/aws/ec2metadata"
 	"github.com/aws/aws-sdk-go/aws/endpoints"
@@ -1545,6 +1546,11 @@ func s3Connection(ctx context.Context, opt *Options, client *http.Client) (*s3.S
 			}),
 			ExpiryWindow: 3 * time.Minute,
 		},
+
+		// Pick up IAM role if we are in EKS
+		&stscreds.WebIdentityRoleProvider{
+			ExpiryWindow: 3 * time.Minute,
+		},
 	}
 	cred := credentials.NewChainCredentials(providers)