OCPBUGS-55324: fix nil field access when describing security groups

Previously, call to DescribeSecurityGroups accesses the session field directly from metadata,
which depends on call to VPC to populate that field. However, function VPC, which
internally call populateSubnets is now constructing the ec2 client differently
so session is field not initialized there, causing nil access.

The commit ensures the session field is initialized by using getting
func Session instead.

Author: tthvo

pkg/asset/installconfig/aws/validation.go

@@ -203,8 +203,9 @@ func validatePublicIpv4Pool(ctx context.Context, meta *Metadata, fldPath *field.
 
 	sess, err := meta.Session(ctx)
 	if err != nil {
-		return append(allErrs, field.Invalid(fldPath, nil, fmt.Sprintf("unable to start a session: %s", err.Error())))
+		return append(allErrs, field.InternalError(fldPath, fmt.Errorf("unable to retrieve aws session: %w", err)))
 	}
+
 	publicIpv4Pool, err := DescribePublicIpv4Pool(ctx, sess, config.Platform.AWS.Region, poolID)
 	if err != nil {
 		return append(allErrs, field.Invalid(fldPath, poolID, err.Error()))
@@ -493,7 +494,12 @@ func validateSecurityGroupIDs(ctx context.Context, meta *Metadata, fldPath *fiel
 		return append(allErrs, field.Invalid(fldPath, vpc, errMsg))
 	}
 
-	securityGroups, err := DescribeSecurityGroups(ctx, meta.session, pool.AdditionalSecurityGroupIDs, platform.Region)
+	session, err := meta.Session(ctx)
+	if err != nil {
+		return append(allErrs, field.InternalError(fldPath, fmt.Errorf("unable to retrieve aws session: %w", err)))
+	}
+
+	securityGroups, err := DescribeSecurityGroups(ctx, session, pool.AdditionalSecurityGroupIDs, platform.Region)
 	if err != nil {
 		return append(allErrs, field.Invalid(fldPath, pool.AdditionalSecurityGroupIDs, err.Error()))
 	}
@@ -773,7 +779,7 @@ func validateServiceEndpoints(fldPath *field.Path, region string, services []aws
 func validateZoneLocal(ctx context.Context, meta *Metadata, fldPath *field.Path, zoneName string) *field.Error {
 	sess, err := meta.Session(ctx)
 	if err != nil {
-		return field.Invalid(fldPath, zoneName, fmt.Sprintf("unable to start a session: %s", err.Error()))
+		return field.Invalid(fldPath, zoneName, fmt.Sprintf("unable to retrieve aws session: %s", err.Error()))
 	}
 	zones, err := describeFilteredZones(ctx, sess, meta.Region, []string{zoneName})
 	if err != nil {
@@ -904,7 +910,7 @@ func isHostedZoneAssociatedWithVPC(hostedZone *route53.GetHostedZoneOutput, vpcI
 func validateInstanceProfile(ctx context.Context, meta *Metadata, fldPath *field.Path, pool *awstypes.MachinePool) *field.Error {
 	session, err := meta.Session(ctx)
 	if err != nil {
-		return field.InternalError(fldPath, fmt.Errorf("unable to start a session: %w", err))
+		return field.InternalError(fldPath, fmt.Errorf("unable to retrieve aws session: %w", err))
 	}
 	client := iam.New(session)
 	res, err := client.GetInstanceProfileWithContext(ctx, &iam.GetInstanceProfileInput{