Amazon root certificate pinning in Flutter, Dart - amazon-web-services

Question

I'm using AWS CA to generate an SSL certificate for ElasticBeanstalk that I'm using in my Flutter app.
Based on the bets practices, I'm trying to pin HTTP client the Root certificate from Amazon Trusted Services
I face 2 issues with the Flutter HTTP client:
Whenever I try to load the certificate it crashes:
[VERBOSE-2:ui_dart_state.cc(209)] Unhandled Exception: TlsException: Failure trusting builtin roots (OS Error: BAD_PKCS12_DATA(pkcs8_x509.c:657), errno = 0)
This is the certificate I use (one of five, I add them all):
final _awsRoot1 = _decodePEM("""-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----""");
And this is what I do to decode PEM :
Uint8List _decodePEM(pem) {
for (var s in _startsWith) {
if (pem.startsWith(s)) pem = pem.substring(s.length);
}
for (var s in _endsWith) {
if (pem.endsWith(s)) pem = pem.substring(0, pem.length - s.length);
}
pem = pem.replaceAll('\n', '');
pem = pem.replaceAll('\r', '');
return Uint8List.fromList(base64.decode(pem));
}
And add it via:
void certificatePinningPem(SecurityContext context) {
context.setTrustedCertificatesBytes(_awsRoot1);
context.setTrustedCertificatesBytes(_awsRoot2);
context.setTrustedCertificatesBytes(_awsRoot3);
context.setTrustedCertificatesBytes(_awsRoot4);
context.setTrustedCertificatesBytes(_awsRoot5);
}
I get the same exception when I read DER file :
final aws1 = await rootBundle.load('assets/cer/aws1.cer');
context.setTrustedCertificatesBytes(aws1.buffer.asUint8List());
PEM file from the connection is different
Despite that, when I use badCertificateCallback, pem file from the certificate doesn't match any of those five from repo So how to get Root certificate from connection?
httpClient.badCertificateCallback = (
X509Certificate certificate,
String host,
int port,
) {
print('Bad certificate: ${certificate.pem} for host $host:$port');
return false;
};
Any suggestion on how to properly do certificate pinning in Flutter with AWS Root certificates?
I found a few related threads but they don't really help, i.e. https://github.com/flutter/flutter/issues/39190#issuecomment-693315205