parsePublicKeyFromPem static method

RSAPublicKey parsePublicKeyFromPem(String pem)

Parses an RSA public key from a PEM-encoded string.

• pem: The PEM-encoded public key string.

Returns an RSAPublicKey object.

Implementation

static RSAPublicKey parsePublicKeyFromPem(String pem) {
  final keyBytes = _decodePem(pem, 'PUBLIC KEY');
  final asn1Parser = ASN1Parser(keyBytes);
  final topLevelSeq = asn1Parser.nextObject() as ASN1Sequence;

  final subjectPublicKey = topLevelSeq.elements![1] as ASN1BitString;
  var rsaKeyBytes = subjectPublicKey.valueBytes!;

  // Remove leading zero byte if present
  if (rsaKeyBytes.isNotEmpty && rsaKeyBytes[0] == 0) {
    rsaKeyBytes = rsaKeyBytes.sublist(1);
  }

  final rsaKeyParser = ASN1Parser(rsaKeyBytes);
  final rsaKeySeq = rsaKeyParser.nextObject() as ASN1Sequence;

  final modulus = rsaKeySeq.elements![0] as ASN1Integer;
  final publicExponent = rsaKeySeq.elements![1] as ASN1Integer;

  return RSAPublicKey(
    _bytesToBigInt(modulus.valueBytes!),
    _bytesToBigInt(publicExponent.valueBytes!),
  );
}