SSHPem.decode constructor

SSHPem.decode(String pem)

Implementation

factory SSHPem.decode(String pem) {
  final lines = pem.trim().split("\n");
  final header = lines.first;
  final footer = lines.last;

  if (!header.startsWith(_pemHeaderBegin)) {
    throw FormatException('PEM header must start with $_pemHeaderBegin');
  }
  if (!footer.startsWith(_pemFooterBegin)) {
    throw FormatException('PEM footer must start with $_pemFooterBegin');
  }
  if (!header.endsWith(_pemEnd)) {
    throw FormatException('PEM header must end with $_pemEnd');
  }
  if (!footer.endsWith(_pemEnd)) {
    throw FormatException('PEM footer must end with $_pemEnd');
  }

  final type = header.substring(
    _pemHeaderBegin.length,
    header.length - _pemEnd.length,
  );
  final footerType = footer.substring(
    _pemFooterBegin.length,
    footer.length - _pemEnd.length,
  );

  if (type != footerType) {
    throw FormatException('Type mismatch: $type != $footerType');
  }

  final pemHeader = <String, String>{};

  final pemBodyLines = <String>[];

  for (final line in lines.sublist(1, lines.length - 1)) {
    if (line.trim().isEmpty) {
      continue;
    }

    if (line.contains(':')) {
      if (pemBodyLines.isNotEmpty) {
        throw FormatException('Unexpected header line: $line');
      } else {
        final parts = line.split(':');
        pemHeader[parts[0].trim()] = parts[1].trim();
        continue;
      }
    }

    pemBodyLines.add(line);
  }

  final pemBody = pemBodyLines.join('');

  final content = base64.decode(pemBody);

  return SSHPem(type, pemHeader, content);
}