[英]Python: Get the RA flag from DNS
我正在尝试从 DNS 中专门获取递归可用 (RA) 标志。 根据 RFC 1035,如果没有递归,它应该返回零,否则返回非零。 如果 DNS 响应被 Quad9 DNS 服务阻止,它将返回带有“RA:0”的“NXDOMAIN”
但是,使用 DNSPython 总是返回非零 (128)。 这可以在库中硬编码吗?
import dns
import dns.resolver
# Allowed Domain
# should return an IP address with "RA" non-zero
domain = "google.com"
# Blocked domain
# Should return NXDOMAIN with "RA" to 0
#domain = "takelady.net" ---> UNCOMMENT
# Set Resolver to Quad9 (quad9.net)
my_resolver = dns.resolver.Resolver()
my_resolver.nameservers = ['9.9.9.9']
try:
dns_response = dns.resolver.query(domain, "A")
for resp in dns_response:
print("[+]", resp.to_text())
print("RA flag:", dns.flags.RA)
except dns.resolver.NXDOMAIN:
print("[+] NXDOMAIN")
print("RA flag:", dns.flags.RA)
pass
except dns.resolver.NoAnswer:
print("[+] NoAnswer")
pass
except dns.resolver.Timeout:
print("[+] Timeout")
pass
允许的响应:
[+] 172.217.214.100
[+] 172.217.214.101
[+] 172.217.214.138
[+] 172.217.214.139
[+] 172.217.214.113
[+] 172.217.214.102
RA flag: 128
阻止响应:
[+] NXDOMAIN
RA flag: 128
您不使用已创建的解析器 object,因此向系统解析器查询 go。 你应该改用这个:
dns_response = my_resolver.query(domain, "A")
query()
执行搜索列表处理,因此您应该先清除搜索列表,如下所示:
my_resolver = dns.resolver.Resolver()
my_resolver.nameservers = ['9.9.9.9']
my_resolver.search = []
最后, NXDOMAIN
响应导致异常,您需要从异常中的响应 object 中读取标志,如下所示:
except dns.resolver.NXDOMAIN as e:
print("[+] NXDOMAIN")
for (name, resp) in e.responses().items():
print(name, "RA flag:", resp.flags & dns.flags.RA)
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