DNS over HTTPS (DoH)

• DNS over HTTPS (DoH) - 通过 HTTPS 传输 DNS 查询（DNS over HTTPS sends DNS queries over HTTPS）

• Cloudflare: DNS over HTTPS

  • Using JSON

• Google Public DNS: DoH JSON API

• Wikipedia: DNS over HTTPS

• JSON

  • 只支持 GET，查询编码在 URL；Cloudflare 需要 Accept: application/dns-json
  • 没有 RFC，Cloudflare 沿用 Google 的 schema，各家行为可能不同；严格场景用 wire format
  • 参数：name（必填）、type（默认 A）、do（DNSSEC）、cd（关闭校验）

• wire format - RFC 8484，application/dns-message

  • GET：?dns=<base64url DNS 报文>
  • POST：body 为二进制报文，必须设置 Content-Type: application/dns-message，否则返回 415

Status Codes复制章节链接

• 400 DNS query not specified or too small.
• 413 DNS query is larger than maximum allowed DNS message size.
• 415 Unsupported content type.
• 504 Resolver timeout while waiting for the query response.

Examples复制章节链接

# Cloudflare JSON
curl -H 'accept: application/dns-json' 'https://cloudflare-dns.com/dns-query?name=example.com&type=AAAA'
curl -H 'accept: application/dns-json' 'https://1.1.1.1/dns-query?name=example.com&type=A&do=1'

# Google JSON
curl 'https://dns.google/resolve?name=example.com&type=AAAA'
# ct=application/x-javascript 显式请求 JSON；ct=application/dns-message 则返回二进制 DNS 报文
curl 'https://dns.google/resolve?name=example.com&type=A&ct=application/x-javascript'

{
  "Status": 0,
  "TC": false,
  "RD": true,
  "RA": true,
  "AD": true,
  "CD": false,
  "Question": [{ "name": "example.com.", "type": 28 }],
  "Answer": [{ "name": "example.com.", "type": 28, "TTL": 1726, "data": "2606:2800:220:1:248:1893:25c8:1946" }]
}

• Status 是 DNS RCODE：0 NOERROR，2 SERVFAIL，3 NXDOMAIN
• type 为数字：1 A，5 CNAME，28 AAAA