c8844a8555
Previously we use io.LimitReader to limit the number of bytes from http request. However, there is a subtle difference between io.LimitReader and io.ReadAll as io.LimitReader will return a Reader, not a ReadCloser. As such the behavior will actually be difference in case of error handling (and when to close). This PR changes io.LimitReader to http.MaxBytesReader so that the behavior can be preserved (except the number of bytes). See https://stackoverflow.com/a/52699702 Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
116 lines
2.6 KiB
Go
116 lines
2.6 KiB
Go
package doh
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import (
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"bytes"
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"encoding/base64"
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"fmt"
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"io"
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"net/http"
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"github.com/miekg/dns"
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)
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// MimeType is the DoH mimetype that should be used.
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const MimeType = "application/dns-message"
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// Path is the URL path that should be used.
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const Path = "/dns-query"
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// NewRequest returns a new DoH request given a method, URL (without any paths, so exclude /dns-query) and dns.Msg.
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func NewRequest(method, url string, m *dns.Msg) (*http.Request, error) {
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buf, err := m.Pack()
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if err != nil {
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return nil, err
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}
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switch method {
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case http.MethodGet:
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b64 := base64.RawURLEncoding.EncodeToString(buf)
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req, err := http.NewRequest(http.MethodGet, "https://"+url+Path+"?dns="+b64, nil)
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if err != nil {
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return req, err
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}
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req.Header.Set("content-type", MimeType)
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req.Header.Set("accept", MimeType)
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return req, nil
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case http.MethodPost:
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req, err := http.NewRequest(http.MethodPost, "https://"+url+Path+"?bla=foo:443", bytes.NewReader(buf))
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if err != nil {
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return req, err
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}
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req.Header.Set("content-type", MimeType)
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req.Header.Set("accept", MimeType)
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return req, nil
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default:
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return nil, fmt.Errorf("method not allowed: %s", method)
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}
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}
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// ResponseToMsg converts a http.Response to a dns message.
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func ResponseToMsg(resp *http.Response) (*dns.Msg, error) {
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defer resp.Body.Close()
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return toMsg(resp.Body)
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}
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// RequestToMsg converts a http.Request to a dns message.
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func RequestToMsg(req *http.Request) (*dns.Msg, error) {
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switch req.Method {
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case http.MethodGet:
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return requestToMsgGet(req)
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case http.MethodPost:
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return requestToMsgPost(req)
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default:
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return nil, fmt.Errorf("method not allowed: %s", req.Method)
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}
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}
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// requestToMsgPost extracts the dns message from the request body.
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func requestToMsgPost(req *http.Request) (*dns.Msg, error) {
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defer req.Body.Close()
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return toMsg(req.Body)
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}
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// requestToMsgGet extract the dns message from the GET request.
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func requestToMsgGet(req *http.Request) (*dns.Msg, error) {
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values := req.URL.Query()
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b64, ok := values["dns"]
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if !ok {
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return nil, fmt.Errorf("no 'dns' query parameter found")
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}
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if len(b64) != 1 {
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return nil, fmt.Errorf("multiple 'dns' query values found")
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}
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return base64ToMsg(b64[0])
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}
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func toMsg(r io.ReadCloser) (*dns.Msg, error) {
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buf, err := io.ReadAll(http.MaxBytesReader(nil, r, 65536))
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if err != nil {
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return nil, err
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}
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m := new(dns.Msg)
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err = m.Unpack(buf)
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return m, err
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}
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func base64ToMsg(b64 string) (*dns.Msg, error) {
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buf, err := b64Enc.DecodeString(b64)
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if err != nil {
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return nil, err
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}
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m := new(dns.Msg)
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err = m.Unpack(buf)
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return m, err
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}
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var b64Enc = base64.RawURLEncoding
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