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moby--moby/cmd/dockerd/hack/malformed_host_override.go

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// +build !windows
package hack
import "net"
// MalformedHostHeaderOverride is a wrapper to be able
// to overcome the 400 Bad request coming from old docker
// clients that send an invalid Host header.
type MalformedHostHeaderOverride struct {
net.Listener
}
// MalformedHostHeaderOverrideConn wraps the underlying unix
// connection and keeps track of the first read from http.Server
// which just reads the headers.
type MalformedHostHeaderOverrideConn struct {
net.Conn
first bool
}
var closeConnHeader = []byte("\r\nConnection: close\r")
// Read reads the first *read* request from http.Server to inspect
// the Host header. If the Host starts with / then we're talking to
// an old docker client which send an invalid Host header. To not
// error out in http.Server we rewrite the first bytes of the request
// to sanitize the Host header itself.
// In case we're not dealing with old docker clients the data is just passed
// to the server w/o modification.
func (l *MalformedHostHeaderOverrideConn) Read(b []byte) (n int, err error) {
// http.Server uses a 4k buffer
if l.first && len(b) == 4096 {
// This keeps track of the first read from http.Server which just reads
// the headers
l.first = false
// The first read of the connection by http.Server is done limited to
// DefaultMaxHeaderBytes (usually 1 << 20) + 4096.
// Here we do the first read which gets us all the http headers to
// be inspected and modified below.
c, err := l.Conn.Read(b)
if err != nil {
return c, err
}
var (
start, end int
firstLineFeed = -1
buf []byte
)
for i := 0; i <= c-1-7; i++ {
if b[i] == '\n' && firstLineFeed == -1 {
firstLineFeed = i
}
if b[i] != '\n' {
continue
}
if b[i+1] == '\r' && b[i+2] == '\n' {
return c, nil
}
if b[i+1] != 'H' {
continue
}
if b[i+2] != 'o' {
continue
}
if b[i+3] != 's' {
continue
}
if b[i+4] != 't' {
continue
}
if b[i+5] != ':' {
continue
}
if b[i+6] != ' ' {
continue
}
if b[i+7] != '/' {
continue
}
// ensure clients other than the docker clients do not get this hack
if i != firstLineFeed {
return c, nil
}
start = i + 7
// now find where the value ends
for ii, bbb := range b[start:c] {
if bbb == '\n' {
end = start + ii
break
}
}
buf = make([]byte, 0, c+len(closeConnHeader)-(end-start))
// strip the value of the host header and
// inject `Connection: close` to ensure we don't reuse this connection
buf = append(buf, b[:start]...)
buf = append(buf, closeConnHeader...)
buf = append(buf, b[end:c]...)
copy(b, buf)
break
}
if len(buf) == 0 {
return c, nil
}
return len(buf), nil
}
return l.Conn.Read(b)
}
// Accept makes the listener accepts connections and wraps the connection
// in a MalformedHostHeaderOverrideConn initilizing first to true.
func (l *MalformedHostHeaderOverride) Accept() (net.Conn, error) {
c, err := l.Listener.Accept()
if err != nil {
return c, err
}
return &MalformedHostHeaderOverrideConn{c, true}, nil
}