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package limits
import (
"io"
"net/http"
"github.com/mholt/caddy/caddyhttp/httpserver"
)
// Limit is a middleware to control request body size
type Limit struct {
Next httpserver.Handler
BodyLimits []httpserver.PathLimit
}
func (l Limit) ServeHTTP(w http.ResponseWriter, r *http.Request) (int, error) {
if r.Body == nil {
return l.Next.ServeHTTP(w, r)
}
// apply the path-based request body size limit.
for _, bl := range l.BodyLimits {
if httpserver.Path(r.URL.Path).Matches(bl.Path) {
r.Body = MaxBytesReader(w, r.Body, bl.Limit)
break
}
}
return l.Next.ServeHTTP(w, r)
}
// MaxBytesReader and its associated methods are borrowed from the
// Go Standard library (comments intact). The only difference is that
// it returns a MaxBytesExceeded error instead of a generic error message
// when the request body has exceeded the requested limit
func MaxBytesReader(w http.ResponseWriter, r io.ReadCloser, n int64) io.ReadCloser {
return &maxBytesReader{w: w, r: r, n: n}
}
type maxBytesReader struct {
w http.ResponseWriter
r io.ReadCloser // underlying reader
n int64 // max bytes remaining
err error // sticky error
}
func (l *maxBytesReader) Read(p []byte) (n int, err error) {
if l.err != nil {
return 0, l.err
}
if len(p) == 0 {
return 0, nil
}
// If they asked for a 32KB byte read but only 5 bytes are
// remaining, no need to read 32KB. 6 bytes will answer the
// question of the whether we hit the limit or go past it.
if int64(len(p)) > l.n+1 {
p = p[:l.n+1]
}
n, err = l.r.Read(p)
if int64(n) <= l.n {
l.n -= int64(n)
l.err = err
return n, err
}
n = int(l.n)
l.n = 0
// The server code and client code both use
// maxBytesReader. This "requestTooLarge" check is
// only used by the server code. To prevent binaries
// which only using the HTTP Client code (such as
// cmd/go) from also linking in the HTTP server, don't
// use a static type assertion to the server
// "*response" type. Check this interface instead:
type requestTooLarger interface {
requestTooLarge()
}
if res, ok := l.w.(requestTooLarger); ok {
res.requestTooLarge()
}
l.err = httpserver.MaxBytesExceededErr
return n, l.err
}
func (l *maxBytesReader) Close() error {
return l.r.Close()
}
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