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package remotecontext
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"net/url"
"regexp"
"github.com/docker/docker/errdefs"
"github.com/docker/docker/pkg/ioutils"
"github.com/pkg/errors"
)
// When downloading remote contexts, limit the amount (in bytes)
// to be read from the response body in order to detect its Content-Type
const maxPreambleLength = 100
const acceptableRemoteMIME = `(?:application/(?:(?:x\-)?tar|octet\-stream|((?:x\-)?(?:gzip|bzip2?|xz)))|(?:text/plain))`
var mimeRe = regexp.MustCompile(acceptableRemoteMIME)
// downloadRemote context from a url and returns it, along with the parsed content type
func downloadRemote(remoteURL string) (string, io.ReadCloser, error) {
response, err := GetWithStatusError(remoteURL)
if err != nil {
return "", nil, errors.Wrapf(err, "error downloading remote context %s", remoteURL)
}
contentType, contextReader, err := inspectResponse(
response.Header.Get("Content-Type"),
response.Body,
response.ContentLength)
if err != nil {
response.Body.Close()
return "", nil, errors.Wrapf(err, "error detecting content type for remote %s", remoteURL)
}
return contentType, ioutils.NewReadCloserWrapper(contextReader, response.Body.Close), nil
}
// GetWithStatusError does an http.Get() and returns an error if the
// status code is 4xx or 5xx.
func GetWithStatusError(address string) (resp *http.Response, err error) {
if resp, err = http.Get(address); err != nil {
if uerr, ok := err.(*url.Error); ok {
if derr, ok := uerr.Err.(*net.DNSError); ok && !derr.IsTimeout {
return nil, errdefs.NotFound(err)
}
}
return nil, errdefs.System(err)
}
if resp.StatusCode < 400 {
return resp, nil
}
msg := fmt.Sprintf("failed to GET %s with status %s", address, resp.Status)
body, err := ioutil.ReadAll(resp.Body)
resp.Body.Close()
if err != nil {
return nil, errdefs.System(errors.New(msg + ": error reading body"))
}
msg += ": " + string(bytes.TrimSpace(body))
switch resp.StatusCode {
case http.StatusNotFound:
return nil, errdefs.NotFound(errors.New(msg))
case http.StatusBadRequest:
return nil, errdefs.InvalidParameter(errors.New(msg))
case http.StatusUnauthorized:
return nil, errdefs.Unauthorized(errors.New(msg))
case http.StatusForbidden:
return nil, errdefs.Forbidden(errors.New(msg))
}
return nil, errdefs.Unknown(errors.New(msg))
}
// inspectResponse looks into the http response data at r to determine whether its
// content-type is on the list of acceptable content types for remote build contexts.
// This function returns:
// - a string representation of the detected content-type
// - an io.Reader for the response body
// - an error value which will be non-nil either when something goes wrong while
// reading bytes from r or when the detected content-type is not acceptable.
func inspectResponse(ct string, r io.Reader, clen int64) (string, io.Reader, error) {
plen := clen
if plen <= 0 || plen > maxPreambleLength {
plen = maxPreambleLength
}
preamble := make([]byte, plen)
rlen, err := r.Read(preamble)
if rlen == 0 {
return ct, r, errors.New("empty response")
}
if err != nil && err != io.EOF {
return ct, r, err
}
preambleR := bytes.NewReader(preamble[:rlen])
bodyReader := io.MultiReader(preambleR, r)
// Some web servers will use application/octet-stream as the default
// content type for files without an extension (e.g. 'Dockerfile')
// so if we receive this value we better check for text content
contentType := ct
if len(ct) == 0 || ct == mimeTypes.OctetStream {
contentType, _, err = detectContentType(preamble)
if err != nil {
return contentType, bodyReader, err
}
}
contentType = selectAcceptableMIME(contentType)
var cterr error
if len(contentType) == 0 {
cterr = fmt.Errorf("unsupported Content-Type %q", ct)
contentType = ct
}
return contentType, bodyReader, cterr
}
func selectAcceptableMIME(ct string) string {
return mimeRe.FindString(ct)
}
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