Commit 9a44023c authored by Bryan C. Mills's avatar Bryan C. Mills

cmd/go/internal/web: include snippets of plain-text server responses in error detail

For the server response to be displayed, the response must be served
as type text/plain with charset us-ascii or utf-8, and must consist of
only graphic characters and whitespace.

We truncate the server response at the first blank line or after 8
lines or a fixed number of characters, and tab-indent (if multiple
lines) to ensure that the response is offset from ordinary go command
output.

Fixes #30748

Change-Id: I0bc1d734737e456e3251aee2252463b6355e8c97
Reviewed-on: https://go-review.googlesource.com/c/go/+/189783
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: default avatarJay Conrod <jayconrod@google.com>
parent 54b7afb4
......@@ -10,12 +10,15 @@
package web
import (
"bytes"
"fmt"
"io"
"io/ioutil"
"net/url"
"os"
"strings"
"unicode"
"unicode/utf8"
)
// SecurityMode specifies whether a function should make network
......@@ -34,9 +37,32 @@ type HTTPError struct {
URL string // redacted
Status string
StatusCode int
Err error // underlying error, if known
Detail string // limited to maxErrorDetailLines and maxErrorDetailBytes
}
const (
maxErrorDetailLines = 8
maxErrorDetailBytes = maxErrorDetailLines * 81
)
func (e *HTTPError) Error() string {
if e.Detail != "" {
detailSep := " "
if strings.ContainsRune(e.Detail, '\n') {
detailSep = "\n\t"
}
return fmt.Sprintf("reading %s: %v\n\tserver response:%s%s", e.URL, e.Status, detailSep, e.Detail)
}
if err := e.Err; err != nil {
if pErr, ok := e.Err.(*os.PathError); ok && strings.HasSuffix(e.URL, pErr.Path) {
// Remove the redundant copy of the path.
err = pErr.Err
}
return fmt.Sprintf("reading %s: %v", e.URL, err)
}
return fmt.Sprintf("reading %s: %v", e.URL, e.Status)
}
......@@ -44,6 +70,10 @@ func (e *HTTPError) Is(target error) bool {
return target == os.ErrNotExist && (e.StatusCode == 404 || e.StatusCode == 410)
}
func (e *HTTPError) Unwrap() error {
return e.Err
}
// GetBytes returns the body of the requested resource, or an error if the
// response status was not http.StatusOK.
//
......@@ -69,16 +99,69 @@ type Response struct {
Status string
StatusCode int
Header map[string][]string
Body io.ReadCloser
Body io.ReadCloser // Either the original body or &errorDetail.
fileErr error
errorDetail errorDetailBuffer
}
// Err returns an *HTTPError corresponding to the response r.
// It returns nil if the response r has StatusCode 200 or 0 (unset).
// If the response r has StatusCode 200 or 0 (unset), Err returns nil.
// Otherwise, Err may read from r.Body in order to extract relevant error detail.
func (r *Response) Err() error {
if r.StatusCode == 200 || r.StatusCode == 0 {
return nil
}
return &HTTPError{URL: r.URL, Status: r.Status, StatusCode: r.StatusCode}
return &HTTPError{
URL: r.URL,
Status: r.Status,
StatusCode: r.StatusCode,
Err: r.fileErr,
Detail: r.formatErrorDetail(),
}
}
// formatErrorDetail converts r.errorDetail (a prefix of the output of r.Body)
// into a short, tab-indented summary.
func (r *Response) formatErrorDetail() string {
if r.Body != &r.errorDetail {
return "" // Error detail collection not enabled.
}
// Ensure that r.errorDetail has been populated.
_, _ = io.Copy(ioutil.Discard, r.Body)
s := r.errorDetail.buf.String()
if !utf8.ValidString(s) {
return "" // Don't try to recover non-UTF-8 error messages.
}
for _, r := range s {
if !unicode.IsGraphic(r) && !unicode.IsSpace(r) {
return "" // Don't let the server do any funny business with the user's terminal.
}
}
var detail strings.Builder
for i, line := range strings.Split(s, "\n") {
if strings.TrimSpace(line) == "" {
break // Stop at the first blank line.
}
if i > 0 {
detail.WriteString("\n\t")
}
if i >= maxErrorDetailLines {
detail.WriteString("[Truncated: too many lines.]")
break
}
if detail.Len()+len(line) > maxErrorDetailBytes {
detail.WriteString("[Truncated: too long.]")
break
}
detail.WriteString(line)
}
return detail.String()
}
// Get returns the body of the HTTP or HTTPS resource specified at the given URL.
......@@ -131,3 +214,39 @@ func Join(u *url.URL, path string) *url.URL {
j.RawPath = strings.TrimSuffix(u.RawPath, "/") + "/" + strings.TrimPrefix(path, "/")
return &j
}
// An errorDetailBuffer is an io.ReadCloser that copies up to
// maxErrorDetailLines into a buffer for later inspection.
type errorDetailBuffer struct {
r io.ReadCloser
buf strings.Builder
bufLines int
}
func (b *errorDetailBuffer) Close() error {
return b.r.Close()
}
func (b *errorDetailBuffer) Read(p []byte) (n int, err error) {
n, err = b.r.Read(p)
// Copy the first maxErrorDetailLines+1 lines into b.buf,
// discarding any further lines.
//
// Note that the read may begin or end in the middle of a UTF-8 character,
// so don't try to do anything fancy with characters that encode to larger
// than one byte.
if b.bufLines <= maxErrorDetailLines {
for _, line := range bytes.SplitAfterN(p[:n], []byte("\n"), maxErrorDetailLines-b.bufLines) {
b.buf.Write(line)
if len(line) > 0 && line[len(line)-1] == '\n' {
b.bufLines++
if b.bufLines > maxErrorDetailLines {
break
}
}
}
}
return n, err
}
......@@ -14,7 +14,7 @@ package web
import (
"crypto/tls"
"fmt"
"io/ioutil"
"mime"
"net/http"
urlpkg "net/url"
"os"
......@@ -64,7 +64,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
Status: "404 testing",
StatusCode: 404,
Header: make(map[string][]string),
Body: ioutil.NopCloser(strings.NewReader("")),
Body: http.NoBody,
}
if cfg.BuildX {
fmt.Fprintf(os.Stderr, "# get %s: %v (%.3fs)\n", Redacted(url), res.Status, time.Since(start).Seconds())
......@@ -167,6 +167,7 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
if cfg.BuildX {
fmt.Fprintf(os.Stderr, "# get %s: %v (%.3fs)\n", Redacted(fetched), res.Status, time.Since(start).Seconds())
}
r := &Response{
URL: Redacted(fetched),
Status: res.Status,
......@@ -174,6 +175,20 @@ func get(security SecurityMode, url *urlpkg.URL) (*Response, error) {
Header: map[string][]string(res.Header),
Body: res.Body,
}
if res.StatusCode != http.StatusOK {
contentType := res.Header.Get("Content-Type")
if mediaType, params, _ := mime.ParseMediaType(contentType); mediaType == "text/plain" {
switch charset := strings.ToLower(params["charset"]); charset {
case "us-ascii", "utf-8", "":
// Body claims to be plain text in UTF-8 or a subset thereof.
// Try to extract a useful error message from it.
r.errorDetail.r = res.Body
r.Body = &r.errorDetail
}
}
}
return r, nil
}
......@@ -190,6 +205,7 @@ func getFile(u *urlpkg.URL) (*Response, error) {
Status: http.StatusText(http.StatusNotFound),
StatusCode: http.StatusNotFound,
Body: http.NoBody,
fileErr: err,
}, nil
}
......@@ -199,6 +215,7 @@ func getFile(u *urlpkg.URL) (*Response, error) {
Status: http.StatusText(http.StatusForbidden),
StatusCode: http.StatusForbidden,
Body: http.NoBody,
fileErr: err,
}, nil
}
......
......@@ -8,6 +8,8 @@ env GOSUMDB=off
# basic auth should fail.
env NETRC=$WORK/empty
! go list all
stderr '^\tserver response: ACCESS DENIED, buddy$'
stderr '^\tserver response: File\? What file\?$'
# With credentials from a netrc file, it should succeed.
env NETRC=$WORK/netrc
......
[!net] skip
env GO111MODULE=on
env GOSUMDB=off
env GOPROXY=direct
# Server responses should be truncated to some reasonable number of lines.
# (For now, exactly eight.)
! go list -m vcs-test.golang.org/auth/ormanylines@latest
stderr '\tserver response:\n(.|\n)*\tline 8\n\t\[Truncated: too many lines.\]$'
# Server responses should be truncated to some reasonable number of characters.
! go list -m vcs-test.golang.org/auth/oronelongline@latest
! stderr 'blah{40}'
stderr '\tserver response: \[Truncated: too long\.\]$'
# Responses from servers using the 'mod' protocol should be propagated.
! go list -m vcs-test.golang.org/go/modauth404@latest
stderr '\tserver response: File\? What file\?'
......@@ -7,10 +7,13 @@ env GOPATH=$WORK/gopath1
# With a file-based proxy with an empty checksum directory,
# downloading a new module should fail, even if a subsequent
# proxy contains a more complete mirror of the sum database.
#
# TODO(bcmills): The error message here is a bit redundant.
# It comes from the sumweb package, which isn't yet producing structured errors.
[windows] env GOPROXY=file:///$WORK/sumproxy,https://proxy.golang.org
[!windows] env GOPROXY=file://$WORK/sumproxy,https://proxy.golang.org
! go get -d golang.org/x/text@v0.3.2
stderr '^verifying golang.org/x/text.*: Not Found'
stderr '^verifying golang.org/x/text@v0.3.2: golang.org/x/text@v0.3.2: reading file://.*/sumdb/sum.golang.org/lookup/golang.org/x/text@v0.3.2: (no such file or directory|.*cannot find the file specified.*)'
# If the proxy does not claim to support the database,
# checksum verification should fall through to the next proxy,
......
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