8000 Fix client hang on receiving a non-EOF error from net.Conn by vzeroupper · Pull Request #676 · emersion/go-imap · GitHub
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Fix client hang on receiving a non-EOF error from net.Conn #676

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Fix client hang on receiving a non-EOF error from net.Conn #676

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18a34bc
fix client hang on receiving a non-EOF error from net.Conn
Mar 17, 2025
325cd60
Merge branch 'v2' into connection-hang-fix
vzeroupper Apr 10, 2025
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18 changes: 13 additions & 5 deletions imapclient/fetch.go
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Original file line number Diff line number Diff line change
Expand Up @@ -652,7 +652,7 @@ func (c *Client) handleFetch(seqNum uint32) error {

var (
item FetchItemData
done chan struct{}
done chan error
)
switch attName {
case "FLAGS":
Expand Down Expand Up @@ -738,7 +738,7 @@ func (c *Client) handleFetch(seqNum uint32) error {

var fetchLit imap.LiteralReader
if lit != nil {
done = make(chan struct{})
done = make(chan error)
fetchLit = &fetchLiteralReader{
LiteralReader: lit,
ch: done,
Expand Down Expand Up @@ -817,7 +817,9 @@ func (c *Client) handleFetch(seqNum uint32) error {
}
items <- item
if done != nil {
<-done
if err := <-done; err != nil {
return err
}
c.setReadTimeout(respReadTimeout)
}
return nil
Expand Down Expand Up @@ -1313,12 +1315,18 @@ func readSectionPart(dec *imapwire.Decoder) (part []int, dot bool) {

type fetchLiteralReader struct {
*imapwire.LiteralReader
ch chan<- struct{}
ch chan<- error
}

func (lit *fetchLiteralReader) Read(b []byte) (int, error) {
n, err := lit.LiteralReader.Read(b)
if err == io.EOF && lit.ch != nil {
if err == nil {
return n, nil
}
if lit.ch != nil {
if err != io.EOF {
lit.ch <- err
}
close(lit.ch)
lit.ch = nil
}
Expand Down
18 changes: 13 additions & 5 deletions internal/imapwire/decoder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -577,7 +577,7 @@ func (dec *Decoder) Literal(ptr *string) bool {
}
if dec.CheckBufferedLiteralFunc != nil {
if err := dec.CheckBufferedLiteralFunc(lit.Size(), nonSync); err != nil {
lit.cancel()
lit.cancel(nil)
return false
}
}
Expand Down Expand Up @@ -607,7 +607,7 @@ func (dec *Decoder) LiteralReader() (lit *LiteralReader, nonSync, ok bool) {
lit = &LiteralReader{
dec: dec,
size: size,
r: io.LimitReader(dec.r, size),
r: newLimitReader(dec.r, int(size)),
}
return lit, nonSync, true
}
Expand Down Expand Up @@ -639,16 +639,24 @@ func (lit *LiteralReader) Size() int64 {

func (lit *LiteralReader) Read(b []byte) (int, error) {
n, err := lit.r.Read(b)
if err == io.EOF {
lit.cancel()
if err != nil {
if err == io.EOF {
lit.cancel(nil)
} else {
lit.cancel(err)
}
}
return n, err
}

func (lit *LiteralReader) cancel() {
func (lit *LiteralReader) cancel(err error) {
if lit.dec == nil {
return
}

if err != nil {
lit.dec.err = err
}
lit.dec.literal = false
lit.dec = nil
}
45 changes: 45 additions & 0 deletions internal/imapwire/limit_reader.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,45 @@
package imapwire

import "io"

// A reader that returns io.EOF after a specified number of bytes.
//
// If EOF is received before the requested number of bytes, io.ErrUnexpectedEOF is returned.
type limitReader struct {
wrapped io.Reader
count int
}

func (reader *limitReader) Read(destination []byte) (int, error) {
if reader.count == 0 {
return 0, io.EOF
}
if len(destination) == 0 {
return 0, nil
}
if len(destination) > reader.count {
destination = destination[:reader.count]
}
read, err := reader.wrapped.Read(destination)
reader.count -= read
if err == nil {
if reader.count == 0 {
return read, io.EOF
}
return read, nil
}
if err == io.EOF {
if reader.count == 0 {
return read, io.EOF
}
return read, io.ErrUnexpectedEOF
}
return read, err
}

func newLimitReader(reader io.Reader, count int) *limitReader {
return &limitReader{
wrapped: reader,
count: count,
}
}
0