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[Qemu-devel] [PATCH] io: return 0 for EOF in TLS session read after shut
From: |
Daniel P . Berrangé |
Subject: |
[Qemu-devel] [PATCH] io: return 0 for EOF in TLS session read after shutdown |
Date: |
Mon, 19 Nov 2018 13:42:28 +0000 |
GNUTLS takes a paranoid approach when seeing 0 bytes returned by the
underlying OS read() function. It will consider this an error and
return GNUTLS_E_PREMATURE_TERMINATION instead of propagating the 0
return value. It expects apps to arrange for clean termination at
the protocol level and not rely on seeing EOF from a read call to
detect shutdown. This is to harden apps against a malicious 3rd party
causing termination of the sockets layer.
This is unhelpful for the QEMU NBD code which does have a clean
protocol level shutdown, but still relies on seeing 0 from the I/O
channel read in the coroutine handling incoming replies.
The upshot is that when using a plain NBD connection shutdown is
silent, but when using TLS, the client spams the console with
Cannot read from TLS channel: Broken pipe
The NBD connection has, however, called qio_channel_shutdown()
at this point to indicate that it is done with I/O. This gives
the opportunity to optimize the code such that when the channel
has been shutdown in the read direction, the error code
GNUTLS_E_PREMATURE_TERMINATION gets turned into a '0' return
instead of an error.
Signed-off-by: Daniel P. Berrangé <address@hidden>
---
crypto/tlssession.c | 3 +++
include/io/channel-tls.h | 1 +
include/io/channel.h | 6 +++---
io/channel-tls.c | 5 +++++
4 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/crypto/tlssession.c b/crypto/tlssession.c
index 2f28fa7f71..0dedd4af52 100644
--- a/crypto/tlssession.c
+++ b/crypto/tlssession.c
@@ -473,6 +473,9 @@ qcrypto_tls_session_read(QCryptoTLSSession *session,
case GNUTLS_E_INTERRUPTED:
errno = EINTR;
break;
+ case GNUTLS_E_PREMATURE_TERMINATION:
+ errno = ECONNABORTED;
+ break;
default:
errno = EIO;
break;
diff --git a/include/io/channel-tls.h b/include/io/channel-tls.h
index 87fcaf9146..fdbdf12feb 100644
--- a/include/io/channel-tls.h
+++ b/include/io/channel-tls.h
@@ -48,6 +48,7 @@ struct QIOChannelTLS {
QIOChannel parent;
QIOChannel *master;
QCryptoTLSSession *session;
+ QIOChannelShutdown shutdown;
};
/**
diff --git a/include/io/channel.h b/include/io/channel.h
index e8cdadb0b0..da2f138200 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -51,9 +51,9 @@ enum QIOChannelFeature {
typedef enum QIOChannelShutdown QIOChannelShutdown;
enum QIOChannelShutdown {
- QIO_CHANNEL_SHUTDOWN_BOTH,
- QIO_CHANNEL_SHUTDOWN_READ,
- QIO_CHANNEL_SHUTDOWN_WRITE,
+ QIO_CHANNEL_SHUTDOWN_READ = 1,
+ QIO_CHANNEL_SHUTDOWN_WRITE = 2,
+ QIO_CHANNEL_SHUTDOWN_BOTH = 3,
};
typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
diff --git a/io/channel-tls.c b/io/channel-tls.c
index 9628e6fa47..c98ead21b0 100644
--- a/io/channel-tls.c
+++ b/io/channel-tls.c
@@ -275,6 +275,9 @@ static ssize_t qio_channel_tls_readv(QIOChannel *ioc,
} else {
return QIO_CHANNEL_ERR_BLOCK;
}
+ } else if (errno == ECONNABORTED &&
+ (tioc->shutdown & QIO_CHANNEL_SHUTDOWN_READ)) {
+ return 0;
}
error_setg_errno(errp, errno,
@@ -357,6 +360,8 @@ static int qio_channel_tls_shutdown(QIOChannel *ioc,
{
QIOChannelTLS *tioc = QIO_CHANNEL_TLS(ioc);
+ tioc->shutdown |= how;
+
return qio_channel_shutdown(tioc->master, how, errp);
}
--
2.19.1
- [Qemu-devel] [PATCH] io: return 0 for EOF in TLS session read after shutdown,
Daniel P . Berrangé <=