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crypto: propagate errors from TLS session I/O callbacks

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GNUTLS doesn't know how to perform I/O on anything other than plain
FDs, so the TLS session provides it with some I/O callbacks. The
GNUTLS API design requires these callbacks to return a unix errno
value, which means we're currently loosing the useful QEMU "Error"
object.

This changes the I/O callbacks in QEMU to stash the "Error" object
in the QCryptoTLSSession class, and fetch it when seeing an I/O
error returned from GNUTLS, thus preserving useful error messages.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2024-03-15 14:29:11 +00:00
parent 57941c9c86
commit 97f7bf113e
4 changed files with 108 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
crypto/tlssession.c
View File

@ -44,6 +44,13 @@ struct QCryptoTLSSession {
QCryptoTLSSessionReadFunc readFunc;
void *opaque;
char *peername;
/*
* Allow concurrent reads and writes, so track
* errors separately
*/
Error *rerr;
Error *werr;
};
@ -54,6 +61,9 @@ qcrypto_tls_session_free(QCryptoTLSSession *session)
return;
}
error_free(session->rerr);
error_free(session->werr);
gnutls_deinit(session->handle);
g_free(session->hostname);
g_free(session->peername);
@ -67,13 +77,26 @@ static ssize_t
qcrypto_tls_session_push(void *opaque, const void *buf, size_t len)
{
QCryptoTLSSession *session = opaque;
ssize_t ret;
if (!session->writeFunc) {
errno = EIO;
return -1;
};
return session->writeFunc(buf, len, session->opaque);
error_free(session->werr);
session->werr = NULL;
ret = session->writeFunc(buf, len, session->opaque, &session->werr);
if (ret == QCRYPTO_TLS_SESSION_ERR_BLOCK) {
errno = EAGAIN;
return -1;
} else if (ret < 0) {
errno = EIO;
return -1;
} else {
return ret;
}
}
@ -81,13 +104,26 @@ static ssize_t
qcrypto_tls_session_pull(void *opaque, void *buf, size_t len)
{
QCryptoTLSSession *session = opaque;
ssize_t ret;
if (!session->readFunc) {
errno = EIO;
return -1;
};
return session->readFunc(buf, len, session->opaque);
error_free(session->rerr);
session->rerr = NULL;
ret = session->readFunc(buf, len, session->opaque, &session->rerr);
if (ret == QCRYPTO_TLS_SESSION_ERR_BLOCK) {
errno = EAGAIN;
return -1;
} else if (ret < 0) {
errno = EIO;
return -1;
} else {
return ret;
}
}
#define TLS_PRIORITY_ADDITIONAL_ANON "+ANON-DH"
@ -449,10 +485,15 @@ qcrypto_tls_session_write(QCryptoTLSSession *session,
if (ret < 0) {
if (ret == GNUTLS_E_AGAIN) {
return QCRYPTO_TLS_SESSION_ERR_BLOCK;
} else {
if (session->werr) {
error_propagate(errp, session->werr);
session->werr = NULL;
} else {
error_setg(errp,
"Cannot write to TLS channel: %s",
gnutls_strerror(ret));
}
return -1;
}
}
@ -476,10 +517,15 @@ qcrypto_tls_session_read(QCryptoTLSSession *session,
} else if ((ret == GNUTLS_E_PREMATURE_TERMINATION) &&
gracefulTermination){
return 0;
} else {
if (session->rerr) {
error_propagate(errp, session->rerr);
session->rerr = NULL;
} else {
error_setg(errp,
"Cannot read from TLS channel: %s",
gnutls_strerror(ret));
}
return -1;
}
}
@ -506,12 +552,22 @@ qcrypto_tls_session_handshake(QCryptoTLSSession *session,
if (ret == GNUTLS_E_INTERRUPTED ||
ret == GNUTLS_E_AGAIN) {
ret = 1;
} else {
if (session->rerr || session->werr) {
error_setg(errp, "TLS handshake failed: %s: %s",
gnutls_strerror(ret),
error_get_pretty(session->rerr ?
session->rerr : session->werr));
} else {
error_setg(errp, "TLS handshake failed: %s",
gnutls_strerror(ret));
}
ret = -1;
}
}
error_free(session->rerr);
error_free(session->werr);
session->rerr = session->werr = NULL;
return ret;
}

10
include/crypto/tlssession.h
View File

@ -178,12 +178,18 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoTLSSession, qcrypto_tls_session_free)
int qcrypto_tls_session_check_credentials(QCryptoTLSSession *sess,
Error **errp);
/*
* These must return QCRYPTO_TLS_SESSION_ERR_BLOCK if the I/O
* would block, but on other errors, must fill 'errp'
*/
typedef ssize_t (*QCryptoTLSSessionWriteFunc)(const char *buf,
size_t len,
void *opaque);
void *opaque,
Error **errp);
typedef ssize_t (*QCryptoTLSSessionReadFunc)(char *buf,
size_t len,
void *opaque);
void *opaque,
Error **errp);
/**
* qcrypto_tls_session_set_callbacks:

18
io/channel-tls.c
View File

@ -28,17 +28,16 @@
static ssize_t qio_channel_tls_write_handler(const char *buf,
size_t len,
void *opaque)
void *opaque,
Error **errp)
{
QIOChannelTLS *tioc = QIO_CHANNEL_TLS(opaque);
ssize_t ret;
ret = qio_channel_write(tioc->master, buf, len, NULL);
ret = qio_channel_write(tioc->master, buf, len, errp);
if (ret == QIO_CHANNEL_ERR_BLOCK) {
errno = EAGAIN;
return -1;
return QCRYPTO_TLS_SESSION_ERR_BLOCK;
} else if (ret < 0) {
errno = EIO;
return -1;
}
return ret;
@ -46,17 +45,16 @@ static ssize_t qio_channel_tls_write_handler(const char *buf,
static ssize_t qio_channel_tls_read_handler(char *buf,
size_t len,
void *opaque)
void *opaque,
Error **errp)
{
QIOChannelTLS *tioc = QIO_CHANNEL_TLS(opaque);
ssize_t ret;
ret = qio_channel_read(tioc->master, buf, len, NULL);
ret = qio_channel_read(tioc->master, buf, len, errp);
if (ret == QIO_CHANNEL_ERR_BLOCK) {
errno = EAGAIN;
return -1;
return QCRYPTO_TLS_SESSION_ERR_BLOCK;
} else if (ret < 0) {
errno = EIO;
return -1;
}
return ret;

30
tests/unit/test-crypto-tlssession.c
View File

@ -35,18 +35,40 @@
#define PSKFILE WORKDIR "keys.psk"
#define KEYFILE WORKDIR "key-ctx.pem"
static ssize_t testWrite(const char *buf, size_t len, void *opaque)
static ssize_t
testWrite(const char *buf, size_t len, void *opaque, Error **errp)
{
int *fd = opaque;
int ret;
return write(*fd, buf, len);
ret = write(*fd, buf, len);
if (ret < 0) {
if (errno == EAGAIN) {
return QCRYPTO_TLS_SESSION_ERR_BLOCK;
} else {
error_setg_errno(errp, errno, "unable to write");
return -1;
}
}
return ret;
}
static ssize_t testRead(char *buf, size_t len, void *opaque)
static ssize_t
testRead(char *buf, size_t len, void *opaque, Error **errp)
{
int *fd = opaque;
int ret;
return read(*fd, buf, len);
ret = read(*fd, buf, len);
if (ret < 0) {
if (errno == EAGAIN) {
return QCRYPTO_TLS_SESSION_ERR_BLOCK;
} else {
error_setg_errno(errp, errno, "unable to read");
return -1;
}
}
return ret;
}
static QCryptoTLSCreds *test_tls_creds_psk_create(