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Merge qcrypto 2017/05/09 v1

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Merge remote-tracking branch 'danpb/tags/pull-qcrypto-2017-05-09-1' into staging

Merge qcrypto 2017/05/09 v1

# gpg: Signature made Tue 09 May 2017 09:43:47 AM EDT
# gpg:                using RSA key 0xBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>"
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>"
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* danpb/tags/pull-qcrypto-2017-05-09-1:
  crypto: qcrypto_random_bytes() now works on windows w/o any other crypto libs
  crypto: move 'opaque' parameter to (nearly) the end of parameter list
  List SASL config file under the cryptography maintainer's realm
  Default to GSSAPI (Kerberos) instead of DIGEST-MD5 for SASL

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2017-05-10 11:22:10 -04:00
commit 1effe6ad5e
12 changed files with 138 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
MAINTAINERS
View File

@ -1487,6 +1487,7 @@ S: Maintained
F: crypto/
F: include/crypto/
F: tests/test-crypto-*
F: qemu.sasl
Coroutines
M: Stefan Hajnoczi <stefanha@redhat.com>

6
block/crypto.c
View File

@ -56,10 +56,10 @@ static int block_crypto_probe_generic(QCryptoBlockFormat format,
static ssize_t block_crypto_read_func(QCryptoBlock *block,
void *opaque,
size_t offset,
uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp)
{
BlockDriverState *bs = opaque;
@ -83,10 +83,10 @@ struct BlockCryptoCreateData {
static ssize_t block_crypto_write_func(QCryptoBlock *block,
void *opaque,
size_t offset,
const uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp)
{
struct BlockCryptoCreateData *data = opaque;
@ -102,8 +102,8 @@ static ssize_t block_crypto_write_func(QCryptoBlock *block,
static ssize_t block_crypto_init_func(QCryptoBlock *block,
void *opaque,
size_t headerlen,
void *opaque,
Error **errp)
{
struct BlockCryptoCreateData *data = opaque;

13
crypto/block-luks.c
View File

@ -473,9 +473,9 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
* then encrypted.
*/
rv = readfunc(block,
opaque,
slot->key_offset * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
splitkey, splitkeylen,
opaque,
errp);
if (rv < 0) {
goto cleanup;
@ -676,9 +676,10 @@ qcrypto_block_luks_open(QCryptoBlock *block,
/* Read the entire LUKS header, minus the key material from
* the underlying device */
rv = readfunc(block, opaque, 0,
rv = readfunc(block, 0,
(uint8_t *)&luks->header,
sizeof(luks->header),
opaque,
errp);
if (rv < 0) {
ret = rv;
@ -1245,7 +1246,7 @@ qcrypto_block_luks_create(QCryptoBlock *block,
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
/* Reserve header space to match payload offset */
initfunc(block, opaque, block->payload_offset, &local_err);
initfunc(block, block->payload_offset, opaque, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto error;
@ -1267,9 +1268,10 @@ qcrypto_block_luks_create(QCryptoBlock *block,
/* Write out the partition header and key slot headers */
writefunc(block, opaque, 0,
writefunc(block, 0,
(const uint8_t *)&luks->header,
sizeof(luks->header),
opaque,
&local_err);
/* Delay checking local_err until we've byte-swapped */
@ -1295,10 +1297,11 @@ qcrypto_block_luks_create(QCryptoBlock *block,
/* Write out the master key material, starting at the
* sector immediately following the partition header. */
if (writefunc(block, opaque,
if (writefunc(block,
luks->header.key_slots[0].key_offset *
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
splitkey, splitkeylen,
opaque,
errp) != splitkeylen) {
goto error;
}

6
crypto/init.c
View File

@ -32,6 +32,8 @@
#include <gcrypt.h>
#endif
#include "crypto/random.h"
/* #define DEBUG_GNUTLS */
/*
@ -146,5 +148,9 @@ int qcrypto_init(Error **errp)
gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
#endif
if (qcrypto_random_init(errp) < 0) {
return -1;
}
return 0;
}

2
crypto/random-gcrypt.c
View File

@ -31,3 +31,5 @@ int qcrypto_random_bytes(uint8_t *buf,
gcry_randomize(buf, buflen, GCRY_STRONG_RANDOM);
return 0;
}
int qcrypto_random_init(Error **errp G_GNUC_UNUSED) { return 0; }

3
crypto/random-gnutls.c
View File

@ -41,3 +41,6 @@ int qcrypto_random_bytes(uint8_t *buf,
return 0;
}
int qcrypto_random_init(Error **errp G_GNUC_UNUSED) { return 0; }

45
crypto/random-platform.c
View File

@ -22,14 +22,16 @@
#include "crypto/random.h"
int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
size_t buflen G_GNUC_UNUSED,
Error **errp)
{
int fd;
int ret = -1;
int got;
#ifdef _WIN32
#include <Wincrypt.h>
static HCRYPTPROV hCryptProv;
#else
static int fd; /* a file handle to either /dev/urandom or /dev/random */
#endif
int qcrypto_random_init(Error **errp)
{
#ifndef _WIN32
/* TBD perhaps also add support for BSD getentropy / Linux
* getrandom syscalls directly */
fd = open("/dev/urandom", O_RDONLY);
@ -41,6 +43,25 @@ int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
error_setg(errp, "No /dev/urandom or /dev/random found");
return -1;
}
#else
if (!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,
CRYPT_SILENT | CRYPT_VERIFYCONTEXT)) {
error_setg_win32(errp, GetLastError(),
"Unable to create cryptographic provider");
return -1;
}
#endif
return 0;
}
int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
size_t buflen G_GNUC_UNUSED,
Error **errp)
{
#ifndef _WIN32
int ret = -1;
int got;
while (buflen > 0) {
got = read(fd, buf, buflen);
@ -59,6 +80,14 @@ int qcrypto_random_bytes(uint8_t *buf G_GNUC_UNUSED,
ret = 0;
cleanup:
close(fd);
return ret;
#else
if (!CryptGenRandom(hCryptProv, buflen, buf)) {
error_setg_win32(errp, GetLastError(),
"Unable to read random bytes");
return -1;
}
return 0;
#endif
}

6
include/crypto/block.h
View File

@ -30,22 +30,22 @@ typedef struct QCryptoBlock QCryptoBlock;
* and QCryptoBlockOpenOptions in qapi/crypto.json */
typedef ssize_t (*QCryptoBlockReadFunc)(QCryptoBlock *block,
void *opaque,
size_t offset,
uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp);
typedef ssize_t (*QCryptoBlockInitFunc)(QCryptoBlock *block,
void *opaque,
size_t headerlen,
void *opaque,
Error **errp);
typedef ssize_t (*QCryptoBlockWriteFunc)(QCryptoBlock *block,
void *opaque,
size_t offset,
const uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp);
/**

9
include/crypto/random.h
View File

@ -40,5 +40,14 @@ int qcrypto_random_bytes(uint8_t *buf,
size_t buflen,
Error **errp);
/**
* qcrypto_random_init:
* @errp: pointer to a NULL-initialized error object
*
* Initializes the handles used by qcrypto_random_bytes
*
* Returns 0 on success, -1 on error
*/
int qcrypto_random_init(Error **errp);
#endif /* QCRYPTO_RANDOM_H */

54
qemu-doc.texi
View File

@ -1732,37 +1732,45 @@ SASL service config /etc/sasl2/qemu.conf. If running QEMU as an
unprivileged user, an environment variable SASL_CONF_PATH can be used
to make it search alternate locations for the service config.
The default configuration might contain
If the TLS option is enabled for VNC, then it will provide session encryption,
otherwise the SASL mechanism will have to provide encryption. In the latter
case the list of possible plugins that can be used is drastically reduced. In
fact only the GSSAPI SASL mechanism provides an acceptable level of security
by modern standards. Previous versions of QEMU referred to the DIGEST-MD5
mechanism, however, it has multiple serious flaws described in detail in
RFC 6331 and thus should never be used any more. The SCRAM-SHA-1 mechanism
provides a simple username/password auth facility similar to DIGEST-MD5, but
does not support session encryption, so can only be used in combination with
TLS.
@example
mech_list: digest-md5
sasldb_path: /etc/qemu/passwd.db
@end example
This says to use the 'Digest MD5' mechanism, which is similar to the HTTP
Digest-MD5 mechanism. The list of valid usernames & passwords is maintained
in the /etc/qemu/passwd.db file, and can be updated using the saslpasswd2
command. While this mechanism is easy to configure and use, it is not
considered secure by modern standards, so only suitable for developers /
ad-hoc testing.
A more serious deployment might use Kerberos, which is done with the 'gssapi'
mechanism
When not using TLS the recommended configuration is
@example
mech_list: gssapi
keytab: /etc/qemu/krb5.tab
@end example
For this to work the administrator of your KDC must generate a Kerberos
principal for the server, with a name of 'qemu/somehost.example.com@@EXAMPLE.COM'
replacing 'somehost.example.com' with the fully qualified host name of the
machine running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
This says to use the 'GSSAPI' mechanism with the Kerberos v5 protocol, with
the server principal stored in /etc/qemu/krb5.tab. For this to work the
administrator of your KDC must generate a Kerberos principal for the server,
with a name of 'qemu/somehost.example.com@@EXAMPLE.COM' replacing
'somehost.example.com' with the fully qualified host name of the machine
running QEMU, and 'EXAMPLE.COM' with the Kerberos Realm.
Other configurations will be left as an exercise for the reader. It should
be noted that only Digest-MD5 and GSSAPI provides a SSF layer for data
encryption. For all other mechanisms, VNC should always be configured to
use TLS and x509 certificates to protect security credentials from snooping.
When using TLS, if username+password authentication is desired, then a
reasonable configuration is
@example
mech_list: scram-sha-1
sasldb_path: /etc/qemu/passwd.db
@end example
The saslpasswd2 program can be used to populate the passwd.db file with
accounts.
Other SASL configurations will be left as an exercise for the reader. Note that
all mechanisms except GSSAPI, should be combined with use of TLS to ensure a
secure data channel.
@node gdb_usage
@section GDB usage

56
qemu.sasl
View File

@ -1,36 +1,44 @@
# If you want to use the non-TLS socket, then you *must* include
# the GSSAPI or DIGEST-MD5 mechanisms, because they are the only
# ones that can offer session encryption as well as authentication.
# If you want to use VNC remotely without TLS, then you *must*
# pick a mechanism which provides session encryption as well
# as authentication.
#
# If you're only using TLS, then you can turn on any mechanisms
# If you are only using TLS, then you can turn on any mechanisms
# you like for authentication, because TLS provides the encryption
#
# Default to a simple username+password mechanism
# NB digest-md5 is no longer considered secure by current standards
mech_list: digest-md5
# Before you can use GSSAPI, you need a service principle on the
# KDC server for libvirt, and that to be exported to the keytab
# file listed below
#mech_list: gssapi
# If you are only using UNIX sockets then encryption is not
# required at all.
#
# You can also list many mechanisms at once, then the user can choose
# by adding '?auth=sasl.gssapi' to their libvirt URI, eg
# qemu+tcp://hostname/system?auth=sasl.gssapi
#mech_list: digest-md5 gssapi
# NB, previously DIGEST-MD5 was set as the default mechanism for
# QEMU VNC. Per RFC 6331 this is vulnerable to many serious security
# flaws as should no longer be used. Thus GSSAPI is now the default.
#
# To use GSSAPI requires that a QEMU service principal is
# added to the Kerberos server for each host running QEMU.
# This principal needs to be exported to the keytab file listed below
mech_list: gssapi
# If using TLS with VNC, or a UNIX socket only, it is possible to
# enable plugins which don't provide session encryption. The
# 'scram-sha-1' plugin allows plain username/password authentication
# to be performed
#
#mech_list: scram-sha-1
# You can also list many mechanisms at once, and the VNC server will
# negotiate which to use by considering the list enabled on the VNC
# client.
#mech_list: scram-sha-1 gssapi
# Some older builds of MIT kerberos on Linux ignore this option &
# instead need KRB5_KTNAME env var.
# For modern Linux, and other OS, this should be sufficient
#
# There is no default value here, uncomment if you need this
#keytab: /etc/qemu/krb5.tab
# This file needs to be populated with the service principal that
# was created on the Kerberos v5 server. If switching to a non-gssapi
# mechanism this can be commented out.
keytab: /etc/qemu/krb5.tab
# If using digest-md5 for username/passwds, then this is the file
# If using scram-sha-1 for username/passwds, then this is the file
# containing the passwds. Use 'saslpasswd2 -a qemu [username]'
# to add entries, and 'sasldblistusers2 -f [sasldb_path]' to browse it
sasldb_path: /etc/qemu/passwd.db
auxprop_plugin: sasldb
#sasldb_path: /etc/qemu/passwd.db

6
tests/test-crypto-block.c
View File

@ -187,10 +187,10 @@ static struct QCryptoBlockTestData {
static ssize_t test_block_read_func(QCryptoBlock *block,
void *opaque,
size_t offset,
uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp)
{
Buffer *header = opaque;
@ -204,8 +204,8 @@ static ssize_t test_block_read_func(QCryptoBlock *block,
static ssize_t test_block_init_func(QCryptoBlock *block,
void *opaque,
size_t headerlen,
void *opaque,
Error **errp)
{
Buffer *header = opaque;
@ -219,10 +219,10 @@ static ssize_t test_block_init_func(QCryptoBlock *block,
static ssize_t test_block_write_func(QCryptoBlock *block,
void *opaque,
size_t offset,
const uint8_t *buf,
size_t buflen,
void *opaque,
Error **errp)
{
Buffer *header = opaque;