crypto: add QCryptoSecret object class for password/key handling

Introduce a new QCryptoSecret object class which will be used
for providing passwords and keys to other objects which need
sensitive credentials.

The new object can provide secret values directly as properties,
or indirectly via a file. The latter includes support for file
descriptor passing syntax on UNIX platforms. Ordinarily passing
secret values directly as properties is insecure, since they
are visible in process listings, or in log files showing the
CLI args / QMP commands. It is possible to use AES-256-CBC to
encrypt the secret values though, in which case all that is
visible is the ciphertext.  For ad hoc developer testing though,
it is fine to provide the secrets directly without encryption
so this is not explicitly forbidden.

The anticipated scenario is that libvirtd will create a random
master key per QEMU instance (eg /var/run/libvirt/qemu/$VMNAME.key)
and will use that key to encrypt all passwords it provides to
QEMU via '-object secret,....'.  This avoids the need for libvirt
(or other mgmt apps) to worry about file descriptor passing.

It also makes life easier for people who are scripting the
management of QEMU, for whom FD passing is significantly more
complex.

Providing data inline (insecure, only for ad hoc dev testing)

  $QEMU -object secret,id=sec0,data=letmein

Providing data indirectly in raw format

  printf "letmein" > mypasswd.txt
  $QEMU -object secret,id=sec0,file=mypasswd.txt

Providing data indirectly in base64 format

  $QEMU -object secret,id=sec0,file=mykey.b64,format=base64

Providing data with encryption

  $QEMU -object secret,id=master0,file=mykey.b64,format=base64 \
        -object secret,id=sec0,data=[base64 ciphertext],\
	           keyid=master0,iv=[base64 IV],format=base64

Note that 'format' here refers to the format of the ciphertext
data. The decrypted data must always be in raw byte format.

More examples are shown in the updated docs.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

2 files changed, 514 insertions, 0 deletions

diff --git a/crypto/Makefile.objs b/crypto/Makefile.objs
index b2a0e0b38e..a3135f1ddf 100644
--- a/crypto/Makefile.objs
+++ b/crypto/Makefile.objs
@@ -7,6 +7,7 @@ crypto-obj-y += tlscreds.o
 crypto-obj-y += tlscredsanon.o
 crypto-obj-y += tlscredsx509.o
 crypto-obj-y += tlssession.o
+crypto-obj-y += secret.o
 
 # Let the userspace emulators avoid linking gnutls/etc
 crypto-aes-obj-y = aes.o
diff --git a/crypto/secret.c b/crypto/secret.c
new file mode 100644
index 0000000000..9a9257a7f0
--- /dev/null
+++ b/crypto/secret.c
@@ -0,0 +1,513 @@
+/*
+ * QEMU crypto secret support
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "crypto/secret.h"
+#include "crypto/cipher.h"
+#include "qom/object_interfaces.h"
+#include "qemu/base64.h"
+#include "trace.h"
+
+
+static void
+qcrypto_secret_load_data(QCryptoSecret *secret,
+                         uint8_t **output,
+                         size_t *outputlen,
+                         Error **errp)
+{
+    char *data = NULL;
+    size_t length = 0;
+    GError *gerr = NULL;
+
+    *output = NULL;
+    *outputlen = 0;
+
+    if (secret->file) {
+        if (secret->data) {
+            error_setg(errp,
+                       "'file' and 'data' are mutually exclusive");
+            return;
+        }
+        if (!g_file_get_contents(secret->file, &data, &length, &gerr)) {
+            error_setg(errp,
+                       "Unable to read %s: %s",
+                       secret->file, gerr->message);
+            g_error_free(gerr);
+            return;
+        }
+        *output = (uint8_t *)data;
+        *outputlen = length;
+    } else if (secret->data) {
+        *outputlen = strlen(secret->data);
+        *output = (uint8_t *)g_strdup(secret->data);
+    } else {
+        error_setg(errp, "Either 'file' or 'data' must be provided");
+    }
+}
+
+
+static void qcrypto_secret_decrypt(QCryptoSecret *secret,
+                                   const uint8_t *input,
+                                   size_t inputlen,
+                                   uint8_t **output,
+                                   size_t *outputlen,
+                                   Error **errp)
+{
+    uint8_t *key = NULL, *ciphertext = NULL, *iv = NULL;
+    size_t keylen, ciphertextlen, ivlen;
+    QCryptoCipher *aes = NULL;
+    uint8_t *plaintext = NULL;
+
+    *output = NULL;
+    *outputlen = 0;
+
+    if (qcrypto_secret_lookup(secret->keyid,
+                              &key, &keylen,
+                              errp) < 0) {
+        goto cleanup;
+    }
+
+    if (keylen != 32) {
+        error_setg(errp, "Key should be 32 bytes in length");
+        goto cleanup;
+    }
+
+    if (!secret->iv) {
+        error_setg(errp, "IV is required to decrypt secret");
+        goto cleanup;
+    }
+
+    iv = qbase64_decode(secret->iv, -1, &ivlen, errp);
+    if (!iv) {
+        goto cleanup;
+    }
+    if (ivlen != 16) {
+        error_setg(errp, "IV should be 16 bytes in length not %zu",
+                   ivlen);
+        goto cleanup;
+    }
+
+    aes = qcrypto_cipher_new(QCRYPTO_CIPHER_ALG_AES_256,
+                             QCRYPTO_CIPHER_MODE_CBC,
+                             key, keylen,
+                             errp);
+    if (!aes) {
+        goto cleanup;
+    }
+
+    if (qcrypto_cipher_setiv(aes, iv, ivlen, errp) < 0) {
+        goto cleanup;
+    }
+
+    if (secret->format == QCRYPTO_SECRET_FORMAT_BASE64) {
+        ciphertext = qbase64_decode((const gchar*)input,
+                                    inputlen,
+                                    &ciphertextlen,
+                                    errp);
+        if (!ciphertext) {
+            goto cleanup;
+        }
+        plaintext = g_new0(uint8_t, ciphertextlen + 1);
+    } else {
+        ciphertextlen = inputlen;
+        plaintext = g_new0(uint8_t, inputlen + 1);
+    }
+    if (qcrypto_cipher_decrypt(aes,
+                               ciphertext ? ciphertext : input,
+                               plaintext,
+                               ciphertextlen,
+                               errp) < 0) {
+        plaintext = NULL;
+        goto cleanup;
+    }
+
+    if (plaintext[ciphertextlen - 1] > 16 ||
+        plaintext[ciphertextlen - 1] > ciphertextlen) {
+        error_setg(errp, "Incorrect number of padding bytes (%d) "
+                   "found on decrypted data",
+                   (int)plaintext[ciphertextlen - 1]);
+        g_free(plaintext);
+        plaintext = NULL;
+        goto cleanup;
+    }
+
+    /* Even though plaintext may contain arbitrary NUL
+     * ensure it is explicitly NUL terminated.
+     */
+    ciphertextlen -= plaintext[ciphertextlen - 1];
+    plaintext[ciphertextlen] = '\0';
+
+    *output = plaintext;
+    *outputlen = ciphertextlen;
+
+ cleanup:
+    g_free(ciphertext);
+    g_free(iv);
+    g_free(key);
+    qcrypto_cipher_free(aes);
+}
+
+
+static void qcrypto_secret_decode(const uint8_t *input,
+                                  size_t inputlen,
+                                  uint8_t **output,
+                                  size_t *outputlen,
+                                  Error **errp)
+{
+    *output = qbase64_decode((const gchar*)input,
+                             inputlen,
+                             outputlen,
+                             errp);
+}
+
+
+static void
+qcrypto_secret_prop_set_loaded(Object *obj,
+                               bool value,
+                               Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    if (value) {
+        Error *local_err = NULL;
+        uint8_t *input = NULL;
+        size_t inputlen = 0;
+        uint8_t *output = NULL;
+        size_t outputlen = 0;
+
+        qcrypto_secret_load_data(secret, &input, &inputlen, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
+
+        if (secret->keyid) {
+            qcrypto_secret_decrypt(secret, input, inputlen,
+                                   &output, &outputlen, &local_err);
+            g_free(input);
+            if (local_err) {
+                error_propagate(errp, local_err);
+                return;
+            }
+            input = output;
+            inputlen = outputlen;
+        } else {
+            if (secret->format != QCRYPTO_SECRET_FORMAT_RAW) {
+                qcrypto_secret_decode(input, inputlen,
+                                      &output, &outputlen, &local_err);
+                g_free(input);
+                if (local_err) {
+                    error_propagate(errp, local_err);
+                    return;
+                }
+                input = output;
+                inputlen = outputlen;
+            }
+        }
+
+        secret->rawdata = input;
+        secret->rawlen = inputlen;
+    } else {
+        g_free(secret->rawdata);
+        secret->rawlen = 0;
+    }
+}
+
+
+static bool
+qcrypto_secret_prop_get_loaded(Object *obj,
+                               Error **errp G_GNUC_UNUSED)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+    return secret->data != NULL;
+}
+
+
+static void
+qcrypto_secret_prop_set_format(Object *obj,
+                               int value,
+                               Error **errp G_GNUC_UNUSED)
+{
+    QCryptoSecret *creds = QCRYPTO_SECRET(obj);
+
+    creds->format = value;
+}
+
+
+static int
+qcrypto_secret_prop_get_format(Object *obj,
+                               Error **errp G_GNUC_UNUSED)
+{
+    QCryptoSecret *creds = QCRYPTO_SECRET(obj);
+
+    return creds->format;
+}
+
+
+static void
+qcrypto_secret_prop_set_data(Object *obj,
+                             const char *value,
+                             Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    g_free(secret->data);
+    secret->data = g_strdup(value);
+}
+
+
+static char *
+qcrypto_secret_prop_get_data(Object *obj,
+                             Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+    return g_strdup(secret->data);
+}
+
+
+static void
+qcrypto_secret_prop_set_file(Object *obj,
+                             const char *value,
+                             Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    g_free(secret->file);
+    secret->file = g_strdup(value);
+}
+
+
+static char *
+qcrypto_secret_prop_get_file(Object *obj,
+                             Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+    return g_strdup(secret->file);
+}
+
+
+static void
+qcrypto_secret_prop_set_iv(Object *obj,
+                           const char *value,
+                           Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    g_free(secret->iv);
+    secret->iv = g_strdup(value);
+}
+
+
+static char *
+qcrypto_secret_prop_get_iv(Object *obj,
+                           Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+    return g_strdup(secret->iv);
+}
+
+
+static void
+qcrypto_secret_prop_set_keyid(Object *obj,
+                              const char *value,
+                              Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    g_free(secret->keyid);
+    secret->keyid = g_strdup(value);
+}
+
+
+static char *
+qcrypto_secret_prop_get_keyid(Object *obj,
+                              Error **errp)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+    return g_strdup(secret->keyid);
+}
+
+
+static void
+qcrypto_secret_complete(UserCreatable *uc, Error **errp)
+{
+    object_property_set_bool(OBJECT(uc), true, "loaded", errp);
+}
+
+
+static void
+qcrypto_secret_init(Object *obj)
+{
+    object_property_add_bool(obj, "loaded",
+                             qcrypto_secret_prop_get_loaded,
+                             qcrypto_secret_prop_set_loaded,
+                             NULL);
+    object_property_add_enum(obj, "format",
+                             "QCryptoSecretFormat",
+                             QCryptoSecretFormat_lookup,
+                             qcrypto_secret_prop_get_format,
+                             qcrypto_secret_prop_set_format,
+                             NULL);
+    object_property_add_str(obj, "data",
+                            qcrypto_secret_prop_get_data,
+                            qcrypto_secret_prop_set_data,
+                            NULL);
+    object_property_add_str(obj, "file",
+                            qcrypto_secret_prop_get_file,
+                            qcrypto_secret_prop_set_file,
+                            NULL);
+    object_property_add_str(obj, "keyid",
+                            qcrypto_secret_prop_get_keyid,
+                            qcrypto_secret_prop_set_keyid,
+                            NULL);
+    object_property_add_str(obj, "iv",
+                            qcrypto_secret_prop_get_iv,
+                            qcrypto_secret_prop_set_iv,
+                            NULL);
+}
+
+
+static void
+qcrypto_secret_finalize(Object *obj)
+{
+    QCryptoSecret *secret = QCRYPTO_SECRET(obj);
+
+    g_free(secret->iv);
+    g_free(secret->file);
+    g_free(secret->keyid);
+    g_free(secret->rawdata);
+    g_free(secret->data);
+}
+
+static void
+qcrypto_secret_class_init(ObjectClass *oc, void *data)
+{
+    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
+
+    ucc->complete = qcrypto_secret_complete;
+}
+
+
+int qcrypto_secret_lookup(const char *secretid,
+                          uint8_t **data,
+                          size_t *datalen,
+                          Error **errp)
+{
+    Object *obj;
+    QCryptoSecret *secret;
+
+    obj = object_resolve_path_component(
+        object_get_objects_root(), secretid);
+    if (!obj) {
+        error_setg(errp, "No secret with id '%s'", secretid);
+        return -1;
+    }
+
+    secret = (QCryptoSecret *)
+        object_dynamic_cast(obj,
+                            TYPE_QCRYPTO_SECRET);
+    if (!secret) {
+        error_setg(errp, "Object with id '%s' is not a secret",
+                   secretid);
+        return -1;
+    }
+
+    if (!secret->rawdata) {
+        error_setg(errp, "Secret with id '%s' has no data",
+                   secretid);
+        return -1;
+    }
+
+    *data = g_new0(uint8, secret->rawlen + 1);
+    memcpy(*data, secret->rawdata, secret->rawlen);
+    (*data)[secret->rawlen] = '\0';
+    *datalen = secret->rawlen;
+
+    return 0;
+}
+
+
+char *qcrypto_secret_lookup_as_utf8(const char *secretid,
+                                    Error **errp)
+{
+    uint8_t *data;
+    size_t datalen;
+
+    if (qcrypto_secret_lookup(secretid,
+                              &data,
+                              &datalen,
+                              errp) < 0) {
+        return NULL;
+    }
+
+    if (!g_utf8_validate((const gchar*)data, datalen, NULL)) {
+        error_setg(errp,
+                   "Data from secret %s is not valid UTF-8",
+                   secretid);
+        g_free(data);
+        return NULL;
+    }
+
+    return (char *)data;
+}
+
+
+char *qcrypto_secret_lookup_as_base64(const char *secretid,
+                                      Error **errp)
+{
+    uint8_t *data;
+    size_t datalen;
+    char *ret;
+
+    if (qcrypto_secret_lookup(secretid,
+                              &data,
+                              &datalen,
+                              errp) < 0) {
+        return NULL;
+    }
+
+    ret = g_base64_encode(data, datalen);
+    g_free(data);
+    return ret;
+}
+
+
+static const TypeInfo qcrypto_secret_info = {
+    .parent = TYPE_OBJECT,
+    .name = TYPE_QCRYPTO_SECRET,
+    .instance_size = sizeof(QCryptoSecret),
+    .instance_init = qcrypto_secret_init,
+    .instance_finalize = qcrypto_secret_finalize,
+    .class_size = sizeof(QCryptoSecretClass),
+    .class_init = qcrypto_secret_class_init,
+    .interfaces = (InterfaceInfo[]) {
+        { TYPE_USER_CREATABLE },
+        { }
+    }
+};
+
+
+static void
+qcrypto_secret_register_types(void)
+{
+    type_register_static(&qcrypto_secret_info);
+}
+
+
+type_init(qcrypto_secret_register_types);