Re: [PATCH v6 4/5] crypto: Add tls-cipher-suites object

[Laszlo Ersek <lersek@redhat.com>]

On 05/19/20 20:20, Philippe Mathieu-Daudé wrote:
> Example of use to dump:
>
>   $ qemu-system-x86_64 -S \
>     -object tls-cipher-suites,id=mysuite,priority=@SYSTEM,verbose=yes
>   Cipher suites for @SYSTEM:
>   - TLS_AES_256_GCM_SHA384                                0x13, 0x02      TLS1.3
>   - TLS_CHACHA20_POLY1305_SHA256                          0x13, 0x03      TLS1.3
>   - TLS_AES_128_GCM_SHA256                                0x13, 0x01      TLS1.3
>   - TLS_AES_128_CCM_SHA256                                0x13, 0x04      TLS1.3
>   - TLS_ECDHE_RSA_AES_256_GCM_SHA384                      0xc0, 0x30      TLS1.2
>   - TLS_ECDHE_RSA_CHACHA20_POLY1305                       0xcc, 0xa8      TLS1.2
>   - TLS_ECDHE_RSA_AES_256_CBC_SHA1                        0xc0, 0x14      TLS1.0
>   - TLS_ECDHE_RSA_AES_128_GCM_SHA256                      0xc0, 0x2f      TLS1.2
>   - TLS_ECDHE_RSA_AES_128_CBC_SHA1                        0xc0, 0x13      TLS1.0
>   - TLS_ECDHE_ECDSA_AES_256_GCM_SHA384                    0xc0, 0x2c      TLS1.2
>   - TLS_ECDHE_ECDSA_CHACHA20_POLY1305                     0xcc, 0xa9      TLS1.2
>   - TLS_ECDHE_ECDSA_AES_256_CCM                           0xc0, 0xad      TLS1.2
>   - TLS_ECDHE_ECDSA_AES_256_CBC_SHA1                      0xc0, 0x0a      TLS1.0
>   - TLS_ECDHE_ECDSA_AES_128_GCM_SHA256                    0xc0, 0x2b      TLS1.2
>   - TLS_ECDHE_ECDSA_AES_128_CCM                           0xc0, 0xac      TLS1.2
>   - TLS_ECDHE_ECDSA_AES_128_CBC_SHA1                      0xc0, 0x09      TLS1.0
>   - TLS_RSA_AES_256_GCM_SHA384                            0x00, 0x9d      TLS1.2
>   - TLS_RSA_AES_256_CCM                                   0xc0, 0x9d      TLS1.2
>   - TLS_RSA_AES_256_CBC_SHA1                              0x00, 0x35      TLS1.0
>   - TLS_RSA_AES_128_GCM_SHA256                            0x00, 0x9c      TLS1.2
>   - TLS_RSA_AES_128_CCM                                   0xc0, 0x9c      TLS1.2
>   - TLS_RSA_AES_128_CBC_SHA1                              0x00, 0x2f      TLS1.0
>   - TLS_DHE_RSA_AES_256_GCM_SHA384                        0x00, 0x9f      TLS1.2
>   - TLS_DHE_RSA_CHACHA20_POLY1305                         0xcc, 0xaa      TLS1.2
>   - TLS_DHE_RSA_AES_256_CCM                               0xc0, 0x9f      TLS1.2
>   - TLS_DHE_RSA_AES_256_CBC_SHA1                          0x00, 0x39      TLS1.0
>   - TLS_DHE_RSA_AES_128_GCM_SHA256                        0x00, 0x9e      TLS1.2
>   - TLS_DHE_RSA_AES_128_CCM                               0xc0, 0x9e      TLS1.2
>   - TLS_DHE_RSA_AES_128_CBC_SHA1                          0x00, 0x33      TLS1.0
>   total: 29 ciphers
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  include/crypto/tls-cipher-suites.h |  39 +++++++++
>  crypto/tls-cipher-suites.c         | 133 +++++++++++++++++++++++++++++
>  crypto/Makefile.objs               |   1 +
>  3 files changed, 173 insertions(+)
>  create mode 100644 include/crypto/tls-cipher-suites.h
>  create mode 100644 crypto/tls-cipher-suites.c
>
> diff --git a/include/crypto/tls-cipher-suites.h b/include/crypto/tls-cipher-suites.h
> new file mode 100644
> index 0000000000..31e92916e1
> --- /dev/null
> +++ b/include/crypto/tls-cipher-suites.h
> @@ -0,0 +1,39 @@
> +/*
> + * QEMU TLS Cipher Suites
> + *
> + * Copyright (c) 2019 Red Hat, Inc.
> + *
> + * Author: Philippe Mathieu-Daudé <philmd@redhat.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef QCRYPTO_TLSCIPHERSUITES_H
> +#define QCRYPTO_TLSCIPHERSUITES_H
> +
> +#include "qom/object.h"
> +#include "crypto/tlscreds.h"
> +
> +#define TYPE_QCRYPTO_TLS_CIPHER_SUITES "tls-cipher-suites"
> +#define QCRYPTO_TLS_CIPHER_SUITES(obj) \
> +    OBJECT_CHECK(QCryptoTLSCipherSuites, (obj), TYPE_QCRYPTO_TLS_CIPHER_SUITES)
> +
> +/*
> + * IANA registered TLS ciphers:
> + * https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-4
> + */
> +typedef struct {
> +    uint8_t data[2];
> +} IANA_TLS_CIPHER;

(1) I propose marking this as QEMU_PACKED, even if only for
documentation purposes.

> +
> +typedef struct QCryptoTLSCipherSuites {
> +    /* <private> */
> +    QCryptoTLSCreds parent_obj;
> +
> +    /* <public> */
> +    bool verbose;
> +    IANA_TLS_CIPHER *cipher_list;
> +    unsigned cipher_count;
> +} QCryptoTLSCipherSuites;
> +
> +#endif /* QCRYPTO_TLSCIPHERSUITES_H */
> diff --git a/crypto/tls-cipher-suites.c b/crypto/tls-cipher-suites.c
> new file mode 100644
> index 0000000000..c6c51359bd
> --- /dev/null
> +++ b/crypto/tls-cipher-suites.c
> @@ -0,0 +1,133 @@
> +/*
> + * QEMU TLS Cipher Suites
> + *
> + * Copyright (c) 2019 Red Hat, Inc.
> + *
> + * Author: Philippe Mathieu-Daudé <philmd@redhat.com>
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qom/object_interfaces.h"
> +#include "qemu/error-report.h"
> +#include "crypto/tlscreds.h"
> +#include "crypto/tls-cipher-suites.h"
> +
> +static void parse_cipher_suites(QCryptoTLSCipherSuites *s,
> +                                const char *priority_name, Error **errp)
> +{
> +#ifdef CONFIG_GNUTLS
> +    int ret;
> +    unsigned int idx;
> +    const char *name;
> +    const char *err;
> +    gnutls_protocol_t version;
> +    gnutls_priority_t pcache;
> +
> +    assert(priority_name);
> +    ret = gnutls_priority_init(&pcache, priority_name, &err);
> +    if (ret < 0) {
> +        error_setg(errp, "Syntax error using priority '%s': %s",
> +                   priority_name, gnutls_strerror(ret));
> +        return;
> +    }
> +
> +    if (s->verbose) {
> +        fprintf(stderr, "Cipher suites for %s:\n", priority_name);
> +    }
> +    for (size_t i = 0;; i++) {
> +        ret = gnutls_priority_get_cipher_suite_index(pcache, i, &idx);
> +        if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {
> +            break;
> +        }
> +        if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE) {
> +            continue;
> +        }
> +        s->cipher_list = g_renew(IANA_TLS_CIPHER,
> +                                 s->cipher_list, s->cipher_count + 1);
> +
> +        name = gnutls_cipher_suite_info(idx,
> +                                        s->cipher_list[s->cipher_count].data,
> +                                        NULL, NULL, NULL, &version);
> +        if (name != NULL) {
> +            if (s->verbose) {
> +                fprintf(stderr, "- %-50s\t0x%02x, 0x%02x\t%s\n", name,
> +                        s->cipher_list[s->cipher_count].data[0],
> +                        s->cipher_list[s->cipher_count].data[1],
> +                        gnutls_protocol_get_name(version));
> +            }
> +            s->cipher_count++;
> +       }
> +    }

(2) I propose turning this into two loops (in sequence), so that we
don't have to call g_renew() in any loop body. The first loop would just
filter & count, then we'd allocate once, and the second loop would
filter and populate.

Alternatively, I sometimes use the following pattern:

    unsigned mode;

    for (mode = 0; mode < 2; mode++) {
        size_t i;

        for (i = 0;; i++) {
            int ret;
            unsigned idx;
            const char *name;
            IANA_TLS_CIPHER cipher;
            gnutls_protocol_t version;

            ret = gnutls_priority_get_cipher_suite_index(pcache, i, &idx);
            if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {
                break;
            }
            if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE) {
               continue;
            }

            name = gnutls_cipher_suite_info(idx, &cipher, NULL, NULL, NULL,
                                            &version);
            if (name == NULL) {
              continue;
            }

            if (mode == 1) {
                if (s->verbose) {
                    /* ... log "name" and "cipher" ... */
                }
                s->cipher_list[s->cipher_count] = cipher;
            }
            s->cipher_count++;
        }

        if (mode == 0) {
            if (s->cipher_count == 0) {
                break;
            }
            s->cipher_list = g_new(IANA_TLS_CIPHER, s->cipher_count);
            s->cipher_count = 0;
        }
    }

Feel free to ignore either point I've brought up.

No other comments from me for this patch.

Thanks,
Laszlo


> +    if (s->verbose) {
> +        fprintf(stderr, "total: %u ciphers\n", s->cipher_count);
> +    }
> +    gnutls_priority_deinit(pcache);
> +#else
> +    error_setg(errp, "GNU TLS not available");
> +#endif /* CONFIG_GNUTLS */
> +}
> +
> +static void qcrypto_tls_cipher_suites_complete(UserCreatable *uc, Error **errp)
> +{
> +    QCryptoTLSCreds *s = QCRYPTO_TLS_CREDS(uc);
> +
> +    if (!s->priority) {
> +        error_setg(errp, "'priority' property is not set");
> +        return;
> +    }
> +    parse_cipher_suites(QCRYPTO_TLS_CIPHER_SUITES(s), s->priority, errp);
> +}
> +
> +static void qcrypto_tls_cipher_suites_set_verbose(Object *obj, bool value,
> +                                                 Error **errp G_GNUC_UNUSED)
> +{
> +    QCRYPTO_TLS_CIPHER_SUITES(obj)->verbose = value;
> +}
> +
> +
> +static bool qcrypto_tls_cipher_suites_get_verbose(Object *obj,
> +                                                 Error **errp G_GNUC_UNUSED)
> +{
> +    return QCRYPTO_TLS_CIPHER_SUITES(obj)->verbose;
> +}
> +
> +static void qcrypto_tls_cipher_suites_finalize(Object *obj)
> +{
> +    QCryptoTLSCipherSuites *s = QCRYPTO_TLS_CIPHER_SUITES(obj);
> +
> +    g_free(s->cipher_list);
> +}
> +
> +static void qcrypto_tls_cipher_suites_class_init(ObjectClass *oc, void *data)
> +{
> +    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);
> +
> +    ucc->complete = qcrypto_tls_cipher_suites_complete;
> +
> +    object_class_property_add_bool(oc, "verbose",
> +                                   qcrypto_tls_cipher_suites_get_verbose,
> +                                   qcrypto_tls_cipher_suites_set_verbose);
> +}
> +
> +static const TypeInfo qcrypto_tls_cipher_suites_info = {
> +    .parent = TYPE_QCRYPTO_TLS_CREDS,
> +    .name = TYPE_QCRYPTO_TLS_CIPHER_SUITES,
> +    .instance_size = sizeof(QCryptoTLSCipherSuites),
> +    .instance_finalize = qcrypto_tls_cipher_suites_finalize,
> +    .class_size = sizeof(QCryptoTLSCredsClass),
> +    .class_init = qcrypto_tls_cipher_suites_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +        { TYPE_USER_CREATABLE },
> +        { }
> +    }
> +};
> +
> +static void qcrypto_tls_cipher_suites_register_types(void)
> +{
> +    type_register_static(&qcrypto_tls_cipher_suites_info);
> +}
> +
> +type_init(qcrypto_tls_cipher_suites_register_types);
> diff --git a/crypto/Makefile.objs b/crypto/Makefile.objs
> index c2a371b0b4..ce706d322a 100644
> --- a/crypto/Makefile.objs
> +++ b/crypto/Makefile.objs
> @@ -13,6 +13,7 @@ crypto-obj-y += cipher.o
>  crypto-obj-$(CONFIG_AF_ALG) += afalg.o
>  crypto-obj-$(CONFIG_AF_ALG) += cipher-afalg.o
>  crypto-obj-$(CONFIG_AF_ALG) += hash-afalg.o
> +crypto-obj-y += tls-cipher-suites.o
>  crypto-obj-y += tlscreds.o
>  crypto-obj-y += tlscredsanon.o
>  crypto-obj-y += tlscredspsk.o
>