tls_gnutls.c

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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#include "common.h"
#include "tls.h"


/*
 * It looks like gnutls does not provide access to client/server_random and
 * master_key. This is somewhat unfortunate since these are needed for key
 * derivation in EAP-{TLS,TTLS,PEAP,FAST}. Workaround for now is a horrible
 * hack that copies the gnutls_session_int definition from gnutls_int.h so that
 * we can get the needed information.
 */

typedef u8 uint8;
#define TLS_RANDOM_SIZE 32
#define TLS_MASTER_SIZE 48
typedef unsigned char opaque;
typedef struct {
    uint8 suite[2];
} cipher_suite_st;

typedef struct {
        gnutls_connection_end_t entity;
        gnutls_kx_algorithm_t kx_algorithm;
        gnutls_cipher_algorithm_t read_bulk_cipher_algorithm;
        gnutls_mac_algorithm_t read_mac_algorithm;
        gnutls_compression_method_t read_compression_algorithm;
        gnutls_cipher_algorithm_t write_bulk_cipher_algorithm;
        gnutls_mac_algorithm_t write_mac_algorithm;
        gnutls_compression_method_t write_compression_algorithm;
        cipher_suite_st current_cipher_suite;
        opaque master_secret[TLS_MASTER_SIZE];
        opaque client_random[TLS_RANDOM_SIZE];
        opaque server_random[TLS_RANDOM_SIZE];
        /* followed by stuff we are not interested in */
} security_parameters_st;

struct gnutls_session_int {
        security_parameters_st security_parameters;
        /* followed by things we are not interested in */
};

static int tls_gnutls_ref_count = 0;

struct tls_connection {
        gnutls_session session;
        char *subject_match, *altsubject_match;
        int read_alerts, write_alerts, failed;

        u8 *pre_shared_secret;
        size_t pre_shared_secret_len;
        int established;
        int verify_peer;

        u8 *push_buf, *pull_buf, *pull_buf_offset;
        size_t push_buf_len, pull_buf_len;

        gnutls_certificate_credentials_t xcred;
};


static void tls_log_func(int level, const char *msg)
{
        char *s, *pos;
        if (level == 6 || level == 7) {
                /* These levels seem to be mostly I/O debug and msg dumps */
                return;
        }

        s = strdup(msg);
        if (s == NULL)
                return;

        pos = s;
        while (*pos != '\0') {
                if (*pos == '\n') {
                        *pos = '\0';
                        break;
                }
                pos++;
        }
        wpa_printf(level > 3 ? MSG_MSGDUMP : MSG_DEBUG,
                   "gnutls<%d> %s", level, s);
        free(s);
}


extern int wpa_debug_show_keys;

void * tls_init(const struct tls_config *conf)
{
        /* Because of the horrible hack to get master_secret and client/server
         * random, we need to make sure that the gnutls version is something
         * that is expected to have same structure definition for the session
         * data.. */
        const char *ver;
        const char *ok_ver[] = { "1.2.3", "1.2.4", "1.2.5", "1.2.6", NULL };
        int i;

        if (tls_gnutls_ref_count == 0 && gnutls_global_init() < 0)
                return NULL;
        tls_gnutls_ref_count++;

        ver = gnutls_check_version(NULL);
        if (ver == NULL)
                return NULL;
        wpa_printf(MSG_DEBUG, "%s - gnutls version %s", __func__, ver);
        for (i = 0; ok_ver[i]; i++) {
                if (strcmp(ok_ver[i], ver) == 0)
                        break;
        }
        if (ok_ver[i] == NULL) {
                wpa_printf(MSG_INFO, "Untested gnutls version %s - this needs "
                           "to be tested and enabled in tls_gnutls.c", ver);
                return NULL;
        }

        gnutls_global_set_log_function(tls_log_func);
        if (wpa_debug_show_keys)
                gnutls_global_set_log_level(11);
        return (void *) 1;
}


void tls_deinit(void *ssl_ctx)
{
        tls_gnutls_ref_count--;
        if (tls_gnutls_ref_count == 0)
                gnutls_global_deinit();
}


int tls_get_errors(void *ssl_ctx)
{
        return 0;
}


static ssize_t tls_pull_func(gnutls_transport_ptr ptr, void *buf,
                             size_t len)
{
        struct tls_connection *conn = (struct tls_connection *) ptr;
        u8 *end;
        if (conn->pull_buf == NULL) {
                errno = EWOULDBLOCK;
                return -1;
        }

        end = conn->pull_buf + conn->pull_buf_len;
        if (end - conn->pull_buf_offset < len)
                len = end - conn->pull_buf_offset;
        memcpy(buf, conn->pull_buf_offset, len);
        conn->pull_buf_offset += len;
        if (conn->pull_buf_offset == end) {
                wpa_printf(MSG_DEBUG, "%s - pull_buf consumed", __func__);
                free(conn->pull_buf);
                conn->pull_buf = conn->pull_buf_offset = NULL;
                conn->pull_buf_len = 0;
        } else {
                wpa_printf(MSG_DEBUG, "%s - %d bytes remaining in pull_buf",
                           __func__, end - conn->pull_buf_offset);
        }
        return len;
}


static ssize_t tls_push_func(gnutls_transport_ptr ptr, const void *buf,
                             size_t len)
{
        struct tls_connection *conn = (struct tls_connection *) ptr;
        u8 *nbuf;

        nbuf = realloc(conn->push_buf, conn->push_buf_len + len);
        if (nbuf == NULL) {
                errno = ENOMEM;
                return -1;
        }
        memcpy(nbuf + conn->push_buf_len, buf, len);
        conn->push_buf = nbuf;
        conn->push_buf_len += len;

        return len;
}


struct tls_connection * tls_connection_init(void *ssl_ctx)
{
        struct tls_connection *conn;
        const int cert_types[2] = { GNUTLS_CRT_X509, 0 };
        const int protos[2] = { GNUTLS_TLS1, 0 };


        conn = malloc(sizeof(*conn));
        if (conn == NULL)
                return NULL;
        memset(conn, 0, sizeof(*conn));
        if (gnutls_init(&conn->session, GNUTLS_CLIENT) < 0) {
                wpa_printf(MSG_INFO, "TLS: Failed to initialize new TLS "
                           "connection");
                free(conn);
                return NULL;
        }

        gnutls_set_default_priority(conn->session);
        gnutls_certificate_type_set_priority(conn->session, cert_types);
        gnutls_protocol_set_priority(conn->session, protos);

        gnutls_transport_set_pull_function(conn->session, tls_pull_func);
        gnutls_transport_set_push_function(conn->session, tls_push_func);
        gnutls_transport_set_ptr(conn->session, (gnutls_transport_ptr) conn);

        gnutls_certificate_allocate_credentials(&conn->xcred);

        return conn;
}


void tls_connection_deinit(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return;
        gnutls_certificate_free_credentials(conn->xcred);
        gnutls_deinit(conn->session);
        free(conn->pre_shared_secret);
        free(conn->subject_match);
        free(conn->altsubject_match);
        free(conn->push_buf);
        free(conn->pull_buf);
        free(conn);
}


int tls_connection_established(void *ssl_ctx, struct tls_connection *conn)
{
        return conn ? conn->established : 0;
}


int tls_connection_shutdown(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return -1;

        /* Shutdown previous TLS connection without notifying the peer
         * because the connection was already terminated in practice
         * and "close notify" shutdown alert would confuse AS. */
        gnutls_bye(conn->session, GNUTLS_SHUT_RDWR);
        free(conn->push_buf);
        conn->push_buf = NULL;
        conn->push_buf_len = 0;
        conn->established = 0;
        /* TODO: what to do trigger new handshake for re-auth? */
        return 0;
}


#if 0
static int tls_match_altsubject(X509 *cert, const char *match)
{
        GENERAL_NAME *gen;
        char *field, *tmp;
        void *ext;
        int i, found = 0;
        size_t len;

        ext = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL);

        for (i = 0; ext && i < sk_GENERAL_NAME_num(ext); i++) {
                gen = sk_GENERAL_NAME_value(ext, i);
                switch (gen->type) {
                case GEN_EMAIL:
                        field = "EMAIL";
                        break;
                case GEN_DNS:
                        field = "DNS";
                        break;
                case GEN_URI:
                        field = "URI";
                        break;
                default:
                        field = NULL;
                        wpa_printf(MSG_DEBUG, "TLS: altSubjectName: "
                                   "unsupported type=%d", gen->type);
                        break;
                }

                if (!field)
                        continue;

                wpa_printf(MSG_DEBUG, "TLS: altSubjectName: %s:%s",
                           field, gen->d.ia5->data);
                len = strlen(field) + 1 + strlen((char *) gen->d.ia5->data) +
                        1;
                tmp = malloc(len);
                if (tmp == NULL)
                        continue;
                snprintf(tmp, len, "%s:%s", field, gen->d.ia5->data);
                if (strstr(tmp, match))
                        found++;
                free(tmp);
        }

        return found;
}
#endif


#if 0
static int tls_verify_cb(int preverify_ok, X509_STORE_CTX *x509_ctx)
{
        char buf[256];
        X509 *err_cert;
        int err, depth;
        SSL *ssl;
        struct tls_connection *conn;
        char *match, *altmatch;

        err_cert = X509_STORE_CTX_get_current_cert(x509_ctx);
        err = X509_STORE_CTX_get_error(x509_ctx);
        depth = X509_STORE_CTX_get_error_depth(x509_ctx);
        ssl = X509_STORE_CTX_get_ex_data(x509_ctx,
                                         SSL_get_ex_data_X509_STORE_CTX_idx());
        X509_NAME_oneline(X509_get_subject_name(err_cert), buf, sizeof(buf));

        conn = SSL_get_app_data(ssl);
        match = conn ? conn->subject_match : NULL;
        altmatch = conn ? conn->altsubject_match : NULL;

        if (!preverify_ok) {
                wpa_printf(MSG_WARNING, "TLS: Certificate verification failed,"
                           " error %d (%s) depth %d for '%s'", err,
                           X509_verify_cert_error_string(err), depth, buf);
        } else {
                wpa_printf(MSG_DEBUG, "TLS: tls_verify_cb - "
                           "preverify_ok=%d err=%d (%s) depth=%d buf='%s'",
                           preverify_ok, err,
                           X509_verify_cert_error_string(err), depth, buf);
                if (depth == 0 && match && strstr(buf, match) == NULL) {
                        wpa_printf(MSG_WARNING, "TLS: Subject '%s' did not "
                                   "match with '%s'", buf, match);
                        preverify_ok = 0;
                } else if (depth == 0 && altmatch &&
                           !tls_match_altsubject(err_cert, altmatch)) {
                        wpa_printf(MSG_WARNING, "TLS: altSubjectName match "
                                   "'%s' not found", altmatch);
                        preverify_ok = 0;
                }
        }

        return preverify_ok;
}
#endif


int tls_connection_set_params(void *tls_ctx, struct tls_connection *conn,
                              const struct tls_connection_params *params)
{
        int ret;

        if (conn == NULL || params == NULL)
                return -1;

        free(conn->subject_match);
        conn->subject_match = NULL;
        if (params->subject_match) {
                conn->subject_match = strdup(params->subject_match);
                if (conn->subject_match == NULL)
                        return -1;
        }

        free(conn->altsubject_match);
        conn->altsubject_match = NULL;
        if (params->altsubject_match) {
                conn->altsubject_match = strdup(params->altsubject_match);
                if (conn->altsubject_match == NULL)
                        return -1;
        }

        /* TODO: gnutls_certificate_set_verify_flags(xcred, flags); 
         * to force peer validation(?) */

        if (params->ca_cert) {
                conn->verify_peer = 1;
                ret = gnutls_certificate_set_x509_trust_file(
                        conn->xcred, params->ca_cert, GNUTLS_X509_FMT_PEM);
                if (ret < 0) {
                        wpa_printf(MSG_DEBUG, "Failed to read CA cert '%s' "
                                   "in PEM format: %s", params->ca_cert,
                                   gnutls_strerror(ret));
                        ret = gnutls_certificate_set_x509_trust_file(
                                conn->xcred, params->ca_cert,
                                GNUTLS_X509_FMT_DER);
                        if (ret < 0) {
                                wpa_printf(MSG_DEBUG, "Failed to read CA cert "
                                           "'%s' in DER format: %s",
                                           params->ca_cert,
                                           gnutls_strerror(ret));
                        }
                }
        }

        if (params->client_cert && params->private_key) {
                /* TODO: private_key_passwd? */
                ret = gnutls_certificate_set_x509_key_file(
                        conn->xcred, params->client_cert, params->private_key,
                        GNUTLS_X509_FMT_PEM);
                if (ret < 0) {
                        wpa_printf(MSG_DEBUG, "Failed to read client cert/key "
                                   "in PEM format: %s", gnutls_strerror(ret));
                        ret = gnutls_certificate_set_x509_key_file(
                                conn->xcred, params->client_cert,
                                params->private_key, GNUTLS_X509_FMT_DER);
                        if (ret < 0) {
                                wpa_printf(MSG_DEBUG, "Failed to read client "
                                           "cert/key in DER format: %s",
                                           gnutls_strerror(ret));
                                return ret;
                        }
                }
        }

        ret = gnutls_credentials_set(conn->session, GNUTLS_CRD_CERTIFICATE,
                                     conn->xcred);
        if (ret < 0) {
                wpa_printf(MSG_INFO, "Failed to configure credentials: %s",
                           gnutls_strerror(ret));
        }

        return ret;
}


int tls_global_ca_cert(void *_ssl_ctx, const char *ca_cert)
{
        /* TODO */
        return -1;
}


int tls_global_set_verify(void *ssl_ctx, int check_crl)
{
        /* TODO */
        return -1;
}


int tls_connection_set_verify(void *ssl_ctx, struct tls_connection *conn,
                              int verify_peer)
{
        if (conn == NULL)
                return -1;

        /* TODO */

        return 1;
}


int tls_global_client_cert(void *_ssl_ctx, const char *client_cert)
{
        /* TODO */
        return -1;
}


int tls_global_private_key(void *_ssl_ctx, const char *private_key,
                           const char *private_key_passwd)
{
        /* TODO */
        return -1;
}


int tls_connection_get_keys(void *ssl_ctx, struct tls_connection *conn,
                            struct tls_keys *keys)
{
        security_parameters_st *sec;

        if (conn == NULL || conn->session == NULL || keys == NULL)
                return -1;

        memset(keys, 0, sizeof(*keys));
        sec = &conn->session->security_parameters;
        keys->master_key = sec->master_secret;
        keys->master_key_len = TLS_MASTER_SIZE;
        keys->client_random = sec->client_random;
        keys->client_random_len = TLS_RANDOM_SIZE;
        keys->server_random = sec->server_random;
        keys->server_random_len = TLS_RANDOM_SIZE;

        return 0;
}


static int tls_connection_verify_peer(struct tls_connection *conn)
{
        unsigned int status, num_certs, i;
        time_t now;
        const gnutls_datum_t *certs;
        gnutls_x509_crt_t cert;

        if (gnutls_certificate_verify_peers2(conn->session, &status) < 0) {
                wpa_printf(MSG_INFO, "TLS: Failed to verify peer "
                           "certificate chain");
                return -1;
        }

        if (conn->verify_peer && (status & GNUTLS_CERT_INVALID)) {
                wpa_printf(MSG_INFO, "TLS: Peer certificate not trusted");
                return -1;
        }

        if (status & GNUTLS_CERT_SIGNER_NOT_FOUND) {
                wpa_printf(MSG_INFO, "TLS: Peer certificate does not have a "
                           "known issuer");
                return -1;
        }

        if (status & GNUTLS_CERT_REVOKED) {
                wpa_printf(MSG_INFO, "TLS: Peer certificate has been revoked");
                return -1;
        }

        now = time(NULL);

        certs = gnutls_certificate_get_peers(conn->session, &num_certs);
        if (certs == NULL) {
                wpa_printf(MSG_INFO, "TLS: No peer certificate chain "
                           "received");
                return -1;
        }

        for (i = 0; i < num_certs; i++) {
                char *buf;
                size_t len;
                if (gnutls_x509_crt_init(&cert) < 0) {
                        wpa_printf(MSG_INFO, "TLS: Certificate initialization "
                                   "failed");
                        return -1;
                }

                if (gnutls_x509_crt_import(cert, &certs[i],
                                           GNUTLS_X509_FMT_DER) < 0) {
                        wpa_printf(MSG_INFO, "TLS: Could not parse peer "
                                   "certificate %d/%d", i + 1, num_certs);
                        gnutls_x509_crt_deinit(cert);
                        return -1;
                }

                gnutls_x509_crt_get_dn(cert, NULL, &len);
                len++;
                buf = malloc(len + 1);
                if (buf) {
                        buf[0] = buf[len] = '\0';
                        gnutls_x509_crt_get_dn(cert, buf, &len);
                }
                wpa_printf(MSG_DEBUG, "TLS: Peer cert chain %d/%d: %s",
                           i + 1, num_certs, buf);

                if (i == 0) {
                        /* TODO: validate subject_match and altsubject_match */
                }

                free(buf);

                if (gnutls_x509_crt_get_expiration_time(cert) < now ||
                    gnutls_x509_crt_get_activation_time(cert) > now) {
                        wpa_printf(MSG_INFO, "TLS: Peer certificate %d/%d is "
                                   "not valid at this time",
                                   i + 1, num_certs);
                        gnutls_x509_crt_deinit(cert);
                        return -1;
                }

                gnutls_x509_crt_deinit(cert);
        }

        return 0;
}


u8 * tls_connection_handshake(void *ssl_ctx, struct tls_connection *conn,
                              const u8 *in_data, size_t in_len,
                              size_t *out_len)
{
        u8 *out_data;
        int ret;

        if (in_data && in_len) {
                if (conn->pull_buf) {
                        wpa_printf(MSG_DEBUG, "%s - %d bytes remaining in "
                                   "pull_buf", __func__, conn->pull_buf_len);
                        free(conn->pull_buf);
                }
                conn->pull_buf = malloc(in_len);
                if (conn->pull_buf == NULL)
                        return NULL;
                memcpy(conn->pull_buf, in_data, in_len);
                conn->pull_buf_offset = conn->pull_buf;
                conn->pull_buf_len = in_len;
        }

        ret = gnutls_handshake(conn->session);
        if (ret < 0) {
                switch (ret) {
                case GNUTLS_E_AGAIN:
                        break;
                case GNUTLS_E_FATAL_ALERT_RECEIVED:
                        wpa_printf(MSG_DEBUG, "%s - received fatal '%s' alert",
                                   __func__, gnutls_alert_get_name(
                                           gnutls_alert_get(conn->session)));
                        conn->read_alerts++;
                        /* continue */
                default:
                        wpa_printf(MSG_DEBUG, "%s - gnutls_handshake failed "
                                   "-> %s", __func__, gnutls_strerror(ret));
                        conn->failed++;
                }
        } else {
                wpa_printf(MSG_DEBUG, "TLS: Handshake completed successfully");
                if (conn->verify_peer && tls_connection_verify_peer(conn)) {
                        wpa_printf(MSG_INFO, "TLS: Peer certificate chain "
                                   "failed validation");
                        conn->failed++;
                        return NULL;
                }
                conn->established = 1;
                if (conn->push_buf == NULL) {
                        /* Need to return something to get final TLS ACK. */
                        conn->push_buf = malloc(1);
                }
        }

        out_data = conn->push_buf;
        *out_len = conn->push_buf_len;
        conn->push_buf = NULL;
        conn->push_buf_len = 0;
        return out_data;
}


u8 * tls_connection_server_handshake(void *ssl_ctx,
                                     struct tls_connection *conn,
                                     const u8 *in_data, size_t in_len,
                                     size_t *out_len)
{
        /* TODO */
        return NULL;
}


int tls_connection_encrypt(void *ssl_ctx, struct tls_connection *conn,
                           const u8 *in_data, size_t in_len,
                           u8 *out_data, size_t out_len)
{
        ssize_t res;
        res = gnutls_record_send(conn->session, in_data, in_len);
        if (conn->push_buf == NULL)
                return -1;
        if (conn->push_buf_len < out_len)
                out_len = conn->push_buf_len;
        memcpy(out_data, conn->push_buf, out_len);
        free(conn->push_buf);
        conn->push_buf = NULL;
        conn->push_buf_len = 0;
        return out_len;
}


int tls_connection_decrypt(void *ssl_ctx, struct tls_connection *conn,
                           const u8 *in_data, size_t in_len,
                           u8 *out_data, size_t out_len)
{
        ssize_t res;

        if (conn->pull_buf) {
                wpa_printf(MSG_DEBUG, "%s - %d bytes remaining in "
                           "pull_buf", __func__, conn->pull_buf_len);
                free(conn->pull_buf);
        }
        conn->pull_buf = malloc(in_len);
        if (conn->pull_buf == NULL)
                return -1;
        memcpy(conn->pull_buf, in_data, in_len);
        conn->pull_buf_offset = conn->pull_buf;
        conn->pull_buf_len = in_len;

        res = gnutls_record_recv(conn->session, out_data, out_len);
        if (res < 0) {
                wpa_printf(MSG_DEBUG, "%s - gnutls_record_recv failed: %d "
                           "(%s)", __func__, res, gnutls_strerror(res));
        }

        return res;
}


int tls_connection_resumed(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return 0;
        return gnutls_session_is_resumed(conn->session);
}


#ifdef EAP_FAST
int tls_connection_set_master_key(void *ssl_ctx, struct tls_connection *conn,
                                  const u8 *key, size_t key_len)
{
        /* TODO */
        return -1;
}
#endif /* EAP_FAST */


int tls_connection_set_anon_dh(void *ssl_ctx, struct tls_connection *conn)
{
        /* TODO: set ADH-AES128-SHA cipher */
        return -1;
}


int tls_get_cipher(void *ssl_ctx, struct tls_connection *conn,
                   char *buf, size_t buflen)
{
        /* TODO */
        buf[0] = '\0';
        return 0;
}


int tls_connection_enable_workaround(void *ssl_ctx,
                                     struct tls_connection *conn)
{
        /* TODO: set SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS */
        return 0;
}


#ifdef EAP_FAST
int tls_connection_client_hello_ext(void *ssl_ctx, struct tls_connection *conn,
                                    int ext_type, const u8 *data,
                                    size_t data_len)
{
        /* TODO */
        return -1;
}
#endif /* EAP_FAST */


int tls_connection_get_failed(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return -1;
        return conn->failed;
}


int tls_connection_get_read_alerts(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return -1;
        return conn->read_alerts;
}


int tls_connection_get_write_alerts(void *ssl_ctx, struct tls_connection *conn)
{
        if (conn == NULL)
                return -1;
        return conn->write_alerts;
}

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