+
+static int version_cmp(SSL *s, int a, int b)
+{
+ int dtls = SSL_IS_DTLS(s);
+
+ if (a == b)
+ return 0;
+ if (!dtls)
+ return a < b ? -1 : 1;
+ return DTLS_VERSION_LT(a, b) ? -1 : 1;
+}
+
+typedef struct {
+ int version;
+ const SSL_METHOD *(*cmeth)(void);
+ const SSL_METHOD *(*smeth)(void);
+} version_info;
+
+#if TLS_MAX_VERSION != TLS1_2_VERSION
+# error Code needs update for TLS_method() support beyond TLS1_2_VERSION.
+#endif
+
+static const version_info tls_version_table[] = {
+ { TLS1_2_VERSION, TLSv1_2_client_method, TLSv1_2_server_method },
+ { TLS1_1_VERSION, TLSv1_1_client_method, TLSv1_1_server_method },
+ { TLS1_VERSION, TLSv1_client_method, TLSv1_server_method },
+#ifndef OPENSSL_NO_SSL3
+ { SSL3_VERSION, SSLv3_client_method, SSLv3_server_method },
+#endif
+ { 0, NULL, NULL },
+};
+
+#if DTLS_MAX_VERSION != DTLS1_2_VERSION
+# error Code needs update for DTLS_method() support beyond DTLS1_2_VERSION.
+#endif
+
+static const version_info dtls_version_table[] = {
+ { DTLS1_2_VERSION, DTLSv1_2_client_method, DTLSv1_2_server_method },
+ { DTLS1_VERSION, DTLSv1_client_method, DTLSv1_server_method },
+ { 0, NULL, NULL },
+};
+
+/*
+ * ssl_method_error - Check whether an SSL_METHOD is enabled.
+ *
+ * @s: The SSL handle for the candidate method
+ * @method: the intended method.
+ *
+ * Returns 0 on success, or an SSL error reason on failure.
+ */
+static int ssl_method_error(SSL *s, const SSL_METHOD *method)
+{
+ int version = method->version;
+
+ if ((s->min_proto_version != 0 &&
+ version_cmp(s, version, s->min_proto_version) < 0) ||
+ ssl_security(s, SSL_SECOP_VERSION, 0, version, NULL) == 0)
+ return SSL_R_VERSION_TOO_LOW;
+
+ if (s->max_proto_version != 0 &&
+ version_cmp(s, version, s->max_proto_version) > 0)
+ return SSL_R_VERSION_TOO_HIGH;
+
+ if ((s->options & method->mask) != 0)
+ return SSL_R_UNSUPPORTED_PROTOCOL;
+ if ((method->flags & SSL_METHOD_NO_SUITEB) != 0 && tls1_suiteb(s))
+ return SSL_R_AT_LEAST_TLS_1_2_NEEDED_IN_SUITEB_MODE;
+ else if ((method->flags & SSL_METHOD_NO_FIPS) != 0 && FIPS_mode())
+ return SSL_R_AT_LEAST_TLS_1_0_NEEDED_IN_FIPS_MODE;
+
+ return 0;
+}
+
+/*
+ * ssl_check_version_downgrade - In response to RFC7507 SCSV version
+ * fallback indication from a client check whether we're using the highest
+ * supported protocol version.
+ *
+ * @s server SSL handle.
+ *
+ * Returns 1 when using the highest enabled version, 0 otherwise.
+ */
+int ssl_check_version_downgrade(SSL *s)
+{
+ const version_info *vent;
+ const version_info *table;
+
+ /*
+ * Check that the current protocol is the highest enabled version
+ * (according to s->ctx->method, as version negotiation may have changed
+ * s->method).
+ */
+ if (s->version == s->ctx->method->version)
+ return 1;
+
+ /*
+ * Apparently we're using a version-flexible SSL_METHOD (not at its
+ * highest protocol version).
+ */
+ if (s->ctx->method->version == TLS_method()->version)
+ table = tls_version_table;
+ else if (s->ctx->method->version == DTLS_method()->version)
+ table = dtls_version_table;
+ else {
+ /* Unexpected state; fail closed. */
+ return 0;
+ }
+
+ for (vent = table; vent->version != 0; ++vent) {
+ if (vent->smeth != NULL &&
+ ssl_method_error(s, vent->smeth()) == 0)
+ return s->version == vent->version;
+ }
+ return 0;
+}
+
+/*
+ * ssl_set_version_bound - set an upper or lower bound on the supported (D)TLS
+ * protocols, provided the initial (D)TLS method is version-flexible. This
+ * function sanity-checks the proposed value and makes sure the method is
+ * version-flexible, then sets the limit if all is well.
+ *
+ * @method_version: The version of the current SSL_METHOD.
+ * @version: the intended limit.
+ * @bound: pointer to limit to be updated.
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+int ssl_set_version_bound(int method_version, int version, int *bound)
+{
+ /*-
+ * Restrict TLS methods to TLS protocol versions.
+ * Restrict DTLS methods to DTLS protocol versions.
+ * Note, DTLS version numbers are decreasing, use comparison macros.
+ *
+ * Note that for both lower-bounds we use explicit versions, not
+ * (D)TLS_MIN_VERSION. This is because we don't want to break user
+ * configurations. If the MIN (supported) version ever rises, the user's
+ * "floor" remains valid even if no longer available. We don't expect the
+ * MAX ceiling to ever get lower, so making that variable makes sense.
+ */
+ switch (method_version) {
+ default:
+ /*
+ * XXX For fixed version methods, should we always fail and not set any
+ * bounds, always succeed and not set any bounds, or set the bounds and
+ * arrange to fail later if they are not met? At present fixed-version
+ * methods are not subject to controls that disable individual protocol
+ * versions.
+ */
+ return 0;
+
+ case TLS_ANY_VERSION:
+ if (version < SSL3_VERSION || version > TLS_MAX_VERSION)
+ return 0;
+ break;
+
+ case DTLS_ANY_VERSION:
+ if (DTLS_VERSION_GT(version, DTLS_MAX_VERSION) ||
+ DTLS_VERSION_LT(version, DTLS1_VERSION))
+ return 0;
+ break;
+ }
+
+ *bound = version;
+ return 1;
+}
+
+/*
+ * ssl_choose_server_version - Choose server (D)TLS version. Called when the
+ * client HELLO is received to select the final server protocol version and
+ * the version specific method.
+ *
+ * @s: server SSL handle.
+ *
+ * Returns 0 on success or an SSL error reason number on failure.
+ */
+int ssl_choose_server_version(SSL *s)
+{
+ /*-
+ * With version-flexible methods we have an initial state with:
+ *
+ * s->method->version == (D)TLS_ANY_VERSION,
+ * s->version == (D)TLS_MAX_VERSION.
+ *
+ * So we detect version-flexible methods via the method version, not the
+ * handle version.
+ */
+ int server_version = s->method->version;
+ int client_version = s->client_version;
+ const version_info *vent;
+ const version_info *table;
+ int disabled = 0;
+
+ switch (server_version) {
+ default:
+ if (version_cmp(s, client_version, s->version) < 0)
+ return SSL_R_WRONG_SSL_VERSION;
+ /*
+ * If this SSL handle is not from a version flexible method we don't
+ * (and never did) check min/max FIPS or Suite B constraints. Hope
+ * that's OK. It is up to the caller to not choose fixed protocol
+ * versions they don't want. If not, then easy to fix, just return
+ * ssl_method_error(s, s->method)
+ */
+ return 0;
+ case TLS_ANY_VERSION:
+ table = tls_version_table;
+ break;
+ case DTLS_ANY_VERSION:
+ table = dtls_version_table;
+ break;
+ }
+
+ for (vent = table; vent->version != 0; ++vent) {
+ const SSL_METHOD *method;
+
+ if (vent->smeth == NULL ||
+ version_cmp(s, client_version, vent->version) < 0)
+ continue;
+ method = vent->smeth();
+ if (ssl_method_error(s, method) == 0) {
+ s->version = vent->version;
+ s->method = method;
+ return 0;
+ }
+ disabled = 1;
+ }
+ return disabled ? SSL_R_UNSUPPORTED_PROTOCOL : SSL_R_VERSION_TOO_LOW;
+}
+
+/*
+ * ssl_choose_client_version - Choose client (D)TLS version. Called when the
+ * server HELLO is received to select the final client protocol version and
+ * the version specific method.
+ *
+ * @s: client SSL handle.
+ * @version: The proposed version from the server's HELLO.
+ *
+ * Returns 0 on success or an SSL error reason number on failure.
+ */
+int ssl_choose_client_version(SSL *s, int version)
+{
+ const version_info *vent;
+ const version_info *table;
+
+ switch (s->method->version) {
+ default:
+ if (version != s->version)
+ return SSL_R_WRONG_SSL_VERSION;
+ /*
+ * If this SSL handle is not from a version flexible method we don't
+ * (and never did) check min/max, FIPS or Suite B constraints. Hope
+ * that's OK. It is up to the caller to not choose fixed protocol
+ * versions they don't want. If not, then easy to fix, just return
+ * ssl_method_error(s, s->method)
+ */
+ s->session->ssl_version = s->version;
+ return 0;
+ case TLS_ANY_VERSION:
+ table = tls_version_table;
+ break;
+ case DTLS_ANY_VERSION:
+ table = dtls_version_table;
+ break;
+ }
+
+ for (vent = table; vent->version != 0; ++vent) {
+ const SSL_METHOD *method;
+ int err;
+
+ if (version != vent->version)
+ continue;
+ if (vent->cmeth == NULL)
+ break;
+ method = vent->cmeth();
+ err = ssl_method_error(s, method);
+ if (err != 0)
+ return err;
+ s->method = method;
+ s->session->ssl_version = s->version = version;
+ return 0;
+ }
+
+ return SSL_R_UNSUPPORTED_PROTOCOL;
+}
+
+/*-
+ * ssl_set_client_hello_version - Work out what version we should be using for
+ * the initial ClientHello if the version is initially (D)TLS_ANY_VERSION. We
+ * apply any explicit SSL_OP_NO_xxx options, the MinProtocol and MaxProtocol
+ * configuration commands, any Suite B or FIPS_mode() constraints and any floor
+ * imposed by the security level here, so we don't advertise the wrong protocol
+ * version to only reject the outcome later.
+ *
+ * Computing the right floor matters. If, e.g., TLS 1.0 and 1.2 are enabled,
+ * TLS 1.1 is disabled, but the security level, Suite-B and/or MinProtocol
+ * only allow TLS 1.2, we want to advertise TLS1.2, *not* TLS1.
+ *
+ * @s: client SSL handle.
+ *
+ * Returns 0 on success or an SSL error reason number on failure.
+ */
+int ssl_set_client_hello_version(SSL *s)
+{
+ int version;
+ int hole;
+ const SSL_METHOD *single = NULL;
+ const SSL_METHOD *method;
+ const version_info *table;
+ const version_info *vent;
+
+ switch (s->method->version) {
+ default:
+ /*
+ * If this SSL handle is not from a version flexible method we don't
+ * (and never did) check min/max FIPS or Suite B constraints. Hope
+ * that's OK. It is up to the caller to not choose fixed protocol
+ * versions they don't want. If not, then easy to fix, just return
+ * ssl_method_error(s, s->method)
+ */
+ s->client_version = s->version;
+ return 0;
+ case TLS_ANY_VERSION:
+ table = tls_version_table;
+ break;
+ case DTLS_ANY_VERSION:
+ table = dtls_version_table;
+ break;
+ }
+
+ /*
+ * SSL_OP_NO_X disables all protocols above X *if* there are some protocols
+ * below X enabled. This is required in order to maintain the "version
+ * capability" vector contiguous. Any versions with a NULL client method
+ * (protocol version client is disabled at compile-time) is also a "hole".
+ *
+ * Our initial state is hole == 1, version == 0. That is, versions above
+ * the first version in the method table are disabled (a "hole" above
+ * the valid protocol entries) and we don't have a selected version yet.
+ *
+ * Whenever "hole == 1", and we hit an enabled method, its version becomes
+ * the selected version, and the method becomes a candidate "single"
+ * method. We're no longer in a hole, so "hole" becomes 0.
+ *
+ * If "hole == 0" and we hit an enabled method, then "single" is cleared,
+ * as we support a contiguous range of at least two methods. If we hit
+ * a disabled method, then hole becomes true again, but nothing else
+ * changes yet, because all the remaining methods may be disabled too.
+ * If we again hit an enabled method after the new hole, it becomes
+ * selected, as we start from scratch.
+ */
+ version = 0;
+ hole = 1;
+ for (vent = table; vent->version != 0; ++vent) {
+ /*
+ * A table entry with a NULL client method is still a hole in the
+ * "version capability" vector.
+ */
+ if (vent->cmeth == NULL) {
+ hole = 1;
+ continue;
+ }
+ method = vent->cmeth();
+ if (ssl_method_error(s, method) != 0) {
+ hole = 1;
+ } else if (!hole) {
+ single = NULL;
+ } else {
+ version = (single = method)->version;
+ hole = 0;
+ }
+ }
+
+ /* Fail if everything is disabled */
+ if (version == 0)
+ return SSL_R_NO_PROTOCOLS_AVAILABLE;
+
+ if (single != NULL)
+ s->method = single;
+ s->client_version = s->version = version;
+ return 0;
+}
projects / openssl.git / commitdiff