1 files changed, 422 insertions, 0 deletions
diff --git a/src/resolve/resolved-dnstls-openssl.c b/src/resolve/resolved-dnstls-openssl.c
new file mode 100644
index 0000000..fbcee7f
--- /dev/null
+++ b/src/resolve/resolved-dnstls-openssl.c
@@ -0,0 +1,422 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#if !ENABLE_DNS_OVER_TLS || !DNS_OVER_TLS_USE_OPENSSL
+#error This source file requires DNS-over-TLS to be enabled and OpenSSL to be available.
+#endif
+
+#include <openssl/bio.h>
+#include <openssl/err.h>
+#include <openssl/x509v3.h>
+
+#include "io-util.h"
+#include "openssl-util.h"
+#include "resolved-dns-stream.h"
+#include "resolved-dnstls.h"
+#include "resolved-manager.h"
+
+static char *dnstls_error_string(int ssl_error, char *buf, size_t count) {
+        assert(buf || count == 0);
+        if (ssl_error == SSL_ERROR_SSL)
+                ERR_error_string_n(ERR_get_error(), buf, count);
+        else
+                snprintf(buf, count, "SSL_get_error()=%d", ssl_error);
+        return buf;
+}
+
+#define DNSTLS_ERROR_BUFSIZE 256
+#define DNSTLS_ERROR_STRING(error) \
+        dnstls_error_string((error), (char[DNSTLS_ERROR_BUFSIZE]){}, DNSTLS_ERROR_BUFSIZE)
+
+static int dnstls_flush_write_buffer(DnsStream *stream) {
+        ssize_t ss;
+
+        assert(stream);
+        assert(stream->encrypted);
+
+        if (stream->dnstls_data.buffer_offset < stream->dnstls_data.write_buffer->length) {
+                assert(stream->dnstls_data.write_buffer->data);
+
+                struct iovec iov[1];
+                iov[0] = IOVEC_MAKE(stream->dnstls_data.write_buffer->data + stream->dnstls_data.buffer_offset,
+                                    stream->dnstls_data.write_buffer->length - stream->dnstls_data.buffer_offset);
+                ss = dns_stream_writev(stream, iov, 1, DNS_STREAM_WRITE_TLS_DATA);
+                if (ss < 0) {
+                        if (ss == -EAGAIN)
+                                stream->dnstls_events |= EPOLLOUT;
+
+                        return ss;
+                } else {
+                        stream->dnstls_data.buffer_offset += ss;
+
+                        if (stream->dnstls_data.buffer_offset < stream->dnstls_data.write_buffer->length) {
+                                stream->dnstls_events |= EPOLLOUT;
+                                return -EAGAIN;
+                        } else {
+                                BIO_reset(SSL_get_wbio(stream->dnstls_data.ssl));
+                                stream->dnstls_data.buffer_offset = 0;
+                        }
+                }
+        }
+
+        return 0;
+}
+
+int dnstls_stream_connect_tls(DnsStream *stream, DnsServer *server) {
+        _cleanup_(BIO_freep) BIO *rb = NULL, *wb = NULL;
+        _cleanup_(SSL_freep) SSL *s = NULL;
+        int error, r;
+
+        assert(stream);
+        assert(stream->manager);
+        assert(server);
+
+        rb = BIO_new_socket(stream->fd, 0);
+        if (!rb)
+                return -ENOMEM;
+
+        wb = BIO_new(BIO_s_mem());
+        if (!wb)
+                return -ENOMEM;
+
+        BIO_get_mem_ptr(wb, &stream->dnstls_data.write_buffer);
+        stream->dnstls_data.buffer_offset = 0;
+
+        s = SSL_new(stream->manager->dnstls_data.ctx);
+        if (!s)
+                return -ENOMEM;
+
+        SSL_set_connect_state(s);
+        r = SSL_set_session(s, server->dnstls_data.session);
+        if (r == 0)
+                return -EIO;
+        SSL_set_bio(s, TAKE_PTR(rb), TAKE_PTR(wb));
+
+        if (server->manager->dns_over_tls_mode == DNS_OVER_TLS_YES) {
+                X509_VERIFY_PARAM *v;
+
+                SSL_set_verify(s, SSL_VERIFY_PEER, NULL);
+                v = SSL_get0_param(s);
+                if (server->server_name) {
+                        X509_VERIFY_PARAM_set_hostflags(v, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);
+                        if (X509_VERIFY_PARAM_set1_host(v, server->server_name, 0) == 0)
+                                return -ECONNREFUSED;
+                } else {
+                        const unsigned char *ip;
+                        ip = server->family == AF_INET ? (const unsigned char*) &server->address.in.s_addr : server->address.in6.s6_addr;
+                        if (X509_VERIFY_PARAM_set1_ip(v, ip, FAMILY_ADDRESS_SIZE(server->family)) == 0)
+                                return -ECONNREFUSED;
+                }
+        }
+
+        if (server->server_name) {
+                r = SSL_set_tlsext_host_name(s, server->server_name);
+                if (r <= 0)
+                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "Failed to set server name: %s", DNSTLS_ERROR_STRING(SSL_ERROR_SSL));
+        }
+
+        ERR_clear_error();
+        stream->dnstls_data.handshake = SSL_do_handshake(s);
+        if (stream->dnstls_data.handshake <= 0) {
+                error = SSL_get_error(s, stream->dnstls_data.handshake);
+                if (!IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE))
+                        return log_debug_errno(SYNTHETIC_ERRNO(ECONNREFUSED),
+                                               "Failed to invoke SSL_do_handshake: %s", DNSTLS_ERROR_STRING(error));
+        }
+
+        stream->encrypted = true;
+        stream->dnstls_data.ssl = TAKE_PTR(s);
+
+        r = dnstls_flush_write_buffer(stream);
+        if (r < 0 && r != -EAGAIN) {
+                SSL_free(TAKE_PTR(stream->dnstls_data.ssl));
+                return r;
+        }
+
+        return 0;
+}
+
+void dnstls_stream_free(DnsStream *stream) {
+        assert(stream);
+        assert(stream->encrypted);
+
+        if (stream->dnstls_data.ssl)
+                SSL_free(stream->dnstls_data.ssl);
+}
+
+int dnstls_stream_on_io(DnsStream *stream, uint32_t revents) {
+        int error, r;
+
+        assert(stream);
+        assert(stream->encrypted);
+        assert(stream->dnstls_data.ssl);
+
+        /* Flush write buffer when requested by OpenSSL */
+        if ((revents & EPOLLOUT) && (stream->dnstls_events & EPOLLOUT)) {
+                r = dnstls_flush_write_buffer(stream);
+                if (r < 0)
+                        return r;
+        }
+
+        if (stream->dnstls_data.shutdown) {
+                ERR_clear_error();
+                r = SSL_shutdown(stream->dnstls_data.ssl);
+                if (r == 0) {
+                        stream->dnstls_events = 0;
+
+                        r = dnstls_flush_write_buffer(stream);
+                        if (r < 0)
+                                return r;
+
+                        return -EAGAIN;
+                } else if (r < 0) {
+                        error = SSL_get_error(stream->dnstls_data.ssl, r);
+                        if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
+                                stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
+
+                                r = dnstls_flush_write_buffer(stream);
+                                if (r < 0)
+                                        return r;
+
+                                return -EAGAIN;
+                        } else if (error == SSL_ERROR_SYSCALL) {
+                                if (errno > 0)
+                                        log_debug_errno(errno, "Failed to invoke SSL_shutdown, ignoring: %m");
+                        } else
+                                log_debug("Failed to invoke SSL_shutdown, ignoring: %s", DNSTLS_ERROR_STRING(error));
+                }
+
+                stream->dnstls_events = 0;
+                stream->dnstls_data.shutdown = false;
+
+                r = dnstls_flush_write_buffer(stream);
+                if (r < 0)
+                        return r;
+
+                dns_stream_unref(stream);
+                return DNSTLS_STREAM_CLOSED;
+        } else if (stream->dnstls_data.handshake <= 0) {
+                ERR_clear_error();
+                stream->dnstls_data.handshake = SSL_do_handshake(stream->dnstls_data.ssl);
+                if (stream->dnstls_data.handshake <= 0) {
+                        error = SSL_get_error(stream->dnstls_data.ssl, stream->dnstls_data.handshake);
+                        if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
+                                stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
+                                r = dnstls_flush_write_buffer(stream);
+                                if (r < 0)
+                                        return r;
+
+                                return -EAGAIN;
+                        } else
+                                return log_debug_errno(SYNTHETIC_ERRNO(ECONNREFUSED),
+                                                       "Failed to invoke SSL_do_handshake: %s",
+                                                       DNSTLS_ERROR_STRING(error));
+                }
+
+                stream->dnstls_events = 0;
+                r = dnstls_flush_write_buffer(stream);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int dnstls_stream_shutdown(DnsStream *stream, int error) {
+        int ssl_error, r;
+        SSL_SESSION *s;
+
+        assert(stream);
+        assert(stream->encrypted);
+        assert(stream->dnstls_data.ssl);
+
+        if (stream->server) {
+                s = SSL_get1_session(stream->dnstls_data.ssl);
+                if (s) {
+                        if (stream->server->dnstls_data.session)
+                                SSL_SESSION_free(stream->server->dnstls_data.session);
+
+                        stream->server->dnstls_data.session = s;
+                }
+        }
+
+        if (error == ETIMEDOUT) {
+                ERR_clear_error();
+                r = SSL_shutdown(stream->dnstls_data.ssl);
+                if (r == 0) {
+                        if (!stream->dnstls_data.shutdown) {
+                                stream->dnstls_data.shutdown = true;
+                                dns_stream_ref(stream);
+                        }
+
+                        stream->dnstls_events = 0;
+
+                        r = dnstls_flush_write_buffer(stream);
+                        if (r < 0)
+                                return r;
+
+                        return -EAGAIN;
+                } else if (r < 0) {
+                        ssl_error = SSL_get_error(stream->dnstls_data.ssl, r);
+                        if (IN_SET(ssl_error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
+                                stream->dnstls_events = ssl_error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
+                                r = dnstls_flush_write_buffer(stream);
+                                if (r < 0 && r != -EAGAIN)
+                                        return r;
+
+                                if (!stream->dnstls_data.shutdown) {
+                                        stream->dnstls_data.shutdown = true;
+                                        dns_stream_ref(stream);
+                                }
+                                return -EAGAIN;
+                        } else if (ssl_error == SSL_ERROR_SYSCALL) {
+                                if (errno > 0)
+                                        log_debug_errno(errno, "Failed to invoke SSL_shutdown, ignoring: %m");
+                        } else
+                                log_debug("Failed to invoke SSL_shutdown, ignoring: %s", DNSTLS_ERROR_STRING(ssl_error));
+                }
+
+                stream->dnstls_events = 0;
+                r = dnstls_flush_write_buffer(stream);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count) {
+        int error, r;
+        ssize_t ss;
+
+        ERR_clear_error();
+        ss = r = SSL_write(stream->dnstls_data.ssl, buf, count);
+        if (r <= 0) {
+                error = SSL_get_error(stream->dnstls_data.ssl, r);
+                if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
+                        stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
+                        ss = -EAGAIN;
+                } else if (error == SSL_ERROR_ZERO_RETURN) {
+                        stream->dnstls_events = 0;
+                        ss = 0;
+                } else {
+                        log_debug("Failed to invoke SSL_write: %s", DNSTLS_ERROR_STRING(error));
+                        stream->dnstls_events = 0;
+                        ss = -EPIPE;
+                }
+        } else
+                stream->dnstls_events = 0;
+
+        r = dnstls_flush_write_buffer(stream);
+        if (r < 0)
+                return r;
+
+        return ss;
+}
+
+ssize_t dnstls_stream_writev(DnsStream *stream, const struct iovec *iov, size_t iovcnt) {
+        _cleanup_free_ char *buf = NULL;
+        size_t count;
+
+        assert(stream);
+        assert(stream->encrypted);
+        assert(stream->dnstls_data.ssl);
+        assert(iov);
+        assert(iovec_total_size(iov, iovcnt) > 0);
+
+        if (iovcnt == 1)
+                return dnstls_stream_write(stream, iov[0].iov_base, iov[0].iov_len);
+
+        /* As of now, OpenSSL cannot accumulate multiple writes, so join into a
+           single buffer. Suboptimal, but better than multiple SSL_write calls. */
+        count = iovec_total_size(iov, iovcnt);
+        buf = new(char, count);
+        for (size_t i = 0, pos = 0; i < iovcnt; pos += iov[i].iov_len, i++)
+                memcpy(buf + pos, iov[i].iov_base, iov[i].iov_len);
+
+        return dnstls_stream_write(stream, buf, count);
+}
+
+ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
+        int error, r;
+        ssize_t ss;
+
+        assert(stream);
+        assert(stream->encrypted);
+        assert(stream->dnstls_data.ssl);
+        assert(buf);
+
+        ERR_clear_error();
+        ss = r = SSL_read(stream->dnstls_data.ssl, buf, count);
+        if (r <= 0) {
+                error = SSL_get_error(stream->dnstls_data.ssl, r);
+                if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
+                        /* If we receive SSL_ERROR_WANT_READ here, there are two possible scenarios:
+                           * OpenSSL needs to renegotiate (so we want to get an EPOLLIN event), or
+                           * There is no more application data is available, so we can just return
+                           And apparently there's no nice way to distinguish between the two.
+                           To handle this, never set EPOLLIN and just continue as usual.
+                           If OpenSSL really wants to read due to renegotiation, it will tell us
+                           again on SSL_write (at which point we will request EPOLLIN force a read);
+                           or we will just eventually read data anyway while we wait for a packet */
+                        stream->dnstls_events = error == SSL_ERROR_WANT_READ ? 0 : EPOLLOUT;
+                        ss = -EAGAIN;
+                } else if (error == SSL_ERROR_ZERO_RETURN) {
+                        stream->dnstls_events = 0;
+                        ss = 0;
+                } else {
+                        log_debug("Failed to invoke SSL_read: %s", DNSTLS_ERROR_STRING(error));
+                        stream->dnstls_events = 0;
+                        ss = -EPIPE;
+                }
+        } else
+                stream->dnstls_events = 0;
+
+        /* flush write buffer in cache of renegotiation */
+        r = dnstls_flush_write_buffer(stream);
+        if (r < 0)
+                return r;
+
+        return ss;
+}
+
+void dnstls_server_free(DnsServer *server) {
+        assert(server);
+
+        if (server->dnstls_data.session)
+                SSL_SESSION_free(server->dnstls_data.session);
+}
+
+int dnstls_manager_init(Manager *manager) {
+        int r;
+
+        assert(manager);
+
+        ERR_load_crypto_strings();
+        SSL_load_error_strings();
+
+        manager->dnstls_data.ctx = SSL_CTX_new(TLS_client_method());
+        if (!manager->dnstls_data.ctx)
+                return -ENOMEM;
+
+        r = SSL_CTX_set_min_proto_version(manager->dnstls_data.ctx, TLS1_2_VERSION);
+        if (r == 0)
+                return -EIO;
+
+        (void) SSL_CTX_set_options(manager->dnstls_data.ctx, SSL_OP_NO_COMPRESSION);
+
+        r = SSL_CTX_set_default_verify_paths(manager->dnstls_data.ctx);
+        if (r == 0)
+                return log_warning_errno(SYNTHETIC_ERRNO(EIO),
+                                         "Failed to load system trust store: %s",
+                                         ERR_error_string(ERR_get_error(), NULL));
+
+        return 0;
+}
+
+void dnstls_manager_free(Manager *manager) {
+        assert(manager);
+
+        if (manager->dnstls_data.ctx)
+                SSL_CTX_free(manager->dnstls_data.ctx);
+}