Split directory.c code into several modules

Parts of this C file naturally belong in dircache, dirclient, and
dircommon: so, move them there.

1 files changed, 1739 insertions, 0 deletions

diff --git a/src/feature/dircache/dircache.c b/src/feature/dircache/dircache.c
new file mode 100644
index 0000000000..ef4fe391ba
--- /dev/null
+++ b/src/feature/dircache/dircache.c
@@ -0,0 +1,1739 @@
+/* Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#define DIRCACHE_PRIVATE
+
+#include "core/or/or.h"
+
+#include "app/config/config.h"
+#include "core/mainloop/connection.h"
+#include "core/or/relay.h"
+#include "feature/dirauth/dirvote.h"
+#include "feature/dirauth/mode.h"
+#include "feature/dirauth/process_descs.h"
+#include "feature/dircache/conscache.h"
+#include "feature/dircache/consdiffmgr.h"
+#include "feature/dircache/dircache.h"
+#include "feature/dircache/dirserv.h"
+#include "feature/dircommon/directory.h"
+#include "feature/dircommon/fp_pair.h"
+#include "feature/hs/hs_cache.h"
+#include "feature/nodelist/authcert.h"
+#include "feature/nodelist/networkstatus.h"
+#include "feature/nodelist/routerlist.h"
+#include "feature/rend/rendcache.h"
+#include "feature/stats/geoip.h"
+#include "feature/stats/rephist.h"
+#include "lib/compress/compress.h"
+
+#include "feature/dircache/cached_dir_st.h"
+#include "feature/dircommon/dir_connection_st.h"
+#include "feature/nodelist/authority_cert_st.h"
+#include "feature/nodelist/networkstatus_st.h"
+#include "feature/nodelist/routerinfo_st.h"
+
+/** Maximum size, in bytes, for any directory object that we're accepting
+ * as an upload. */
+#define MAX_DIR_UL_SIZE ((1<<24)-1) /* 16MB-1 */
+
+/** HTTP cache control: how long do we tell proxies they can cache each
+ * kind of document we serve? */
+#define FULL_DIR_CACHE_LIFETIME (60*60)
+#define RUNNINGROUTERS_CACHE_LIFETIME (20*60)
+#define DIRPORTFRONTPAGE_CACHE_LIFETIME (20*60)
+#define NETWORKSTATUS_CACHE_LIFETIME (5*60)
+#define ROUTERDESC_CACHE_LIFETIME (30*60)
+#define ROUTERDESC_BY_DIGEST_CACHE_LIFETIME (48*60*60)
+#define ROBOTS_CACHE_LIFETIME (24*60*60)
+#define MICRODESC_CACHE_LIFETIME (48*60*60)
+
+/** Parse an HTTP request string <b>headers</b> of the form
+ * \verbatim
+ * "\%s [http[s]://]\%s HTTP/1..."
+ * \endverbatim
+ * If it's well-formed, strdup the second \%s into *<b>url</b>, and
+ * nul-terminate it. If the url doesn't start with "/tor/", rewrite it
+ * so it does. Return 0.
+ * Otherwise, return -1.
+ */
+STATIC int
+parse_http_url(const char *headers, char **url)
+{
+  char *command = NULL;
+  if (parse_http_command(headers, &command, url) < 0) {
+    return -1;
+  }
+  if (strcmpstart(*url, "/tor/")) {
+    char *new_url = NULL;
+    tor_asprintf(&new_url, "/tor%s%s",
+                 *url[0] == '/' ? "" : "/",
+                 *url);
+    tor_free(*url);
+    *url = new_url;
+  }
+  tor_free(command);
+  return 0;
+}
+
+/** Create an http response for the client <b>conn</b> out of
+ * <b>status</b> and <b>reason_phrase</b>. Write it to <b>conn</b>.
+ */
+static void
+write_short_http_response(dir_connection_t *conn, int status,
+                       const char *reason_phrase)
+{
+  char *buf = NULL;
+  char *datestring = NULL;
+
+  IF_BUG_ONCE(!reason_phrase) { /* bullet-proofing */
+    reason_phrase = "unspecified";
+  }
+
+  if (server_mode(get_options())) {
+    /* include the Date: header, but only if we're a relay or bridge */
+    char datebuf[RFC1123_TIME_LEN+1];
+    format_rfc1123_time(datebuf, time(NULL));
+    tor_asprintf(&datestring, "Date: %s\r\n", datebuf);
+  }
+
+  tor_asprintf(&buf, "HTTP/1.0 %d %s\r\n%s\r\n",
+               status, reason_phrase, datestring?datestring:"");
+
+  log_debug(LD_DIRSERV,"Wrote status 'HTTP/1.0 %d %s'", status, reason_phrase);
+  connection_buf_add(buf, strlen(buf), TO_CONN(conn));
+
+  tor_free(datestring);
+  tor_free(buf);
+}
+
+/** Write the header for an HTTP/1.0 response onto <b>conn</b>-\>outbuf,
+ * with <b>type</b> as the Content-Type.
+ *
+ * If <b>length</b> is nonnegative, it is the Content-Length.
+ * If <b>encoding</b> is provided, it is the Content-Encoding.
+ * If <b>cache_lifetime</b> is greater than 0, the content may be cached for
+ * up to cache_lifetime seconds.  Otherwise, the content may not be cached. */
+static void
+write_http_response_header_impl(dir_connection_t *conn, ssize_t length,
+                           const char *type, const char *encoding,
+                           const char *extra_headers,
+                           long cache_lifetime)
+{
+  char date[RFC1123_TIME_LEN+1];
+  time_t now = time(NULL);
+  buf_t *buf = buf_new_with_capacity(1024);
+
+  tor_assert(conn);
+
+  format_rfc1123_time(date, now);
+
+  buf_add_printf(buf, "HTTP/1.0 200 OK\r\nDate: %s\r\n", date);
+  if (type) {
+    buf_add_printf(buf, "Content-Type: %s\r\n", type);
+  }
+  if (!is_local_addr(&conn->base_.addr)) {
+    /* Don't report the source address for a nearby/private connection.
+     * Otherwise we tend to mis-report in cases where incoming ports are
+     * being forwarded to a Tor server running behind the firewall. */
+    buf_add_printf(buf, X_ADDRESS_HEADER "%s\r\n", conn->base_.address);
+  }
+  if (encoding) {
+    buf_add_printf(buf, "Content-Encoding: %s\r\n", encoding);
+  }
+  if (length >= 0) {
+    buf_add_printf(buf, "Content-Length: %ld\r\n", (long)length);
+  }
+  if (cache_lifetime > 0) {
+    char expbuf[RFC1123_TIME_LEN+1];
+    format_rfc1123_time(expbuf, (time_t)(now + cache_lifetime));
+    /* We could say 'Cache-control: max-age=%d' here if we start doing
+     * http/1.1 */
+    buf_add_printf(buf, "Expires: %s\r\n", expbuf);
+  } else if (cache_lifetime == 0) {
+    /* We could say 'Cache-control: no-cache' here if we start doing
+     * http/1.1 */
+    buf_add_string(buf, "Pragma: no-cache\r\n");
+  }
+  if (extra_headers) {
+    buf_add_string(buf, extra_headers);
+  }
+  buf_add_string(buf, "\r\n");
+
+  connection_buf_add_buf(TO_CONN(conn), buf);
+  buf_free(buf);
+}
+
+/** As write_http_response_header_impl, but sets encoding and content-typed
+ * based on whether the response will be <b>compressed</b> or not. */
+static void
+write_http_response_headers(dir_connection_t *conn, ssize_t length,
+                            compress_method_t method,
+                            const char *extra_headers, long cache_lifetime)
+{
+  const char *methodname = compression_method_get_name(method);
+  const char *doctype;
+  if (method == NO_METHOD)
+    doctype = "text/plain";
+  else
+    doctype = "application/octet-stream";
+  write_http_response_header_impl(conn, length,
+                                  doctype,
+                                  methodname,
+                                  extra_headers,
+                                  cache_lifetime);
+}
+
+/** As write_http_response_headers, but assumes extra_headers is NULL */
+static void
+write_http_response_header(dir_connection_t *conn, ssize_t length,
+                           compress_method_t method,
+                           long cache_lifetime)
+{
+  write_http_response_headers(conn, length, method, NULL, cache_lifetime);
+}
+
+/** Array of compression methods to use (if supported) for serving
+ * precompressed data, ordered from best to worst. */
+static compress_method_t srv_meth_pref_precompressed[] = {
+  LZMA_METHOD,
+  ZSTD_METHOD,
+  ZLIB_METHOD,
+  GZIP_METHOD,
+  NO_METHOD
+};
+
+/** Array of compression methods to use (if supported) for serving
+ * streamed data, ordered from best to worst. */
+static compress_method_t srv_meth_pref_streaming_compression[] = {
+  ZSTD_METHOD,
+  ZLIB_METHOD,
+  GZIP_METHOD,
+  NO_METHOD
+};
+
+/** Parse the compression methods listed in an Accept-Encoding header <b>h</b>,
+ * and convert them to a bitfield where compression method x is supported if
+ * and only if 1 &lt;&lt; x is set in the bitfield. */
+STATIC unsigned
+parse_accept_encoding_header(const char *h)
+{
+  unsigned result = (1u << NO_METHOD);
+  smartlist_t *methods = smartlist_new();
+  smartlist_split_string(methods, h, ",",
+             SPLIT_SKIP_SPACE|SPLIT_STRIP_SPACE|SPLIT_IGNORE_BLANK, 0);
+
+  SMARTLIST_FOREACH_BEGIN(methods, const char *, m) {
+    compress_method_t method = compression_method_get_by_name(m);
+    if (method != UNKNOWN_METHOD) {
+      tor_assert(((unsigned)method) < 8*sizeof(unsigned));
+      result |= (1u << method);
+    }
+  } SMARTLIST_FOREACH_END(m);
+  SMARTLIST_FOREACH_BEGIN(methods, char *, m) {
+    tor_free(m);
+  } SMARTLIST_FOREACH_END(m);
+  smartlist_free(methods);
+  return result;
+}
+
+/** Decide whether a client would accept the consensus we have.
+ *
+ * Clients can say they only want a consensus if it's signed by more
+ * than half the authorities in a list.  They pass this list in
+ * the url as "...consensus/<b>fpr</b>+<b>fpr</b>+<b>fpr</b>".
+ *
+ * <b>fpr</b> may be an abbreviated fingerprint, i.e. only a left substring
+ * of the full authority identity digest. (Only strings of even length,
+ * i.e. encodings of full bytes, are handled correctly.  In the case
+ * of an odd number of hex digits the last one is silently ignored.)
+ *
+ * Returns 1 if more than half of the requested authorities signed the
+ * consensus, 0 otherwise.
+ */
+static int
+client_likes_consensus(const struct consensus_cache_entry_t *ent,
+                       const char *want_url)
+{
+  smartlist_t *voters = smartlist_new();
+  int need_at_least;
+  int have = 0;
+
+  if (consensus_cache_entry_get_voter_id_digests(ent, voters) != 0) {
+    smartlist_free(voters);
+    return 1; // We don't know the voters; assume the client won't mind. */
+  }
+
+  smartlist_t *want_authorities = smartlist_new();
+  dir_split_resource_into_fingerprints(want_url, want_authorities, NULL, 0);
+  need_at_least = smartlist_len(want_authorities)/2+1;
+
+  SMARTLIST_FOREACH_BEGIN(want_authorities, const char *, want_digest) {
+
+    SMARTLIST_FOREACH_BEGIN(voters, const char *, digest) {
+      if (!strcasecmpstart(digest, want_digest)) {
+        have++;
+        break;
+      };
+    } SMARTLIST_FOREACH_END(digest);
+
+    /* early exit, if we already have enough */
+    if (have >= need_at_least)
+      break;
+  } SMARTLIST_FOREACH_END(want_digest);
+
+  SMARTLIST_FOREACH(want_authorities, char *, d, tor_free(d));
+  smartlist_free(want_authorities);
+  SMARTLIST_FOREACH(voters, char *, cp, tor_free(cp));
+  smartlist_free(voters);
+  return (have >= need_at_least);
+}
+
+/** Return the compression level we should use for sending a compressed
+ * response of size <b>n_bytes</b>. */
+STATIC compression_level_t
+choose_compression_level(ssize_t n_bytes)
+{
+  if (! have_been_under_memory_pressure()) {
+    return HIGH_COMPRESSION; /* we have plenty of RAM. */
+  } else if (n_bytes < 0) {
+    return HIGH_COMPRESSION; /* unknown; might be big. */
+  } else if (n_bytes < 1024) {
+    return LOW_COMPRESSION;
+  } else if (n_bytes < 2048) {
+    return MEDIUM_COMPRESSION;
+  } else {
+    return HIGH_COMPRESSION;
+  }
+}
+
+/** Information passed to handle a GET request. */
+typedef struct get_handler_args_t {
+  /** Bitmask of compression methods that the client said (or implied) it
+   * supported. */
+  unsigned compression_supported;
+  /** If nonzero, the time included an if-modified-since header with this
+   * value. */
+  time_t if_modified_since;
+  /** String containing the requested URL or resource. */
+  const char *url;
+  /** String containing the HTTP headers */
+  const char *headers;
+} get_handler_args_t;
+
+/** Entry for handling an HTTP GET request.
+ *
+ * This entry matches a request if "string" is equal to the requested
+ * resource, or if "is_prefix" is true and "string" is a prefix of the
+ * requested resource.
+ *
+ * The 'handler' function is called to handle the request.  It receives
+ * an arguments structure, and must return 0 on success or -1 if we should
+ * close the connection.
+ **/
+typedef struct url_table_ent_s {
+  const char *string;
+  int is_prefix;
+  int (*handler)(dir_connection_t *conn, const get_handler_args_t *args);
+} url_table_ent_t;
+
+static int handle_get_frontpage(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_current_consensus(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_status_vote(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_microdesc(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_descriptor(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_keys(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_hs_descriptor_v2(dir_connection_t *conn,
+                                       const get_handler_args_t *args);
+static int handle_get_robots(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+static int handle_get_networkstatus_bridges(dir_connection_t *conn,
+                                const get_handler_args_t *args);
+
+/** Table for handling GET requests. */
+static const url_table_ent_t url_table[] = {
+  { "/tor/", 0, handle_get_frontpage },
+  { "/tor/status-vote/current/consensus", 1, handle_get_current_consensus },
+  { "/tor/status-vote/current/", 1, handle_get_status_vote },
+  { "/tor/status-vote/next/", 1, handle_get_status_vote },
+  { "/tor/micro/d/", 1, handle_get_microdesc },
+  { "/tor/server/", 1, handle_get_descriptor },
+  { "/tor/extra/", 1, handle_get_descriptor },
+  { "/tor/keys/", 1, handle_get_keys },
+  { "/tor/rendezvous2/", 1, handle_get_hs_descriptor_v2 },
+  { "/tor/hs/3/", 1, handle_get_hs_descriptor_v3 },
+  { "/tor/robots.txt", 0, handle_get_robots },
+  { "/tor/networkstatus-bridges", 0, handle_get_networkstatus_bridges },
+  { NULL, 0, NULL },
+};
+
+/** Helper function: called when a dirserver gets a complete HTTP GET
+ * request.  Look for a request for a directory or for a rendezvous
+ * service descriptor.  On finding one, write a response into
+ * conn-\>outbuf.  If the request is unrecognized, send a 404.
+ * Return 0 if we handled this successfully, or -1 if we need to close
+ * the connection. */
+MOCK_IMPL(STATIC int,
+directory_handle_command_get,(dir_connection_t *conn, const char *headers,
+                              const char *req_body, size_t req_body_len))
+{
+  char *url, *url_mem, *header;
+  time_t if_modified_since = 0;
+  int zlib_compressed_in_url;
+  unsigned compression_methods_supported;
+
+  /* We ignore the body of a GET request. */
+  (void)req_body;
+  (void)req_body_len;
+
+  log_debug(LD_DIRSERV,"Received GET command.");
+
+  conn->base_.state = DIR_CONN_STATE_SERVER_WRITING;
+
+  if (parse_http_url(headers, &url) < 0) {
+    write_short_http_response(conn, 400, "Bad request");
+    return 0;
+  }
+  if ((header = http_get_header(headers, "If-Modified-Since: "))) {
+    struct tm tm;
+    if (parse_http_time(header, &tm) == 0) {
+      if (tor_timegm(&tm, &if_modified_since)<0) {
+        if_modified_since = 0;
+      } else {
+        log_debug(LD_DIRSERV, "If-Modified-Since is '%s'.", escaped(header));
+      }
+    }
+    /* The correct behavior on a malformed If-Modified-Since header is to
+     * act as if no If-Modified-Since header had been given. */
+    tor_free(header);
+  }
+  log_debug(LD_DIRSERV,"rewritten url as '%s'.", escaped(url));
+
+  url_mem = url;
+  {
+    size_t url_len = strlen(url);
+
+    zlib_compressed_in_url = url_len > 2 && !strcmp(url+url_len-2, ".z");
+    if (zlib_compressed_in_url) {
+      url[url_len-2] = '\0';
+    }
+  }
+
+  if ((header = http_get_header(headers, "Accept-Encoding: "))) {
+    compression_methods_supported = parse_accept_encoding_header(header);
+    tor_free(header);
+  } else {
+    compression_methods_supported = (1u << NO_METHOD);
+  }
+  if (zlib_compressed_in_url) {
+    compression_methods_supported |= (1u << ZLIB_METHOD);
+  }
+
+  /* Remove all methods that we don't both support. */
+  compression_methods_supported &= tor_compress_get_supported_method_bitmask();
+
+  get_handler_args_t args;
+  args.url = url;
+  args.headers = headers;
+  args.if_modified_since = if_modified_since;
+  args.compression_supported = compression_methods_supported;
+
+  int i, result = -1;
+  for (i = 0; url_table[i].string; ++i) {
+    int match;
+    if (url_table[i].is_prefix) {
+      match = !strcmpstart(url, url_table[i].string);
+    } else {
+      match = !strcmp(url, url_table[i].string);
+    }
+    if (match) {
+      result = url_table[i].handler(conn, &args);
+      goto done;
+    }
+  }
+
+  /* we didn't recognize the url */
+  write_short_http_response(conn, 404, "Not found");
+  result = 0;
+
+ done:
+  tor_free(url_mem);
+  return result;
+}
+
+/** Helper function for GET / or GET /tor/
+ */
+static int
+handle_get_frontpage(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  (void) args; /* unused */
+  const char *frontpage = get_dirportfrontpage();
+
+  if (frontpage) {
+    size_t dlen;
+    dlen = strlen(frontpage);
+    /* Let's return a disclaimer page (users shouldn't use V1 anymore,
+       and caches don't fetch '/', so this is safe). */
+
+    /* [We don't check for write_bucket_low here, since we want to serve
+     *  this page no matter what.] */
+    write_http_response_header_impl(conn, dlen, "text/html", "identity",
+                                    NULL, DIRPORTFRONTPAGE_CACHE_LIFETIME);
+    connection_buf_add(frontpage, dlen, TO_CONN(conn));
+  } else {
+    write_short_http_response(conn, 404, "Not found");
+  }
+  return 0;
+}
+
+/** Warn that the cached consensus <b>consensus</b> of type
+ * <b>flavor</b> is too old and will not be served to clients. Rate-limit the
+ * warning to avoid logging an entry on every request.
+ */
+static void
+warn_consensus_is_too_old(const struct consensus_cache_entry_t *consensus,
+                          const char *flavor, time_t now)
+{
+#define TOO_OLD_WARNING_INTERVAL (60*60)
+  static ratelim_t warned = RATELIM_INIT(TOO_OLD_WARNING_INTERVAL);
+  char timestamp[ISO_TIME_LEN+1];
+  time_t valid_until;
+  char *dupes;
+
+  if (consensus_cache_entry_get_valid_until(consensus, &valid_until))
+    return;
+
+  if ((dupes = rate_limit_log(&warned, now))) {
+    format_local_iso_time(timestamp, valid_until);
+    log_warn(LD_DIRSERV, "Our %s%sconsensus is too old, so we will not "
+             "serve it to clients. It was valid until %s local time and we "
+             "continued to serve it for up to 24 hours after it expired.%s",
+             flavor ? flavor : "", flavor ? " " : "", timestamp, dupes);
+    tor_free(dupes);
+  }
+}
+
+/**
+ * Parse a single hex-encoded sha3-256 digest from <b>hex</b> into
+ * <b>digest</b>. Return 0 on success.  On failure, report that the hash came
+ * from <b>location</b>, report that we are taking <b>action</b> with it, and
+ * return -1.
+ */
+static int
+parse_one_diff_hash(uint8_t *digest, const char *hex, const char *location,
+                    const char *action)
+{
+  if (base16_decode((char*)digest, DIGEST256_LEN, hex, strlen(hex)) ==
+      DIGEST256_LEN) {
+    return 0;
+  } else {
+    log_fn(LOG_PROTOCOL_WARN, LD_DIR,
+           "%s contained bogus digest %s; %s.",
+           location, escaped(hex), action);
+    return -1;
+  }
+}
+
+/** If there is an X-Or-Diff-From-Consensus header included in <b>headers</b>,
+ * set <b>digest_out<b> to a new smartlist containing every 256-bit
+ * hex-encoded digest listed in that header and return 0.  Otherwise return
+ * -1.  */
+static int
+parse_or_diff_from_header(smartlist_t **digests_out, const char *headers)
+{
+  char *hdr = http_get_header(headers, X_OR_DIFF_FROM_CONSENSUS_HEADER);
+  if (hdr == NULL) {
+    return -1;
+  }
+  smartlist_t *hex_digests = smartlist_new();
+  *digests_out = smartlist_new();
+  smartlist_split_string(hex_digests, hdr, " ",
+                         SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, -1);
+  SMARTLIST_FOREACH_BEGIN(hex_digests, const char *, hex) {
+    uint8_t digest[DIGEST256_LEN];
+    if (!parse_one_diff_hash(digest, hex, "X-Or-Diff-From-Consensus header",
+                             "ignoring")) {
+      smartlist_add(*digests_out, tor_memdup(digest, sizeof(digest)));
+    }
+  } SMARTLIST_FOREACH_END(hex);
+  SMARTLIST_FOREACH(hex_digests, char *, cp, tor_free(cp));
+  smartlist_free(hex_digests);
+  tor_free(hdr);
+  return 0;
+}
+
+/** Fallback compression method.  The fallback compression method is used in
+ * case a client requests a non-compressed document. We only store compressed
+ * documents, so we use this compression method to fetch the document and let
+ * the spooling system do the streaming decompression.
+ */
+#define FALLBACK_COMPRESS_METHOD ZLIB_METHOD
+
+/**
+ * Try to find the best consensus diff possible in order to serve a client
+ * request for a diff from one of the consensuses in <b>digests</b> to the
+ * current consensus of flavor <b>flav</b>.  The client supports the
+ * compression methods listed in the <b>compression_methods</b> bitfield:
+ * place the method chosen (if any) into <b>compression_used_out</b>.
+ */
+static struct consensus_cache_entry_t *
+find_best_diff(const smartlist_t *digests, int flav,
+               unsigned compression_methods,
+               compress_method_t *compression_used_out)
+{
+  struct consensus_cache_entry_t *result = NULL;
+
+  SMARTLIST_FOREACH_BEGIN(digests, const uint8_t *, diff_from) {
+    unsigned u;
+    for (u = 0; u < ARRAY_LENGTH(srv_meth_pref_precompressed); ++u) {
+      compress_method_t method = srv_meth_pref_precompressed[u];
+      if (0 == (compression_methods & (1u<<method)))
+        continue; // client doesn't like this one, or we don't have it.
+      if (consdiffmgr_find_diff_from(&result, flav, DIGEST_SHA3_256,
+                                     diff_from, DIGEST256_LEN,
+                                     method) == CONSDIFF_AVAILABLE) {
+        tor_assert_nonfatal(result);
+        *compression_used_out = method;
+        return result;
+      }
+    }
+  } SMARTLIST_FOREACH_END(diff_from);
+
+  SMARTLIST_FOREACH_BEGIN(digests, const uint8_t *, diff_from) {
+    if (consdiffmgr_find_diff_from(&result, flav, DIGEST_SHA3_256, diff_from,
+          DIGEST256_LEN, FALLBACK_COMPRESS_METHOD) == CONSDIFF_AVAILABLE) {
+      tor_assert_nonfatal(result);
+      *compression_used_out = FALLBACK_COMPRESS_METHOD;
+      return result;
+    }
+  } SMARTLIST_FOREACH_END(diff_from);
+
+  return NULL;
+}
+
+/** Lookup the cached consensus document by the flavor found in <b>flav</b>.
+ * The preferred set of compression methods should be listed in the
+ * <b>compression_methods</b> bitfield. The compression method chosen (if any)
+ * is stored in <b>compression_used_out</b>. */
+static struct consensus_cache_entry_t *
+find_best_consensus(int flav,
+                    unsigned compression_methods,
+                    compress_method_t *compression_used_out)
+{
+  struct consensus_cache_entry_t *result = NULL;
+  unsigned u;
+
+  for (u = 0; u < ARRAY_LENGTH(srv_meth_pref_precompressed); ++u) {
+    compress_method_t method = srv_meth_pref_precompressed[u];
+
+    if (0 == (compression_methods & (1u<<method)))
+      continue;
+
+    if (consdiffmgr_find_consensus(&result, flav,
+                                   method) == CONSDIFF_AVAILABLE) {
+      tor_assert_nonfatal(result);
+      *compression_used_out = method;
+      return result;
+    }
+  }
+
+  if (consdiffmgr_find_consensus(&result, flav,
+        FALLBACK_COMPRESS_METHOD) == CONSDIFF_AVAILABLE) {
+    tor_assert_nonfatal(result);
+    *compression_used_out = FALLBACK_COMPRESS_METHOD;
+    return result;
+  }
+
+  return NULL;
+}
+
+/** Try to find the best supported compression method possible from a given
+ * <b>compression_methods</b>. Return NO_METHOD if no mutually supported
+ * compression method could be found. */
+static compress_method_t
+find_best_compression_method(unsigned compression_methods, int stream)
+{
+  unsigned u;
+  compress_method_t *methods;
+  size_t length;
+
+  if (stream) {
+    methods = srv_meth_pref_streaming_compression;
+    length = ARRAY_LENGTH(srv_meth_pref_streaming_compression);
+  } else {
+    methods = srv_meth_pref_precompressed;
+    length = ARRAY_LENGTH(srv_meth_pref_precompressed);
+  }
+
+  for (u = 0; u < length; ++u) {
+    compress_method_t method = methods[u];
+    if (compression_methods & (1u<<method))
+      return method;
+  }
+
+  return NO_METHOD;
+}
+
+/** Check if any of the digests in <b>digests</b> matches the latest consensus
+ *  flavor (given in <b>flavor</b>) that we have available. */
+static int
+digest_list_contains_best_consensus(consensus_flavor_t flavor,
+                                    const smartlist_t *digests)
+{
+  const networkstatus_t *ns = NULL;
+
+  if (digests == NULL)
+    return 0;
+
+  ns = networkstatus_get_latest_consensus_by_flavor(flavor);
+
+  if (ns == NULL)
+    return 0;
+
+  SMARTLIST_FOREACH_BEGIN(digests, const uint8_t *, digest) {
+    if (tor_memeq(ns->digest_sha3_as_signed, digest, DIGEST256_LEN))
+      return 1;
+  } SMARTLIST_FOREACH_END(digest);
+
+  return 0;
+}
+
+/** Encodes the results of parsing a consensus request to figure out what
+ * consensus, and possibly what diffs, the user asked for. */
+typedef struct {
+  /** name of the flavor to retrieve. */
+  char *flavor;
+  /** flavor to retrive, as enum. */
+  consensus_flavor_t flav;
+  /** plus-separated list of authority fingerprints; see
+   * client_likes_consensus(). Aliases the URL in the request passed to
+   * parse_consensus_request(). */
+  const char *want_fps;
+  /** Optionally, a smartlist of sha3 digests-as-signed of the consensuses
+   * to return a diff from. */
+  smartlist_t *diff_from_digests;
+  /** If true, never send a full consensus. If there is no diff, send
+   * a 404 instead. */
+  int diff_only;
+} parsed_consensus_request_t;
+
+/** Remove all data held in <b>req</b>. Do not free <b>req</b> itself, since
+ * it is stack-allocated. */
+static void
+parsed_consensus_request_clear(parsed_consensus_request_t *req)
+{
+  if (!req)
+    return;
+  tor_free(req->flavor);
+  if (req->diff_from_digests) {
+    SMARTLIST_FOREACH(req->diff_from_digests, uint8_t *, d, tor_free(d));
+    smartlist_free(req->diff_from_digests);
+  }
+  memset(req, 0, sizeof(parsed_consensus_request_t));
+}
+
+/**
+ * Parse the URL and relevant headers of <b>args</b> for a current-consensus
+ * request to learn what flavor of consensus we want, what keys it must be
+ * signed with, and what diffs we would accept (or demand) instead. Return 0
+ * on success and -1 on failure.
+ */
+static int
+parse_consensus_request(parsed_consensus_request_t *out,
+                        const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  memset(out, 0, sizeof(parsed_consensus_request_t));
+  out->flav = FLAV_NS;
+
+  const char CONSENSUS_URL_PREFIX[] = "/tor/status-vote/current/consensus/";
+  const char CONSENSUS_FLAVORED_PREFIX[] =
+    "/tor/status-vote/current/consensus-";
+
+  /* figure out the flavor if any, and who we wanted to sign the thing */
+  const char *after_flavor = NULL;
+
+  if (!strcmpstart(url, CONSENSUS_FLAVORED_PREFIX)) {
+    const char *f, *cp;
+    f = url + strlen(CONSENSUS_FLAVORED_PREFIX);
+    cp = strchr(f, '/');
+    if (cp) {
+      after_flavor = cp+1;
+      out->flavor = tor_strndup(f, cp-f);
+    } else {
+      out->flavor = tor_strdup(f);
+    }
+    int flav = networkstatus_parse_flavor_name(out->flavor);
+    if (flav < 0)
+      flav = FLAV_NS;
+    out->flav = flav;
+  } else {
+    if (!strcmpstart(url, CONSENSUS_URL_PREFIX))
+      after_flavor = url+strlen(CONSENSUS_URL_PREFIX);
+  }
+
+  /* see whether we've been asked explicitly for a diff from an older
+   * consensus. (The user might also have said that a diff would be okay,
+   * via X-Or-Diff-From-Consensus */
+  const char DIFF_COMPONENT[] = "diff/";
+  char *diff_hash_in_url = NULL;
+  if (after_flavor && !strcmpstart(after_flavor, DIFF_COMPONENT)) {
+    after_flavor += strlen(DIFF_COMPONENT);
+    const char *cp = strchr(after_flavor, '/');
+    if (cp) {
+      diff_hash_in_url = tor_strndup(after_flavor, cp-after_flavor);
+      out->want_fps = cp+1;
+    } else {
+      diff_hash_in_url = tor_strdup(after_flavor);
+      out->want_fps = NULL;
+    }
+  } else {
+    out->want_fps = after_flavor;
+  }
+
+  if (diff_hash_in_url) {
+    uint8_t diff_from[DIGEST256_LEN];
+    out->diff_from_digests = smartlist_new();
+    out->diff_only = 1;
+    int ok = !parse_one_diff_hash(diff_from, diff_hash_in_url, "URL",
+                                  "rejecting");
+    tor_free(diff_hash_in_url);
+    if (ok) {
+      smartlist_add(out->diff_from_digests,
+                    tor_memdup(diff_from, DIGEST256_LEN));
+    } else {
+      return -1;
+    }
+  } else {
+    parse_or_diff_from_header(&out->diff_from_digests, args->headers);
+  }
+
+  return 0;
+}
+
+/** Helper function for GET /tor/status-vote/current/consensus
+ */
+static int
+handle_get_current_consensus(dir_connection_t *conn,
+                             const get_handler_args_t *args)
+{
+  const compress_method_t compress_method =
+    find_best_compression_method(args->compression_supported, 0);
+  const time_t if_modified_since = args->if_modified_since;
+  int clear_spool = 0;
+
+  /* v3 network status fetch. */
+  long lifetime = NETWORKSTATUS_CACHE_LIFETIME;
+
+  time_t now = time(NULL);
+  parsed_consensus_request_t req;
+
+  if (parse_consensus_request(&req, args) < 0) {
+    write_short_http_response(conn, 404, "Couldn't parse request");
+    goto done;
+  }
+
+  if (digest_list_contains_best_consensus(req.flav,
+                                          req.diff_from_digests)) {
+    write_short_http_response(conn, 304, "Not modified");
+    geoip_note_ns_response(GEOIP_REJECT_NOT_MODIFIED);
+    goto done;
+  }
+
+  struct consensus_cache_entry_t *cached_consensus = NULL;
+
+  compress_method_t compression_used = NO_METHOD;
+  if (req.diff_from_digests) {
+    cached_consensus = find_best_diff(req.diff_from_digests, req.flav,
+                                      args->compression_supported,
+                                      &compression_used);
+  }
+
+  if (req.diff_only && !cached_consensus) {
+    write_short_http_response(conn, 404, "No such diff available");
+    // XXXX warn_consensus_is_too_old(v, req.flavor, now);
+    geoip_note_ns_response(GEOIP_REJECT_NOT_FOUND);
+    goto done;
+  }
+
+  if (! cached_consensus) {
+    cached_consensus = find_best_consensus(req.flav,
+                                           args->compression_supported,
+                                           &compression_used);
+  }
+
+  time_t fresh_until, valid_until;
+  int have_fresh_until = 0, have_valid_until = 0;
+  if (cached_consensus) {
+    have_fresh_until =
+      !consensus_cache_entry_get_fresh_until(cached_consensus, &fresh_until);
+    have_valid_until =
+      !consensus_cache_entry_get_valid_until(cached_consensus, &valid_until);
+  }
+
+  if (cached_consensus && have_valid_until &&
+      !networkstatus_valid_until_is_reasonably_live(valid_until, now)) {
+    write_short_http_response(conn, 404, "Consensus is too old");
+    warn_consensus_is_too_old(cached_consensus, req.flavor, now);
+    geoip_note_ns_response(GEOIP_REJECT_NOT_FOUND);
+    goto done;
+  }
+
+  if (cached_consensus && req.want_fps &&
+      !client_likes_consensus(cached_consensus, req.want_fps)) {
+    write_short_http_response(conn, 404, "Consensus not signed by sufficient "
+                           "number of requested authorities");
+    geoip_note_ns_response(GEOIP_REJECT_NOT_ENOUGH_SIGS);
+    goto done;
+  }
+
+  conn->spool = smartlist_new();
+  clear_spool = 1;
+  {
+    spooled_resource_t *spooled;
+    if (cached_consensus) {
+      spooled = spooled_resource_new_from_cache_entry(cached_consensus);
+      smartlist_add(conn->spool, spooled);
+    }
+  }
+
+  lifetime = (have_fresh_until && fresh_until > now) ? fresh_until - now : 0;
+
+  size_t size_guess = 0;
+  int n_expired = 0;
+  dirserv_spool_remove_missing_and_guess_size(conn, if_modified_since,
+                                              compress_method != NO_METHOD,
+                                              &size_guess,
+                                              &n_expired);
+
+  if (!smartlist_len(conn->spool) && !n_expired) {
+    write_short_http_response(conn, 404, "Not found");
+    geoip_note_ns_response(GEOIP_REJECT_NOT_FOUND);
+    goto done;
+  } else if (!smartlist_len(conn->spool)) {
+    write_short_http_response(conn, 304, "Not modified");
+    geoip_note_ns_response(GEOIP_REJECT_NOT_MODIFIED);
+    goto done;
+  }
+
+  if (global_write_bucket_low(TO_CONN(conn), size_guess, 2)) {
+    log_debug(LD_DIRSERV,
+              "Client asked for network status lists, but we've been "
+              "writing too many bytes lately. Sending 503 Dir busy.");
+    write_short_http_response(conn, 503, "Directory busy, try again later");
+    geoip_note_ns_response(GEOIP_REJECT_BUSY);
+    goto done;
+  }
+
+  tor_addr_t addr;
+  if (tor_addr_parse(&addr, (TO_CONN(conn))->address) >= 0) {
+    geoip_note_client_seen(GEOIP_CLIENT_NETWORKSTATUS,
+                           &addr, NULL,
+                           time(NULL));
+    geoip_note_ns_response(GEOIP_SUCCESS);
+    /* Note that a request for a network status has started, so that we
+     * can measure the download time later on. */
+    if (conn->dirreq_id)
+      geoip_start_dirreq(conn->dirreq_id, size_guess, DIRREQ_TUNNELED);
+    else
+      geoip_start_dirreq(TO_CONN(conn)->global_identifier, size_guess,
+                         DIRREQ_DIRECT);
+  }
+
+  /* Use this header to tell caches that the response depends on the
+   * X-Or-Diff-From-Consensus header (or lack thereof). */
+  const char vary_header[] = "Vary: X-Or-Diff-From-Consensus\r\n";
+
+  clear_spool = 0;
+
+  // The compress_method might have been NO_METHOD, but we store the data
+  // compressed. Decompress them using `compression_used`. See fallback code in
+  // find_best_consensus() and find_best_diff().
+  write_http_response_headers(conn, -1,
+                             compress_method == NO_METHOD ?
+                               NO_METHOD : compression_used,
+                             vary_header,
+                             smartlist_len(conn->spool) == 1 ? lifetime : 0);
+
+  if (compress_method == NO_METHOD && smartlist_len(conn->spool))
+    conn->compress_state = tor_compress_new(0, compression_used,
+                                            HIGH_COMPRESSION);
+
+  /* Prime the connection with some data. */
+  const int initial_flush_result = connection_dirserv_flushed_some(conn);
+  tor_assert_nonfatal(initial_flush_result == 0);
+  goto done;
+
+ done:
+  parsed_consensus_request_clear(&req);
+  if (clear_spool) {
+    dir_conn_clear_spool(conn);
+  }
+  return 0;
+}
+
+/** Helper function for GET /tor/status-vote/{current,next}/...
+ */
+static int
+handle_get_status_vote(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  {
+    ssize_t body_len = 0;
+    ssize_t estimated_len = 0;
+    int lifetime = 60; /* XXXX?? should actually use vote intervals. */
+    /* This smartlist holds strings that we can compress on the fly. */
+    smartlist_t *items = smartlist_new();
+    /* This smartlist holds cached_dir_t objects that have a precompressed
+     * deflated version. */
+    smartlist_t *dir_items = smartlist_new();
+    dirvote_dirreq_get_status_vote(url, items, dir_items);
+    if (!smartlist_len(dir_items) && !smartlist_len(items)) {
+      write_short_http_response(conn, 404, "Not found");
+      goto vote_done;
+    }
+
+    /* We're sending items from at most one kind of source */
+    tor_assert_nonfatal(smartlist_len(items) == 0 ||
+                        smartlist_len(dir_items) == 0);
+
+    int streaming;
+    unsigned mask;
+    if (smartlist_len(items)) {
+      /* We're taking strings and compressing them on the fly. */
+      streaming = 1;
+      mask = ~0u;
+    } else {
+      /* We're taking cached_dir_t objects. We only have them uncompressed
+       * or deflated. */
+      streaming = 0;
+      mask = (1u<<NO_METHOD) | (1u<<ZLIB_METHOD);
+    }
+    const compress_method_t compress_method = find_best_compression_method(
+                              args->compression_supported&mask, streaming);
+
+    SMARTLIST_FOREACH(dir_items, cached_dir_t *, d,
+                      body_len += compress_method != NO_METHOD ?
+                        d->dir_compressed_len : d->dir_len);
+    estimated_len += body_len;
+    SMARTLIST_FOREACH(items, const char *, item, {
+        size_t ln = strlen(item);
+        if (compress_method != NO_METHOD) {
+          estimated_len += ln/2;
+        } else {
+          body_len += ln; estimated_len += ln;
+        }
+      });
+
+    if (global_write_bucket_low(TO_CONN(conn), estimated_len, 2)) {
+      write_short_http_response(conn, 503, "Directory busy, try again later");
+      goto vote_done;
+    }
+    write_http_response_header(conn, body_len ? body_len : -1,
+                 compress_method,
+                 lifetime);
+
+    if (smartlist_len(items)) {
+      if (compress_method != NO_METHOD) {
+        conn->compress_state = tor_compress_new(1, compress_method,
+                           choose_compression_level(estimated_len));
+        SMARTLIST_FOREACH(items, const char *, c,
+                 connection_buf_add_compress(c, strlen(c), conn, 0));
+        connection_buf_add_compress("", 0, conn, 1);
+      } else {
+        SMARTLIST_FOREACH(items, const char *, c,
+                         connection_buf_add(c, strlen(c), TO_CONN(conn)));
+      }
+    } else {
+      SMARTLIST_FOREACH(dir_items, cached_dir_t *, d,
+          connection_buf_add(compress_method != NO_METHOD ?
+                                    d->dir_compressed : d->dir,
+                                  compress_method != NO_METHOD ?
+                                    d->dir_compressed_len : d->dir_len,
+                                  TO_CONN(conn)));
+    }
+  vote_done:
+    smartlist_free(items);
+    smartlist_free(dir_items);
+    goto done;
+  }
+ done:
+  return 0;
+}
+
+/** Helper function for GET /tor/micro/d/...
+ */
+static int
+handle_get_microdesc(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  const compress_method_t compress_method =
+    find_best_compression_method(args->compression_supported, 1);
+  int clear_spool = 1;
+  {
+    conn->spool = smartlist_new();
+
+    dir_split_resource_into_spoolable(url+strlen("/tor/micro/d/"),
+                                      DIR_SPOOL_MICRODESC,
+                                      conn->spool, NULL,
+                                      DSR_DIGEST256|DSR_BASE64|DSR_SORT_UNIQ);
+
+    size_t size_guess = 0;
+    dirserv_spool_remove_missing_and_guess_size(conn, 0,
+                                                compress_method != NO_METHOD,
+                                                &size_guess, NULL);
+    if (smartlist_len(conn->spool) == 0) {
+      write_short_http_response(conn, 404, "Not found");
+      goto done;
+    }
+    if (global_write_bucket_low(TO_CONN(conn), size_guess, 2)) {
+      log_info(LD_DIRSERV,
+               "Client asked for server descriptors, but we've been "
+               "writing too many bytes lately. Sending 503 Dir busy.");
+      write_short_http_response(conn, 503, "Directory busy, try again later");
+      goto done;
+    }
+
+    clear_spool = 0;
+    write_http_response_header(conn, -1,
+                               compress_method,
+                               MICRODESC_CACHE_LIFETIME);
+
+    if (compress_method != NO_METHOD)
+      conn->compress_state = tor_compress_new(1, compress_method,
+                                      choose_compression_level(size_guess));
+
+    const int initial_flush_result = connection_dirserv_flushed_some(conn);
+    tor_assert_nonfatal(initial_flush_result == 0);
+    goto done;
+  }
+
+ done:
+  if (clear_spool) {
+    dir_conn_clear_spool(conn);
+  }
+  return 0;
+}
+
+/** Helper function for GET /tor/{server,extra}/...
+ */
+static int
+handle_get_descriptor(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  const compress_method_t compress_method =
+    find_best_compression_method(args->compression_supported, 1);
+  const or_options_t *options = get_options();
+  int clear_spool = 1;
+  if (!strcmpstart(url,"/tor/server/") ||
+      (!options->BridgeAuthoritativeDir &&
+       !options->BridgeRelay && !strcmpstart(url,"/tor/extra/"))) {
+    int res;
+    const char *msg = NULL;
+    int cache_lifetime = 0;
+    int is_extra = !strcmpstart(url,"/tor/extra/");
+    url += is_extra ? strlen("/tor/extra/") : strlen("/tor/server/");
+    dir_spool_source_t source;
+    time_t publish_cutoff = 0;
+    if (!strcmpstart(url, "d/")) {
+      source =
+        is_extra ? DIR_SPOOL_EXTRA_BY_DIGEST : DIR_SPOOL_SERVER_BY_DIGEST;
+    } else {
+      source =
+        is_extra ? DIR_SPOOL_EXTRA_BY_FP : DIR_SPOOL_SERVER_BY_FP;
+      /* We only want to apply a publish cutoff when we're requesting
+       * resources by fingerprint. */
+      publish_cutoff = time(NULL) - ROUTER_MAX_AGE_TO_PUBLISH;
+    }
+
+    conn->spool = smartlist_new();
+    res = dirserv_get_routerdesc_spool(conn->spool, url,
+                                       source,
+                                       connection_dir_is_encrypted(conn),
+                                       &msg);
+
+    if (!strcmpstart(url, "all")) {
+      cache_lifetime = FULL_DIR_CACHE_LIFETIME;
+    } else if (smartlist_len(conn->spool) == 1) {
+      cache_lifetime = ROUTERDESC_BY_DIGEST_CACHE_LIFETIME;
+    }
+
+    size_t size_guess = 0;
+    int n_expired = 0;
+    dirserv_spool_remove_missing_and_guess_size(conn, publish_cutoff,
+                                                compress_method != NO_METHOD,
+                                                &size_guess, &n_expired);
+
+    /* If we are the bridge authority and the descriptor is a bridge
+     * descriptor, remember that we served this descriptor for desc stats. */
+    /* XXXX it's a bit of a kludge to have this here. */
+    if (get_options()->BridgeAuthoritativeDir &&
+        source == DIR_SPOOL_SERVER_BY_FP) {
+      SMARTLIST_FOREACH_BEGIN(conn->spool, spooled_resource_t *, spooled) {
+        const routerinfo_t *router =
+          router_get_by_id_digest((const char *)spooled->digest);
+        /* router can be NULL here when the bridge auth is asked for its own
+         * descriptor. */
+        if (router && router->purpose == ROUTER_PURPOSE_BRIDGE)
+          rep_hist_note_desc_served(router->cache_info.identity_digest);
+      } SMARTLIST_FOREACH_END(spooled);
+    }
+
+    if (res < 0 || size_guess == 0 || smartlist_len(conn->spool) == 0) {
+      if (msg == NULL)
+        msg = "Not found";
+      write_short_http_response(conn, 404, msg);
+    } else {
+      if (global_write_bucket_low(TO_CONN(conn), size_guess, 2)) {
+        log_info(LD_DIRSERV,
+                 "Client asked for server descriptors, but we've been "
+                 "writing too many bytes lately. Sending 503 Dir busy.");
+        write_short_http_response(conn, 503,
+                                  "Directory busy, try again later");
+        dir_conn_clear_spool(conn);
+        goto done;
+      }
+      write_http_response_header(conn, -1, compress_method, cache_lifetime);
+      if (compress_method != NO_METHOD)
+        conn->compress_state = tor_compress_new(1, compress_method,
+                                        choose_compression_level(size_guess));
+      clear_spool = 0;
+      /* Prime the connection with some data. */
+      int initial_flush_result = connection_dirserv_flushed_some(conn);
+      tor_assert_nonfatal(initial_flush_result == 0);
+    }
+    goto done;
+  }
+ done:
+  if (clear_spool)
+    dir_conn_clear_spool(conn);
+  return 0;
+}
+
+/** Helper function for GET /tor/keys/...
+ */
+static int
+handle_get_keys(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  const compress_method_t compress_method =
+    find_best_compression_method(args->compression_supported, 1);
+  const time_t if_modified_since = args->if_modified_since;
+  {
+    smartlist_t *certs = smartlist_new();
+    ssize_t len = -1;
+    if (!strcmp(url, "/tor/keys/all")) {
+      authority_cert_get_all(certs);
+    } else if (!strcmp(url, "/tor/keys/authority")) {
+      authority_cert_t *cert = get_my_v3_authority_cert();
+      if (cert)
+        smartlist_add(certs, cert);
+    } else if (!strcmpstart(url, "/tor/keys/fp/")) {
+      smartlist_t *fps = smartlist_new();
+      dir_split_resource_into_fingerprints(url+strlen("/tor/keys/fp/"),
+                                           fps, NULL,
+                                           DSR_HEX|DSR_SORT_UNIQ);
+      SMARTLIST_FOREACH(fps, char *, d, {
+          authority_cert_t *c = authority_cert_get_newest_by_id(d);
+          if (c) smartlist_add(certs, c);
+          tor_free(d);
+      });
+      smartlist_free(fps);
+    } else if (!strcmpstart(url, "/tor/keys/sk/")) {
+      smartlist_t *fps = smartlist_new();
+      dir_split_resource_into_fingerprints(url+strlen("/tor/keys/sk/"),
+                                           fps, NULL,
+                                           DSR_HEX|DSR_SORT_UNIQ);
+      SMARTLIST_FOREACH(fps, char *, d, {
+          authority_cert_t *c = authority_cert_get_by_sk_digest(d);
+          if (c) smartlist_add(certs, c);
+          tor_free(d);
+      });
+      smartlist_free(fps);
+    } else if (!strcmpstart(url, "/tor/keys/fp-sk/")) {
+      smartlist_t *fp_sks = smartlist_new();
+      dir_split_resource_into_fingerprint_pairs(url+strlen("/tor/keys/fp-sk/"),
+                                                fp_sks);
+      SMARTLIST_FOREACH(fp_sks, fp_pair_t *, pair, {
+          authority_cert_t *c = authority_cert_get_by_digests(pair->first,
+                                                              pair->second);
+          if (c) smartlist_add(certs, c);
+          tor_free(pair);
+      });
+      smartlist_free(fp_sks);
+    } else {
+      write_short_http_response(conn, 400, "Bad request");
+      goto keys_done;
+    }
+    if (!smartlist_len(certs)) {
+      write_short_http_response(conn, 404, "Not found");
+      goto keys_done;
+    }
+    SMARTLIST_FOREACH(certs, authority_cert_t *, c,
+      if (c->cache_info.published_on < if_modified_since)
+        SMARTLIST_DEL_CURRENT(certs, c));
+    if (!smartlist_len(certs)) {
+      write_short_http_response(conn, 304, "Not modified");
+      goto keys_done;
+    }
+    len = 0;
+    SMARTLIST_FOREACH(certs, authority_cert_t *, c,
+                      len += c->cache_info.signed_descriptor_len);
+
+    if (global_write_bucket_low(TO_CONN(conn),
+                                compress_method != NO_METHOD ? len/2 : len,
+                                2)) {
+      write_short_http_response(conn, 503, "Directory busy, try again later");
+      goto keys_done;
+    }
+
+    write_http_response_header(conn,
+                               compress_method != NO_METHOD ? -1 : len,
+                               compress_method,
+                               60*60);
+    if (compress_method != NO_METHOD) {
+      conn->compress_state = tor_compress_new(1, compress_method,
+                                              choose_compression_level(len));
+      SMARTLIST_FOREACH(certs, authority_cert_t *, c,
+            connection_buf_add_compress(
+                c->cache_info.signed_descriptor_body,
+                c->cache_info.signed_descriptor_len,
+                conn, 0));
+      connection_buf_add_compress("", 0, conn, 1);
+    } else {
+      SMARTLIST_FOREACH(certs, authority_cert_t *, c,
+            connection_buf_add(c->cache_info.signed_descriptor_body,
+                                    c->cache_info.signed_descriptor_len,
+                                    TO_CONN(conn)));
+    }
+  keys_done:
+    smartlist_free(certs);
+    goto done;
+  }
+ done:
+  return 0;
+}
+
+/** Helper function for GET /tor/rendezvous2/
+ */
+static int
+handle_get_hs_descriptor_v2(dir_connection_t *conn,
+                            const get_handler_args_t *args)
+{
+  const char *url = args->url;
+  if (connection_dir_is_encrypted(conn)) {
+    /* Handle v2 rendezvous descriptor fetch request. */
+    const char *descp;
+    const char *query = url + strlen("/tor/rendezvous2/");
+    if (rend_valid_descriptor_id(query)) {
+      log_info(LD_REND, "Got a v2 rendezvous descriptor request for ID '%s'",
+               safe_str(escaped(query)));
+      switch (rend_cache_lookup_v2_desc_as_dir(query, &descp)) {
+        case 1: /* valid */
+          write_http_response_header(conn, strlen(descp), NO_METHOD, 0);
+          connection_buf_add(descp, strlen(descp), TO_CONN(conn));
+          break;
+        case 0: /* well-formed but not present */
+          write_short_http_response(conn, 404, "Not found");
+          break;
+        case -1: /* not well-formed */
+          write_short_http_response(conn, 400, "Bad request");
+          break;
+      }
+    } else { /* not well-formed */
+      write_short_http_response(conn, 400, "Bad request");
+    }
+    goto done;
+  } else {
+    /* Not encrypted! */
+    write_short_http_response(conn, 404, "Not found");
+  }
+ done:
+  return 0;
+}
+
+/** Helper function for GET /tor/hs/3/<z>. Only for version 3.
+ */
+STATIC int
+handle_get_hs_descriptor_v3(dir_connection_t *conn,
+                            const get_handler_args_t *args)
+{
+  int retval;
+  const char *desc_str = NULL;
+  const char *pubkey_str = NULL;
+  const char *url = args->url;
+
+  /* Reject unencrypted dir connections */
+  if (!connection_dir_is_encrypted(conn)) {
+    write_short_http_response(conn, 404, "Not found");
+    goto done;
+  }
+
+  /* After the path prefix follows the base64 encoded blinded pubkey which we
+   * use to get the descriptor from the cache. Skip the prefix and get the
+   * pubkey. */
+  tor_assert(!strcmpstart(url, "/tor/hs/3/"));
+  pubkey_str = url + strlen("/tor/hs/3/");
+  retval = hs_cache_lookup_as_dir(HS_VERSION_THREE,
+                                  pubkey_str, &desc_str);
+  if (retval <= 0 || desc_str == NULL) {
+    write_short_http_response(conn, 404, "Not found");
+    goto done;
+  }
+
+  /* Found requested descriptor! Pass it to this nice client. */
+  write_http_response_header(conn, strlen(desc_str), NO_METHOD, 0);
+  connection_buf_add(desc_str, strlen(desc_str), TO_CONN(conn));
+
+ done:
+  return 0;
+}
+
+/** Helper function for GET /tor/networkstatus-bridges
+ */
+static int
+handle_get_networkstatus_bridges(dir_connection_t *conn,
+                                 const get_handler_args_t *args)
+{
+  const char *headers = args->headers;
+
+  const or_options_t *options = get_options();
+  if (options->BridgeAuthoritativeDir &&
+      options->BridgePassword_AuthDigest_ &&
+      connection_dir_is_encrypted(conn)) {
+    char *status;
+    char digest[DIGEST256_LEN];
+
+    char *header = http_get_header(headers, "Authorization: Basic ");
+    if (header)
+      crypto_digest256(digest, header, strlen(header), DIGEST_SHA256);
+
+    /* now make sure the password is there and right */
+    if (!header ||
+        tor_memneq(digest,
+                   options->BridgePassword_AuthDigest_, DIGEST256_LEN)) {
+      write_short_http_response(conn, 404, "Not found");
+      tor_free(header);
+      goto done;
+    }
+    tor_free(header);
+
+    /* all happy now. send an answer. */
+    status = networkstatus_getinfo_by_purpose("bridge", time(NULL));
+    size_t dlen = strlen(status);
+    write_http_response_header(conn, dlen, NO_METHOD, 0);
+    connection_buf_add(status, dlen, TO_CONN(conn));
+    tor_free(status);
+    goto done;
+  }
+ done:
+  return 0;
+}
+
+/** Helper function for GET robots.txt or /tor/robots.txt */
+static int
+handle_get_robots(dir_connection_t *conn, const get_handler_args_t *args)
+{
+  (void)args;
+  {
+    const char robots[] = "User-agent: *\r\nDisallow: /\r\n";
+    size_t len = strlen(robots);
+    write_http_response_header(conn, len, NO_METHOD, ROBOTS_CACHE_LIFETIME);
+    connection_buf_add(robots, len, TO_CONN(conn));
+  }
+  return 0;
+}
+
+/* Given the <b>url</b> from a POST request, try to extract the version number
+ * using the provided <b>prefix</b>. The version should be after the prefix and
+ * ending with the separator "/". For instance:
+ *      /tor/hs/3/publish
+ *
+ * On success, <b>end_pos</b> points to the position right after the version
+ * was found. On error, it is set to NULL.
+ *
+ * Return version on success else negative value. */
+STATIC int
+parse_hs_version_from_post(const char *url, const char *prefix,
+                           const char **end_pos)
+{
+  int ok;
+  unsigned long version;
+  const char *start;
+  char *end = NULL;
+
+  tor_assert(url);
+  tor_assert(prefix);
+  tor_assert(end_pos);
+
+  /* Check if the prefix does start the url. */
+  if (strcmpstart(url, prefix)) {
+    goto err;
+  }
+  /* Move pointer to the end of the prefix string. */
+  start = url + strlen(prefix);
+  /* Try this to be the HS version and if we are still at the separator, next
+   * will be move to the right value. */
+  version = tor_parse_long(start, 10, 0, INT_MAX, &ok, &end);
+  if (!ok) {
+    goto err;
+  }
+
+  *end_pos = end;
+  return (int) version;
+ err:
+  *end_pos = NULL;
+  return -1;
+}
+
+/* Handle the POST request for a hidden service descripror. The request is in
+ * <b>url</b>, the body of the request is in <b>body</b>. Return 200 on success
+ * else return 400 indicating a bad request. */
+STATIC int
+handle_post_hs_descriptor(const char *url, const char *body)
+{
+  int version;
+  const char *end_pos;
+
+  tor_assert(url);
+  tor_assert(body);
+
+  version = parse_hs_version_from_post(url, "/tor/hs/", &end_pos);
+  if (version < 0) {
+    goto err;
+  }
+
+  /* We have a valid version number, now make sure it's a publish request. Use
+   * the end position just after the version and check for the command. */
+  if (strcmpstart(end_pos, "/publish")) {
+    goto err;
+  }
+
+  switch (version) {
+  case HS_VERSION_THREE:
+    if (hs_cache_store_as_dir(body) < 0) {
+      goto err;
+    }
+    log_info(LD_REND, "Publish request for HS descriptor handled "
+                      "successfully.");
+    break;
+  default:
+    /* Unsupported version, return a bad request. */
+    goto err;
+  }
+
+  return 200;
+ err:
+  /* Bad request. */
+  return 400;
+}
+
+/** Helper function: called when a dirserver gets a complete HTTP POST
+ * request.  Look for an uploaded server descriptor or rendezvous
+ * service descriptor.  On finding one, process it and write a
+ * response into conn-\>outbuf.  If the request is unrecognized, send a
+ * 400.  Always return 0. */
+MOCK_IMPL(STATIC int,
+directory_handle_command_post,(dir_connection_t *conn, const char *headers,
+                               const char *body, size_t body_len))
+{
+  char *url = NULL;
+  const or_options_t *options = get_options();
+
+  log_debug(LD_DIRSERV,"Received POST command.");
+
+  conn->base_.state = DIR_CONN_STATE_SERVER_WRITING;
+
+  if (!public_server_mode(options)) {
+    log_info(LD_DIR, "Rejected dir post request from %s "
+             "since we're not a public relay.", conn->base_.address);
+    write_short_http_response(conn, 503, "Not acting as a public relay");
+    goto done;
+  }
+
+  if (parse_http_url(headers, &url) < 0) {
+    write_short_http_response(conn, 400, "Bad request");
+    return 0;
+  }
+  log_debug(LD_DIRSERV,"rewritten url as '%s'.", escaped(url));
+
+  /* Handle v2 rendezvous service publish request. */
+  if (connection_dir_is_encrypted(conn) &&
+      !strcmpstart(url,"/tor/rendezvous2/publish")) {
+    if (rend_cache_store_v2_desc_as_dir(body) < 0) {
+      log_warn(LD_REND, "Rejected v2 rend descriptor (body size %d) from %s.",
+               (int)body_len, conn->base_.address);
+      write_short_http_response(conn, 400,
+                             "Invalid v2 service descriptor rejected");
+    } else {
+      write_short_http_response(conn, 200, "Service descriptor (v2) stored");
+      log_info(LD_REND, "Handled v2 rendezvous descriptor post: accepted");
+    }
+    goto done;
+  }
+
+  /* Handle HS descriptor publish request. */
+  /* XXX: This should be disabled with a consensus param until we want to
+   * the prop224 be deployed and thus use. */
+  if (connection_dir_is_encrypted(conn) && !strcmpstart(url, "/tor/hs/")) {
+    const char *msg = "HS descriptor stored successfully.";
+
+    /* We most probably have a publish request for an HS descriptor. */
+    int code = handle_post_hs_descriptor(url, body);
+    if (code != 200) {
+      msg = "Invalid HS descriptor. Rejected.";
+    }
+    write_short_http_response(conn, code, msg);
+    goto done;
+  }
+
+  if (!authdir_mode(options)) {
+    /* we just provide cached directories; we don't want to
+     * receive anything. */
+    write_short_http_response(conn, 400, "Nonauthoritative directory does not "
+                           "accept posted server descriptors");
+    goto done;
+  }
+
+  if (authdir_mode(options) &&
+      !strcmp(url,"/tor/")) { /* server descriptor post */
+    const char *msg = "[None]";
+    uint8_t purpose = authdir_mode_bridge(options) ?
+                      ROUTER_PURPOSE_BRIDGE : ROUTER_PURPOSE_GENERAL;
+    was_router_added_t r = dirserv_add_multiple_descriptors(body, purpose,
+                                             conn->base_.address, &msg);
+    tor_assert(msg);
+
+    if (r == ROUTER_ADDED_SUCCESSFULLY) {
+      write_short_http_response(conn, 200, msg);
+    } else if (WRA_WAS_OUTDATED(r)) {
+      write_http_response_header_impl(conn, -1, NULL, NULL,
+                                      "X-Descriptor-Not-New: Yes\r\n", -1);
+    } else {
+      log_info(LD_DIRSERV,
+               "Rejected router descriptor or extra-info from %s "
+               "(\"%s\").",
+               conn->base_.address, msg);
+      write_short_http_response(conn, 400, msg);
+    }
+    goto done;
+  }
+
+  if (authdir_mode_v3(options) &&
+      !strcmp(url,"/tor/post/vote")) { /* v3 networkstatus vote */
+    const char *msg = "OK";
+    int status;
+    if (dirvote_add_vote(body, &msg, &status)) {
+      write_short_http_response(conn, status, "Vote stored");
+    } else {
+      tor_assert(msg);
+      log_warn(LD_DIRSERV, "Rejected vote from %s (\"%s\").",
+               conn->base_.address, msg);
+      write_short_http_response(conn, status, msg);
+    }
+    goto done;
+  }
+
+  if (authdir_mode_v3(options) &&
+      !strcmp(url,"/tor/post/consensus-signature")) { /* sigs on consensus. */
+    const char *msg = NULL;
+    if (dirvote_add_signatures(body, conn->base_.address, &msg)>=0) {
+      write_short_http_response(conn, 200, msg?msg:"Signatures stored");
+    } else {
+      log_warn(LD_DIR, "Unable to store signatures posted by %s: %s",
+               conn->base_.address, msg?msg:"???");
+      write_short_http_response(conn, 400,
+                                msg?msg:"Unable to store signatures");
+    }
+    goto done;
+  }
+
+  /* we didn't recognize the url */
+  write_short_http_response(conn, 404, "Not found");
+
+ done:
+  tor_free(url);
+  return 0;
+}
+
+/** If <b>headers</b> indicates that a proxy was involved, then rewrite
+ * <b>conn</b>-\>address to describe our best guess of the address that
+ * originated this HTTP request. */
+static void
+http_set_address_origin(const char *headers, connection_t *conn)
+{
+  char *fwd;
+
+  fwd = http_get_header(headers, "Forwarded-For: ");
+  if (!fwd)
+    fwd = http_get_header(headers, "X-Forwarded-For: ");
+  if (fwd) {
+    tor_addr_t toraddr;
+    if (tor_addr_parse(&toraddr,fwd) == -1 ||
+        tor_addr_is_internal(&toraddr,0)) {
+      log_debug(LD_DIR, "Ignoring local/internal IP %s", escaped(fwd));
+      tor_free(fwd);
+      return;
+    }
+
+    tor_free(conn->address);
+    conn->address = tor_strdup(fwd);
+    tor_free(fwd);
+  }
+}
+
+/** Called when a dirserver receives data on a directory connection;
+ * looks for an HTTP request.  If the request is complete, remove it
+ * from the inbuf, try to process it; otherwise, leave it on the
+ * buffer.  Return a 0 on success, or -1 on error.
+ */
+int
+directory_handle_command(dir_connection_t *conn)
+{
+  char *headers=NULL, *body=NULL;
+  size_t body_len=0;
+  int r;
+
+  tor_assert(conn);
+  tor_assert(conn->base_.type == CONN_TYPE_DIR);
+
+  switch (connection_fetch_from_buf_http(TO_CONN(conn),
+                              &headers, MAX_HEADERS_SIZE,
+                              &body, &body_len, MAX_DIR_UL_SIZE, 0)) {
+    case -1: /* overflow */
+      log_warn(LD_DIRSERV,
+               "Request too large from address '%s' to DirPort. Closing.",
+               safe_str(conn->base_.address));
+      return -1;
+    case 0:
+      log_debug(LD_DIRSERV,"command not all here yet.");
+      return 0;
+    /* case 1, fall through */
+  }
+
+  http_set_address_origin(headers, TO_CONN(conn));
+  // we should escape headers here as well,
+  // but we can't call escaped() twice, as it uses the same buffer
+  //log_debug(LD_DIRSERV,"headers %s, body %s.", headers, escaped(body));
+
+  if (!strncasecmp(headers,"GET",3))
+    r = directory_handle_command_get(conn, headers, body, body_len);
+  else if (!strncasecmp(headers,"POST",4))
+    r = directory_handle_command_post(conn, headers, body, body_len);
+  else {
+    log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
+           "Got headers %s with unknown command. Closing.",
+           escaped(headers));
+    r = -1;
+  }
+
+  tor_free(headers); tor_free(body);
+  return r;
+}