tor/src/or/protover.c

#define PROTOVER_PRIVATE

#include "protover.h"
#include "compat.h"
#include "torlog.h"

static const smartlist_t *get_supported_protocol_list(void);
static int protocol_list_contains(const smartlist_t *protos,
                                  protocol_type_t pr, uint32_t ver);

/** Mapping between protocol type string and protocol type. */
static const struct {
  protocol_type_t protover_type;
  const char *name;
} PROTOCOL_NAMES[] = {
  { PRT_LINK, "Link" },
  { PRT_LINKAUTH, "LinkAuth" },
  { PRT_RELAY, "Relay" },
  { PRT_HSMID, "HSMid" },
  { PRT_DIRCACHE, "DirCache" },
  { PRT_HSDIR, "HSDir" },
  { PRT_DESC, "Desc" },
  { PRT_MICRODESC, "Microdesc"},
  { PRT_CONS, "Cons" }
};

#define N_PROTOCOL_NAMES ARRAY_LENGTH(PROTOCOL_NAMES)

/**
 * Given a protocol_type_t, return the corresponding string used in
 * descriptors.
 */
STATIC const char *
protocol_type_to_str(protocol_type_t pr)
{
  unsigned i;
  for (i=0; i < N_PROTOCOL_NAMES; ++i) {
    if (PROTOCOL_NAMES[i].protover_type == pr)
      return PROTOCOL_NAMES[i].name;
  }
  tor_assert_nonfatal_unreached_once();
  return "UNKNOWN";
}

/**
 * Given a string, find the corresponding protocol type and store it in
 * <b>pr_out</b>. Return 0 on success, -1 on failure.
 */
STATIC int
str_to_protocol_type(const char *s, protocol_type_t *pr_out)
{
  if (BUG(!pr_out))
    return -1;

  unsigned i;
  for (i=0; i < N_PROTOCOL_NAMES; ++i) {
    if (0 == strcmp(s, PROTOCOL_NAMES[i].name)) {
      *pr_out = PROTOCOL_NAMES[i].protover_type;
      return 0;
    }
  }

  return -1;
}

/**
 * Release all space held by a single proto_entry_t structure
 */
STATIC void
proto_entry_free(proto_entry_t *entry)
{
  if (!entry)
    return;
  tor_free(entry->name);
  SMARTLIST_FOREACH(entry->ranges, proto_range_t *, r, tor_free(r));
  smartlist_free(entry->ranges);
  tor_free(entry);
}

/**
 * Given a string <b>s</b> and optional end-of-string pointer
 * <b>end_of_range</b>, parse the protocol range and store it in
 * <b>low_out</b> and <b>high_out</b>.  A protocol range has the format U, or
 * U-U, where U is an unsigned 32-bit integer.
 */
static int
parse_version_range(const char *s, const char *end_of_range,
                    uint32_t *low_out, uint32_t *high_out)
{
  uint32_t low, high;
  char *next = NULL;
  int ok;

  tor_assert(high_out);
  tor_assert(low_out);

  if (BUG(!end_of_range))
    end_of_range = s + strlen(s); // LCOV_EXCL_LINE

  /* Note that this wouldn't be safe if we didn't know that eventually,
   * we'd hit a NUL */
  low = (uint32_t) tor_parse_ulong(s, 10, 0, UINT32_MAX, &ok, &next);
  if (!ok)
    goto error;
  if (next > end_of_range)
    goto error;
  if (next == end_of_range) {
    high = low;
    goto done;
  }

  if (*next != '-')
    goto error;
  s = next+1;
  /* ibid */
  high = (uint32_t) tor_parse_ulong(s, 10, 0, UINT32_MAX, &ok, &next);
  if (!ok)
    goto error;
  if (next != end_of_range)
    goto error;

 done:
  *high_out = high;
  *low_out = low;
  return 0;

 error:
  return -1;
}

/** Parse a single protocol entry from <b>s</b> up to an optional
 * <b>end_of_entry</b> pointer, and return that protocol entry. Return NULL
 * on error.
 *
 * A protocol entry has a keyword, an = sign, and zero or more ranges. */
static proto_entry_t *
parse_single_entry(const char *s, const char *end_of_entry)
{
  proto_entry_t *out = tor_malloc_zero(sizeof(proto_entry_t));
  const char *equals;

  out->ranges = smartlist_new();

  if (BUG (!end_of_entry))
    end_of_entry = s + strlen(s); // LCOV_EXCL_LINE

  /* There must be an =. */
  equals = memchr(s, '=', end_of_entry - s);
  if (!equals)
    goto error;

  out->name = tor_strndup(s, equals-s);

  tor_assert(equals < end_of_entry);

  s = equals + 1;
  while (s < end_of_entry) {
    const char *comma = memchr(s, ',', end_of_entry-s);
    proto_range_t *range = tor_malloc_zero(sizeof(proto_range_t));
    if (! comma)
      comma = end_of_entry;

    smartlist_add(out->ranges, range);
    if (parse_version_range(s, comma, &range->low, &range->high) < 0) {
      goto error;
    }

    if (range->low > range->high) {
      goto error;
    }

    s = comma;
    while (*s == ',' && s < end_of_entry)
      ++s;
  }

  return out;

 error:
  proto_entry_free(out);
  return NULL;
}

/**
 * Parse the protocol list from <b>s</b> and return it as a smartlist of
 * proto_entry_t
 */
STATIC smartlist_t *
parse_protocol_list(const char *s)
{
  smartlist_t *entries = smartlist_new();

  while (*s) {
    /* Find the next space or the NUL. */
    const char *end_of_entry = strchr(s, ' ');
    proto_entry_t *entry;
    if (!end_of_entry)
      end_of_entry = s + strlen(s);

    entry = parse_single_entry(s, end_of_entry);

    if (! entry)
      goto error;

    smartlist_add(entries, entry);

    s = end_of_entry;
    while (*s == ' ')
      ++s;
  }

  return entries;

 error:
  SMARTLIST_FOREACH(entries, proto_entry_t *, ent, proto_entry_free(ent));
  smartlist_free(entries);
  return NULL;
}

/**
 * Given a protocol type and version number, return true iff we know
 * how to speak that protocol.
 */
int
protover_is_supported_here(protocol_type_t pr, uint32_t ver)
{
  const smartlist_t *ours = get_supported_protocol_list();
  return protocol_list_contains(ours, pr, ver);
}

/** Return the canonical string containing the list of protocols
 * that we support. */
const char *
get_supported_protocols(void)
{
  return
    "Cons=1-2 "
    "Desc=1-2 "
    "DirCache=1 "
    "HSDir=1 "
    "HSMid=1 "
    "Link=1-4 "
    "LinkAuth=1 "
    "Microdesc=1-2 "
    "Relay=1-2";
}

/** The protocols from get_supported_protocols(), as parsed into a list of
 * proto_entry_t values. Access this via get_supported_protocol_list. */
static smartlist_t *supported_protocol_list = NULL;

/** Return a pointer to a smartlist of proto_entry_t for the protocols
 * we support. */
static const smartlist_t *
get_supported_protocol_list(void)
{
  if (PREDICT_UNLIKELY(supported_protocol_list == NULL)) {
    supported_protocol_list = parse_protocol_list(get_supported_protocols());
  }
  return supported_protocol_list;
}

/**
 * Given a protocol entry, encode it at the end of the smartlist <b>chunks</b>
 * as one or more newly allocated strings.
 */
static void
proto_entry_encode_into(smartlist_t *chunks, const proto_entry_t *entry)
{
  smartlist_add_asprintf(chunks, "%s=", entry->name);

  SMARTLIST_FOREACH_BEGIN(entry->ranges, proto_range_t *, range) {
    const char *comma = "";
    if (range_sl_idx != 0)
      comma = ",";

    if (range->low == range->high) {
      smartlist_add_asprintf(chunks, "%s%lu",
                             comma, (unsigned long)range->low);
    } else {
      smartlist_add_asprintf(chunks, "%s%lu-%lu",
                             comma, (unsigned long)range->low,
                             (unsigned long)range->high);
    }
  } SMARTLIST_FOREACH_END(range);
}

/** Given a list of space-separated proto_entry_t items,
 * encode it into a newly allocated space-separated string. */
STATIC char *
encode_protocol_list(const smartlist_t *sl)
{
  const char *separator = "";
  smartlist_t *chunks = smartlist_new();
  SMARTLIST_FOREACH_BEGIN(sl, const proto_entry_t *, ent) {
    smartlist_add(chunks, tor_strdup(separator));

    proto_entry_encode_into(chunks, ent);

    separator = " ";
  } SMARTLIST_FOREACH_END(ent);

  char *result = smartlist_join_strings(chunks, "", 0, NULL);

  SMARTLIST_FOREACH(chunks, char *, cp, tor_free(cp));
  smartlist_free(chunks);

  return result;
}

/** Return true if every protocol version described in the string <b>s</b> is
 * one that we support, and false otherwise.  If <b>missing_out</b> is
 * provided, set it to the list of protocols we do not support.
 *
 * NOTE: This is quadratic, but we don't do it much: only a few times per
 * consensus. Checking signatures should be way more expensive than this
 * ever would be.
 **/
int
protover_all_supported(const char *s, char **missing_out)
{
  int all_supported = 1;
  smartlist_t *missing;

  if (!s) {
    return 1;
  }

  smartlist_t *entries = parse_protocol_list(s);

  missing = smartlist_new();

  SMARTLIST_FOREACH_BEGIN(entries, const proto_entry_t *, ent) {
    protocol_type_t tp;
    if (str_to_protocol_type(ent->name, &tp) < 0) {
      if (smartlist_len(ent->ranges)) {
        goto unsupported;
      }
      continue;
    }

    SMARTLIST_FOREACH_BEGIN(ent->ranges, const proto_range_t *, range) {
      uint32_t i;
      for (i = range->low; i <= range->high; ++i) {
        if (!protover_is_supported_here(tp, i)) {
          goto unsupported;
        }
      }
    } SMARTLIST_FOREACH_END(range);

    continue;

  unsupported:
    all_supported = 0;
    smartlist_add(missing, (void*) ent);
  } SMARTLIST_FOREACH_END(ent);


  if (missing_out && !all_supported) {
    tor_assert(0 != smartlist_len(missing));
    *missing_out = encode_protocol_list(missing);
  }
  smartlist_free(missing);

  SMARTLIST_FOREACH(entries, proto_entry_t *, ent, proto_entry_free(ent));
  smartlist_free(entries);

  return all_supported;
}

static int
protocol_list_contains(const smartlist_t *protos,
                       protocol_type_t pr, uint32_t ver)
{
  if (BUG(protos == NULL)) {
    return 0;
  }
  const char *pr_name = protocol_type_to_str(pr);
  if (BUG(pr_name == NULL)) {
    return 0;
  }

  SMARTLIST_FOREACH_BEGIN(protos, const proto_entry_t *, ent) {
    if (strcasecmp(ent->name, pr_name))
      continue;
    /* name matches; check the ranges */
    SMARTLIST_FOREACH_BEGIN(ent->ranges, const proto_range_t *, range) {
      if (ver >= range->low && ver <= range->high)
        return 1;
    } SMARTLIST_FOREACH_END(range);
  } SMARTLIST_FOREACH_END(ent);

  return 0;
}

void
protover_free_all(void)
{
  if (supported_protocol_list) {
    smartlist_t *entries = supported_protocol_list;
    SMARTLIST_FOREACH(entries, proto_entry_t *, ent, proto_entry_free(ent));
    smartlist_free(entries);
    supported_protocol_list = NULL;
  }
}