compat.c

关于tor匿名通信的源代码

#endif /* HAVE_GETRLIMIT */

  if (limit < ULIMIT_BUFFER) {
    log_warn(LD_CONFIG,
             "ConnLimit must be at least %d. Failing.", ULIMIT_BUFFER);
    return -1;
  }
  if (limit > INT_MAX)
    limit = INT_MAX;
  tor_assert(max_out);
  *max_out = (int)limit - ULIMIT_BUFFER;
  return 0;
}

/** Call setuid and setgid to run as <b>user</b>:<b>group</b>.  Return 0 on
 * success.  On failure, log and return -1.
 */
int
switch_id(const char *user, const char *group)
{
#ifndef MS_WINDOWS
  struct passwd *pw = NULL;
  struct group *gr = NULL;

  if (user) {
    pw = getpwnam(user);
    if (pw == NULL) {
      log_warn(LD_CONFIG,"User '%s' not found.", user);
      return -1;
    }
  }

  /* switch the group first, while we still have the privileges to do so */
  if (group) {
    gr = getgrnam(group);
    if (gr == NULL) {
      log_warn(LD_CONFIG,"Group '%s' not found.", group);
      return -1;
    }

    if (setgid(gr->gr_gid) != 0) {
      log_warn(LD_GENERAL,"Error setting to configured GID: %s",
               strerror(errno));
      return -1;
    }
  } else if (user) {
    if (setgid(pw->pw_gid) != 0) {
      log_warn(LD_GENERAL,"Error setting to user GID: %s", strerror(errno));
      return -1;
    }
  }

  /* now that the group is switched, we can switch users and lose
     privileges */
  if (user) {
    if (setuid(pw->pw_uid) != 0) {
      log_warn(LD_GENERAL,"Error setting UID: %s", strerror(errno));
      return -1;
    }
  }

  return 0;
#else
  (void)user;
  (void)group;
#endif

  log_warn(LD_CONFIG,
           "User or group specified, but switching users is not supported.");
  return -1;
}

#ifdef HAVE_PWD_H
/** Allocate and return a string containing the home directory for the
 * user <b>username</b>. Only works on posix-like systems. */
char *
get_user_homedir(const char *username)
{
  struct passwd *pw;
  tor_assert(username);

  if (!(pw = getpwnam(username))) {
    log_err(LD_CONFIG,"User \"%s\" not found.", username);
    return NULL;
  }
  return tor_strdup(pw->pw_dir);
}
#endif

/** Set *addr to the IP address (in dotted-quad notation) stored in c.
 * Return 1 on success, 0 if c is badly formatted.  (Like inet_aton(c,addr),
 * but works on Windows and Solaris.)
 */
int
tor_inet_aton(const char *c, struct in_addr* addr)
{
#ifdef HAVE_INET_ATON
  return inet_aton(c, addr);
#else
  uint32_t r;
  tor_assert(c);
  tor_assert(addr);
  if (strcmp(c, "255.255.255.255") == 0) {
    addr->s_addr = 0xFFFFFFFFu;
    return 1;
  }
  r = inet_addr(c);
  if (r == INADDR_NONE)
    return 0;
  addr->s_addr = r;
  return 1;
#endif
}

/** Given <b>af</b>==AF_INET and <b>src</b> a struct in_addr, or
 * <b>af</b>==AF_INET6 and <b>src</b> a struct in6_addr, try to format the
 * address and store it in the <b>len</b>-byte buffer <b>dst</b>.  Returns
 * <b>dst</b> on success, NULL on failure.
 *
 * (Like inet_ntop(af,src,dst,len), but works on platforms that don't have it:
 * Tor sometimes needs to format ipv6 addresses even on platforms without ipv6
 * support.) */
const char *
tor_inet_ntop(int af, const void *src, char *dst, size_t len)
{
  if (af == AF_INET) {
    if (tor_inet_ntoa(src, dst, len) < 0)
      return NULL;
    else
      return dst;
  } else if (af == AF_INET6) {
    const struct in6_addr *addr = src;
    char buf[64], *cp;
    int longestGapLen = 0, longestGapPos = -1, i,
      curGapPos = -1, curGapLen = 0;
    uint16_t words[8];
    for (i = 0; i < 8; ++i) {
      words[i] = (((uint16_t)addr->s6_addr[2*i])<<8) + addr->s6_addr[2*i+1];
    }
    if (words[0] == 0 && words[1] == 0 && words[2] == 0 && words[3] == 0 &&
        words[4] == 0 && ((words[5] == 0 && words[6] && words[7]) ||
                          (words[5] == 0xffff))) {
      /* This is an IPv4 address. */
      if (words[5] == 0) {
        tor_snprintf(buf, sizeof(buf), "::%d.%d.%d.%d",
                     addr->s6_addr[12], addr->s6_addr[13],
                     addr->s6_addr[14], addr->s6_addr[15]);
      } else {
        tor_snprintf(buf, sizeof(buf), "::%x:%d.%d.%d.%d", words[5],
                     addr->s6_addr[12], addr->s6_addr[13],
                     addr->s6_addr[14], addr->s6_addr[15]);
      }
      if (strlen(buf) > len)
        return NULL;
      strlcpy(dst, buf, len);
      return dst;
    }
    i = 0;
    while (i < 8) {
      if (words[i] == 0) {
        curGapPos = i++;
        curGapLen = 1;
        while (i<8 && words[i] == 0) {
          ++i; ++curGapLen;
        }
        if (curGapLen > longestGapLen) {
          longestGapPos = curGapPos;
          longestGapLen = curGapLen;
        }
      } else {
        ++i;
      }
    }
    if (longestGapLen<=1)
      longestGapPos = -1;

    cp = buf;
    for (i = 0; i < 8; ++i) {
      if (words[i] == 0 && longestGapPos == i) {
        if (i == 0)
          *cp++ = ':';
        *cp++ = ':';
        while (i < 8 && words[i] == 0)
          ++i;
        --i; /* to compensate for loop increment. */
      } else {
        tor_snprintf(cp, sizeof(buf)-(cp-buf), "%x", (unsigned)words[i]);
        cp += strlen(cp);
        if (i != 7)
          *cp++ = ':';
      }
    }
    *cp = '\0';
    if (strlen(buf) > len)
      return NULL;
    strlcpy(dst, buf, len);
    return dst;
  } else {
    return NULL;
  }
}

/** Given <b>af</b>==AF_INET or <b>af</b>==AF_INET6, and a string <b>src</b>
 * encoding an IPv4 address or IPv6 address correspondingly, try to parse the
 * address and store the result in <b>dst</b> (which must have space for a
 * struct in_addr or a struct in6_addr, as appropriate).  Return 1 on success,
 * 0 on a bad parse, and -1 on a bad <b>af</b>.
 *
 * (Like inet_pton(af,src,dst) but works on platforms that don't have it: Tor
 * sometimes needs to format ipv6 addresses even on platforms without ipv6
 * support.) */
int
tor_inet_pton(int af, const char *src, void *dst)
{
  if (af == AF_INET) {
    return tor_inet_aton(src, dst);
  } else if (af == AF_INET6) {
    struct in6_addr *out = dst;
    uint16_t words[8];
    int gapPos = -1, i, setWords=0;
    const char *dot = strchr(src, '.');
    const char *eow; /* end of words. */
    if (dot == src)
      return 0;
    else if (!dot)
      eow = src+strlen(src);
    else {
      int byte1,byte2,byte3,byte4;
      char more;
      for (eow = dot-1; eow >= src && TOR_ISDIGIT(*eow); --eow)
        ;
      ++eow;

      /* We use "scanf" because some platform inet_aton()s are too lax
       * about IPv4 addresses of the form "1.2.3" */
      if (sscanf(eow, "%d.%d.%d.%d%c", &byte1,&byte2,&byte3,&byte4,&more) != 4)
        return 0;

      if (byte1 > 255 || byte1 < 0 ||
          byte2 > 255 || byte2 < 0 ||
          byte3 > 255 || byte3 < 0 ||
          byte4 > 255 || byte4 < 0)
        return 0;

      words[6] = (byte1<<8) | byte2;
      words[7] = (byte3<<8) | byte4;
      setWords += 2;
    }

    i = 0;
    while (src < eow) {
      if (i > 7)
        return 0;
      if (TOR_ISXDIGIT(*src)) {
        char *next;
        long r = strtol(src, &next, 16);
        if (next > 4+src)
          return 0;
        if (next == src)
          return 0;
        if (r<0 || r>65536)
          return 0;

        words[i++] = (uint16_t)r;
        setWords++;
        src = next;
        if (*src != ':' && src != eow)
          return 0;
        ++src;
      } else if (*src == ':' && i > 0 && gapPos==-1) {
        gapPos = i;
        ++src;
      } else if (*src == ':' && i == 0 && src[1] == ':' && gapPos==-1) {
        gapPos = i;
        src += 2;
      } else {
        return 0;
      }
    }

    if (setWords > 8 ||
        (setWords == 8 && gapPos != -1) ||
        (setWords < 8 && gapPos == -1))
      return 0;

    if (gapPos >= 0) {
      int nToMove = setWords - (dot ? 2 : 0) - gapPos;
      int gapLen = 8 - setWords;
      tor_assert(nToMove >= 0);
      memmove(&words[gapPos+gapLen], &words[gapPos],
              sizeof(uint16_t)*nToMove);
      memset(&words[gapPos], 0, sizeof(uint16_t)*gapLen);
    }
    for (i = 0; i < 8; ++i) {
      out->s6_addr[2*i  ] = words[i] >> 8;
      out->s6_addr[2*i+1] = words[i] & 0xff;
    }

    return 1;
  } else {
    return -1;
  }
}

/** Similar behavior to Unix gethostbyname: resolve <b>name</b>, and set
 * *<b>addr</b> to the proper IP address, in host byte order.  Returns 0
 * on success, -1 on failure; 1 on transient failure.
 *
 * (This function exists because standard windows gethostbyname
 * doesn't treat raw IP addresses properly.)
 */
int
tor_lookup_hostname(const char *name, uint32_t *addr)
{
  tor_addr_t myaddr;
  int ret;

  if ((ret = tor_addr_lookup(name, AF_INET, &myaddr)))
    return ret;

  if (IN_FAMILY(&myaddr) == AF_INET) {
    *addr = IPV4IPh(&myaddr);
    return ret;
  }

  return -1;
}

/** Similar behavior to Unix gethostbyname: resolve <b>name</b>, and set
 * *<b>addr</b> to the proper IP address and family. The <b>family</b>
 * argument (which must be AF_INET, AF_INET6, or AF_UNSPEC) declares a
 * <i>preferred</i> family, though another one may be returned if only one
 * family is implemented for this address.
 *
 * Return 0 on success, -1 on failure; 1 on transient failure.
 */
int
tor_addr_lookup(const char *name, uint16_t family, tor_addr_t *addr)
{
  /* Perhaps eventually this should be replaced by a tor_getaddrinfo or
   * something.
   */
  struct in_addr iaddr;
  struct in6_addr iaddr6;
  tor_assert(name);
  tor_assert(addr);
  tor_assert(family == AF_INET || family == AF_UNSPEC);
  memset(addr, 0, sizeof(addr)); /* Clear the extraneous fields. */
  if (!*name) {
    /* Empty address is an error. */
    return -1;
  } else if (tor_inet_pton(AF_INET, name, &iaddr)) {
    /* It's an IPv4 IP. */
    addr->family = AF_INET;
    memcpy(&addr->addr.in_addr, &iaddr, sizeof(struct in_addr));
    return 0;
  } else if (tor_inet_pton(AF_INET6, name, &iaddr6)) {
    addr->family = AF_INET6;
    memcpy(&addr->addr.in6_addr, &iaddr6, sizeof(struct in6_addr));
    return 0;
  } else {
#ifdef HAVE_GETADDRINFO
    int err;
    struct addrinfo *res=NULL, *res_p;
    struct addrinfo *best=NULL;
    struct addrinfo hints;
    int result = -1;
    memset(&hints, 0, sizeof(hints));
    hints.ai_family = family;
    hints.ai_socktype = SOCK_STREAM;
    err = getaddrinfo(name, NULL, &hints, &res);
    if (!err) {
      best = NULL;
      for (res_p = res; res_p; res_p = res_p->ai_next) {
        if (family == AF_UNSPEC) {
          if (res_p->ai_family == AF_INET) {
            best = res_p;
            break;
          } else if (res_p->ai_family == AF_INET6 && !best) {
            best = res_p;
          }
        } else if (family == res_p->ai_family) {
          best = res_p;
          break;
        }
      }
      if (!best)
        best = res;
      if (best->ai_family == AF_INET) {
        addr->family = AF_INET;
        memcpy(&addr->addr.in_addr,
               &((struct sockaddr_in*)best->ai_addr)->sin_addr,
               sizeof(struct in_addr));
        result = 0;
      } else if (best->ai_family == AF_INET6) {
        addr->family = AF_INET6;
        memcpy(&addr->addr.in6_addr,
               &((struct sockaddr_in6*)best->ai_addr)->sin6_addr,
               sizeof(struct in6_addr));
        result = 0;
      }
      freeaddrinfo(res);
      return result;
    }
    return (err == EAI_AGAIN) ? 1 : -1;
#else
    struct hostent *ent;
    int err;
#ifdef HAVE_GETHOSTBYNAME_R_6_ARG
    char buf[2048];
    struct hostent hostent;
    int r;
    r = gethostbyname_r(name, &hostent, buf, sizeof(buf), &ent, &err);
#elif defined(HAVE_GETHOSTBYNAME_R_5_ARG)
    char buf[2048];
    struct hostent hostent;
    ent = gethostbyname_r(name, &hostent, buf, sizeof(buf), &err);
#elif defined(HAVE_GETHOSTBYNAME_R_3_ARG)
    struct hostent_data data;
    struct hostent hent;
    memset(&data, 0, sizeof(data));
    err = gethostbyname_r(name, &hent, &data);
    ent = err ? NULL : &hent;
#else