net.c

   1 /*
   2  * Copyright (C) 2005-2007 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file net.c networking-related helper functions */
   8
   9 #include "para.h"
  10 #include "net.h"
  11 #include "string.h"
  12 #include "error.h"
  13
  14
  15 /** Information about one encrypted connection. */
  16 struct crypt_data {
  17         /** Function used to decrypt received data. */
  18         crypt_function *recv;
  19         /** Function used to encrypt data to be sent. */
  20         crypt_function *send;
  21         /**
  22          * Context-dependent data (crypt keys), passed verbatim to the above
  23          * crypt functions.
  24          */
  25         void *private_data;
  26 };
  27 /** Array holding per fd crypt data. */
  28 static struct crypt_data *crypt_data_array;
  29 /** Current size of the crypt data array. */
  30 static unsigned cda_size = 0;
  31
  32 /**
  33  * activate encryption for one file descriptor
  34  *
  35  * \param fd the file descriptor
  36  * \param recv_f the function used for decrypting received data
  37  * \param send_f the function used for encrypting before sending
  38  * \param private_data user data supplied by the caller
  39  */
  40 void enable_crypt(int fd, crypt_function *recv_f, crypt_function *send_f,
  41         void *private_data)
  42 {
  43         if (fd + 1 > cda_size) {
  44                 crypt_data_array = para_realloc(crypt_data_array,
  45                         (fd + 1) * sizeof(struct crypt_data));
  46                 memset(crypt_data_array + cda_size, 0,
  47                         (fd + 1 - cda_size) * sizeof(struct crypt_data));
  48                 cda_size = fd + 1;
  49         }
  50         crypt_data_array[fd].recv = recv_f;
  51         crypt_data_array[fd].send = send_f;
  52         crypt_data_array[fd].private_data = private_data;
  53         PARA_INFO_LOG("rc4 encryption activated for fd %d\n", fd);
  54 }
  55
  56 /**
  57  * deactivate encryption for a given fd
  58  *
  59  * \param fd the file descriptor
  60  *
  61  * This must be called if and only if \p fd was activated via enable_crypt().
  62  */
  63 void disable_crypt(int fd)
  64 {
  65         if (cda_size < fd + 1)
  66                 return;
  67         crypt_data_array[fd].recv = NULL;
  68         crypt_data_array[fd].send = NULL;
  69         crypt_data_array[fd].private_data = NULL;
  70 }
  71
  72
  73 /**
  74  * initialize a struct sockaddr_in
  75  *
  76  * \param addr A pointer to the struct to be initialized
  77  * \param port The port number to use
  78  * \param he The address to use
  79  *
  80  * If \a he is null (server mode), \a addr->sin_addr is initialized with \p
  81  * INADDR_ANY.  Otherwise, the address given by \a he is copied to addr.
  82  */
  83 void init_sockaddr(struct sockaddr_in *addr, int port, const struct hostent *he)
  84 {
  85         /* host byte order */
  86         addr->sin_family = AF_INET;
  87         /* short, network byte order */
  88         addr->sin_port = htons(port);
  89         if (he)
  90                 addr->sin_addr = *((struct in_addr *)he->h_addr);
  91         else
  92                 addr->sin_addr.s_addr = INADDR_ANY;
  93         /* zero the rest of the struct */
  94         memset(&addr->sin_zero, '\0', 8);
  95 }
  96
  97 /*
  98  * send out a buffer, resend on short writes
  99  *
 100  * \param fd the file descriptor
 101  * \param buf The buffer to be sent
 102  * \param len The length of \a buf
 103  *
 104  * Due to circumstances beyond your control, the kernel might not send all the
 105  * data out in one chunk, and now, my friend, it's up to us to get the data out
 106  * there (Beej's Guide to Network Programming).
 107  *
 108  * \return This function returns 1 on success and \a -E_SEND on errors. The
 109  * number of bytes actually sent is stored upon successful return in \a len.
 110  */
 111 static int sendall(int fd, const char *buf, size_t *len)
 112 {
 113         size_t total = 0, bytesleft = *len; /* how many we have left to send */
 114         int n = -1;
 115
 116         while (total < *len) {
 117                 n = send(fd, buf + total, bytesleft, 0);
 118                 if (n == -1)
 119                         break;
 120                 total += n;
 121                 bytesleft -= n;
 122                 if (total < *len)
 123                         PARA_DEBUG_LOG("short write (%zd byte(s) left)",
 124                                 *len - total);
 125         }
 126         *len = total; /* return number actually sent here */
 127         return n == -1? -E_SEND : 1; /* return 1 on success */
 128 }
 129
 130 /**
 131  * encrypt and send buffer
 132  *
 133  * \param fd:  the file descriptor
 134  * \param buf the buffer to be encrypted and sent
 135  * \param len the length of \a buf
 136  *
 137  * Check if encrytpion is available. If yes, encrypt the given buffer.  Send out
 138  * the buffer, encrypted or not, and try to resend the remaing part in case of
 139  * short writes.
 140  *
 141  * \return Positive on success, \p -E_SEND on errors.
 142  */
 143 int send_bin_buffer(int fd, const char *buf, size_t len)
 144 {
 145         int ret;
 146         crypt_function *cf = NULL;
 147
 148         if (!len)
 149                 PARA_CRIT_LOG("%s", "len == 0\n");
 150         if (fd + 1 <= cda_size)
 151                 cf = crypt_data_array[fd].send;
 152         if (cf) {
 153                 void *private = crypt_data_array[fd].private_data;
 154                 unsigned char *outbuf = para_malloc(len);
 155                 (*cf)(len, (unsigned char *)buf, outbuf, private);
 156                 ret = sendall(fd, (char *)outbuf, &len);
 157                 free(outbuf);
 158         } else
 159                 ret = sendall(fd, buf, &len);
 160         return ret;
 161 }
 162
 163 /**
 164  * encrypt and send null terminated buffer.
 165  *
 166  * \param fd the file descriptor
 167  * \param buf the null-terminated buffer to be send
 168  *
 169  * This is equivalent to send_bin_buffer(fd, buf, strlen(buf)).
 170  *
 171  * \return Positive on success, \p -E_SEND on errors.
 172  */
 173 int send_buffer(int fd, const char *buf)
 174 {
 175         return send_bin_buffer(fd, buf, strlen(buf));
 176 }
 177
 178
 179 /**
 180  * send and encrypt a buffer given by a format string
 181  *
 182  * \param fd the file descriptor
 183  * \param fmt a format string
 184  *
 185  * \return Positive on success, \p -E_SEND on errors.
 186  */
 187 __printf_2_3 int send_va_buffer(int fd, const char *fmt, ...)
 188 {
 189         char *msg;
 190         int ret;
 191
 192         PARA_VSPRINTF(fmt, msg);
 193         ret = send_buffer(fd, msg);
 194         free(msg);
 195         return ret;
 196 }
 197
 198 /**
 199  * receive and decrypt.
 200  *
 201  * \param fd the file descriptor
 202  * \param buf the buffer to write the decrypted data to
 203  * \param size the size of \a buf
 204  *
 205  * Receive at most \a size bytes from filedescriptor fd. If encryption is
 206  * available, decrypt the received buffer.
 207  *
 208  * \return The number of bytes received on success. On receive errors, -E_RECV
 209  * is returned. On crypt errors, the corresponding crypt error number is
 210  * returned.
 211  *
 212  * \sa recv(2)
 213  */
 214 __must_check int recv_bin_buffer(int fd, char *buf, size_t size)
 215 {
 216         ssize_t n;
 217         crypt_function *cf = NULL;
 218
 219         if (fd + 1 <= cda_size)
 220                 cf = crypt_data_array[fd].recv;
 221         if (cf) {
 222                 unsigned char *tmp = para_malloc(size);
 223                 void *private = crypt_data_array[fd].private_data;
 224                 n = recv(fd, tmp, size, 0);
 225                 if (n > 0) {
 226                         size_t numbytes = n;
 227                         unsigned char *b = (unsigned char *)buf;
 228                         (*cf)(numbytes, tmp, b, private);
 229                 }
 230                 free(tmp);
 231         } else
 232                 n = recv(fd, buf, size, 0);
 233         if (n == -1)
 234                 n = -E_RECV;
 235         return n;
 236 }
 237
 238 /**
 239  * receive, decrypt and write terminating NULL byte
 240  *
 241  * \param fd the file descriptor
 242  * \param buf the buffer to write the decrypted data to
 243  * \param size the size of \a buf
 244  *
 245  * Read and decrypt at most \a size - 1 bytes from file descriptor \a fd and
 246  * write a NULL byte at the end of the received data.
 247  *
 248  * \return: The return value of the underlying call to \a recv_bin_buffer().
 249  *
 250  * \sa recv_bin_buffer()
 251  */
 252 int recv_buffer(int fd, char *buf, size_t size)
 253 {
 254         int n;
 255
 256         if (!size)
 257                 return -E_RECV;
 258         n = recv_bin_buffer(fd, buf, size - 1);
 259         if (n >= 0)
 260                 buf[n] = '\0';
 261         else
 262                 *buf = '\0';
 263         return n;
 264 }
 265
 266 /**
 267  * wrapper around gethostbyname
 268  *
 269  * \param host hostname or IPv4 address
 270  * \param ret the hostent structure is returned here
 271  *
 272  * \return positive on success, negative on errors. On success, \a ret
 273  * contains the return value of the underlying gethostbyname() call.
 274  *
 275  * \sa gethostbyname(2)
 276  */
 277 int get_host_info(char *host, struct hostent **ret)
 278 {
 279         PARA_INFO_LOG("getting host info of %s\n", host);
 280         /* FIXME: gethostbyname() is obsolete */
 281         *ret = gethostbyname(host);
 282         return *ret? 1 : -E_HOST_INFO;
 283 }
 284
 285 /**
 286  * a wrapper around socket(2)
 287  *
 288  * Create an IPv4 socket for sequenced, reliable, two-way, connection-based
 289  * byte streams.
 290  *
 291  * \return The socket fd on success, -E_SOCKET on errors.
 292  *
 293  * \sa socket(2)
 294  */
 295 int get_stream_socket(int domain)
 296 {
 297         int socket_fd;
 298
 299         if ((socket_fd = socket(domain, SOCK_STREAM, 0)) == -1)
 300                 return -E_SOCKET;
 301         return socket_fd;
 302 }
 303
 304 /**
 305  * a wrapper around connect(2)
 306  *
 307  * \param fd the file descriptor
 308  * \param their_addr the address to connect
 309  *
 310  * \return \p -E_CONNECT on errors, 1 on success
 311  *
 312  * \sa connect(2)
 313  */
 314 int para_connect(int fd, struct sockaddr_in *their_addr)
 315 {
 316         int ret;
 317
 318         if ((ret = connect(fd, (struct sockaddr *)their_addr,
 319                         sizeof(struct sockaddr))) == -1)
 320                 return -E_CONNECT;
 321         return 1;
 322 }
 323
 324 /**
 325  * paraslash's wrapper around the accept system call
 326  *
 327  * \param fd the listening socket
 328  * \param addr structure which is filled in with the address of the peer socket
 329  * \param size should contain the size of the structure pointed to by \a addr
 330  *
 331  * Accept incoming connections on \a addr. Retry if interrupted.
 332  *
 333  * \return The new file descriptor on success, \a -E_ACCEPT on errors.
 334  *
 335  * \sa accept(2).
 336  */
 337 int para_accept(int fd, void *addr, socklen_t size)
 338 {
 339         int new_fd;
 340
 341         do
 342                 new_fd = accept(fd, (struct sockaddr *) addr, &size);
 343         while (new_fd < 0 && errno == EINTR);
 344         return new_fd < 0? -E_ACCEPT : new_fd;
 345 }
 346
 347 static int setserversockopts(int socket_fd)
 348 {
 349         int yes = 1;
 350
 351         if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &yes,
 352                         sizeof(int)) == -1)
 353                 return -E_SETSOCKOPT;
 354         return 1;
 355 }
 356
 357 /**
 358  * prepare a structure for \p AF_UNIX socket addresses
 359  *
 360  * \param u pointer to the struct to be prepared
 361  * \param name the socket pathname
 362  *
 363  * This just copies \a name to the sun_path component of \a u.
 364  *
 365  * \return Positive on success, \p -E_NAME_TOO_LONG if \a name is longer
 366  * than \p UNIX_PATH_MAX.
 367  */
 368 int init_unix_addr(struct sockaddr_un *u, const char *name)
 369 {
 370         if (strlen(name) >= UNIX_PATH_MAX)
 371                 return -E_NAME_TOO_LONG;
 372         memset(u->sun_path, 0, UNIX_PATH_MAX);
 373         u->sun_family = PF_UNIX;
 374         strcpy(u->sun_path, name);
 375         return 1;
 376 }
 377
 378 /**
 379  * Prepare, create, and bind a socket for local communication.
 380  *
 381  * \param name The socket pathname.
 382  * \param unix_addr Pointer to the \p AF_UNIX socket structure.
 383  * \param mode The desired mode of the socket.
 384  *
 385  * This functions creates a local socket for sequenced, reliable,
 386  * two-way, connection-based byte streams.
 387  *
 388  * \return The file descriptor, on success, negative on errors.
 389  *
 390  * \sa socket(2)
 391  * \sa bind(2)
 392  * \sa chmod(2)
 393  */
 394 int create_local_socket(const char *name, struct sockaddr_un *unix_addr,
 395                 mode_t mode)
 396 {
 397         int fd, ret;
 398
 399         ret = init_unix_addr(unix_addr, name);
 400         if (ret < 0)
 401                 return ret;
 402         fd = socket(PF_UNIX, SOCK_STREAM, 0);
 403         if (fd < 0)
 404                 return -E_SOCKET;
 405         ret = -E_BIND;
 406         if (bind(fd, (struct sockaddr *) unix_addr, UNIX_PATH_MAX) < 0)
 407                 goto err;
 408         ret = -E_CHMOD;
 409         if (chmod(name, mode) < 0)
 410                 goto err;
 411         return fd;
 412 err:
 413         close(fd);
 414         return ret;
 415 }
 416
 417 #ifndef HAVE_UCRED
 418 ssize_t send_cred_buffer(int sock, char *buf)
 419 {
 420         return send_buffer(sock, buf);
 421 }
 422 int recv_cred_buffer(int fd, char *buf, size_t size)
 423 {
 424         return recv_buffer(fd, buf, size) > 0? 1 : -E_RECVMSG;
 425 }
 426 #else /* HAVE_UCRED */
 427 /**
 428  * send NULL terminated buffer and Unix credentials of the current process
 429  *
 430  * \param sock the socket file descriptor
 431  * \param buf the buffer to be sent
 432  *
 433  * \return On success, this call returns the number of characters sent.  On
 434  * error, \p -E_SENDMSG ist returned.
 435  *
 436  * \sa  okir's Black Hats Manual
 437  * \sa sendmsg(2)
 438  */
 439 ssize_t send_cred_buffer(int sock, char *buf)
 440 {
 441         char control[sizeof(struct cmsghdr) + 10];
 442         struct msghdr msg;
 443         struct cmsghdr *cmsg;
 444         static struct iovec iov;
 445         struct ucred c;
 446         int ret;
 447
 448         /* Response data */
 449         iov.iov_base = buf;
 450         iov.iov_len  = strlen(buf);
 451         c.pid = getpid();
 452         c.uid = getuid();
 453         c.gid = getgid();
 454         /* compose the message */
 455         memset(&msg, 0, sizeof(msg));
 456         msg.msg_iov = &iov;
 457         msg.msg_iovlen = 1;
 458         msg.msg_control = control;
 459         msg.msg_controllen = sizeof(control);
 460         /* attach the ucred struct */
 461         cmsg = CMSG_FIRSTHDR(&msg);
 462         cmsg->cmsg_level = SOL_SOCKET;
 463         cmsg->cmsg_type = SCM_CREDENTIALS;
 464         cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
 465         *(struct ucred *)CMSG_DATA(cmsg) = c;
 466         msg.msg_controllen = cmsg->cmsg_len;
 467         ret = sendmsg(sock, &msg, 0);
 468         if (ret  < 0)
 469                 ret = -E_SENDMSG;
 470         return ret;
 471 }
 472
 473 static void dispose_fds(int *fds, unsigned num)
 474 {
 475         int i;
 476
 477         for (i = 0; i < num; i++)
 478                 close(fds[i]);
 479 }
 480
 481 /**
 482  * receive a buffer and the Unix credentials of the sending process
 483  *
 484  * \param fd the socket file descriptor
 485  * \param buf the buffer to store the message
 486  * \param size the size of \a buffer
 487  *
 488  * \return negative on errors, the user id on success.
 489  *
 490  * \sa okir's Black Hats Manual
 491  * \sa recvmsg(2)
 492  */
 493 int recv_cred_buffer(int fd, char *buf, size_t size)
 494 {
 495         char control[255];
 496         struct msghdr msg;
 497         struct cmsghdr *cmsg;
 498         struct iovec iov;
 499         int result = 0;
 500         int yes = 1;
 501         struct ucred cred;
 502
 503         setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &yes, sizeof(int));
 504         memset(&msg, 0, sizeof(msg));
 505         memset(buf, 0, size);
 506         iov.iov_base = buf;
 507         iov.iov_len = size;
 508         msg.msg_iov = &iov;
 509         msg.msg_iovlen = 1;
 510         msg.msg_control = control;
 511         msg.msg_controllen = sizeof(control);
 512         if (recvmsg(fd, &msg, 0) < 0)
 513                 return -E_RECVMSG;
 514         result = -E_SCM_CREDENTIALS;
 515         cmsg = CMSG_FIRSTHDR(&msg);
 516         while (cmsg) {
 517                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type
 518                                 == SCM_CREDENTIALS) {
 519                         memcpy(&cred, CMSG_DATA(cmsg), sizeof(struct ucred));
 520                         result = cred.uid;
 521                 } else
 522                         if (cmsg->cmsg_level == SOL_SOCKET
 523                                         && cmsg->cmsg_type == SCM_RIGHTS) {
 524                                 dispose_fds((int *) CMSG_DATA(cmsg),
 525                                         (cmsg->cmsg_len - CMSG_LEN(0))
 526                                         / sizeof(int));
 527                         }
 528                 cmsg = CMSG_NXTHDR(&msg, cmsg);
 529         }
 530         return result;
 531 }
 532 #endif /* HAVE_UCRED */
 533
 534 /** how many pending connections queue will hold */
 535 #define BACKLOG 10
 536
 537 /**
 538  * create a socket, bind it and listen
 539  *
 540  * \param port the tcp port to listen on
 541  *
 542  * \return The file descriptor of the created socket, negative
 543  * on errors.
 544  *
 545  * \sa get_stream_socket()
 546  * \sa setsockopt(2)
 547  * \sa bind(2)
 548  * \sa listen(2)
 549  */
 550 int init_tcp_socket(int port)
 551 {
 552         struct sockaddr_in my_addr;
 553         int fd, ret = get_stream_socket(AF_INET);
 554
 555         if (ret < 0)
 556                 return ret;
 557         fd = ret;
 558         ret = setserversockopts(fd);
 559         if (ret < 0)
 560                 goto err;
 561         init_sockaddr(&my_addr, port, NULL);
 562         ret = -E_BIND;
 563         if (bind(fd, (struct sockaddr *)&my_addr,
 564                         sizeof(struct sockaddr)) == -1) {
 565                 PARA_CRIT_LOG("bind error: %s\n", strerror(errno));
 566                 goto err;
 567         }
 568         ret = -E_LISTEN;
 569         if (listen(fd, BACKLOG) == -1)
 570                 goto err;
 571         PARA_INFO_LOG("listening on port %d, fd %d\n", port, fd);
 572         return fd;
 573 err:
 574         close(fd);
 575         return ret;
 576 }
 577
 578 /**
 579  * receive a buffer and check for a pattern
 580  *
 581  * \param fd the file descriptor to receive from
 582  * \param pattern the expected pattern
 583  * \param bufsize the size of the internal buffer
 584  *
 585  * \return Positive if \a pattern was received, negative otherwise.
 586  *
 587  * This function creates a buffer of size \a bufsize and tries
 588  * to receive at most \a bufsize bytes from file descriptor \a fd.
 589  * If at least \p strlen(\a pattern) bytes were received, the beginning of
 590  * the received buffer is compared with \a pattern, ignoring case.
 591  *
 592  * \sa recv_buffer()
 593  * \sa strncasecmp(3)
 594  */
 595 int recv_pattern(int fd, const char *pattern, size_t bufsize)
 596 {
 597         size_t len = strlen(pattern);
 598         char *buf = para_malloc(bufsize + 1);
 599         int ret = -E_RECV_PATTERN, n = recv_buffer(fd, buf, bufsize);
 600
 601         if (n < len)
 602                 goto out;
 603         if (strncasecmp(buf, pattern, len))
 604                 goto out;
 605         ret = 1;
 606 out:
 607         if (ret < 0) {
 608                 PARA_NOTICE_LOG("n = %d, did not receive pattern '%s'\n", n, pattern);
 609                 if (n > 0)
 610                         PARA_NOTICE_LOG("recvd: %s\n", buf);
 611         }
 612         free(buf);
 613         return ret;
 614 }