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 "error.h"
  10 #include "para.h"
  11 #include "net.h"
  12 #include "string.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 a binary 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 encryption is available. If yes, encrypt the given buffer.  Send
 138  * out the buffer, encrypted or not, and try to resend the remaing part in case
 139  * of 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                 /* RC4 may write more than len to the output buffer */
 155                 unsigned char *outbuf = para_malloc(ROUND_UP(len, 8));
 156                 (*cf)(len, (unsigned char *)buf, outbuf, private);
 157                 ret = sendall(fd, (char *)outbuf, &len);
 158                 free(outbuf);
 159         } else
 160                 ret = sendall(fd, buf, &len);
 161         return ret;
 162 }
 163
 164 /**
 165  * encrypt and send null terminated buffer.
 166  *
 167  * \param fd the file descriptor
 168  * \param buf the null-terminated buffer to be send
 169  *
 170  * This is equivalent to send_bin_buffer(fd, buf, strlen(buf)).
 171  *
 172  * \return Positive on success, \p -E_SEND on errors.
 173  */
 174 int send_buffer(int fd, const char *buf)
 175 {
 176         return send_bin_buffer(fd, buf, strlen(buf));
 177 }
 178
 179
 180 /**
 181  * send and encrypt a buffer given by a format string
 182  *
 183  * \param fd the file descriptor
 184  * \param fmt a format string
 185  *
 186  * \return Positive on success, \p -E_SEND on errors.
 187  */
 188 __printf_2_3 int send_va_buffer(int fd, const char *fmt, ...)
 189 {
 190         char *msg;
 191         int ret;
 192
 193         PARA_VSPRINTF(fmt, msg);
 194         ret = send_buffer(fd, msg);
 195         free(msg);
 196         return ret;
 197 }
 198
 199 /**
 200  * receive and decrypt.
 201  *
 202  * \param fd the file descriptor
 203  * \param buf the buffer to write the decrypted data to
 204  * \param size the size of \a buf
 205  *
 206  * Receive at most \a size bytes from filedescriptor fd. If encryption is
 207  * available, decrypt the received buffer.
 208  *
 209  * \return The number of bytes received on success. On receive errors, -E_RECV
 210  * is returned. On crypt errors, the corresponding crypt error number is
 211  * returned.
 212  *
 213  * \sa recv(2)
 214  */
 215 __must_check int recv_bin_buffer(int fd, char *buf, size_t size)
 216 {
 217         ssize_t n;
 218         crypt_function *cf = NULL;
 219
 220         if (fd + 1 <= cda_size)
 221                 cf = crypt_data_array[fd].recv;
 222         if (cf) {
 223                 unsigned char *tmp = para_malloc(size);
 224                 void *private = crypt_data_array[fd].private_data;
 225                 n = recv(fd, tmp, size, 0);
 226                 if (n > 0) {
 227                         size_t numbytes = n;
 228                         unsigned char *b = (unsigned char *)buf;
 229                         (*cf)(numbytes, tmp, b, private);
 230                 }
 231                 free(tmp);
 232         } else
 233                 n = recv(fd, buf, size, 0);
 234         if (n == -1)
 235                 n = -E_RECV;
 236         return n;
 237 }
 238
 239 /**
 240  * receive, decrypt and write terminating NULL byte
 241  *
 242  * \param fd the file descriptor
 243  * \param buf the buffer to write the decrypted data to
 244  * \param size the size of \a buf
 245  *
 246  * Read and decrypt at most \a size - 1 bytes from file descriptor \a fd and
 247  * write a NULL byte at the end of the received data.
 248  *
 249  * \return: The return value of the underlying call to \a recv_bin_buffer().
 250  *
 251  * \sa recv_bin_buffer()
 252  */
 253 int recv_buffer(int fd, char *buf, size_t size)
 254 {
 255         int n;
 256
 257         if (!size)
 258                 return -E_RECV;
 259         n = recv_bin_buffer(fd, buf, size - 1);
 260         if (n >= 0)
 261                 buf[n] = '\0';
 262         else
 263                 *buf = '\0';
 264         return n;
 265 }
 266
 267 /**
 268  * wrapper around gethostbyname
 269  *
 270  * \param host hostname or IPv4 address
 271  * \param ret the hostent structure is returned here
 272  *
 273  * \return positive on success, negative on errors. On success, \a ret
 274  * contains the return value of the underlying gethostbyname() call.
 275  *
 276  * \sa gethostbyname(2)
 277  */
 278 int get_host_info(char *host, struct hostent **ret)
 279 {
 280         PARA_INFO_LOG("getting host info of %s\n", host);
 281         /* FIXME: gethostbyname() is obsolete */
 282         *ret = gethostbyname(host);
 283         return *ret? 1 : -E_HOST_INFO;
 284 }
 285
 286 /**
 287  * a wrapper around socket(2)
 288  *
 289  * Create an IPv4 socket for sequenced, reliable, two-way, connection-based
 290  * byte streams.
 291  *
 292  * \return The socket fd on success, -E_SOCKET on errors.
 293  *
 294  * \sa socket(2)
 295  */
 296 int get_stream_socket(int domain)
 297 {
 298         int socket_fd;
 299
 300         if ((socket_fd = socket(domain, SOCK_STREAM, 0)) == -1)
 301                 return -E_SOCKET;
 302         return socket_fd;
 303 }
 304
 305 /**
 306  * paraslash's wrapper around the accept system call
 307  *
 308  * \param fd the listening socket
 309  * \param addr structure which is filled in with the address of the peer socket
 310  * \param size should contain the size of the structure pointed to by \a addr
 311  *
 312  * Accept incoming connections on \a addr. Retry if interrupted.
 313  *
 314  * \return The new file descriptor on success, \a -E_ACCEPT on errors.
 315  *
 316  * \sa accept(2).
 317  */
 318 int para_accept(int fd, void *addr, socklen_t size)
 319 {
 320         int new_fd;
 321
 322         do
 323                 new_fd = accept(fd, (struct sockaddr *) addr, &size);
 324         while (new_fd < 0 && errno == EINTR);
 325         return new_fd < 0? -E_ACCEPT : new_fd;
 326 }
 327
 328 static int setserversockopts(int socket_fd)
 329 {
 330         int yes = 1;
 331
 332         if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &yes,
 333                         sizeof(int)) == -1)
 334                 return -E_SETSOCKOPT;
 335         return 1;
 336 }
 337
 338 /**
 339  * prepare a structure for \p AF_UNIX socket addresses
 340  *
 341  * \param u pointer to the struct to be prepared
 342  * \param name the socket pathname
 343  *
 344  * This just copies \a name to the sun_path component of \a u.
 345  *
 346  * \return Positive on success, \p -E_NAME_TOO_LONG if \a name is longer
 347  * than \p UNIX_PATH_MAX.
 348  */
 349 int init_unix_addr(struct sockaddr_un *u, const char *name)
 350 {
 351         if (strlen(name) >= UNIX_PATH_MAX)
 352                 return -E_NAME_TOO_LONG;
 353         memset(u->sun_path, 0, UNIX_PATH_MAX);
 354         u->sun_family = PF_UNIX;
 355         strcpy(u->sun_path, name);
 356         return 1;
 357 }
 358
 359 /**
 360  * Prepare, create, and bind a socket for local communication.
 361  *
 362  * \param name The socket pathname.
 363  * \param unix_addr Pointer to the \p AF_UNIX socket structure.
 364  * \param mode The desired mode of the socket.
 365  *
 366  * This functions creates a local socket for sequenced, reliable,
 367  * two-way, connection-based byte streams.
 368  *
 369  * \return The file descriptor, on success, negative on errors.
 370  *
 371  * \sa socket(2)
 372  * \sa bind(2)
 373  * \sa chmod(2)
 374  */
 375 int create_local_socket(const char *name, struct sockaddr_un *unix_addr,
 376                 mode_t mode)
 377 {
 378         int fd, ret;
 379
 380         ret = init_unix_addr(unix_addr, name);
 381         if (ret < 0)
 382                 return ret;
 383         fd = socket(PF_UNIX, SOCK_STREAM, 0);
 384         if (fd < 0)
 385                 return -E_SOCKET;
 386         ret = -E_BIND;
 387         if (bind(fd, (struct sockaddr *) unix_addr, UNIX_PATH_MAX) < 0)
 388                 goto err;
 389         ret = -E_CHMOD;
 390         if (chmod(name, mode) < 0)
 391                 goto err;
 392         return fd;
 393 err:
 394         close(fd);
 395         return ret;
 396 }
 397
 398 #ifndef HAVE_UCRED
 399 ssize_t send_cred_buffer(int sock, char *buf)
 400 {
 401         return send_buffer(sock, buf);
 402 }
 403 int recv_cred_buffer(int fd, char *buf, size_t size)
 404 {
 405         return recv_buffer(fd, buf, size) > 0? 1 : -E_RECVMSG;
 406 }
 407 #else /* HAVE_UCRED */
 408 /**
 409  * send NULL terminated buffer and Unix credentials of the current process
 410  *
 411  * \param sock the socket file descriptor
 412  * \param buf the buffer to be sent
 413  *
 414  * \return On success, this call returns the number of characters sent.  On
 415  * error, \p -E_SENDMSG ist returned.
 416  *
 417  * \sa  okir's Black Hats Manual
 418  * \sa sendmsg(2)
 419  */
 420 ssize_t send_cred_buffer(int sock, char *buf)
 421 {
 422         char control[sizeof(struct cmsghdr) + 10];
 423         struct msghdr msg;
 424         struct cmsghdr *cmsg;
 425         static struct iovec iov;
 426         struct ucred c;
 427         int ret;
 428
 429         /* Response data */
 430         iov.iov_base = buf;
 431         iov.iov_len  = strlen(buf);
 432         c.pid = getpid();
 433         c.uid = getuid();
 434         c.gid = getgid();
 435         /* compose the message */
 436         memset(&msg, 0, sizeof(msg));
 437         msg.msg_iov = &iov;
 438         msg.msg_iovlen = 1;
 439         msg.msg_control = control;
 440         msg.msg_controllen = sizeof(control);
 441         /* attach the ucred struct */
 442         cmsg = CMSG_FIRSTHDR(&msg);
 443         cmsg->cmsg_level = SOL_SOCKET;
 444         cmsg->cmsg_type = SCM_CREDENTIALS;
 445         cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
 446         *(struct ucred *)CMSG_DATA(cmsg) = c;
 447         msg.msg_controllen = cmsg->cmsg_len;
 448         ret = sendmsg(sock, &msg, 0);
 449         if (ret  < 0)
 450                 ret = -E_SENDMSG;
 451         return ret;
 452 }
 453
 454 static void dispose_fds(int *fds, unsigned num)
 455 {
 456         int i;
 457
 458         for (i = 0; i < num; i++)
 459                 close(fds[i]);
 460 }
 461
 462 /**
 463  * receive a buffer and the Unix credentials of the sending process
 464  *
 465  * \param fd the socket file descriptor
 466  * \param buf the buffer to store the message
 467  * \param size the size of \a buffer
 468  *
 469  * \return negative on errors, the user id on success.
 470  *
 471  * \sa okir's Black Hats Manual
 472  * \sa recvmsg(2)
 473  */
 474 int recv_cred_buffer(int fd, char *buf, size_t size)
 475 {
 476         char control[255];
 477         struct msghdr msg;
 478         struct cmsghdr *cmsg;
 479         struct iovec iov;
 480         int result = 0;
 481         int yes = 1;
 482         struct ucred cred;
 483
 484         setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &yes, sizeof(int));
 485         memset(&msg, 0, sizeof(msg));
 486         memset(buf, 0, size);
 487         iov.iov_base = buf;
 488         iov.iov_len = size;
 489         msg.msg_iov = &iov;
 490         msg.msg_iovlen = 1;
 491         msg.msg_control = control;
 492         msg.msg_controllen = sizeof(control);
 493         if (recvmsg(fd, &msg, 0) < 0)
 494                 return -E_RECVMSG;
 495         result = -E_SCM_CREDENTIALS;
 496         cmsg = CMSG_FIRSTHDR(&msg);
 497         while (cmsg) {
 498                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type
 499                                 == SCM_CREDENTIALS) {
 500                         memcpy(&cred, CMSG_DATA(cmsg), sizeof(struct ucred));
 501                         result = cred.uid;
 502                 } else
 503                         if (cmsg->cmsg_level == SOL_SOCKET
 504                                         && cmsg->cmsg_type == SCM_RIGHTS) {
 505                                 dispose_fds((int *) CMSG_DATA(cmsg),
 506                                         (cmsg->cmsg_len - CMSG_LEN(0))
 507                                         / sizeof(int));
 508                         }
 509                 cmsg = CMSG_NXTHDR(&msg, cmsg);
 510         }
 511         return result;
 512 }
 513 #endif /* HAVE_UCRED */
 514
 515 /** how many pending connections queue will hold */
 516 #define BACKLOG 10
 517
 518 /**
 519  * create a socket, bind it and listen
 520  *
 521  * \param port the tcp port to listen on
 522  *
 523  * \return The file descriptor of the created socket, negative
 524  * on errors.
 525  *
 526  * \sa get_stream_socket()
 527  * \sa setsockopt(2)
 528  * \sa bind(2)
 529  * \sa listen(2)
 530  */
 531 int init_tcp_socket(int port)
 532 {
 533         struct sockaddr_in my_addr;
 534         int fd, ret = get_stream_socket(AF_INET);
 535
 536         if (ret < 0)
 537                 return ret;
 538         fd = ret;
 539         ret = setserversockopts(fd);
 540         if (ret < 0)
 541                 goto err;
 542         init_sockaddr(&my_addr, port, NULL);
 543         ret = -E_BIND;
 544         if (bind(fd, (struct sockaddr *)&my_addr,
 545                         sizeof(struct sockaddr)) == -1) {
 546                 PARA_CRIT_LOG("bind error: %s\n", strerror(errno));
 547                 goto err;
 548         }
 549         ret = -E_LISTEN;
 550         if (listen(fd, BACKLOG) == -1)
 551                 goto err;
 552         PARA_INFO_LOG("listening on port %d, fd %d\n", port, fd);
 553         return fd;
 554 err:
 555         close(fd);
 556         return ret;
 557 }
 558
 559 /**
 560  * receive a buffer and check for a pattern
 561  *
 562  * \param fd the file descriptor to receive from
 563  * \param pattern the expected pattern
 564  * \param bufsize the size of the internal buffer
 565  *
 566  * \return Positive if \a pattern was received, negative otherwise.
 567  *
 568  * This function creates a buffer of size \a bufsize and tries
 569  * to receive at most \a bufsize bytes from file descriptor \a fd.
 570  * If at least \p strlen(\a pattern) bytes were received, the beginning of
 571  * the received buffer is compared with \a pattern, ignoring case.
 572  *
 573  * \sa recv_buffer()
 574  * \sa strncasecmp(3)
 575  */
 576 int recv_pattern(int fd, const char *pattern, size_t bufsize)
 577 {
 578         size_t len = strlen(pattern);
 579         char *buf = para_malloc(bufsize + 1);
 580         int ret = -E_RECV_PATTERN, n = recv_buffer(fd, buf, bufsize);
 581
 582         if (n < len)
 583                 goto out;
 584         if (strncasecmp(buf, pattern, len))
 585                 goto out;
 586         ret = 1;
 587 out:
 588         if (ret < 0) {
 589                 PARA_NOTICE_LOG("n = %d, did not receive pattern '%s'\n", n, pattern);
 590                 if (n > 0)
 591                         PARA_NOTICE_LOG("recvd: %s\n", buf);
 592         }
 593         free(buf);
 594         return ret;
 595 }