net.c

   1 /*
   2  * Copyright (C) 2005-2006 Andre Noll <maan@systemlinux.org>
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     This program is distributed in the hope that it will be useful,
  10  *     but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *     GNU General Public License for more details.
  13  *
  14  *     You should have received a copy of the GNU General Public License
  15  *     along with this program; if not, write to the Free Software
  16  *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
  17  */
  18
  19 /** \file net.c networking-related helper functions */
  20
  21 #include "para.h"
  22 #include "net.h"
  23 #include "string.h"
  24 #include <netdb.h>
  25 #include "error.h"
  26
  27 extern void (*crypt_function_recv)(unsigned long len, const unsigned char *indata, unsigned char *outdata);
  28 extern void (*crypt_function_send)(unsigned long len, const unsigned char *indata, unsigned char *outdata);
  29
  30
  31 /**
  32  * initialize a struct sockaddr_in
  33  * @param addr A pointer to the struct to be initialized
  34  * @param port The port number to use
  35  * @param he The address to use
  36  *
  37  * If \a he is null (server mode), \a addr->sin_addr is initialized with \p INADDR_ANY.
  38  * Otherwise, the address given by \a he is copied to addr.
  39  */
  40 void init_sockaddr(struct sockaddr_in *addr, int port, const struct hostent *he)
  41 {
  42         /* host byte order */
  43         addr->sin_family = AF_INET;
  44         /* short, network byte order */
  45         addr->sin_port = htons(port);
  46         if (he)
  47                 addr->sin_addr = *((struct in_addr *)he->h_addr);
  48         else
  49                 addr->sin_addr.s_addr = INADDR_ANY;
  50         /* zero the rest of the struct */
  51         memset(&addr->sin_zero, '\0', 8);
  52 }
  53
  54 /*
  55  * send out a buffer, resend on short writes
  56  * @param fd the file descriptor
  57  * @param buf The buffer to be sent
  58  * @len The length of \a buf
  59  *
  60  * Due to circumstances beyond your control, the kernel might not send all the
  61  * data out in one chunk, and now, my friend, it's up to us to get the data out
  62  * there (Beej's Guide to Network Programming).
  63  */
  64 static int sendall(int fd, const char *buf, size_t *len)
  65 {
  66         int total = 0;        /* how many bytes we've sent */
  67         int bytesleft = *len; /* how many we have left to send */
  68         int n = -1;
  69
  70         while (total < *len) {
  71                 n = send(fd, buf + total, bytesleft, 0);
  72                 if (n == -1)
  73                         break;
  74                 total += n;
  75                 bytesleft -= n;
  76                 if (total < *len)
  77                         PARA_DEBUG_LOG("short write (%zd byte(s) left)",
  78                                 *len - total);
  79         }
  80         *len = total; /* return number actually sent here */
  81         return n == -1? -E_SEND : 1; /* return 1 on success */
  82 }
  83
  84 /**
  85  * encrypt and send buffer
  86  * @param fd:  the file descriptor
  87  * @param buf the buffer to be encrypted and sent
  88  * @param len the length of \a buf
  89  *
  90  * Check if encrytion is available. If yes, encrypt the given buffer.  Send out
  91  * the buffer, encrypted or not, and try to resend the remaing part in case of
  92  * short writes.
  93  *
  94  * @return Positive on success, \p -E_SEND on errors.
  95  */
  96 int send_bin_buffer(int fd, const char *buf, size_t len)
  97 {
  98         int ret;
  99
 100         if (!len)
 101                 PARA_CRIT_LOG("%s", "len == 0\n");
 102         if (crypt_function_send) {
 103                 unsigned char *outbuf = para_malloc(len);
 104                 crypt_function_send(len, (unsigned char *)buf, outbuf);
 105                 ret = sendall(fd, (char *)outbuf, &len);
 106                 free(outbuf);
 107         } else
 108                 ret = sendall(fd, buf, &len);
 109         return ret;
 110 }
 111
 112 /**
 113  * encrypt and send null terminated buffer.
 114  * @param fd the file descriptor
 115  * @param buf the null-terminated buffer to be send
 116  *
 117  * This is equivalent to send_bin_buffer(fd, buf, strlen(buf)).
 118  *
 119  * @return Positive on success, \p -E_SEND on errors.
 120  */
 121 int send_buffer(int fd, const char *buf)
 122 {
 123         return send_bin_buffer(fd, buf, strlen(buf));
 124 }
 125
 126
 127 /**
 128  * send and encrypt a buffer given by a format string
 129  * @param fd the file descriptor
 130  * @param fmt a format string
 131  *
 132  * @return Positive on success, \p -E_SEND on errors.
 133  */
 134 __printf_2_3 int send_va_buffer(int fd, const char *fmt, ...)
 135 {
 136         char *msg;
 137         int ret;
 138
 139         PARA_VSPRINTF(fmt, msg);
 140         ret = send_buffer(fd, msg);
 141         free(msg);
 142         return ret;
 143 }
 144
 145 /**
 146  * receive and decrypt.
 147  *
 148  * @param fd the file descriptor
 149  * @param buf the buffer to write the decrypted data to
 150  * @param size the size of @param buf
 151  *
 152  * Receive at most \a size bytes from filedescriptor fd. If encrytion is
 153  * available, decrypt the received buffer.
 154  *
 155  * @return the number of bytes received on success. On receive errors, -E_RECV
 156  * is returned. On crypt errors, the corresponding crypt error number is
 157  * returned.
 158  * \sa recv(2)
 159  */
 160 __must_check int recv_bin_buffer(int fd, char *buf, ssize_t size)
 161 {
 162         int n;
 163
 164         if (crypt_function_recv) {
 165                 unsigned char *tmp = para_malloc(size);
 166                 n = recv(fd, tmp, size, 0);
 167                 if (n > 0)
 168                         crypt_function_recv(n, tmp, (unsigned char *)buf);
 169                 free(tmp);
 170         } else
 171                 n = recv(fd, buf, size, 0);
 172         if (n == -1)
 173                 n = -E_RECV;
 174         return n;
 175 }
 176
 177 /**
 178  * receive, decrypt and write terminating NULL byte
 179  *
 180  * @param fd the file descriptor
 181  * @param buf the buffer to write the decrypted data to
 182  * @param size the size of \a buf
 183  *
 184  * Read and decrypt at most size - 1 bytes from file descriptor \a fd and write
 185  * a NULL byte at the end of the received data.
 186  *
 187 */
 188 int recv_buffer(int fd, char *buf, ssize_t size)
 189 {
 190         int n;
 191
 192         n = recv_bin_buffer(fd, buf, size - 1);
 193         if (n >= 0)
 194                 buf[n] = '\0';
 195         else
 196                 *buf = '\0';
 197         return n;
 198 }
 199
 200 /**
 201  * wrapper around gethostbyname
 202  *
 203  * @param host hostname or IPv4 address
 204  * \return The hostent structure or a NULL pointer if an error occurs
 205  * \sa gethostbyname(2)
 206  */
 207 struct hostent *get_host_info(char *host)
 208 {
 209         PARA_INFO_LOG("getting host info of %s\n", host);
 210         /* FIXME: gethostbyname() is obsolete */
 211         return gethostbyname(host);
 212 }
 213
 214 /**
 215  * a wrapper around socket(2)
 216  *
 217  * Create an IPv4 socket for sequenced, reliable, two-way, connection-based
 218  * byte streams.
 219  *
 220  * @return The socket fd on success, -E_SOCKET on errors.
 221  * \sa socket(2)
 222  */
 223 int get_socket(void)
 224 {
 225         int socket_fd;
 226
 227         if ((socket_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
 228                 return -E_SOCKET;
 229         return socket_fd;
 230 }
 231
 232 /**
 233  * a wrapper around connect(2)
 234  *
 235  * @param fd the file descriptor
 236  * @param their_addr the address to connect
 237  *
 238  * @return \p -E_CONNECT on errors, 1 on success
 239  * \sa connect(2)
 240  */
 241 int para_connect(int fd, struct sockaddr_in *their_addr)
 242 {
 243         int ret;
 244
 245         if ((ret = connect(fd, (struct sockaddr *)their_addr,
 246                         sizeof(struct sockaddr))) == -1)
 247                 return -E_CONNECT;
 248         return 1;
 249 }
 250
 251 /**
 252  * paraslash's wrapper around the accept system call
 253  *
 254  * @param fd the listening socket
 255  * @param addr structure which is filled in with the address of the peer socket
 256  * @param size should contain the size of the structure pointed to by \a addr
 257  *
 258  * \sa accept(2).
 259  */
 260 int para_accept(int fd, void *addr, socklen_t size)
 261 {
 262         int new_fd;
 263
 264         new_fd = accept(fd, (struct sockaddr *) addr, &size);
 265         return new_fd == -1? -E_ACCEPT : new_fd;
 266 }
 267
 268 static int setserversockopts(int socket_fd)
 269 {
 270         int yes = 1;
 271
 272         if (setsockopt(socket_fd, SOL_SOCKET, SO_REUSEADDR, &yes,
 273                         sizeof(int)) == -1)
 274                 return -E_SETSOCKOPT;
 275         return 1;
 276 }
 277
 278 static int do_bind(int socket_fd, struct sockaddr_in *my_addr)
 279 {
 280         if (bind(socket_fd, (struct sockaddr *)my_addr,
 281                 sizeof(struct sockaddr)) == -1)
 282                 return -E_BIND;
 283         return 1;
 284 }
 285
 286 /**
 287  * prepare a structure for \p AF_UNIX socket addresses
 288  *
 289  * \param u pointer to the struct to be prepared
 290  * \param name the socket pathname
 291  *
 292  * This just copies \a name to the sun_path component of \a u.
 293  *
 294  * \return Positive on success, \p -E_NAME_TOO_LONG if \a name is longer
 295  * than \p UNIX_PATH_MAX.
 296  */
 297 int init_unix_addr(struct sockaddr_un *u, const char *name)
 298 {
 299         if (strlen(name) >= UNIX_PATH_MAX)
 300                 return -E_NAME_TOO_LONG;
 301         memset(u->sun_path, 0, UNIX_PATH_MAX);
 302         u->sun_family = PF_UNIX;
 303         strcpy(u->sun_path, name);
 304         return 1;
 305 }
 306
 307 /**
 308  * prepare, create, and bind and socket for local communication
 309  *
 310  * \param name the socket pathname
 311  * \param unix_addr pointer to the \p AF_UNIX socket structure
 312  * \param mode the desired mode of the socket
 313  *
 314  * This functions creates a local socket for sequenced, reliable,
 315  * two-way, connection-based byte streams.
 316  * \sa socket(2)
 317  * \sa bind(2)
 318  * \sa chmod(2)
 319  */
 320 int create_pf_socket(const char *name, struct sockaddr_un *unix_addr, int mode)
 321 {
 322         int fd, ret;
 323
 324         fd = socket(PF_UNIX, SOCK_STREAM, 0);
 325         if (fd < 0)
 326                 return -E_SOCKET;
 327 //      unlink(name);
 328         ret = init_unix_addr(unix_addr, name);
 329         if (ret < 0)
 330                 return ret;
 331         if (bind(fd, (struct sockaddr *) unix_addr, UNIX_PATH_MAX) < 0)
 332                 return -E_BIND;
 333         if (chmod(name, mode) < 0)
 334                 return -E_CHMOD;
 335         return fd;
 336 }
 337
 338 #ifndef HAVE_UCRED
 339         struct ucred {
 340         uid_t uid, pid, gid;
 341 };
 342 ssize_t send_cred_buffer(int sock, char *buf)
 343 {
 344         return send_buffer(sock, buf);
 345 }
 346 int recv_cred_buffer(int fd, char *buf, size_t size)
 347 {
 348         return recv_buffer(fd, buf, size) > 0? 1 : -E_RECVMSG;
 349 }
 350 #else /* HAVE_UCRED */
 351 /**
 352  * send NULL terminated buffer and Unix credentials of the current process
 353  *
 354  * \param sock the socket file descriptor
 355  * \param buf the buffer to be sent
 356  *
 357  * \return On success, this call returns the number of characters sent.  On
 358  * error, \p -E_SENDMSG ist returned.
 359  * \sa  okir's Black Hats Manual
 360  * \sa sendmsg(2)
 361  */
 362 ssize_t send_cred_buffer(int sock, char *buf)
 363 {
 364         char control[sizeof(struct cmsghdr) + 10];
 365         struct msghdr msg;
 366         struct cmsghdr *cmsg;
 367         static struct iovec iov;
 368         struct ucred c;
 369         int ret;
 370
 371         /* Response data */
 372         iov.iov_base = buf;
 373         iov.iov_len  = strlen(buf);
 374         c.pid = getpid();
 375         c.uid = getuid();
 376         c.gid = getgid();
 377         /* compose the message */
 378         memset(&msg, 0, sizeof(msg));
 379         msg.msg_iov = &iov;
 380         msg.msg_iovlen = 1;
 381         msg.msg_control = control;
 382         msg.msg_controllen = sizeof(control);
 383         /* attach the ucred struct */
 384         cmsg = CMSG_FIRSTHDR(&msg);
 385         cmsg->cmsg_level = SOL_SOCKET;
 386         cmsg->cmsg_type = SCM_CREDENTIALS;
 387         cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
 388         *(struct ucred *)CMSG_DATA(cmsg) = c;
 389         msg.msg_controllen = cmsg->cmsg_len;
 390         ret = sendmsg(sock, &msg, 0);
 391         if (ret  < 0)
 392                 ret = -E_SENDMSG;
 393         return ret;
 394 }
 395
 396 static void dispose_fds(int *fds, int num)
 397 {
 398         int i;
 399
 400         for (i = 0; i < num; i++)
 401                 close(fds[i]);
 402 }
 403
 404 /**
 405  * receive a buffer and the Unix credentials of the sending process
 406  *
 407  * \param fd the socket file descriptor
 408  * \param buf the buffer to store the message
 409  * \param size the size of \a buffer
 410  *
 411  * \return negative on errors, the user id on success.
 412  *
 413  * \sa okir's Black Hats Manual
 414  * \sa recvmsg(2)
 415  */
 416 int recv_cred_buffer(int fd, char *buf, size_t size)
 417 {
 418         char control[255];
 419         struct msghdr msg;
 420         struct cmsghdr *cmsg;
 421         struct iovec iov;
 422         int result = 0;
 423         int yes = 1;
 424         struct ucred cred;
 425
 426         setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &yes, sizeof(int));
 427         memset(&msg, 0, sizeof(msg));
 428         memset(buf, 0, size);
 429         iov.iov_base = buf;
 430         iov.iov_len = size;
 431         msg.msg_iov = &iov;
 432         msg.msg_iovlen = 1;
 433         msg.msg_control = control;
 434         msg.msg_controllen = sizeof(control);
 435         if (recvmsg(fd, &msg, 0) < 0)
 436                 return -E_RECVMSG;
 437         result = -E_SCM_CREDENTIALS;
 438         cmsg = CMSG_FIRSTHDR(&msg);
 439         while (cmsg) {
 440                 if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type
 441                                 == SCM_CREDENTIALS) {
 442                         memcpy(&cred, CMSG_DATA(cmsg), sizeof(struct ucred));
 443                         result = cred.uid;
 444                 } else
 445                         if (cmsg->cmsg_level == SOL_SOCKET
 446                                         && cmsg->cmsg_type == SCM_RIGHTS) {
 447                                 dispose_fds((int *) CMSG_DATA(cmsg),
 448                                         (cmsg->cmsg_len - CMSG_LEN(0))
 449                                         / sizeof(int));
 450                         }
 451                 cmsg = CMSG_NXTHDR(&msg, cmsg);
 452         }
 453         return result;
 454 }
 455 #endif /* HAVE_UCRED */
 456
 457 /** how many pending connections queue will hold */
 458 #define BACKLOG 10
 459
 460 /**
 461  * create a socket, bind it and listen
 462  * \param port the tcp port to listen on
 463  *
 464  * \return The file descriptor of the created socket, negative
 465  * on errors.
 466  *
 467  * \sa get_socket()
 468  * \sa setsockopt(2)
 469  * \sa bind(2)
 470  * \sa listen(2)
 471  */
 472 int init_tcp_socket(int port)
 473 {
 474         int sockfd, ret;
 475         struct sockaddr_in my_addr;
 476
 477         if ((sockfd = get_socket()) < 0)
 478                 return sockfd;
 479         ret = setserversockopts(sockfd);
 480         if (ret < 0)
 481                 return ret;
 482         init_sockaddr(&my_addr, port, NULL);
 483         ret = do_bind(sockfd, &my_addr);
 484         if (ret < 0)
 485                 return ret;
 486         if (listen(sockfd, BACKLOG) == -1)
 487                 return -E_LISTEN;
 488         PARA_INFO_LOG("listening on port %d, fd %d\n", port, sockfd);
 489         return sockfd;
 490 }
 491
 492 /**
 493  * receive a buffer and check for a pattern
 494  *
 495  * \param fd the file descriptor to receive from
 496  * \param pattern the expected pattern
 497  * \param bufsize the size of the internal buffer
 498  *
 499  * \return Positive if \a pattern was received, negative otherwise.
 500  *
 501  * This function creates a buffer of size \a bufsize and tries
 502  * to receive at most \a bufsize bytes from file descriptor \a fd.
 503  * If at least \p strlen(\a pattern) bytes were received, the beginning of
 504  * the received buffer is compared with \a pattern, ignoring case.
 505  * \sa recv_buffer()
 506  * \sa strncasecmp(3)
 507  */
 508 int recv_pattern(int fd, const char *pattern, size_t bufsize)
 509 {
 510         size_t len = strlen(pattern);
 511         char *buf = para_malloc(bufsize + 1);
 512         int ret = -E_RECV_PATTERN, n = recv_buffer(fd, buf, bufsize);
 513
 514         if (n < len)
 515                 goto out;
 516         if (strncasecmp(buf, pattern, len))
 517                 goto out;
 518         ret = 1;
 519 out:
 520         if (ret < 0)
 521                 PARA_NOTICE_LOG("did not receive pattern '%s'\n", pattern);
 522         free(buf);
 523         return ret;
 524 }