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