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