mdw@git.distorted.org.uk Git - sgt/agedu/blob - httpd.c

   1 /*
   2  * httpd.c: implementation of httpd.h.
   3  */
   4
   5 #include "agedu.h"
   6 #include "alloc.h"
   7 #include "html.h"
   8 #include "httpd.h"
   9
  10 /* --- Logic driving what the web server's responses are. --- */
  11
  12 enum { /* connctx states */
  13     READING_REQ_LINE,
  14     READING_HEADERS,
  15     DONE
  16 };
  17
  18 struct connctx {
  19     const void *t;
  20     char *data;
  21     int datalen, datasize;
  22     char *method, *url, *headers, *auth;
  23     int state;
  24 };
  25
  26 /*
  27  * Called when a new connection arrives on a listening socket.
  28  * Returns a connctx for the new connection.
  29  */
  30 struct connctx *new_connection(const void *t)
  31 {
  32     struct connctx *cctx = snew(struct connctx);
  33     cctx->t = t;
  34     cctx->data = NULL;
  35     cctx->datalen = cctx->datasize = 0;
  36     cctx->state = READING_REQ_LINE;
  37     cctx->method = cctx->url = cctx->headers = cctx->auth = NULL;
  38     return cctx;
  39 }
  40
  41 void free_connection(struct connctx *cctx)
  42 {
  43     sfree(cctx->data);
  44     sfree(cctx);
  45 }
  46
  47 static char *http_error(char *code, char *errmsg, char *extraheader,
  48                         char *errtext, ...)
  49 {
  50     return dupfmt("HTTP/1.1 %s %s\r\n"
  51                   "Date: %D\r\n"
  52                   "Server: " PNAME "\r\n"
  53                   "Connection: close\r\n"
  54                   "%s"
  55                   "Content-Type: text/html; charset=US-ASCII\r\n"
  56                   "\r\n"
  57                   "<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">\r\n"
  58                   "<HTML><HEAD>\r\n"
  59                   "<TITLE>%s %s</TITLE>\r\n"
  60                   "</HEAD><BODY>\r\n"
  61                   "<H1>%s %s</H1>\r\n"
  62                   "<P>%s</P>\r\n"
  63                   "</BODY></HTML>\r\n", code, errmsg,
  64                   extraheader ? extraheader : "",
  65                   code, errmsg, code, errmsg, errtext);
  66 }
  67
  68 static char *http_success(char *mimetype, int stuff_cr, char *document)
  69 {
  70     return dupfmt("HTTP/1.1 200 OK\r\n"
  71                   "Date: %D\r\n"
  72                   "Expires: %D\r\n"
  73                   "Server: " PNAME "\r\n"
  74                   "Connection: close\r\n"
  75                   "Content-Type: %s\r\n"
  76                   "\r\n"
  77                   "%S", mimetype, stuff_cr, document);
  78 }
  79
  80 /*
  81  * Called when data comes in on a connection.
  82  *
  83  * If this function returns NULL, the platform code continues
  84  * reading from the socket. Otherwise, it returns some dynamically
  85  * allocated data which the platform code will then write to the
  86  * socket before closing it.
  87  */
  88 char *got_data(struct connctx *ctx, char *data, int length,
  89                int magic_access, const char *auth_string,
  90                const struct html_config *cfg)
  91 {
  92     char *line, *p, *q, *r, *z1, *z2, c1, c2;
  93     int auth_correct = 0;
  94     unsigned long index;
  95     char *document, *ret;
  96
  97     /*
  98      * Add the data we've just received to our buffer.
  99      */
 100     if (ctx->datasize < ctx->datalen + length) {
 101         ctx->datasize = (ctx->datalen + length) * 3 / 2 + 4096;
 102         ctx->data = sresize(ctx->data, ctx->datasize, char);
 103     }
 104     memcpy(ctx->data + ctx->datalen, data, length);
 105     ctx->datalen += length;
 106
 107     /*
 108      * Gradually process the HTTP request as we receive it.
 109      */
 110     if (ctx->state == READING_REQ_LINE) {
 111         /*
 112          * We're waiting for the first line of the input, which
 113          * contains the main HTTP request. See if we've got it
 114          * yet.
 115          */
 116
 117         line = ctx->data;
 118         /*
 119          * RFC 2616 section 4.1: `In the interest of robustness,
 120          * [...] if the server is reading the protocol stream at
 121          * the beginning of a message and receives a CRLF first,
 122          * it should ignore the CRLF.'
 123          */
 124         while (line - ctx->data < ctx->datalen &&
 125                (*line == '\r' || *line == '\n'))
 126             line++;
 127         q = line;
 128         while (q - ctx->data < ctx->datalen && *q != '\n')
 129             q++;
 130         if (q - ctx->data >= ctx->datalen)
 131             return NULL;               /* not got request line yet */
 132
 133         /*
 134          * We've got the first line of the request. Zero-terminate
 135          * and parse it into method, URL and optional HTTP
 136          * version.
 137          */
 138         *q = '\0';
 139         ctx->headers = q+1;
 140         if (q > line && q[-1] == '\r')
 141             *--q = '\0';
 142         z1 = z2 = q;
 143         c1 = c2 = *q;
 144         p = line;
 145         while (*p && !isspace((unsigned char)*p)) p++;
 146         if (*p) {
 147             z1 = p++;
 148             c1 = *z1;
 149             *z1 = '\0';
 150         }
 151         while (*p && isspace((unsigned char)*p)) p++;
 152         q = p;
 153         while (*q && !isspace((unsigned char)*q)) q++;
 154         z2 = q++;
 155         c2 = *z2;
 156         *z2 = '\0';
 157         while (*q && isspace((unsigned char)*q)) q++;
 158
 159         /*
 160          * Now `line' points at the method name; p points at the
 161          * URL, if any; q points at the HTTP version, if any.
 162          */
 163
 164         /*
 165          * There should _be_ a URL, on any request type at all.
 166          */
 167         if (!*p) {
 168             char *ret, *text;
 169             /* Restore the request to the way we received it. */
 170             *z2 = c2;
 171             *z1 = c1;
 172             text = dupfmt("<code>" PNAME "</code> received the HTTP request"
 173                           " \"<code>%h</code>\", which contains no URL.",
 174                           line);
 175             ret = http_error("400", "Bad request", NULL, text);
 176             sfree(text);
 177             return ret;
 178         }
 179
 180         ctx->method = line;
 181         ctx->url = p;
 182
 183         /*
 184          * If there was an HTTP version, we might need to see
 185          * headers. Otherwise, the request is done.
 186          */
 187         if (*q) {
 188             ctx->state = READING_HEADERS;
 189         } else {
 190             ctx->state = DONE;
 191         }
 192     }
 193
 194     if (ctx->state == READING_HEADERS) {
 195         /*
 196          * While we're receiving the HTTP request headers, all we
 197          * do is to keep scanning to see if we find two newlines
 198          * next to each other.
 199          */
 200         q = ctx->data + ctx->datalen;
 201         for (p = ctx->headers; p < q; p++) {
 202             if (*p == '\n' &&
 203                 ((p+1 < q && p[1] == '\n') ||
 204                  (p+2 < q && p[1] == '\r' && p[2] == '\n'))) {
 205                 p[1] = '\0';
 206                 ctx->state = DONE;
 207                 break;
 208             }
 209         }
 210     }
 211
 212     if (ctx->state == DONE) {
 213         /*
 214          * Now we have the entire HTTP request. Decide what to do
 215          * with it.
 216          */
 217         if (auth_string) {
 218             /*
 219              * Search the request headers for Authorization.
 220              */
 221             q = ctx->data + ctx->datalen;
 222             for (p = ctx->headers; p < q; p++) {
 223                 const char *hdr = "Authorization:";
 224                 int i;
 225                 for (i = 0; hdr[i]; i++) {
 226                     if (p >= q || tolower((unsigned char)*p) !=
 227                         tolower((unsigned char)hdr[i]))
 228                         break;
 229                     p++;
 230                 }
 231                 if (!hdr[i])
 232                     break;             /* found our header */
 233                 p = memchr(p, '\n', q - p);
 234                 if (!p)
 235                     p = q;
 236             }
 237             if (p < q) {
 238                 while (p < q && isspace((unsigned char)*p))
 239                     p++;
 240                 r = p;
 241                 while (p < q && !isspace((unsigned char)*p))
 242                     p++;
 243                 if (p < q) {
 244                     *p++ = '\0';
 245                     if (!strcasecmp(r, "Basic")) {
 246                         while (p < q && isspace((unsigned char)*p))
 247                             p++;
 248                         r = p;
 249                         while (p < q && !isspace((unsigned char)*p))
 250                             p++;
 251                         if (p < q) {
 252                             *p++ = '\0';
 253                             if (!strcmp(r, auth_string))
 254                                 auth_correct = 1;
 255                         }
 256                     }
 257                 }
 258             }
 259         }
 260
 261         if (!magic_access && !auth_correct) {
 262             if (auth_string) {
 263                 ret = http_error("401", "Unauthorized",
 264                                  "WWW-Authenticate: Basic realm=\""PNAME"\"\r\n",
 265                                  "\nYou must authenticate to view these pages.");
 266             } else {
 267                 ret = http_error("403", "Forbidden", NULL,
 268                                  "This is a restricted-access set of pages.");
 269             }
 270         } else {
 271             char *q;
 272             p = ctx->url;
 273             p += strspn(p, "/?");
 274             index = strtoul(p, &q, 10);
 275             if (*q) {
 276                 ret = http_error("404", "Not Found", NULL,
 277                                  "This is not a valid pathname index.");
 278             } else {
 279                 document = html_query(ctx->t, index, cfg, 1);
 280                 if (document) {
 281                     ret = http_success("text/html", 1, document);
 282                     sfree(document);
 283                 } else {
 284                     ret = http_error("404", "Not Found", NULL,
 285                                      "Pathname index out of range.");
 286                 }
 287             }
 288         }
 289         return ret;
 290     } else
 291         return NULL;
 292 }
 293
 294 /* --- Platform support for running a web server. --- */
 295
 296 enum { FD_CLIENT, FD_LISTENER, FD_CONNECTION };
 297
 298 struct fd {
 299     int fd;
 300     int type;
 301     int deleted;
 302     char *wdata;
 303     int wdatalen, wdatapos;
 304     int magic_access;
 305     struct connctx *cctx;
 306 };
 307
 308 struct fd *fds = NULL;
 309 int nfds = 0, fdsize = 0;
 310
 311 struct fd *new_fdstruct(int fd, int type)
 312 {
 313     struct fd *ret;
 314
 315     if (nfds >= fdsize) {
 316         fdsize = nfds * 3 / 2 + 32;
 317         fds = sresize(fds, fdsize, struct fd);
 318     }
 319
 320     ret = &fds[nfds++];
 321
 322     ret->fd = fd;
 323     ret->type = type;
 324     ret->wdata = NULL;
 325     ret->wdatalen = ret->wdatapos = 0;
 326     ret->cctx = NULL;
 327     ret->deleted = 0;
 328     ret->magic_access = 0;
 329
 330     return ret;
 331 }
 332
 333 int check_owning_uid(int fd, int flip)
 334 {
 335     struct sockaddr_in sock, peer;
 336     socklen_t addrlen;
 337     char linebuf[4096], matchbuf[80];
 338     FILE *fp;
 339
 340     addrlen = sizeof(sock);
 341     if (getsockname(fd, (struct sockaddr *)&sock, &addrlen)) {
 342         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 343         exit(1);
 344     }
 345     addrlen = sizeof(peer);
 346     if (getpeername(fd, (struct sockaddr *)&peer, &addrlen)) {
 347         if (errno == ENOTCONN) {
 348             peer.sin_addr.s_addr = htonl(0);
 349             peer.sin_port = htons(0);
 350         } else {
 351             fprintf(stderr, "getpeername: %s\n", strerror(errno));
 352             exit(1);
 353         }
 354     }
 355
 356     if (flip) {
 357         struct sockaddr_in tmp = sock;
 358         sock = peer;
 359         peer = tmp;
 360     }
 361
 362     sprintf(matchbuf, "%08X:%04X %08X:%04X",
 363             peer.sin_addr.s_addr, ntohs(peer.sin_port),
 364             sock.sin_addr.s_addr, ntohs(sock.sin_port));
 365     fp = fopen("/proc/net/tcp", "r");
 366     if (fp) {
 367         while (fgets(linebuf, sizeof(linebuf), fp)) {
 368             if (strlen(linebuf) >= 75 &&
 369                 !strncmp(linebuf+6, matchbuf, strlen(matchbuf))) {
 370                 fclose(fp);
 371                 return atoi(linebuf + 75);
 372             }
 373         }
 374         fclose(fp);
 375     }
 376
 377     return -1;
 378 }
 379
 380 void check_magic_access(struct fd *fd)
 381 {
 382     if (check_owning_uid(fd->fd, 0) == getuid())
 383         fd->magic_access = 1;
 384 }
 385
 386 static void base64_encode_atom(unsigned char *data, int n, char *out)
 387 {
 388     static const char base64_chars[] =
 389         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 390
 391     unsigned word;
 392
 393     word = data[0] << 16;
 394     if (n > 1)
 395         word |= data[1] << 8;
 396     if (n > 2)
 397         word |= data[2];
 398     out[0] = base64_chars[(word >> 18) & 0x3F];
 399     out[1] = base64_chars[(word >> 12) & 0x3F];
 400     if (n > 1)
 401         out[2] = base64_chars[(word >> 6) & 0x3F];
 402     else
 403         out[2] = '=';
 404     if (n > 2)
 405         out[3] = base64_chars[word & 0x3F];
 406     else
 407         out[3] = '=';
 408 }
 409
 410 void run_httpd(const void *t, int authmask, const struct httpd_config *dcfg,
 411                const struct html_config *incfg)
 412 {
 413     int fd, ret;
 414     int authtype;
 415     char *authstring = NULL;
 416     struct sockaddr_in addr;
 417     socklen_t addrlen;
 418     struct html_config cfg = *incfg;
 419
 420     cfg.format = "%.0lu";
 421
 422     /*
 423      * Establish the listening socket and retrieve its port
 424      * number.
 425      */
 426     fd = socket(PF_INET, SOCK_STREAM, 0);
 427     if (fd < 0) {
 428         fprintf(stderr, "socket(PF_INET): %s\n", strerror(errno));
 429         exit(1);
 430     }
 431     memset(&addr, 0, sizeof(addr));
 432     addr.sin_family = AF_INET;
 433     if (!dcfg->address) {
 434 #ifdef RANDOM_LOCALHOST
 435         unsigned long ipaddr;
 436         srand(0L);
 437         ipaddr = 0x7f000000;
 438         ipaddr += (1 + rand() % 255) << 16;
 439         ipaddr += (1 + rand() % 255) << 8;
 440         ipaddr += (1 + rand() % 255);
 441         addr.sin_addr.s_addr = htonl(ipaddr);
 442 #else
 443         addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 444 #endif
 445         addr.sin_port = htons(0);
 446     } else {
 447         addr.sin_addr.s_addr = inet_addr(dcfg->address);
 448         addr.sin_port = dcfg->port ? htons(dcfg->port) : 0;
 449     }
 450     addrlen = sizeof(addr);
 451     ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 452 #ifdef RANDOM_LOCALHOST
 453     if (ret < 0 && errno == EADDRNOTAVAIL && !dcfg->address) {
 454         /*
 455          * Some systems don't like us binding to random weird
 456          * localhost-space addresses. Try again with the official
 457          * INADDR_LOOPBACK.
 458          */
 459         addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 460         addr.sin_port = htons(0);
 461         ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 462     }
 463 #endif
 464     if (ret < 0) {
 465         fprintf(stderr, "bind: %s\n", strerror(errno));
 466         exit(1);
 467     }
 468     if (listen(fd, 5) < 0) {
 469         fprintf(stderr, "listen: %s\n", strerror(errno));
 470         exit(1);
 471     }
 472     addrlen = sizeof(addr);
 473     if (getsockname(fd, (struct sockaddr *)&addr, &addrlen)) {
 474         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 475         exit(1);
 476     }
 477     if ((authmask & HTTPD_AUTH_MAGIC) &&
 478         (check_owning_uid(fd, 1) == getuid())) {
 479         authtype = HTTPD_AUTH_MAGIC;
 480         if (authmask != HTTPD_AUTH_MAGIC)
 481             printf("Using Linux /proc/net magic authentication\n");
 482     } else if ((authmask & HTTPD_AUTH_BASIC)) {
 483         char username[128], password[128], userpassbuf[259];
 484         const char *userpass;
 485         const char *rname;
 486         unsigned char passbuf[10];
 487         int i, j, k, fd;
 488
 489         authtype = HTTPD_AUTH_BASIC;
 490
 491         if (authmask != HTTPD_AUTH_BASIC)
 492             printf("Using HTTP Basic authentication\n");
 493
 494         if (dcfg->basicauthdata) {
 495             userpass = dcfg->basicauthdata;
 496         } else {
 497             strcpy(username, PNAME);
 498             rname = "/dev/urandom";
 499             fd = open(rname, O_RDONLY);
 500             if (fd < 0) {
 501                 int err = errno;
 502                 rname = "/dev/random";
 503                 fd = open(rname, O_RDONLY);
 504                 if (fd < 0) {
 505                     int err2 = errno;
 506                     fprintf(stderr, "/dev/urandom: open: %s\n", strerror(err));
 507                     fprintf(stderr, "/dev/random: open: %s\n", strerror(err2));
 508                     exit(1);
 509                 }
 510             }
 511             for (i = 0; i < 10 ;) {
 512                 j = read(fd, passbuf + i, 10 - i);
 513                 if (j <= 0) {
 514                     fprintf(stderr, "%s: read: %s\n", rname,
 515                             j < 0 ? strerror(errno) : "unexpected EOF");
 516                     exit(1);
 517                 }
 518                 i += j;
 519             }
 520             close(fd);
 521             for (i = 0; i < 16; i++) {
 522                 /*
 523                  * 32 characters out of the 36 alphanumerics gives
 524                  * me the latitude to discard i,l,o for being too
 525                  * numeric-looking, and w because it has two too
 526                  * many syllables and one too many presidential
 527                  * associations.
 528                  */
 529                 static const char chars[32] =
 530                     "0123456789abcdefghjkmnpqrstuvxyz";
 531                 int v = 0;
 532
 533                 k = i / 8 * 5;
 534                 for (j = 0; j < 5; j++)
 535                     v |= ((passbuf[k+j] >> (i%8)) & 1) << j;
 536
 537                 password[i] = chars[v];
 538             }
 539             password[i] = '\0';
 540
 541             sprintf(userpassbuf, "%s:%s", username, password);
 542             userpass = userpassbuf;
 543
 544             printf("Username: %s\nPassword: %s\n", username, password);
 545         }
 546
 547         k = strlen(userpass);
 548         authstring = snewn(k * 4 / 3 + 16, char);
 549         for (i = j = 0; i < k ;) {
 550             int s = k-i < 3 ? k-i : 3;
 551             base64_encode_atom((unsigned char *)(userpass+i), s, authstring+j);
 552             i += s;
 553             j += 4;
 554         }
 555         authstring[j] = '\0';
 556     } else if ((authmask & HTTPD_AUTH_NONE)) {
 557         authtype = HTTPD_AUTH_NONE;
 558         if (authmask != HTTPD_AUTH_NONE)
 559             printf("Web server is unauthenticated\n");
 560     } else {
 561         fprintf(stderr, PNAME ": authentication method not supported\n");
 562         exit(1);
 563     }
 564     if (ntohs(addr.sin_addr.s_addr) == INADDR_ANY) {
 565         printf("Server port: %d\n", ntohs(addr.sin_port));
 566     } else if (ntohs(addr.sin_port) == 80) {
 567         printf("URL: http://%s/\n", inet_ntoa(addr.sin_addr));
 568     } else {
 569         printf("URL: http://%s:%d/\n",
 570                inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
 571     }
 572
 573     /*
 574      * Now construct an fd structure to hold it.
 575      */
 576     new_fdstruct(fd, FD_LISTENER);
 577
 578     /*
 579      * Read from standard input, and treat EOF as a notification
 580      * to exit.
 581      */
 582     new_fdstruct(0, FD_CLIENT);
 583
 584     /*
 585      * Now we're ready to run our main loop. Keep looping round on
 586      * select.
 587      */
 588     while (1) {
 589         fd_set rfds, wfds;
 590         int i, j;
 591         SELECT_TYPE_ARG1 maxfd;
 592         int ret;
 593
 594 #define FD_SET_MAX(fd, set, max) \
 595         do { FD_SET((fd),(set)); (max) = ((max)<=(fd)?(fd)+1:(max)); } while(0)
 596
 597         /*
 598          * Loop round the fd list putting fds into our select
 599          * sets. Also in this loop we remove any that were marked
 600          * as deleted in the previous loop.
 601          */
 602         FD_ZERO(&rfds);
 603         FD_ZERO(&wfds);
 604         maxfd = 0;
 605         for (i = j = 0; j < nfds; j++) {
 606
 607             if (fds[j].deleted) {
 608                 sfree(fds[j].wdata);
 609                 free_connection(fds[j].cctx);
 610                 continue;
 611             }
 612             fds[i] = fds[j];
 613
 614             switch (fds[i].type) {
 615               case FD_CLIENT:
 616                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 617                 break;
 618               case FD_LISTENER:
 619                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 620                 break;
 621               case FD_CONNECTION:
 622                 /*
 623                  * Always read from a connection socket. Even
 624                  * after we've started writing, the peer might
 625                  * still be sending (e.g. because we shamefully
 626                  * jumped the gun before waiting for the end of
 627                  * the HTTP request) and so we should be prepared
 628                  * to read data and throw it away.
 629                  */
 630                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 631                 /*
 632                  * Also attempt to write, if we have data to write.
 633                  */
 634                 if (fds[i].wdatapos < fds[i].wdatalen)
 635                     FD_SET_MAX(fds[i].fd, &wfds, maxfd);
 636                 break;
 637             }
 638
 639             i++;
 640         }
 641         nfds = i;
 642
 643         ret = select(maxfd, SELECT_TYPE_ARG234 &rfds,
 644                      SELECT_TYPE_ARG234 &wfds, SELECT_TYPE_ARG234 NULL,
 645                      SELECT_TYPE_ARG5 NULL);
 646         if (ret <= 0) {
 647             if (ret < 0 && (errno != EINTR)) {
 648                 fprintf(stderr, "select: %s", strerror(errno));
 649                 exit(1);
 650             }
 651             continue;
 652         }
 653
 654         for (i = 0; i < nfds; i++) {
 655             switch (fds[i].type) {
 656               case FD_CLIENT:
 657                 if (FD_ISSET(fds[i].fd, &rfds)) {
 658                     char buf[4096];
 659                     int ret = read(fds[i].fd, buf, sizeof(buf));
 660                     if (ret <= 0) {
 661                         if (ret < 0) {
 662                             fprintf(stderr, "standard input: read: %s\n",
 663                                     strerror(errno));
 664                             exit(1);
 665                         }
 666                         return;
 667                     }
 668                 }
 669                 break;
 670               case FD_LISTENER:
 671                 if (FD_ISSET(fds[i].fd, &rfds)) {
 672                     /*
 673                      * New connection has come in. Accept it.
 674                      */
 675                     struct fd *f;
 676                     struct sockaddr_in addr;
 677                     socklen_t addrlen = sizeof(addr);
 678                     int newfd = accept(fds[i].fd, (struct sockaddr *)&addr,
 679                                        &addrlen);
 680                     if (newfd < 0)
 681                         break;         /* not sure what happened there */
 682
 683                     f = new_fdstruct(newfd, FD_CONNECTION);
 684                     f->cctx = new_connection(t);
 685                     if (authtype == HTTPD_AUTH_MAGIC)
 686                         check_magic_access(f);
 687                 }
 688                 break;
 689               case FD_CONNECTION:
 690                 if (FD_ISSET(fds[i].fd, &rfds)) {
 691                     /*
 692                      * There's data to be read.
 693                      */
 694                     char readbuf[4096];
 695                     int ret;
 696
 697                     ret = read(fds[i].fd, readbuf, sizeof(readbuf));
 698                     if (ret <= 0) {
 699                         /*
 700                          * This shouldn't happen in a sensible
 701                          * HTTP connection, so we abandon the
 702                          * connection if it does.
 703                          */
 704                         close(fds[i].fd);
 705                         fds[i].deleted = 1;
 706                         break;
 707                     } else {
 708                         if (!fds[i].wdata) {
 709                             /*
 710                              * If we haven't got an HTTP response
 711                              * yet, keep processing data in the
 712                              * hope of acquiring one.
 713                              */
 714                             fds[i].wdata = got_data
 715                                 (fds[i].cctx, readbuf, ret,
 716                                  (authtype == HTTPD_AUTH_NONE ||
 717                                   fds[i].magic_access), authstring, &cfg);
 718                             if (fds[i].wdata) {
 719                                 fds[i].wdatalen = strlen(fds[i].wdata);
 720                                 fds[i].wdatapos = 0;
 721                             }
 722                         } else {
 723                             /*
 724                              * Otherwise, just drop our read data
 725                              * on the floor.
 726                              */
 727                         }
 728                     }
 729                 }
 730                 if (FD_ISSET(fds[i].fd, &wfds) &&
 731                     fds[i].wdatapos < fds[i].wdatalen) {
 732                     /*
 733                      * The socket is writable, and we have data to
 734                      * write. Write it.
 735                      */
 736                     int ret = write(fds[i].fd, fds[i].wdata + fds[i].wdatapos,
 737                                     fds[i].wdatalen - fds[i].wdatapos);
 738                     if (ret <= 0) {
 739                         /*
 740                          * Shouldn't happen; abandon the connection.
 741                          */
 742                         close(fds[i].fd);
 743                         fds[i].deleted = 1;
 744                         break;
 745                     } else {
 746                         fds[i].wdatapos += ret;
 747                         if (fds[i].wdatapos == fds[i].wdatalen) {
 748                             shutdown(fds[i].fd, SHUT_WR);
 749                         }
 750                     }
 751                 }
 752                 break;
 753             }
 754         }
 755
 756     }
 757 }