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_provided = 0, 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                 auth_provided = 1;
 239                 while (p < q && isspace((unsigned char)*p))
 240                     p++;
 241                 r = p;
 242                 while (p < q && !isspace((unsigned char)*p))
 243                     p++;
 244                 if (p < q) {
 245                     *p++ = '\0';
 246                     if (!strcasecmp(r, "Basic")) {
 247                         while (p < q && isspace((unsigned char)*p))
 248                             p++;
 249                         r = p;
 250                         while (p < q && !isspace((unsigned char)*p))
 251                             p++;
 252                         if (p < q) {
 253                             *p++ = '\0';
 254                             if (!strcmp(r, auth_string))
 255                                 auth_correct = 1;
 256                         }
 257                     }
 258                 }
 259             }
 260         }
 261
 262         if (!magic_access && !auth_correct) {
 263             if (auth_string) {
 264                 ret = http_error("401", "Unauthorized",
 265                                  "WWW-Authenticate: Basic realm=\""PNAME"\"\r\n",
 266                                  "\nYou must authenticate to view these pages.");
 267             } else {
 268                 ret = http_error("403", "Forbidden", NULL,
 269                                  "This is a restricted-access set of pages.");
 270             }
 271         } else {
 272             char *q;
 273             p = ctx->url;
 274             p += strspn(p, "/?");
 275             index = strtoul(p, &q, 10);
 276             if (*q) {
 277                 ret = http_error("404", "Not Found", NULL,
 278                                  "This is not a valid pathname index.");
 279             } else {
 280                 document = html_query(ctx->t, index, cfg);
 281                 if (document) {
 282                     ret = http_success("text/html", 1, document);
 283                     sfree(document);
 284                 } else {
 285                     ret = http_error("404", "Not Found", NULL,
 286                                      "Pathname index out of range.");
 287                 }
 288             }
 289         }
 290         return ret;
 291     } else
 292         return NULL;
 293 }
 294
 295 /* --- Platform support for running a web server. --- */
 296
 297 enum { FD_CLIENT, FD_LISTENER, FD_CONNECTION };
 298
 299 struct fd {
 300     int fd;
 301     int type;
 302     int deleted;
 303     char *wdata;
 304     int wdatalen, wdatapos;
 305     int magic_access;
 306     struct connctx *cctx;
 307 };
 308
 309 struct fd *fds = NULL;
 310 int nfds = 0, fdsize = 0;
 311
 312 struct fd *new_fdstruct(int fd, int type)
 313 {
 314     struct fd *ret;
 315
 316     if (nfds >= fdsize) {
 317         fdsize = nfds * 3 / 2 + 32;
 318         fds = sresize(fds, fdsize, struct fd);
 319     }
 320
 321     ret = &fds[nfds++];
 322
 323     ret->fd = fd;
 324     ret->type = type;
 325     ret->wdata = NULL;
 326     ret->wdatalen = ret->wdatapos = 0;
 327     ret->cctx = NULL;
 328     ret->deleted = 0;
 329     ret->magic_access = 0;
 330
 331     return ret;
 332 }
 333
 334 int check_owning_uid(int fd, int flip)
 335 {
 336     struct sockaddr_in sock, peer;
 337     socklen_t addrlen;
 338     char linebuf[4096], matchbuf[80];
 339     FILE *fp;
 340
 341     addrlen = sizeof(sock);
 342     if (getsockname(fd, (struct sockaddr *)&sock, &addrlen)) {
 343         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 344         exit(1);
 345     }
 346     addrlen = sizeof(peer);
 347     if (getpeername(fd, (struct sockaddr *)&peer, &addrlen)) {
 348         if (errno == ENOTCONN) {
 349             peer.sin_addr.s_addr = htonl(0);
 350             peer.sin_port = htons(0);
 351         } else {
 352             fprintf(stderr, "getpeername: %s\n", strerror(errno));
 353             exit(1);
 354         }
 355     }
 356
 357     if (flip) {
 358         struct sockaddr_in tmp = sock;
 359         sock = peer;
 360         peer = tmp;
 361     }
 362
 363     sprintf(matchbuf, "%08X:%04X %08X:%04X",
 364             peer.sin_addr.s_addr, ntohs(peer.sin_port),
 365             sock.sin_addr.s_addr, ntohs(sock.sin_port));
 366     fp = fopen("/proc/net/tcp", "r");
 367     if (fp) {
 368         while (fgets(linebuf, sizeof(linebuf), fp)) {
 369             if (strlen(linebuf) >= 75 &&
 370                 !strncmp(linebuf+6, matchbuf, strlen(matchbuf))) {
 371                 fclose(fp);
 372                 return atoi(linebuf + 75);
 373             }
 374         }
 375         fclose(fp);
 376     }
 377
 378     return -1;
 379 }
 380
 381 void check_magic_access(struct fd *fd)
 382 {
 383     if (check_owning_uid(fd->fd, 0) == getuid())
 384         fd->magic_access = 1;
 385 }
 386
 387 static void base64_encode_atom(unsigned char *data, int n, char *out)
 388 {
 389     static const char base64_chars[] =
 390         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 391
 392     unsigned word;
 393
 394     word = data[0] << 16;
 395     if (n > 1)
 396         word |= data[1] << 8;
 397     if (n > 2)
 398         word |= data[2];
 399     out[0] = base64_chars[(word >> 18) & 0x3F];
 400     out[1] = base64_chars[(word >> 12) & 0x3F];
 401     if (n > 1)
 402         out[2] = base64_chars[(word >> 6) & 0x3F];
 403     else
 404         out[2] = '=';
 405     if (n > 2)
 406         out[3] = base64_chars[word & 0x3F];
 407     else
 408         out[3] = '=';
 409 }
 410
 411 void run_httpd(const void *t, int authmask, const struct httpd_config *dcfg,
 412                const struct html_config *incfg)
 413 {
 414     int fd, ret;
 415     int authtype;
 416     char *authstring = NULL;
 417     unsigned long ipaddr;
 418     struct fd *f;
 419     struct sockaddr_in addr;
 420     socklen_t addrlen;
 421     struct html_config cfg = *incfg;
 422
 423     cfg.format = "%.0lu";
 424
 425     /*
 426      * Establish the listening socket and retrieve its port
 427      * number.
 428      */
 429     fd = socket(PF_INET, SOCK_STREAM, 0);
 430     if (fd < 0) {
 431         fprintf(stderr, "socket(PF_INET): %s\n", strerror(errno));
 432         exit(1);
 433     }
 434     addr.sin_family = AF_INET;
 435     if (!dcfg->address) {
 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         addr.sin_port = htons(0);
 443
 444     } else {
 445         addr.sin_addr.s_addr = inet_addr(dcfg->address);
 446         addr.sin_port = dcfg->port ? htons(dcfg->port) : 0;
 447     }
 448     addrlen = sizeof(addr);
 449     ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 450     if (ret < 0 && errno == EADDRNOTAVAIL && !dcfg->address) {
 451         /*
 452          * Some systems don't like us binding to random weird
 453          * localhost-space addresses. Try again with the official
 454          * INADDR_LOOPBACK.
 455          */
 456         addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 457         addr.sin_port = htons(0);
 458         ret = bind(fd, (const struct sockaddr *)&addr, addrlen);
 459     }
 460     if (ret < 0) {
 461         fprintf(stderr, "bind: %s\n", strerror(errno));
 462         exit(1);
 463     }
 464     if (listen(fd, 5) < 0) {
 465         fprintf(stderr, "listen: %s\n", strerror(errno));
 466         exit(1);
 467     }
 468     addrlen = sizeof(addr);
 469     if (getsockname(fd, (struct sockaddr *)&addr, &addrlen)) {
 470         fprintf(stderr, "getsockname: %s\n", strerror(errno));
 471         exit(1);
 472     }
 473     if ((authmask & HTTPD_AUTH_MAGIC) &&
 474         (check_owning_uid(fd, 1) == getuid())) {
 475         authtype = HTTPD_AUTH_MAGIC;
 476         if (authmask != HTTPD_AUTH_MAGIC)
 477             printf("Using Linux /proc/net magic authentication\n");
 478     } else if ((authmask & HTTPD_AUTH_BASIC)) {
 479         char username[128], password[128], userpassbuf[259];
 480         const char *userpass;
 481         const char *rname;
 482         unsigned char passbuf[10];
 483         int i, j, k, fd;
 484
 485         authtype = HTTPD_AUTH_BASIC;
 486
 487         if (authmask != HTTPD_AUTH_BASIC)
 488             printf("Using HTTP Basic authentication\n");
 489
 490         if (dcfg->basicauthdata) {
 491             userpass = dcfg->basicauthdata;
 492         } else {
 493             strcpy(username, PNAME);
 494             rname = "/dev/urandom";
 495             fd = open(rname, O_RDONLY);
 496             if (fd < 0) {
 497                 int err = errno;
 498                 rname = "/dev/random";
 499                 fd = open(rname, O_RDONLY);
 500                 if (fd < 0) {
 501                     int err2 = errno;
 502                     fprintf(stderr, "/dev/urandom: open: %s\n", strerror(err));
 503                     fprintf(stderr, "/dev/random: open: %s\n", strerror(err2));
 504                     exit(1);
 505                 }
 506             }
 507             for (i = 0; i < 10 ;) {
 508                 j = read(fd, passbuf + i, 10 - i);
 509                 if (j <= 0) {
 510                     fprintf(stderr, "%s: read: %s\n", rname,
 511                             j < 0 ? strerror(errno) : "unexpected EOF");
 512                     exit(1);
 513                 }
 514                 i += j;
 515             }
 516             close(fd);
 517             for (i = 0; i < 16; i++) {
 518                 /*
 519                  * 32 characters out of the 36 alphanumerics gives
 520                  * me the latitude to discard i,l,o for being too
 521                  * numeric-looking, and w because it has two too
 522                  * many syllables and one too many presidential
 523                  * associations.
 524                  */
 525                 static const char chars[32] =
 526                     "0123456789abcdefghjkmnpqrstuvxyz";
 527                 int v = 0;
 528
 529                 k = i / 8 * 5;
 530                 for (j = 0; j < 5; j++)
 531                     v |= ((passbuf[k+j] >> (i%8)) & 1) << j;
 532
 533                 password[i] = chars[v];
 534             }
 535             password[i] = '\0';
 536
 537             sprintf(userpassbuf, "%s:%s", username, password);
 538             userpass = userpassbuf;
 539
 540             printf("Username: %s\nPassword: %s\n", username, password);
 541         }
 542
 543         k = strlen(userpass);
 544         authstring = snewn(k * 4 / 3 + 16, char);
 545         for (i = j = 0; i < k ;) {
 546             int s = k-i < 3 ? k-i : 3;
 547             base64_encode_atom((unsigned char *)(userpass+i), s, authstring+j);
 548             i += s;
 549             j += 4;
 550         }
 551         authstring[j] = '\0';
 552     } else if ((authmask & HTTPD_AUTH_NONE)) {
 553         authtype = HTTPD_AUTH_NONE;
 554         if (authmask != HTTPD_AUTH_NONE)
 555             printf("Web server is unauthenticated\n");
 556     } else {
 557         fprintf(stderr, PNAME ": authentication method not supported\n");
 558         exit(1);
 559     }
 560     if (ntohs(addr.sin_addr.s_addr) == INADDR_ANY) {
 561         printf("Server port: %d\n", ntohs(addr.sin_port));
 562     } else if (ntohs(addr.sin_port) == 80) {
 563         printf("URL: http://%s/\n", inet_ntoa(addr.sin_addr));
 564     } else {
 565         printf("URL: http://%s:%d/\n",
 566                inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
 567     }
 568
 569     /*
 570      * Now construct an fd structure to hold it.
 571      */
 572     f = new_fdstruct(fd, FD_LISTENER);
 573
 574     /*
 575      * Read from standard input, and treat EOF as a notification
 576      * to exit.
 577      */
 578     new_fdstruct(0, FD_CLIENT);
 579
 580     /*
 581      * Now we're ready to run our main loop. Keep looping round on
 582      * select.
 583      */
 584     while (1) {
 585         fd_set rfds, wfds;
 586         int i, j;
 587         SELECT_TYPE_ARG1 maxfd;
 588         int ret;
 589
 590 #define FD_SET_MAX(fd, set, max) \
 591         do { FD_SET((fd),(set)); (max) = ((max)<=(fd)?(fd)+1:(max)); } while(0)
 592
 593         /*
 594          * Loop round the fd list putting fds into our select
 595          * sets. Also in this loop we remove any that were marked
 596          * as deleted in the previous loop.
 597          */
 598         FD_ZERO(&rfds);
 599         FD_ZERO(&wfds);
 600         maxfd = 0;
 601         for (i = j = 0; j < nfds; j++) {
 602
 603             if (fds[j].deleted) {
 604                 sfree(fds[j].wdata);
 605                 free_connection(fds[j].cctx);
 606                 continue;
 607             }
 608             fds[i] = fds[j];
 609
 610             switch (fds[i].type) {
 611               case FD_CLIENT:
 612                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 613                 break;
 614               case FD_LISTENER:
 615                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 616                 break;
 617               case FD_CONNECTION:
 618                 /*
 619                  * Always read from a connection socket. Even
 620                  * after we've started writing, the peer might
 621                  * still be sending (e.g. because we shamefully
 622                  * jumped the gun before waiting for the end of
 623                  * the HTTP request) and so we should be prepared
 624                  * to read data and throw it away.
 625                  */
 626                 FD_SET_MAX(fds[i].fd, &rfds, maxfd);
 627                 /*
 628                  * Also attempt to write, if we have data to write.
 629                  */
 630                 if (fds[i].wdatapos < fds[i].wdatalen)
 631                     FD_SET_MAX(fds[i].fd, &wfds, maxfd);
 632                 break;
 633             }
 634
 635             i++;
 636         }
 637         nfds = i;
 638
 639         ret = select(maxfd, SELECT_TYPE_ARG234 &rfds,
 640                      SELECT_TYPE_ARG234 &wfds, SELECT_TYPE_ARG234 NULL,
 641                      SELECT_TYPE_ARG5 NULL);
 642         if (ret <= 0) {
 643             if (ret < 0 && (errno != EINTR)) {
 644                 fprintf(stderr, "select: %s", strerror(errno));
 645                 exit(1);
 646             }
 647             continue;
 648         }
 649
 650         for (i = 0; i < nfds; i++) {
 651             switch (fds[i].type) {
 652               case FD_CLIENT:
 653                 if (FD_ISSET(fds[i].fd, &rfds)) {
 654                     char buf[4096];
 655                     int ret = read(fds[i].fd, buf, sizeof(buf));
 656                     if (ret <= 0) {
 657                         if (ret < 0) {
 658                             fprintf(stderr, "standard input: read: %s\n",
 659                                     strerror(errno));
 660                             exit(1);
 661                         }
 662                         return;
 663                     }
 664                 }
 665                 break;
 666               case FD_LISTENER:
 667                 if (FD_ISSET(fds[i].fd, &rfds)) {
 668                     /*
 669                      * New connection has come in. Accept it.
 670                      */
 671                     struct fd *f;
 672                     struct sockaddr_in addr;
 673                     socklen_t addrlen = sizeof(addr);
 674                     int newfd = accept(fds[i].fd, (struct sockaddr *)&addr,
 675                                        &addrlen);
 676                     if (newfd < 0)
 677                         break;         /* not sure what happened there */
 678
 679                     f = new_fdstruct(newfd, FD_CONNECTION);
 680                     f->cctx = new_connection(t);
 681                     if (authtype == HTTPD_AUTH_MAGIC)
 682                         check_magic_access(f);
 683                 }
 684                 break;
 685               case FD_CONNECTION:
 686                 if (FD_ISSET(fds[i].fd, &rfds)) {
 687                     /*
 688                      * There's data to be read.
 689                      */
 690                     char readbuf[4096];
 691                     int ret;
 692
 693                     ret = read(fds[i].fd, readbuf, sizeof(readbuf));
 694                     if (ret <= 0) {
 695                         /*
 696                          * This shouldn't happen in a sensible
 697                          * HTTP connection, so we abandon the
 698                          * connection if it does.
 699                          */
 700                         close(fds[i].fd);
 701                         fds[i].deleted = 1;
 702                         break;
 703                     } else {
 704                         if (!fds[i].wdata) {
 705                             /*
 706                              * If we haven't got an HTTP response
 707                              * yet, keep processing data in the
 708                              * hope of acquiring one.
 709                              */
 710                             fds[i].wdata = got_data
 711                                 (fds[i].cctx, readbuf, ret,
 712                                  (authtype == HTTPD_AUTH_NONE ||
 713                                   fds[i].magic_access), authstring, &cfg);
 714                             if (fds[i].wdata) {
 715                                 fds[i].wdatalen = strlen(fds[i].wdata);
 716                                 fds[i].wdatapos = 0;
 717                             }
 718                         } else {
 719                             /*
 720                              * Otherwise, just drop our read data
 721                              * on the floor.
 722                              */
 723                         }
 724                     }
 725                 }
 726                 if (FD_ISSET(fds[i].fd, &wfds) &&
 727                     fds[i].wdatapos < fds[i].wdatalen) {
 728                     /*
 729                      * The socket is writable, and we have data to
 730                      * write. Write it.
 731                      */
 732                     int ret = write(fds[i].fd, fds[i].wdata + fds[i].wdatapos,
 733                                     fds[i].wdatalen - fds[i].wdatapos);
 734                     if (ret <= 0) {
 735                         /*
 736                          * Shouldn't happen; abandon the connection.
 737                          */
 738                         close(fds[i].fd);
 739                         fds[i].deleted = 1;
 740                         break;
 741                     } else {
 742                         fds[i].wdatapos += ret;
 743                         if (fds[i].wdatapos == fds[i].wdatalen) {
 744                             shutdown(fds[i].fd, SHUT_WR);
 745                         }
 746                     }
 747                 }
 748                 break;
 749             }
 750         }
 751
 752     }
 753 }