gemscgi.c

   1 #include <stdbool.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <sys/socket.h>
   6 #include <sys/types.h>
   7 #include <sys/un.h>
   8 #include <unistd.h>
   9
  10 #include "gemscgi.h"
  11
  12 /* Decode percent-escapes in place */
  13 static void urldecode(char *p) {
  14     char *w = p;
  15     bool escaped = false;
  16
  17     while (*p) {
  18         if (*p == '%') {
  19             escaped = true;
  20             ++p;
  21             if (sscanf(p, "%2hhx", w) == 1) {
  22                 ++w;
  23                 p+=2;
  24             }
  25         } else {
  26             if (escaped) *w = *p;
  27             ++p;
  28             ++w;
  29         }
  30     }
  31     *w = 0;
  32 }
  33
  34 #define MAX_REQUEST_SZ 4096
  35 static void handle_connection(int s, respond_cb respond, void *respond_object)
  36 {
  37     char buf[MAX_REQUEST_SZ];
  38     int r = 0;
  39     while (1) {
  40         int r2 = read(s, buf + r, MAX_REQUEST_SZ - r);
  41         if (r2 <= 0) {
  42             perror("read");
  43             return;
  44         }
  45         r += r2;
  46
  47         int sz;
  48         if (sscanf(buf, "%u:", &sz) == 1) {
  49             char buf2[16];
  50             snprintf(buf2, 16, "%u:,", sz);
  51             const int full_sz = sz + strlen(buf2);
  52
  53             if (full_sz > MAX_REQUEST_SZ) {
  54                 fprintf(stderr, "Oversized request %u", sz);
  55                 return;
  56             }
  57
  58             if (r == full_sz) {
  59                 break;
  60             }
  61         }
  62     }
  63
  64     Request_Info requestInfo = { };
  65
  66     if (buf[r-1] == ',' && buf[r-2] == ':') {
  67         /* Null request */
  68     } else if (buf[r-1] != ',' || buf[r-2] != 0) {
  69         fprintf(stderr, "Bad request.");
  70         return;
  71     } else {
  72         /* Parse headers */
  73         char *p = buf;
  74         while (*p != ':') p++;
  75         p++;
  76
  77         while (*p != ',') {
  78             const char* key = p;
  79             while (*p) ++p;
  80             ++p;
  81             if (*p == ',') {
  82                 fprintf(stderr, "Bad request.");
  83                 return;
  84             }
  85
  86             char* val = p;
  87             while (*p) ++p;
  88             ++p;
  89
  90             if (strcmp(key, "QUERY_STRING") == 0) {
  91                 urldecode(val);
  92                 requestInfo.query_string_decoded = val;
  93             }
  94             else if (strcmp(key, "SCRIPT_PATH") == 0) requestInfo.script_path = val;
  95             else if (strcmp(key, "PATH_INFO") == 0) requestInfo.path_info = val;
  96             else if (strcmp(key, "SERVER_NAME") == 0) requestInfo.server_name = val;
  97             else if (strcmp(key, "SERVER_PORT") == 0) requestInfo.server_port = val;
  98             else if (strcmp(key, "REMOTE_ADDR") == 0) requestInfo.remote_addr = val;
  99             else if (strcmp(key, "TLS_CLIENT_HASH") == 0) requestInfo.tls_client_hash = val;
 100             else if (strcmp(key, "TLS_CLIENT_ISSUER") == 0) requestInfo.tls_client_issuer = val;
 101             else if (strcmp(key, "TLS_CLIENT_ISSUER_CN") == 0) requestInfo.tls_client_issuer_cn = val;
 102             else if (strcmp(key, "TLS_CLIENT_SUBJECT") == 0) requestInfo.tls_client_subject = val;
 103             else if (strcmp(key, "TLS_CLIENT_SUBJECT_CN") == 0) requestInfo.tls_client_subject_cn = val;
 104         }
 105     }
 106
 107     respond(respond_object, &requestInfo, s);
 108 }
 109
 110 void runSCGI(const char *socket_path, respond_cb respond, void *respond_object)
 111 {
 112     // Unix socket gubbins based on
 113     // https://beej.us/guide/bgipc/html/multi/unixsock.html
 114
 115     const int s = socket(AF_UNIX, SOCK_STREAM, 0);
 116     if (s == -1) {
 117         perror("socket");
 118         exit(1);
 119     }
 120
 121     struct sockaddr_un local;
 122     local.sun_family = AF_UNIX;
 123     strcpy(local.sun_path, socket_path);
 124     unlink(local.sun_path);
 125     if (bind(s, (struct sockaddr *)&local,
 126                 strlen(local.sun_path) + sizeof(local.sun_family)) == -1) {
 127         perror("bind");
 128         exit(1);
 129     }
 130
 131     if (listen(s, 20) == -1) {
 132         perror("listen");
 133         exit(1);
 134     }
 135
 136     while (1) {
 137         const int s2 = accept(s, NULL, NULL);
 138         if (s2 == -1) {
 139             perror("accept");
 140             exit(1);
 141         }
 142
 143         handle_connection(s2, respond, respond_object);
 144         close(s2);
 145     }
 146 }