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 void write_response(const void *object, const char* buf, size_t n)
  13 {
  14     int sockfd = *(int *)object;
  15     write(sockfd, buf, n);
  16     // TODO: error checking; repeat until all written.
  17 }
  18
  19 /* Decode percent-escapes in place */
  20 static void urldecode(char *p) {
  21     char *w = p;
  22     bool escaped = false;
  23
  24     while (*p) {
  25         if (*p == '%') {
  26             escaped = true;
  27             ++p;
  28             if (sscanf(p, "%2hhx", w) == 1) {
  29                 ++w;
  30                 p+=2;
  31             }
  32         } else {
  33             if (escaped) *w = *p;
  34             ++p;
  35             ++w;
  36         }
  37     }
  38     *w = 0;
  39 }
  40
  41 #define MAX_REQUEST_SZ 4096
  42 static void handle_connection(int s, respond_cb respond, void *respond_object)
  43 {
  44     char buf[MAX_REQUEST_SZ];
  45     int r = 0;
  46     while (1) {
  47         int r2 = read(s, buf + r, MAX_REQUEST_SZ - r);
  48         if (r2 <= 0) {
  49             perror("read");
  50             return;
  51         }
  52         r += r2;
  53
  54         int sz;
  55         if (sscanf(buf, "%u:", &sz) == 1) {
  56             char buf2[16];
  57             snprintf(buf2, 16, "%u:,", sz);
  58             const int full_sz = sz + strlen(buf2);
  59
  60             if (full_sz > MAX_REQUEST_SZ) {
  61                 fprintf(stderr, "Oversized request %u", sz);
  62                 return;
  63             }
  64
  65             if (r == full_sz) {
  66                 break;
  67             }
  68         }
  69     }
  70
  71     Request_Info requestInfo = { };
  72
  73     if (buf[r-1] == ',' && buf[r-2] == ':') {
  74         /* Null request */
  75     } else if (buf[r-1] != ',' || buf[r-2] != 0) {
  76         fprintf(stderr, "Bad request.");
  77         return;
  78     } else {
  79         /* Parse headers */
  80         char *p = buf;
  81         while (*p != ':') p++;
  82         p++;
  83
  84         while (*p != ',') {
  85             const char* key = p;
  86             while (*p) ++p;
  87             ++p;
  88             if (*p == ',') {
  89                 fprintf(stderr, "Bad request.");
  90                 return;
  91             }
  92
  93             char* val = p;
  94             while (*p) ++p;
  95             ++p;
  96
  97             if (strcmp(key, "QUERY_STRING") == 0) {
  98                 urldecode(val);
  99                 requestInfo.query_string_decoded = val;
 100             }
 101             else if (strcmp(key, "SCRIPT_PATH") == 0) requestInfo.script_path = val;
 102             else if (strcmp(key, "PATH_INFO") == 0) requestInfo.path_info = val;
 103             else if (strcmp(key, "SERVER_NAME") == 0) requestInfo.server_name = val;
 104             else if (strcmp(key, "SERVER_PORT") == 0) requestInfo.server_port = val;
 105             else if (strcmp(key, "REMOTE_ADDR") == 0) requestInfo.remote_addr = val;
 106             else if (strcmp(key, "TLS_CLIENT_HASH") == 0) requestInfo.tls_client_hash = val;
 107             else if (strcmp(key, "TLS_CLIENT_ISSUER") == 0) requestInfo.tls_client_issuer = val;
 108             else if (strcmp(key, "TLS_CLIENT_ISSUER_CN") == 0) requestInfo.tls_client_issuer_cn = val;
 109             else if (strcmp(key, "TLS_CLIENT_SUBJECT") == 0) requestInfo.tls_client_subject = val;
 110             else if (strcmp(key, "TLS_CLIENT_SUBJECT_CN") == 0) requestInfo.tls_client_subject_cn = val;
 111         }
 112     }
 113
 114     respond(respond_object, &requestInfo, write_response, &s);
 115 }
 116
 117 void runSCGI(const char *socket_path, respond_cb respond, void *respond_object)
 118 {
 119     // Unix socket gubbins based on
 120     // https://beej.us/guide/bgipc/html/multi/unixsock.html
 121
 122     const int s = socket(AF_UNIX, SOCK_STREAM, 0);
 123     if (s == -1) {
 124         perror("socket");
 125         exit(1);
 126     }
 127
 128     struct sockaddr_un local;
 129     local.sun_family = AF_UNIX;
 130     strcpy(local.sun_path, socket_path);
 131     unlink(local.sun_path);
 132     if (bind(s, (struct sockaddr *)&local,
 133                 strlen(local.sun_path) + sizeof(local.sun_family)) == -1) {
 134         perror("bind");
 135         exit(1);
 136     }
 137
 138     if (listen(s, 20) == -1) {
 139         perror("listen");
 140         exit(1);
 141     }
 142
 143     while (1) {
 144         const int s2 = accept(s, NULL, NULL);
 145         if (s2 == -1) {
 146             perror("accept");
 147             exit(1);
 148         }
 149
 150         handle_connection(s2, respond, respond_object);
 151         close(s2);
 152     }
 153 }