xmit.c

#include <stdio.h>    /* xmit.c *prototype* RFC-1867 file transfer w/:        */
#include <string.h>   /* http://libccgi.sourceforge.net - cgi by Losen        */
#include <stdlib.h>   /* http://bradconte.com/sha256_c  - sha by Conte        */
#include <unistd.h>   /* Copyright 2015 Charles Fisher. Distributed           */
#include <time.h>     /* under the terms of the GNU Lesser General            */
#include <sys/stat.h> /* Public License (LGPL 2.1)                            */
#include <sys/types.h>/* $Revision: 1.3 $ Compile with:
cc -Wall -I. -O2 -o xmit.cgi xmit.c ccgi.c strlcpy.c strlcat.c sha256.c
http://www.slideshare.net/phdays/chw00t-breaking-unices-chroot-solutions
BEWARE above, and: https://matt.sh/howto-c -- also consider -static           */

#include "ccgi.h"    
#define UPL_PATH "/upload/" /* Trailing slash/filename prefix perm 400        */
#define TMP_PATH "/upload/cgi-upload" /* Must lie in same filesystem.         */
#define LOG_PATH "/upload/upload.log" /* Must exist and be writable.          */
#define uchar unsigned char /*  8-bit byte                                    */
#define uint unsigned int /*   32-bit word                                    */
typedef struct
{ uchar data[64]; uint datalen; uint bitlen[2]; uint state[8]; } SHA256_CTX;
void sha256_init(SHA256_CTX *);
void sha256_update(SHA256_CTX *, uchar *, uint len);
void sha256_final(SHA256_CTX *, uchar *hash);
size_t strlcat(char *, const char *, size_t);
size_t strlcpy(char *, const char *, size_t);

int main(int argc, char **argv)
{CGI_varlist *vl; int tlen = strlen(TMP_PATH); FILE *log; const char *name;
 char prefix[BUFSIZ] = UPL_PATH, dst[BUFSIZ], *p = getenv("SCRIPT_NAME"), *q;

 umask(umask((mode_t)0)|S_IWUSR|S_IWGRP|S_IWOTH|S_IXUSR|S_IXGRP|S_IXOTH);

 if(p != NULL) /* Use the SCRIPT_NAME as a filename local prefix.             */
 {char genbuf[BUFSIZ];

  if(strlcpy(dst, p, BUFSIZ) >= BUFSIZ) return 1;
  if((p = strrchr(dst, '/')) != NULL) p++; else p = dst;
  if(strlcpy(genbuf, p, BUFSIZ) >= BUFSIZ) return 1;
  if((p = strchr(genbuf, '.')) != NULL) *p = '\0';
  if(strlcat(prefix, genbuf, BUFSIZ) >= BUFSIZ ||
   strlcat(prefix, "-", BUFSIZ) >= BUFSIZ) return 1;
 } else if(strlcat(prefix, "IN-", BUFSIZ) >= BUFSIZ) return 1;

 printf("Content-type: text/plain\r\n\r\n");

 if((log = fopen(LOG_PATH,"a"))==NULL) { printf("log error\n"); return 1; }

 if((vl=CGI_get_all(TMP_PATH"-XXXXXX")) == 0) { printf("nodata\n"); return 1; }

 sync(); /* Rather: sync && echo 3 > /proc/sys/vm/drop_caches                 */

 for(name = CGI_first_name(vl); name != 0; name = CGI_next_name(vl))
 {FILE *fp; CGI_value *val; struct stat junk_buf; int i, j;

  if(!(val = CGI_lookup_all(vl, 0))) continue;
  for(i = 0; val[i]; i++) /* Does filename match TMP_PATH, and exist?         */
   if(!strncmp(val[i], TMP_PATH, tlen) && !stat(val[i], &junk_buf))
   {time_t epoch = time(NULL); struct tm *now = localtime(&epoch);

    j = i++; /* Now, val[j] == tmp_name, val[i] == user's sent name.          */
    strftime(dst, BUFSIZ, "%y/%m/%d %H:%M:%S", now);
    fprintf(log, "%s %s %s", dst, getenv("REMOTE_ADDR"), val[i]);

    if((p = strrchr(val[i], '/')) != NULL) p++; else p = (char *) val[i];
    if((q = strrchr(p, '\\')) != NULL) p = q + 1; /* IE sends full path.      */

    if(strlcpy(dst, prefix, BUFSIZ) >= BUFSIZ ||
     strlcat(dst, p, BUFSIZ) >= BUFSIZ) /* Skip if basename oversized.        */
    {printf("error\n"); fprintf(log, " _FLEN-RETAINED_ %s\n", val[j]);
     continue;
    }

    if(link(val[j], dst) && /* On link failure, try to keep this data.        */
     (strlcat(dst, val[j] + tlen, BUFSIZ) >= BUFSIZ ||
     link(val[j], dst))) /* mkstemp suffix appended to filename.              */
    {printf("name_error\t%s\n", val[i]);
     fprintf(log, " _LINK-RETAINED_ %s\n", val[j]); continue;
    } else fprintf(log, " _RENAMED_ %s", dst);

    if(unlink(val[j]))
    {printf("tmp_error\t%s\n", val[i]);
     fprintf(log, " _UNLINK-RETAINED_ %s\n", val[j]);
    }

    fprintf(log,"\n");

    if((fp = fopen(dst, "r")))
    {SHA256_CTX ctx; uchar buf[BUFSIZ];

     sha256_init(&ctx);
     while((j = fread(buf, 1, BUFSIZ, fp))) sha256_update(&ctx, buf, j);
     sha256_final(&ctx, buf); fclose(fp);
     for(j = 0; j < 32; j++) printf("%02x", buf[j]); printf("\t%s\n", val[i]);
 } }}
 CGI_free_varlist(vl); return 0; fclose(log);
}