ClamAV is an open source (GPLv2) anti-virus toolkit.
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clamav/clamsubmit/clamsubmit.c

700 lines
23 KiB

/*
* ClamAV Malware and False Positive Reporting Tool
*
* Copyright (C) 2014-2025 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
*
* Authors: Shawn Webb, Steve Morgan
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "clamav-config.h"
#endif
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#ifdef _WIN32
#include <Windows.h>
#include <wincrypt.h>
#endif
#include <curl/curl.h>
#include <json.h>
#include "target.h"
// libclamav
#include "clamav.h"
#include "others.h"
// common
#include "misc.h"
#include "getopt.h"
#include "cert_util.h"
#include "output.h"
#define OPTS "e:p:n:N:V:H:h?v?d"
char *read_stream(void);
void usage(char *name);
void version(void);
typedef struct _header_data {
int len;
char *session;
} header_data;
typedef struct _write_data {
int len;
char *str;
} write_data;
bool g_debug = false;
void usage(char *name)
{
printf("\n");
printf(" Clam AntiVirus: Malware and False Positive Reporting Tool %s\n", get_version());
printf(" By The ClamAV Team: https://www.clamav.net/about.html#credits\n");
printf(" (C) 2025 Cisco Systems, Inc.\n");
printf("\n");
printf(" %s -hHinpVvd?\n", name);
printf("\n");
printf(" -h or -? Show this help\n");
printf(" -v Show version\n");
printf(" -e [EMAIL] Your email address (required)\n");
printf(" -n [FILE/-] Submit a false negative (FN)\n");
printf(" -N [NAME] Your name contained in quotation marks (required)\n");
printf(" -p [FILE/-] Submit a false positive (FP)\n");
printf(" -V [VIRUS] Detected virus name (required with -p)\n");
printf(" -d Enable debug output\n");
printf("\n");
printf("You must specify -n or -p. Both are mutually exclusive. Pass in - as the filename for stdin.\n\n");
exit(0);
}
void version(void)
{
print_version(NULL);
exit(0);
}
size_t header_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
{
int len = size * nmemb;
char *sp, *ep, *mem;
header_data *hd = (header_data *)userdata;
const char *set_cookie = "Set-Cookie:";
int clen = strlen(set_cookie);
if (len > clen) {
if (strncmp(ptr, set_cookie, clen))
return len;
sp = ptr + clen + 1;
ep = strchr(sp, ';');
if (ep == NULL) {
logg(LOGG_ERROR, "header_cb(): malformed cookie\n");
return 0;
}
mem = malloc(ep - sp + 1);
if (mem == NULL) {
logg(LOGG_ERROR, "header_cb(): malloc failed\n");
return 0;
}
memcpy(mem, sp, ep - sp);
mem[ep - sp] = '\0';
if (!strncmp(mem, "_clamav-net_session", strlen("_clamav-net_session")))
hd->session = mem;
else {
logg(LOGG_ERROR, "header_cb(): unrecognized cookie\n");
free(mem);
}
}
return len;
}
size_t write_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
{
int len = size * nmemb;
char *str;
write_data *wd = (write_data *)userdata;
if (len) {
str = realloc(wd->str, wd->len + len + 1);
if (str == NULL) {
logg(LOGG_ERROR, "write_cb() realloc failure\n");
return 0;
}
memcpy(str + wd->len, ptr, len);
str[wd->len + len] = '\0';
wd->str = str;
wd->len += len;
}
return len;
}
/**
* @brief Parse a value from a JSON object, given a key.
*
* @param ps_json_obj The JSON object
* @param key The Key
* @return const char* The Value on Success, NULL on Failure.
*/
const char *presigned_get_string(json_object *ps_json_obj, char *key)
{
json_object *json_obj = NULL;
const char *json_str = NULL;
if (json_object_object_get_ex(ps_json_obj, key, &json_obj)) {
json_str = json_object_get_string(json_obj);
if (json_str == NULL) {
logg(LOGG_ERROR, "Error: json_object_get_string() for %s.\n", key);
}
} else {
logg(LOGG_ERROR, "Error: json_object_object_get_ex() for %s.\n", key);
}
return json_str;
}
int main(int argc, char *argv[])
{
int status = 1;
char userAgent[128];
CURL *clam_curl = NULL, *aws_curl = NULL;
CURLcode res;
int ch;
struct curl_httppost *post = NULL, *last = NULL;
struct curl_slist *slist = NULL;
char *name = NULL, *email = NULL, *filename = NULL;
int setURL = 0, fromStream = 0;
const char *json_str;
write_data wd = {0, NULL};
header_data hd_malware = {0, NULL};
header_data hd_presigned = {0, NULL};
json_object *ps_json_obj = NULL;
bool malware = false;
int len = 0;
char *submissionID = NULL;
char *fpvname = NULL;
char *sp, *ep;
char *authenticity_token_header = NULL;
char *authenticity_token = NULL;
char *session_cookie = NULL;
char *url_for_auth_token;
char *url_for_presigned_cookie;
curl_global_init(CURL_GLOBAL_ALL);
clam_curl = curl_easy_init();
if (clam_curl == NULL) {
logg(LOGG_ERROR, "ERROR: Could not initialize libcurl.\n");
goto done;
}
memset(userAgent, 0, sizeof(userAgent));
snprintf(userAgent, sizeof(userAgent),
PACKAGE "/%s (OS: " TARGET_OS_TYPE ", ARCH: " TARGET_ARCH_TYPE ", CPU: " TARGET_CPU_TYPE ")",
get_version());
userAgent[sizeof(userAgent) - 1] = 0;
if (CURLE_OK != curl_easy_setopt(clam_curl, CURLOPT_USERAGENT, userAgent)) {
logg(LOGG_ERROR, "!create_curl_handle: Failed to set CURLOPT_USERAGENT (%s)!\n", userAgent);
}
while ((ch = my_getopt(argc, argv, OPTS)) > 0) {
switch (ch) {
case 'v':
version();
break;
case 'e':
email = optarg;
break;
case 'N':
name = optarg;
break;
case 'p':
if (setURL)
usage(argv[0]);
filename = optarg;
break;
case 'n':
if (setURL)
usage(argv[0]);
malware = true;
filename = optarg;
break;
case 'V':
fpvname = optarg;
break;
case 'd':
g_debug = true;
break;
case 'h':
case '?':
default:
usage(argv[0]);
}
}
if (!(name) || !(email) || !(filename))
usage(argv[0]);
if (malware == false && fpvname == NULL) {
logg(LOGG_ERROR, "Detected virus name(-V) required for false positive submissions.\n");
usage(argv[0]);
}
if (strlen(filename) == 1 && filename[0] == '-') {
filename = read_stream();
if (!(filename)) {
logg(LOGG_ERROR, "ERROR: Unable to read stream\n");
goto done;
}
fromStream = 1;
}
if (g_debug) {
/* ask libcurl to show us the verbose output */
if (CURLE_OK != curl_easy_setopt(clam_curl, CURLOPT_VERBOSE, 1L)) {
logg(LOGG_ERROR, "!ERROR: Failed to set CURLOPT_VERBOSE!\n");
}
if (CURLE_OK != curl_easy_setopt(clam_curl, CURLOPT_STDERR, stdout)) {
logg(LOGG_ERROR, "!ERROR: Failed to direct curl debug output to stdout!\n");
}
}
if (CURLE_OK != curl_easy_setopt(clam_curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1)) {
logg(LOGG_ERROR, "ERROR: Failed to set HTTP version to 1.1 (to prevent 2.0 responses which we don't yet parse properly)!\n");
}
#if defined(C_DARWIN) || defined(_WIN32)
if (CURLE_OK != curl_easy_setopt(clam_curl, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function)) {
logg(LOGG_ERROR, "ERROR: Failed to set SSL CTX function!\n");
}
#else
/* Use an alternate CA bundle, if specified by the CURL_CA_BUNDLE environment variable. */
set_tls_ca_bundle(clam_curl);
#endif
/*
* GET authenticity token
*/
if (malware == true) {
url_for_auth_token = "https://www.clamav.net/reports/malware";
} else {
url_for_auth_token = "https://www.clamav.net/reports/fp";
}
curl_easy_setopt(clam_curl, CURLOPT_URL, url_for_auth_token);
curl_easy_setopt(clam_curl, CURLOPT_HTTPGET, 1);
curl_easy_setopt(clam_curl, CURLOPT_WRITEDATA, &wd);
curl_easy_setopt(clam_curl, CURLOPT_WRITEFUNCTION, write_cb);
curl_easy_setopt(clam_curl, CURLOPT_HEADERDATA, &hd_malware);
curl_easy_setopt(clam_curl, CURLOPT_HEADERFUNCTION, header_cb);
res = curl_easy_perform(clam_curl);
if (res != CURLE_OK) {
logg(LOGG_ERROR, "Error in GET %s: %s\n", url_for_auth_token, curl_easy_strerror(res));
goto done;
}
if (wd.str != NULL) {
sp = strstr(wd.str, "name=\"authenticity_token\"");
if (sp == NULL) {
logg(LOGG_ERROR, "Authenticity token element not found.\n");
goto done;
}
sp = strstr(sp, "value=");
if (sp == NULL) {
logg(LOGG_ERROR, "Authenticity token value not found.\n");
goto done;
}
sp += 7;
ep = strchr(sp, '"');
if (ep == NULL) {
logg(LOGG_ERROR, "Authenticity token malformed.\n");
goto done;
}
authenticity_token = malloc(ep - sp + 1);
if (authenticity_token == NULL) {
logg(LOGG_ERROR, "no memory for authenticity token.\n");
goto done;
}
memcpy(authenticity_token, sp, ep - sp);
authenticity_token[ep - sp] = '\0';
free(wd.str);
wd.str = NULL;
}
wd.len = 0;
/* record the session cookie for later use, if exists */
if (NULL == hd_malware.session) {
logg(LOGG_ERROR, "clamav.net/presigned response missing session ID cookie.\nWill try without the cookie.\n");
// goto done; // Note: unclear if the session cookie is required. Can't hurt to try w/out it?
} else {
len = strlen(hd_malware.session) + 3;
session_cookie = malloc(len);
if (session_cookie == NULL) {
logg(LOGG_ERROR, "No memory for GET presigned cookies\n");
goto done;
}
if (snprintf(session_cookie, len, "%s;", hd_malware.session) > len) {
logg(LOGG_ERROR, "snprintf() failed formatting GET presigned cookies\n");
goto done;
}
}
/*
* GET presigned cookie
*/
if (malware == true) {
url_for_presigned_cookie = "https://www.clamav.net/presigned?type=malware";
} else {
url_for_presigned_cookie = "https://www.clamav.net/presigned?type=fp";
}
curl_easy_setopt(clam_curl, CURLOPT_URL, url_for_presigned_cookie);
curl_easy_setopt(clam_curl, CURLOPT_HTTPGET, 1);
if (NULL != session_cookie) {
curl_easy_setopt(clam_curl, CURLOPT_COOKIE, session_cookie);
}
/* Include an X-CSRF-Token header using the authenticity token retrieved with the presigned GET request */
len = strlen(authenticity_token) + strlen("X-CSRF-Token: ") + 1;
authenticity_token_header = malloc(len);
if (authenticity_token_header == NULL) {
logg(LOGG_ERROR, "No memory for GET presigned X-CSRF-Token\n");
goto done;
}
if (snprintf(authenticity_token_header, len, "X-CSRF-Token: %s", authenticity_token) > len) {
logg(LOGG_ERROR, "snprintf() failed for GET presigned X-CSRF-Token\n");
goto done;
}
slist = curl_slist_append(slist, authenticity_token_header);
free(authenticity_token_header);
authenticity_token_header = NULL;
curl_easy_setopt(clam_curl, CURLOPT_HTTPHEADER, slist);
curl_easy_setopt(clam_curl, CURLOPT_HEADERDATA, &hd_presigned);
curl_easy_setopt(clam_curl, CURLOPT_HEADERFUNCTION, header_cb);
curl_easy_setopt(clam_curl, CURLOPT_REFERER, url_for_auth_token);
res = curl_easy_perform(clam_curl);
if (res != CURLE_OK) {
logg(LOGG_ERROR, "Error in GET reports: %s\n", curl_easy_strerror(res));
goto done;
}
curl_slist_free_all(slist);
slist = NULL;
/*
* POST the report to AWS
*/
ps_json_obj = json_tokener_parse(wd.str);
if (ps_json_obj == NULL) {
logg(LOGG_ERROR, "Error in json_tokener_parse of %.*s\n", wd.len, wd.str);
goto done;
}
json_str = presigned_get_string(ps_json_obj, "key");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing key from json object\n");
goto done;
}
sp = strchr(json_str, '/');
if (sp == NULL) {
logg(LOGG_ERROR, "Error: malformed 'key' string in GET presigned response (missing '/'.\n");
goto done;
}
sp++;
ep = strchr(sp, '-');
if (ep == NULL) {
logg(LOGG_ERROR, "Error: malformed 'key' string in GET presigned response (missing '-'.\n");
goto done;
}
submissionID = malloc(ep - sp + 1);
if (submissionID == NULL) {
logg(LOGG_ERROR, "Error: malloc submissionID.\n");
goto done;
}
memcpy(submissionID, sp, ep - sp);
submissionID[ep - sp] = '\0';
aws_curl = curl_easy_init();
if (!(aws_curl)) {
logg(LOGG_ERROR, "ERROR: Could not initialize libcurl POST presigned\n");
goto done;
}
if (CURLE_OK != curl_easy_setopt(aws_curl, CURLOPT_USERAGENT, userAgent)) {
logg(LOGG_ERROR, "!create_curl_handle: Failed to set CURLOPT_USERAGENT (%s)!\n", userAgent);
}
if (g_debug) {
/* ask libcurl to show us the verbose output */
if (CURLE_OK != curl_easy_setopt(aws_curl, CURLOPT_VERBOSE, 1L)) {
logg(LOGG_ERROR, "!ERROR: Failed to set CURLOPT_VERBOSE!\n");
}
if (CURLE_OK != curl_easy_setopt(aws_curl, CURLOPT_STDERR, stdout)) {
logg(LOGG_ERROR, "!ERROR: Failed to direct curl debug output to stdout!\n");
}
}
if (CURLE_OK != curl_easy_setopt(aws_curl, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1)) {
logg(LOGG_ERROR, "ERROR: Failed to set HTTP version to 1.1 (to prevent 2.0 responses which we don't yet parse properly)!\n");
}
#if defined(C_DARWIN) || defined(_WIN32)
if (CURLE_OK != curl_easy_setopt(aws_curl, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function)) {
logg(LOGG_ERROR, "ERROR: Failed to set SSL CTX function!\n");
}
#else
/* Use an alternate CA bundle, if specified by the CURL_CA_BUNDLE environment variable. */
set_tls_ca_bundle(aws_curl);
#endif
curl_formadd(&post, &last, CURLFORM_COPYNAME, "key", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "acl");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing acl from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "acl", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "policy");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing policy from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "policy", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "x-amz-meta-original-filename");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing x-amz-meta-original-filename from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "x-amz-meta-original-filename", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "x-amz-credential");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing x-amz-credential from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "x-amz-credential", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "x-amz-algorithm");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing x-amz-algorithm from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "x-amz-algorithm", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "x-amz-date");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing x-amz-date from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "x-amz-date", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
json_str = presigned_get_string(ps_json_obj, "x-amz-signature");
if (json_str == NULL) {
logg(LOGG_ERROR, "Error in presigned_get_string parsing x-amz-signature from json object\n");
goto done;
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "x-amz-signature", CURLFORM_COPYCONTENTS, json_str, CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "file", CURLFORM_FILE, filename, CURLFORM_END);
slist = curl_slist_append(slist, "Expect:");
curl_easy_setopt(aws_curl, CURLOPT_HTTPHEADER, slist);
curl_easy_setopt(aws_curl, CURLOPT_URL, "https://clamav-site.s3.amazonaws.com/");
curl_easy_setopt(aws_curl, CURLOPT_HTTPPOST, post);
res = curl_easy_perform(aws_curl);
if (res != CURLE_OK) {
logg(LOGG_ERROR, "Error in POST AWS: %s\n", curl_easy_strerror(res));
goto done;
}
curl_slist_free_all(slist);
slist = NULL;
curl_formfree(post);
post = NULL;
last = NULL;
curl_easy_cleanup(aws_curl);
aws_curl = NULL;
json_object_put(ps_json_obj);
if (wd.str != NULL) {
free(wd.str);
wd.str = NULL;
}
wd.len = 0;
/*** The POST submit to clamav.net ***/
slist = curl_slist_append(slist, "Expect:");
if (NULL != session_cookie) {
curl_easy_setopt(clam_curl, CURLOPT_COOKIE, session_cookie);
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "utf8", CURLFORM_COPYCONTENTS, "\x27\x13", CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "authenticity_token", CURLFORM_COPYCONTENTS, authenticity_token, CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "submissionID", CURLFORM_COPYCONTENTS, submissionID, CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "type", CURLFORM_COPYCONTENTS, malware ? "malware" : "fp", CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "sendername", CURLFORM_COPYCONTENTS, name, CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "email", CURLFORM_COPYCONTENTS, email, CURLFORM_END);
if (malware == true) {
curl_formadd(&post, &last, CURLFORM_COPYNAME, "shareSample", CURLFORM_COPYCONTENTS, "on", CURLFORM_END);
} else {
curl_formadd(&post, &last, CURLFORM_COPYNAME, "virusname", CURLFORM_COPYCONTENTS, fpvname, CURLFORM_END);
}
curl_formadd(&post, &last, CURLFORM_COPYNAME, "description", CURLFORM_COPYCONTENTS, "clamsubmit", CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "notify", CURLFORM_COPYCONTENTS, "on", CURLFORM_END);
curl_formadd(&post, &last, CURLFORM_COPYNAME, "privacy", CURLFORM_COPYCONTENTS, "on", CURLFORM_END);
curl_easy_setopt(clam_curl, CURLOPT_HTTPHEADER, slist);
curl_easy_setopt(clam_curl, CURLOPT_URL, "https://www.clamav.net/reports/submit");
curl_easy_setopt(clam_curl, CURLOPT_HTTPPOST, post);
curl_easy_setopt(clam_curl, CURLOPT_HEADERFUNCTION, NULL);
res = curl_easy_perform(clam_curl);
if (res != CURLE_OK) {
logg(LOGG_ERROR, "Error in POST submit: %s\n", curl_easy_strerror(res));
goto done;
} else {
long response_code;
curl_easy_getinfo(clam_curl, CURLINFO_RESPONSE_CODE, &response_code);
if (response_code / 100 == 3) {
curl_easy_getinfo(clam_curl, CURLINFO_REDIRECT_URL, &url_for_auth_token);
if (url_for_auth_token == NULL) {
logg(LOGG_ERROR, "POST submit Location URL is NULL.\n");
goto done;
}
sp = strstr(url_for_auth_token, "/reports/");
if (sp == NULL) {
logg(LOGG_ERROR, "POST submit Location URL is malformed.\n");
} else if (!strcmp(sp, "/reports/success")) {
logg(LOGG_INFO, "Submission success!\n");
status = 0;
} else if (!strcmp(sp, "/reports/failure")) {
logg(LOGG_INFO, "Submission failed\n");
} else {
logg(LOGG_INFO, "Unknown submission status %s\n", sp);
}
} else {
logg(LOGG_ERROR, "Unexpected POST submit response code: %li\n", response_code);
}
}
done:
/*
* Cleanup
*/
if (authenticity_token_header != NULL) {
free(authenticity_token_header);
}
if (session_cookie != NULL) {
free(session_cookie);
}
if (slist != NULL) {
curl_slist_free_all(slist);
}
if (post != NULL) {
curl_formfree(post);
}
if (clam_curl != NULL) {
curl_easy_cleanup(clam_curl);
}
if (aws_curl != NULL) {
curl_easy_cleanup(aws_curl);
}
curl_global_cleanup();
if (wd.str != NULL) {
free(wd.str);
wd.str = NULL;
wd.len = 0;
}
if (hd_malware.session != NULL) {
free(hd_malware.session);
}
if (hd_presigned.session != NULL) {
free(hd_presigned.session);
}
if (submissionID != NULL) {
free(submissionID);
}
if (authenticity_token != NULL) {
free(authenticity_token);
}
if ((fromStream != 0) && (filename != NULL)) {
remove(filename);
free(filename);
}
return status;
}
char *read_stream(void)
{
char *filename;
char buf[512];
size_t nread, nwritten;
FILE *fp;
filename = cli_gentemp(NULL);
if (!(filename)) {
return NULL;
}
fp = fopen(filename, "w");
if (!(fp)) {
free(filename);
return NULL;
}
while (!feof(stdin)) {
nwritten = 0;
nread = fread(buf, 1, sizeof(buf), stdin);
if (nread == 0) {
fclose(fp);
remove(filename);
free(filename);
return NULL;
}
while (nwritten < nread) {
size_t i;
i = fwrite(buf, 1, nread, fp);
if (i == 0) {
fclose(fp);
remove(filename);
free(filename);
return NULL;
}
nwritten += i;
}
}
fclose(fp);
return filename;
}