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ngx_http_secure_download_module.c
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ngx_http_secure_download_module.c
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#include <ngx_core.h>
#include <ngx_string.h>
#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <mhash.h>
#include <openssl/md5.h>
#include <ctype.h>
#define FOLDER_MODE 0
#define FILE_MODE 1
typedef struct {
const char *timestamp;
const char *md5;
const char *path;
int path_len;
int path_to_hash_len;
} ngx_http_secure_download_split_uri_t;
static ngx_int_t ngx_http_secure_download_split_uri (ngx_http_request_t*, ngx_http_secure_download_split_uri_t*);
static ngx_int_t ngx_http_secure_download_check_hash(ngx_http_request_t*, ngx_http_secure_download_split_uri_t*, ngx_str_t*);
static void * ngx_http_secure_download_create_loc_conf(ngx_conf_t*);
static char * ngx_http_secure_download_merge_loc_conf (ngx_conf_t*, void*, void*);
static ngx_int_t ngx_http_secure_download_add_variables(ngx_conf_t *cf);
static ngx_int_t ngx_http_secure_download_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data);
static char * ngx_conf_set_path_mode(ngx_conf_t*, ngx_command_t*, void*);
static char *ngx_http_secure_download_secret(ngx_conf_t *cf, void *post, void *data);
static ngx_conf_post_handler_pt ngx_http_secure_download_secret_p =
ngx_http_secure_download_secret;
typedef struct {
ngx_flag_t enable;
ngx_flag_t path_mode;
ngx_str_t secret;
ngx_array_t *secret_lengths;
ngx_array_t *secret_values;
} ngx_http_secure_download_loc_conf_t;
static ngx_command_t ngx_http_secure_download_commands[] = {
{
ngx_string("secure_download"),
NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
ngx_conf_set_flag_slot,
NGX_HTTP_LOC_CONF_OFFSET,
offsetof(ngx_http_secure_download_loc_conf_t, enable),
NULL
},
{
ngx_string("secure_download_path_mode"),
NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
ngx_conf_set_path_mode,
NGX_HTTP_LOC_CONF_OFFSET,
offsetof(ngx_http_secure_download_loc_conf_t, path_mode),
NULL
},
{
ngx_string("secure_download_secret"),
NGX_HTTP_LOC_CONF|NGX_CONF_TAKE1,
ngx_conf_set_str_slot,
NGX_HTTP_LOC_CONF_OFFSET,
offsetof(ngx_http_secure_download_loc_conf_t, secret),
&ngx_http_secure_download_secret_p
}
};
static ngx_http_module_t ngx_http_secure_download_module_ctx = {
ngx_http_secure_download_add_variables,
NULL,
NULL,
NULL,
NULL,
NULL,
ngx_http_secure_download_create_loc_conf,
ngx_http_secure_download_merge_loc_conf
};
ngx_module_t ngx_http_secure_download_module = {
NGX_MODULE_V1,
&ngx_http_secure_download_module_ctx,
ngx_http_secure_download_commands,
NGX_HTTP_MODULE,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NULL,
NGX_MODULE_V1_PADDING
};
static ngx_str_t ngx_http_secure_download = ngx_string("secure_download");
static char * ngx_conf_set_path_mode(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
ngx_str_t *d = cf->args->elts;
ngx_http_secure_download_loc_conf_t *sdlc = conf;
if ((d[1].len == 6) && (strncmp((char*)d[1].data, "folder", 6) == 0))
{
sdlc->path_mode = FOLDER_MODE;
}
else if((d[1].len == 4) && (strncmp((char*)d[1].data, "file", 4) == 0))
{
sdlc->path_mode = FILE_MODE;
}
else
{
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "secure_download_path_mode should be folder or file", 0);
return NGX_CONF_ERROR;
}
return NGX_CONF_OK;
}
static void * ngx_http_secure_download_create_loc_conf(ngx_conf_t *cf)
{
ngx_http_secure_download_loc_conf_t *conf;
conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_secure_download_loc_conf_t));
if (conf == NULL) {
return NGX_CONF_ERROR;
}
conf->enable = NGX_CONF_UNSET;
conf->path_mode = NGX_CONF_UNSET;
conf->secret.data = NULL;
conf->secret.len = 0;
return conf;
}
static char * ngx_http_secure_download_merge_loc_conf (ngx_conf_t *cf, void *parent, void *child)
{
ngx_http_secure_download_loc_conf_t *prev = parent;
ngx_http_secure_download_loc_conf_t *conf = child;
ngx_conf_merge_value(conf->enable, prev->enable, 0);
ngx_conf_merge_value(conf->path_mode, prev->path_mode, FOLDER_MODE);
ngx_conf_merge_str_value(conf->secret, prev->secret, "");
if (conf->enable == 1) {
if (conf->secret.len == 0) {
ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
"no secure_download_secret specified");
return NGX_CONF_ERROR;
}
}
return NGX_CONF_OK;
}
static ngx_int_t ngx_http_secure_download_variable(ngx_http_request_t *r, ngx_http_variable_value_t *v, uintptr_t data) {
unsigned timestamp;
unsigned remaining_time = 0;
ngx_http_secure_download_loc_conf_t *sdc;
ngx_http_secure_download_split_uri_t sdsu;
ngx_str_t secret;
int value = 0;
sdc = ngx_http_get_module_loc_conf(r, ngx_http_secure_download_module);
if (sdc->enable != 1)
{
ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
"securedownload: module not enabled");
value = -3;
goto finish;
}
if (!sdc->secret_lengths || !sdc->secret_values) {
ngx_log_error(NGX_LOG_ERR, r->connection->log, 0,
"securedownload: module enabled, but secret key not configured!");
value = -3;
goto finish;
}
if (ngx_http_secure_download_split_uri(r, &sdsu) == NGX_ERROR)
{
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: received an error from ngx_http_secure_download_split_uri", 0);
value = -3;
goto finish;
}
if (sscanf(sdsu.timestamp, "%08X", ×tamp) != 1)
{
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: error in timestamp hex-dec conversion", 0);
value = -3;
goto finish;
}
remaining_time = timestamp - (unsigned) time(NULL);
if ((int)remaining_time <= 0)
{
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: expired timestamp", 0);
value = -1;
goto finish;
}
if (ngx_http_script_run(r, &secret, sdc->secret_lengths->elts, 0, sdc->secret_values->elts) == NULL) {
ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
"securedownload: evaluation failed");
value = -3;
goto finish;
}
ngx_log_error(NGX_LOG_INFO, r->connection->log, 0,
"securedownload: evaluated value of secret: \"%V\"", &secret);
if (ngx_http_secure_download_check_hash(r, &sdsu, &secret) != NGX_OK)
{
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: bad hash", 0);
value = -2;
goto finish;
}
finish:
v->not_found = 0;
v->valid = 1;
v->no_cacheable = 0;
v->not_found = 0;
if (value == 0)
{
v->data = ngx_pcalloc(r->pool, sizeof(char) * 12);
if (v->data == NULL) {
return NGX_ERROR;
}
v->len = (int) sprintf((char *)v->data, "%i", remaining_time);
//printf("valid, %i\n", remaining_time);
} else {
v->data = ngx_pcalloc(r->pool, sizeof(char) * 3);
if (v->data == NULL) {
return NGX_ERROR;
}
v->len = (int) sprintf((char*)v->data, "%i", value);
//printf("problem %i\n", value);
}
return NGX_OK;
}
//////////////////////
static char *
ngx_http_secure_download_compile_secret(ngx_conf_t *cf, ngx_http_secure_download_loc_conf_t *sdc)
{
ngx_http_script_compile_t sc;
ngx_memzero(&sc, sizeof(ngx_http_script_compile_t));
sc.cf = cf;
sc.source = &sdc->secret;
sc.lengths = &sdc->secret_lengths;
sc.values = &sdc->secret_values;
sc.variables = ngx_http_script_variables_count(&sdc->secret);
sc.complete_lengths = 1;
sc.complete_values = 1;
if (ngx_http_script_compile(&sc) != NGX_OK) {
return NGX_CONF_ERROR;
}
return NGX_CONF_OK;
}
static char *
ngx_http_secure_download_secret(ngx_conf_t *cf, void *post, void *data)
{
ngx_http_secure_download_loc_conf_t *sdc =
ngx_http_conf_get_module_loc_conf(cf, ngx_http_secure_download_module);
return ngx_http_secure_download_compile_secret(cf, sdc);
}
////////////////////////
static ngx_int_t ngx_http_secure_download_check_hash(ngx_http_request_t *r, ngx_http_secure_download_split_uri_t *sdsu, ngx_str_t *secret)
{
int i;
unsigned char generated_hash[16];
char hash[33];
MHASH td;
char *hash_data, *str;
int data_len;
static const char xtoc[] = "0123456789abcdef";
/* rel_path_to_hash/secret/timestamp\0 */
data_len = sdsu->path_to_hash_len + secret->len + 10;
hash_data = malloc(data_len + 1);
if (hash_data == NULL)
{
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: error in allocating memory for string_to_hash.data", 0);
return NGX_ERROR;
}
str = hash_data;
memcpy(str, sdsu->path, sdsu->path_to_hash_len);
str += sdsu->path_to_hash_len;
*str++ = '/';
memcpy(str, secret->data, secret->len);
str += secret->len;
*str++ = '/';
memcpy(str, sdsu->timestamp, 8);
str[8] = 0;
td = mhash_init(MHASH_MD5);
if (td == MHASH_FAILED)
{
free(hash_data);
return NGX_ERROR;
}
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: hashing string \"%s\" with len %i", hash_data, data_len);
mhash(td, hash_data, data_len);
mhash_deinit(td, generated_hash);
free(hash_data);
for (i = 0; i < 16; ++i) {
hash[2 * i + 0] = xtoc[generated_hash[i] >> 4];
hash[2 * i + 1] = xtoc[generated_hash[i] & 0xf];
}
hash[32] = 0; //because %.32 doesn't work
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: computed hash: %32s", hash);
// ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "hash from uri: %.32s", sdsu->md5);
if(memcmp(hash, sdsu->md5, 32) != 0) {
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: hash mismatch", 0);
return NGX_ERROR;
}
return NGX_OK;
}
static ngx_int_t ngx_http_secure_download_split_uri(ngx_http_request_t *r, ngx_http_secure_download_split_uri_t *sdsu)
{
int md5_len = 0;
int tstamp_len = 0;
int len = r->uri.len;
const char *uri = (char*)r->uri.data;
ngx_http_secure_download_loc_conf_t *sdc = ngx_http_get_module_loc_conf(r, ngx_http_secure_download_module);
while(len && uri[--len] != '/')
++tstamp_len;
if(tstamp_len != 8) {
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: timestamp size mismatch: %d", tstamp_len);
return NGX_ERROR;
}
sdsu->timestamp = uri + len + 1;
while(len && uri[--len] != '/')
++md5_len;
if(md5_len != 32) {
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: md5 size mismatch: %d", md5_len);
return NGX_ERROR;
}
sdsu->md5 = uri + len + 1;
if(len == 0) {
ngx_log_debug(NGX_LOG_DEBUG_HTTP, r->connection->log, 0, "securedownload: bad path", 0);
return NGX_ERROR;
}
sdsu->path = uri;
sdsu->path_len = len;
if(sdc->path_mode == FOLDER_MODE) {
while(len && uri[--len] != '/');
}
sdsu->path_to_hash_len = len;
return NGX_OK;
}
static ngx_int_t
ngx_http_secure_download_add_variables(ngx_conf_t *cf)
{
ngx_http_variable_t *var;
var = ngx_http_add_variable(cf, &ngx_http_secure_download, NGX_HTTP_VAR_NOHASH);
if (var == NULL) {
return NGX_ERROR;
}
var->get_handler = ngx_http_secure_download_variable;
return NGX_OK;
}