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rcosnitarcosnita
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An IV should be generated for each encryption
We now have the ability to decide if the IV is communicated to the client in a non forgeable manner or we only keep it on the server side. Closes #2
1 parent 99662f8 commit 5150790

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3 files changed

+210
-13
lines changed

3 files changed

+210
-13
lines changed

‎src/ngx_http_encrypted_session_cipher.c‎

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@
1212

1313
#include "ngx_http_encrypted_session_cipher.h"
1414
#include <openssl/evp.h>
15+
#include <openssl/hmac.h>
1516
#include <openssl/md5.h>
1617
#include <stdint.h>
1718

@@ -291,3 +292,21 @@ ngx_http_encrypted_session_htonll(uint64_t n)
291292
+ htonl((unsigned long) (n >> 32));
292293
#endif
293294
}
295+
296+
unsigned char*
297+
ngx_http_encrypted_session_hmac(ngx_pool_t *pool,
298+
const u_char *key, size_t key_len,
299+
const u_char *data, size_t data_len, u_char **dst, size_t *dst_len)
300+
{
301+
u_char *result = NULL;
302+
u_char *input = ngx_pcalloc(pool, data_len + 1);
303+
memcpy(input, data, data_len);
304+
305+
unsigned int len;
306+
result = HMAC(EVP_sha256(), key, key_len, input, data_len, result, &len);
307+
*dst_len = len;
308+
*dst = (u_char*)ngx_pcalloc(pool, len + 1);
309+
memcpy(*dst, result, len);
310+
311+
return *dst;
312+
}

‎src/ngx_http_encrypted_session_cipher.h‎

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -5,6 +5,7 @@
55
#include <ngx_core.h>
66
#include <ngx_http.h>
77
#include <openssl/evp.h>
8+
#include <openssl/hmac.h>
89

910

1011
typedef int (*cipher_ctx_reset_handle) (EVP_CIPHER_CTX *ctx);
@@ -34,6 +35,10 @@ ngx_int_t ngx_http_encrypted_session_aes_mac_decrypt(
3435
size_t key_len, const u_char *in, size_t in_len, u_char **dst,
3536
size_t *dst_len);
3637

38+
unsigned char* ngx_http_encrypted_session_hmac(
39+
ngx_pool_t *pool,
40+
const u_char *key, size_t key_len,
41+
const u_char *data, size_t data_len, u_char **dst, size_t *dst_len);
3742

3843
#endif /* NGX_HTTP_ENCRYPTED_SESSION_CIPHER_H */
3944

‎src/ngx_http_encrypted_session_module.c‎

Lines changed: 186 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,7 @@
1010
#include "ddebug.h"
1111

1212
#include <ndk.h>
13+
#include <string.h>
1314
#include "ngx_http_encrypted_session_cipher.h"
1415

1516
#define ngx_http_encrypted_session_default_iv (u_char *) "deadbeefdeadbeef"
@@ -19,11 +20,16 @@
1920

2021
typedef struct {
2122
u_char *key;
23+
size_t key_len;
2224
u_char *iv;
25+
size_t iv_len;
2326
time_t expires;
24-
27+
ngx_flag_t iv_in_content;
2528
} ngx_http_encrypted_session_conf_t;
2629

30+
const char *PARTS_DELIMITER = ":";
31+
const size_t PARTS_DELIMITER_LEN = 1;
32+
const size_t NUM_OF_DELIMITERS = 2;
2733

2834
static ngx_int_t ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
2935
ngx_str_t *res, ngx_http_variable_value_t *v);
@@ -42,6 +48,8 @@ static char *ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd,
4248
static char *ngx_http_encrypted_session_expires(ngx_conf_t *cf,
4349
ngx_command_t *cmd, void *conf);
4450

51+
static char *ngx_http_encrypted_iv_in_content(ngx_conf_t *cf,
52+
ngx_command_t *cmd, void *conf);
4553

4654
static ngx_int_t ngx_http_encrypted_session_init(ngx_conf_t *cf);
4755
static void *ngx_http_encrypted_session_create_main_conf(ngx_conf_t *cf);
@@ -53,7 +61,6 @@ static void *ngx_http_encrypted_session_create_conf(ngx_conf_t *cf);
5361
static char *ngx_http_encrypted_session_merge_conf(ngx_conf_t *cf, void *parent,
5462
void *child);
5563

56-
5764
static ndk_set_var_t ngx_http_set_encode_encrypted_session_filter = {
5865
NDK_SET_VAR_VALUE,
5966
(void *) ngx_http_set_encode_encrypted_session,
@@ -115,7 +122,14 @@ static ngx_command_t ngx_http_encrypted_session_commands[] = {
115122
0,
116123
&ngx_http_set_decode_encrypted_session_filter
117124
},
118-
125+
{ ngx_string("include_iv_in_encrypted_payload"),
126+
NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_SIF_CONF
127+
|NGX_HTTP_LOC_CONF|NGX_HTTP_LIF_CONF|NGX_CONF_NOARGS,
128+
ngx_http_encrypted_iv_in_content,
129+
NGX_HTTP_LOC_CONF_OFFSET,
130+
0,
131+
NULL
132+
},
119133
ngx_null_command
120134
};
121135

@@ -151,14 +165,14 @@ ngx_module_t ngx_http_encrypted_session_module = {
151165
};
152166

153167
static ngx_str_t ngx_http_get_variable_by_name(ngx_http_request_t *r,
154-
unsigned char *name, ngx_http_encrypted_session_conf_t *conf)
168+
unsigned char *name, size_t name_len, ngx_http_encrypted_session_conf_t *conf)
155169
{
156170
ngx_http_variable_value_t *v;
157171
ngx_str_t name_str;
158172
name_str.data = name;
159-
name_str.len = strlen((const char *)name);
173+
name_str.len = name_len;
160174

161-
ngx_uint_t key = ngx_hash_strlow(name, name, name_str.len);
175+
ngx_uint_t key = ngx_hash_strlow(name, name, name_len);
162176
v = ngx_http_get_variable(r, &name_str, key);
163177

164178
if (v->not_found) {
@@ -171,6 +185,37 @@ static ngx_str_t ngx_http_get_variable_by_name(ngx_http_request_t *r,
171185
return var_value;
172186
}
173187

188+
static char*
189+
ngx_http_encrypted_session_build_payload(ngx_http_request_t *r,
190+
char *input, size_t input_len, ngx_str_t *iv)
191+
{
192+
size_t new_len = input_len + iv->len + PARTS_DELIMITER_LEN;
193+
char *data = (char *)ngx_pcalloc(r->pool, new_len + 1);
194+
data = strncat(data, (char *)iv->data, iv->len);
195+
data = strcat(data, PARTS_DELIMITER);
196+
data = strncat(data, input, input_len);
197+
198+
return data;
199+
}
200+
201+
static ngx_str_t*
202+
ngx_http_session_encrypted_compute_hmac(ngx_http_request_t *r,
203+
ngx_str_t *key, ngx_str_t *content)
204+
{
205+
size_t signature_len;
206+
u_char* signature;
207+
208+
ngx_http_encrypted_session_hmac(r->pool, key->data, key->len,
209+
content->data, content->len,
210+
&signature, &signature_len);
211+
212+
ngx_str_t *result = (ngx_str_t*)ngx_pcalloc(r->pool, sizeof(ngx_str_t));
213+
result->len = signature_len;
214+
result->data = (u_char*)ngx_pcalloc(r->pool, signature_len + 1);
215+
result->data = signature;
216+
return result;
217+
}
218+
174219
static ngx_int_t
175220
ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
176221
ngx_str_t *res, ngx_http_variable_value_t *v)
@@ -196,12 +241,23 @@ ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
196241
ngx_log_debug1(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
197242
"encrypted_session: expires=%T", conf->expires);
198243

199-
ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf);
200-
ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf);
244+
ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf->iv_len,
245+
conf);
246+
ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf->key_len,
247+
conf);
248+
249+
char *data = (char *)v->data;
250+
if (conf->iv_in_content) {
251+
data = ngx_http_encrypted_session_build_payload(r, data, v->len, &iv);
252+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
253+
"encrypted_session: content to encrypt=%s",
254+
data);
255+
v->len = strlen(data);
256+
}
201257

202258
rc = ngx_http_encrypted_session_aes_mac_encrypt(emcf, r->pool,
203259
r->connection->log, iv.data, iv.len, key.data, key.len,
204-
v->data, v->len, (ngx_uint_t) conf->expires, &dst, &len);
260+
(u_char*)data, v->len, (ngx_uint_t) conf->expires, &dst, &len);
205261

206262
if (rc != NGX_OK) {
207263
dst = NULL;
@@ -211,6 +267,33 @@ ngx_http_set_encode_encrypted_session(ngx_http_request_t *r,
211267
"encrypted_session: failed to encrypt");
212268
}
213269

270+
if (conf->iv_in_content) {
271+
size_t signature_content_len = iv.len + len;
272+
char* signature_content = (char*)ngx_pcalloc(r->pool, signature_content_len + 1);
273+
signature_content = strncat(signature_content, (char*)iv.data, iv.len);
274+
signature_content = strncat(signature_content, (char*)dst, len);
275+
276+
ngx_str_t signature_input;
277+
signature_input.len = signature_content_len;
278+
signature_input.data = (u_char*)signature_content;
279+
ngx_str_t *signature = ngx_http_session_encrypted_compute_hmac(r, &key,
280+
&signature_input);
281+
282+
size_t new_len = iv.len + len + signature->len + NUM_OF_DELIMITERS * PARTS_DELIMITER_LEN;
283+
char *new_content = (char*)ngx_pcalloc(r->pool, new_len + 1);
284+
new_content = strncat(new_content, (char*)iv.data, iv.len);
285+
new_content = strcat(new_content, PARTS_DELIMITER);
286+
new_content = strncat(new_content, (char*)dst, len);
287+
new_content = strcat(new_content, PARTS_DELIMITER);
288+
new_content = strncat(new_content, (char*)signature->data, signature->len);
289+
len = new_len;
290+
dst = (u_char*)new_content;
291+
292+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
293+
"encrypted_session: full response=%s",
294+
dst);
295+
}
296+
214297
res->data = dst;
215298
res->len = len;
216299

@@ -240,18 +323,88 @@ ngx_http_set_decode_encrypted_session(ngx_http_request_t *r,
240323
return NGX_ERROR;
241324
}
242325

243-
ngx_str_t iv = ngx_http_get_variable_by_name(r, conf->iv, conf);
244-
ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf);
326+
ngx_str_t key = ngx_http_get_variable_by_name(r, conf->key, conf->key_len,
327+
conf);
328+
329+
ngx_str_t iv;
330+
char *data = (char*)v->data;
331+
size_t data_len = v->len;
332+
333+
334+
if (!conf->iv_in_content)
335+
{
336+
iv = ngx_http_get_variable_by_name(r, conf->iv, conf->iv_len, conf);
337+
}
338+
else
339+
{
340+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
341+
"encrypted_session: input to decrypt=%s",
342+
data);
343+
iv.len = strcspn(data, PARTS_DELIMITER);
344+
iv.data = (u_char*)ngx_pcalloc(r->pool, iv.len + 1);
345+
strncpy((char*)iv.data, (char*)v->data, iv.len);
346+
347+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
348+
"encrypted_session: iv=%s", iv.data);
349+
350+
size_t signature_start = iv.len + strcspn(&data[iv.len + 1], PARTS_DELIMITER) + NUM_OF_DELIMITERS * PARTS_DELIMITER_LEN;
351+
size_t signature_len = v->len - signature_start;
352+
353+
u_char* signature = (u_char*)ngx_pcalloc(r->pool, signature_len + 1);
354+
strncpy((char*)signature, &data[data_len - signature_len], signature_len);
355+
356+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
357+
"encrypted_session: signature=%s", signature);
358+
359+
data_len = v->len - iv.len - signature_len - NUM_OF_DELIMITERS * PARTS_DELIMITER_LEN;
360+
data = (char*)ngx_pcalloc(r->pool, data_len + 1);
361+
strncpy(data, (char*)(&v->data[iv.len + 1]), data_len);
362+
363+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
364+
"encrypted_session: data=%s", data);
365+
366+
ngx_str_t signature_input;
367+
signature_input.len = iv.len + data_len;
368+
signature_input.data = (u_char*)ngx_pcalloc(r->pool, signature_input.len + 1);
369+
strncat((char*)signature_input.data, (char*)iv.data, iv.len);
370+
strncat((char*)signature_input.data, (char*)data, data_len);
371+
372+
ngx_str_t *computed_signature = ngx_http_session_encrypted_compute_hmac(r,
373+
&key, &signature_input);
374+
if (signature_len != computed_signature->len ||
375+
strncmp((char*)computed_signature->data, (char*)signature, signature_len) != 0)
376+
{
377+
ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,
378+
"encrypted_session: signatures do not match");
379+
res->data = NULL;
380+
res->len = 0;
381+
382+
return NGX_OK;
383+
}
384+
}
245385

246386
rc = ngx_http_encrypted_session_aes_mac_decrypt(emcf, r->pool,
247387
r->connection->log, iv.data, iv.len, key.data, key.len,
248-
v->data, v->len, &dst, &len);
388+
(u_char*)data, data_len, &dst, &len);
249389

250390
if (rc != NGX_OK) {
391+
ngx_log_error(NGX_LOG_WARN, r->connection->log, 0,
392+
"encrypted_session: failed to decrypt");
251393
dst = NULL;
252394
len = 0;
253395
}
254396

397+
if (conf->iv_in_content) {
398+
size_t payload_len = len - iv.len - 1;
399+
u_char *result = ngx_pcalloc(r->pool, payload_len + 1);
400+
memcpy(result, &dst[iv.len + 1], payload_len);
401+
dst = result;
402+
len = payload_len;
403+
ngx_log_error(NGX_LOG_DEBUG, r->connection->log, 0,
404+
"encrypted_session: decrypted content=%s",
405+
dst);
406+
}
407+
255408
res->data = dst;
256409
res->len = len;
257410

@@ -273,7 +426,9 @@ ngx_http_encrypted_session_key(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
273426
value = cf->args->elts;
274427

275428
if (value[1].len > 1 && value[1].data[0] == '$') {
276-
llcf->key = &(value[1].data[1]);
429+
llcf->key_len = value[1].len - 1;
430+
llcf->key = (u_char*)ngx_pcalloc(cf->pool, llcf->key_len);
431+
strncpy((char*)llcf->key, (char*)&(value[1].data[1]), llcf->key_len);
277432
return NGX_CONF_OK;
278433
}
279434

@@ -287,6 +442,7 @@ ngx_http_encrypted_session_key(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
287442
}
288443

289444
llcf->key = value[1].data;
445+
llcf->key_len = value[1].len;
290446

291447
return NGX_CONF_OK;
292448
}
@@ -307,6 +463,7 @@ ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
307463

308464
if (value[1].len > 1 && value[1].data[0] == '$') {
309465
llcf->iv = &(value[1].data[1]);
466+
llcf->iv_len = value[1].len - 1;
310467
return NGX_CONF_OK;
311468
}
312469

@@ -320,6 +477,7 @@ ngx_http_encrypted_session_iv(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
320477
}
321478

322479
llcf->iv = ngx_pcalloc(cf->pool, ngx_http_encrypted_session_iv_length);
480+
llcf->iv_len = ngx_http_encrypted_session_iv_length;
323481

324482
if (llcf->iv == NULL) {
325483
return NGX_CONF_ERROR;
@@ -360,6 +518,13 @@ ngx_http_encrypted_session_expires(ngx_conf_t *cf, ngx_command_t *cmd,
360518
return NGX_CONF_OK;
361519
}
362520

521+
static char *ngx_http_encrypted_iv_in_content(ngx_conf_t *cf,
522+
ngx_command_t *cmd, void *conf)
523+
{
524+
ngx_http_encrypted_session_conf_t *llcf = conf;
525+
llcf->iv_in_content = 1;
526+
return NGX_CONF_OK;
527+
}
363528

364529
static void
365530
ngx_http_encrypted_session_free_cipher_ctx(void *data)
@@ -435,8 +600,11 @@ ngx_http_encrypted_session_create_conf(ngx_conf_t *cf)
435600
}
436601

437602
conf->key = NGX_CONF_UNSET_PTR;
603+
conf->key_len = NGX_CONF_UNSET;
438604
conf->iv = NGX_CONF_UNSET_PTR;
605+
conf->iv_len = NGX_CONF_UNSET;
439606
conf->expires = NGX_CONF_UNSET;
607+
conf->iv_in_content = NGX_CONF_UNSET;
440608

441609
return conf;
442610
}
@@ -449,12 +617,17 @@ ngx_http_encrypted_session_merge_conf(ngx_conf_t *cf, void *parent, void *child)
449617
ngx_http_encrypted_session_conf_t *conf = child;
450618

451619
ngx_conf_merge_ptr_value(conf->key, prev->key, NULL);
620+
ngx_conf_merge_size_value(conf->key_len, prev->key_len,
621+
(size_t)ngx_http_encrypted_session_key_length);
452622

453623
ngx_conf_merge_ptr_value(conf->iv, prev->iv,
454624
ngx_http_encrypted_session_default_iv);
625+
ngx_conf_merge_size_value(conf->iv_len, prev->iv_len,
626+
(size_t)ngx_http_encrypted_session_iv_length);
455627

456628
ngx_conf_merge_value(conf->expires, prev->expires,
457629
ngx_http_encrypted_session_default_expires);
630+
ngx_conf_merge_value(conf->iv_in_content, prev->iv_in_content, 0);
458631

459632
return NGX_CONF_OK;
460633
}

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