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/* Copyright 2001,2002,2003 Roger Dingledine, Matej Pfajfar. */
/* See LICENSE for licensing information */
/* $Id$ */
/**
* \file onion.c
* \brief Functions to queue create cells, and handle onionskin
* parsing and creation.
**/
#include "or.h"
extern or_options_t options; /**< command-line and config-file options */
struct onion_queue_t {
circuit_t *circ;
struct onion_queue_t *next;
};
/** global (within this file) variables used by the next few functions */
static struct onion_queue_t *ol_list=NULL;
static struct onion_queue_t *ol_tail=NULL;
/** length of ol_list */
static int ol_length=0;
/** Add <b>circ</b> to the end of ol_list and return 0, except
* if ol_list is too long, in which case do nothing and return -1.
*/
int onion_pending_add(circuit_t *circ) {
struct onion_queue_t *tmp;
tmp = tor_malloc(sizeof(struct onion_queue_t));
tmp->circ = circ;
tmp->next = NULL;
if(!ol_tail) {
tor_assert(!ol_list);
tor_assert(!ol_length);
ol_list = tmp;
ol_tail = tmp;
ol_length++;
return 0;
}
tor_assert(ol_list);
tor_assert(!ol_tail->next);
if(ol_length >= options.MaxOnionsPending) {
log_fn(LOG_WARN,"Already have %d onions queued. Closing.", ol_length);
tor_free(tmp);
return -1;
}
ol_length++;
ol_tail->next = tmp;
ol_tail = tmp;
return 0;
}
/** Remove the first item from ol_list and return it, or return
* NULL if the list is empty.
*/
circuit_t *onion_next_task(void) {
circuit_t *circ;
if(!ol_list)
return NULL; /* no onions pending, we're done */
tor_assert(ol_list->circ);
tor_assert(ol_list->circ->p_conn); /* make sure it's still valid */
tor_assert(ol_length > 0);
circ = ol_list->circ;
onion_pending_remove(ol_list->circ);
return circ;
}
/** Go through ol_list, find the onion_queue_t element which points to
* circ, remove and free that element. Leave circ itself alone.
*/
void onion_pending_remove(circuit_t *circ) {
struct onion_queue_t *tmpo, *victim;
if(!ol_list)
return; /* nothing here. */
/* first check to see if it's the first entry */
tmpo = ol_list;
if(tmpo->circ == circ) {
/* it's the first one. remove it from the list. */
ol_list = tmpo->next;
if(!ol_list)
ol_tail = NULL;
ol_length--;
victim = tmpo;
} else { /* we need to hunt through the rest of the list */
for( ;tmpo->next && tmpo->next->circ != circ; tmpo=tmpo->next) ;
if(!tmpo->next) {
log_fn(LOG_DEBUG,"circ (p_circ_id %d) not in list, probably at cpuworker.",circ->p_circ_id);
return;
}
/* now we know tmpo->next->circ == circ */
victim = tmpo->next;
tmpo->next = victim->next;
if(ol_tail == victim)
ol_tail = tmpo;
ol_length--;
}
/* now victim points to the element that needs to be removed */
tor_free(victim);
}
/*----------------------------------------------------------------------*/
/** Given a router's 128 byte public key,
* stores the following in onion_skin_out:
* - [42 bytes] OAEP padding
* - [16 bytes] Symmetric key for encrypting blob past RSA
* - [70 bytes] g^x part 1 (inside the RSA)
* - [58 bytes] g^x part 2 (symmetrically encrypted)
*
* Stores the DH private key into handshake_state_out for later completion
* of the handshake.
*
* The meeting point/cookies and auth are zeroed out for now.
*/
int
onion_skin_create(crypto_pk_env_t *dest_router_key,
crypto_dh_env_t **handshake_state_out,
char *onion_skin_out) /* Must be ONIONSKIN_CHALLENGE_LEN bytes */
{
char *challenge = NULL;
crypto_dh_env_t *dh = NULL;
int dhbytes, pkbytes;
*handshake_state_out = NULL;
memset(onion_skin_out, 0, ONIONSKIN_CHALLENGE_LEN);
if (!(dh = crypto_dh_new()))
goto err;
dhbytes = crypto_dh_get_bytes(dh);
pkbytes = crypto_pk_keysize(dest_router_key);
tor_assert(dhbytes == 128);
tor_assert(pkbytes == 128);
challenge = tor_malloc_zero(DH_KEY_LEN);
if (crypto_dh_get_public(dh, challenge, dhbytes))
goto err;
#ifdef DEBUG_ONION_SKINS
#define PA(a,n) \
{ int _i; for (_i = 0; _i<n; ++_i) printf("%02x ",((int)(a)[_i])&0xFF); }
printf("Client: client g^x:");
PA(challenge+16,3);
printf("...");
PA(challenge+141,3);
puts("");
printf("Client: client symkey:");
PA(challenge+0,16);
puts("");
#endif
/* set meeting point, meeting cookie, etc here. Leave zero for now. */
if (crypto_pk_public_hybrid_encrypt(dest_router_key, challenge,
DH_KEY_LEN,
onion_skin_out, PK_PKCS1_OAEP_PADDING, 1)<0)
goto err;
tor_free(challenge);
*handshake_state_out = dh;
return 0;
err:
tor_free(challenge);
if (dh) crypto_dh_free(dh);
return -1;
}
/** Given an encrypted DH public key as generated by onion_skin_create,
* and the private key for this onion router, generate the reply (128-byte
* DH plus the first 20 bytes of shared key material), and store the
* next key_out_len bytes of key material in key_out.
*/
int
onion_skin_server_handshake(char *onion_skin, /* ONIONSKIN_CHALLENGE_LEN bytes */
crypto_pk_env_t *private_key,
crypto_pk_env_t *prev_private_key,
char *handshake_reply_out, /* ONIONSKIN_REPLY_LEN bytes */
char *key_out,
int key_out_len)
{
char challenge[ONIONSKIN_CHALLENGE_LEN];
crypto_dh_env_t *dh = NULL;
int len;
char *key_material=NULL;
int i;
crypto_pk_env_t *k;
len = -1;
for (i=0;i<2;++i) {
k = i==0?private_key:prev_private_key;
if (!k)
break;
len = crypto_pk_private_hybrid_decrypt(k,
onion_skin, ONIONSKIN_CHALLENGE_LEN,
challenge, PK_PKCS1_OAEP_PADDING,0);
if (len>0)
break;
}
if (len<0) {
log_fn(LOG_WARN, "Couldn't decrypt onionskin: client may be using old onion key");
goto err;
} else if (len != DH_KEY_LEN) {
log_fn(LOG_WARN, "Unexpected onionskin length after decryption: %d",
len);
goto err;
}
dh = crypto_dh_new();
if (crypto_dh_get_public(dh, handshake_reply_out, DH_KEY_LEN))
goto err;
#ifdef DEBUG_ONION_SKINS
printf("Server: server g^y:");
PA(handshake_reply_out+0,3);
printf("...");
PA(handshake_reply_out+125,3);
puts("");
#endif
key_material = tor_malloc(DIGEST_LEN+key_out_len);
len = crypto_dh_compute_secret(dh, challenge, DH_KEY_LEN,
key_material, DIGEST_LEN+key_out_len);
if (len < 0)
goto err;
/* send back H(K|0) as proof that we learned K. */
memcpy(handshake_reply_out+DH_KEY_LEN, key_material, DIGEST_LEN);
/* use the rest of the key material for our shared keys, digests, etc */
memcpy(key_out, key_material+DIGEST_LEN, key_out_len);
#ifdef DEBUG_ONION_SKINS
printf("Server: key material:");
PA(buf, DH_KEY_LEN);
puts("");
printf("Server: keys out:");
PA(key_out, key_out_len);
puts("");
#endif
tor_free(key_material);
crypto_dh_free(dh);
return 0;
err:
tor_free(key_material);
if (dh) crypto_dh_free(dh);
return -1;
}
/** Finish the client side of the DH handshake.
* Given the 128 byte DH reply + 20 byte hash as generated by
* onion_skin_server_handshake and the handshake state generated by
* onion_skin_create, verify H(K) with the first 20 bytes of shared
* key material, then generate key_out_len more bytes of shared key
* material and store them in key_out.
*
* After the invocation, call crypto_dh_free on handshake_state.
*/
int
onion_skin_client_handshake(crypto_dh_env_t *handshake_state,
char *handshake_reply, /* Must be ONIONSKIN_REPLY_LEN bytes */
char *key_out,
int key_out_len)
{
int len;
char *key_material=NULL;
tor_assert(crypto_dh_get_bytes(handshake_state) == DH_KEY_LEN);
#ifdef DEBUG_ONION_SKINS
printf("Client: server g^y:");
PA(handshake_reply+0,3);
printf("...");
PA(handshake_reply+125,3);
puts("");
#endif
key_material = tor_malloc(20+key_out_len);
len = crypto_dh_compute_secret(handshake_state, handshake_reply, DH_KEY_LEN,
key_material, 20+key_out_len);
if (len < 0)
return -1;
if(memcmp(key_material, handshake_reply+DH_KEY_LEN, 20)) {
/* H(K) does *not* match. Something fishy. */
tor_free(key_material);
log_fn(LOG_WARN,"Digest DOES NOT MATCH on onion handshake. Bug or attack.");
return -1;
}
/* use the rest of the key material for our shared keys, digests, etc */
memcpy(key_out, key_material+20, key_out_len);
#ifdef DEBUG_ONION_SKINS
printf("Client: keys out:");
PA(key_out, key_out_len);
puts("");
#endif
tor_free(key_material);
return 0;
}
/*
Local Variables:
mode:c
indent-tabs-mode:nil
c-basic-offset:2
End:
*/
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