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tor/src/or/onion.c
Roger Dingledine 22285e6ff1 cleanup 
prkey is only fetched when it's needed
tor nodes who aren't dirservers now fetch directories and autoconnect
  to new nodes listed in the directory
default role is a non-dirserver node


svn:r120
2002-09-28 00:52:59 +00:00

714 lines
22 KiB
C
Raw Blame History

/* Copyright 2001,2002 Roger Dingledine, Matej Pfajfar. */
/* See LICENSE for licensing information */
/* $Id$ */
#include "or.h"
extern int global_role; /* from main.c */
/********* START VARIABLES **********/
tracked_onion_t *tracked_onions = NULL; /* linked list of tracked onions */
tracked_onion_t *last_tracked_onion = NULL;
/********* END VARIABLES ************/
int decide_aci_type(uint32_t local_addr, uint16_t local_port,
uint32_t remote_addr, uint16_t remote_port) {
if(local_addr > remote_addr)
return ACI_TYPE_HIGHER;
if(local_addr < remote_addr)
return ACI_TYPE_LOWER;
if(local_port > remote_port)
return ACI_TYPE_HIGHER;
/* else */
return ACI_TYPE_LOWER;
}
int process_onion(circuit_t *circ, connection_t *conn) {
aci_t aci_type;
if(!decrypt_onion((onion_layer_t *)circ->onion,circ->onionlen,getprivatekey())) {
log(LOG_DEBUG,"command_process_create_cell(): decrypt_onion() failed, closing circuit.");
return -1;
}
log(LOG_DEBUG,"command_process_create_cell(): Onion decrypted.");
/* check freshness */
if (((onion_layer_t *)circ->onion)->expire < time(NULL)) /* expired onion */
{
log(LOG_NOTICE,"I have just received an expired onion. This could be a replay attack.");
return -1;
}
aci_type = decide_aci_type(conn->local.sin_addr.s_addr, ntohs(conn->local.sin_port),
((onion_layer_t *)circ->onion)->addr,((onion_layer_t *)circ->onion)->port);
if(circuit_init(circ, aci_type) < 0) {
log(LOG_ERR,"process_onion(): init_circuit() failed.");
return -1;
}
/* check for replay */
if(id_tracked_onion(circ->onion, circ->onionlen, tracked_onions)) {
log(LOG_NOTICE,"process_onion(): I have just received a replayed onion. This could be a replay attack.");
return -1;
}
/* track the new onion */
if(!new_tracked_onion(circ->onion,circ->onionlen, &tracked_onions, &last_tracked_onion)) {
log(LOG_DEBUG,"process_onion(): Onion tracking failed. Will ignore.");
}
return 0;
}
/* uses a weighted coin with weight cw to choose a route length */
int chooselen(double cw)
{
int len = 2;
int retval = 0;
unsigned char coin;
if ((cw < 0) || (cw >= 1)) /* invalid parameter */
return -1;
while(1)
{
retval = crypto_pseudo_rand(1, &coin);
if (retval)
return -1;
if (coin > cw*255) /* don't extend */
break;
else
len++;
}
return len;
}
/* returns an array of pointers to routent that define a new route through the OR network
* int cw is the coin weight to use when choosing the route
* order of routers is from last to first
*/
unsigned int *new_route(double cw, routerinfo_t **rarray, int rarray_len, int *routelen)
{
int i, j;
int num_acceptable_routers = 0;
unsigned int *route = NULL;
unsigned int oldchoice, choice;
assert((cw >= 0) && (cw < 1) && (rarray) && (routelen) ); /* valid parameters */
*routelen = chooselen(cw);
if (*routelen == -1) {
log(LOG_ERR,"Choosing route length failed.");
return NULL;
}
log(LOG_DEBUG,"new_route(): Chosen route length %d.",*routelen);
for(i=0;i<rarray_len;i++) {
log(LOG_DEBUG,"Contemplating whether router %d is a new option...",i);
if( (global_role & ROLE_OR_CONNECT_ALL) &&
!connection_exact_get_by_addr_port(rarray[i]->addr, rarray[i]->or_port)) {
log(LOG_DEBUG,"Nope, %d is not connected.",i);
goto next_i_loop;
}
for(j=0;j<i;j++) {
if(!crypto_pk_cmp_keys(rarray[i]->pkey, rarray[j]->pkey)) {
/* these guys are twins. so we've already counted him. */
log(LOG_DEBUG,"Nope, %d is a twin of %d.",i,j);
goto next_i_loop;
}
}
num_acceptable_routers++;
log(LOG_DEBUG,"I like %d. num_acceptable_routers now %d.",i, num_acceptable_routers);
next_i_loop:
; /* our compiler may need an explicit statement after the label */
}
if(num_acceptable_routers < *routelen) {
log(LOG_DEBUG,"new_route(): Cutting routelen from %d to %d.",*routelen, num_acceptable_routers);
*routelen = num_acceptable_routers;
}
if(*routelen < 1) {
log(LOG_ERR,"new_route(): Didn't find any acceptable routers. Failing.");
return NULL;
}
/* allocate memory for the new route */
route = (unsigned int *)malloc(*routelen * sizeof(unsigned int));
if (!route) {
log(LOG_ERR,"Memory allocation failed.");
return NULL;
}
oldchoice = rarray_len;
for(i=0;i<*routelen;i++) {
log(LOG_DEBUG,"new_route(): Choosing hop %u.",i);
if(crypto_pseudo_rand(sizeof(unsigned int),(unsigned char *)&choice)) {
free((void *)route);
return NULL;
}
choice = choice % (rarray_len);
log(LOG_DEBUG,"new_route(): Contemplating router %u.",choice);
if(choice == oldchoice ||
(oldchoice < rarray_len && !crypto_pk_cmp_keys(rarray[choice]->pkey, rarray[oldchoice]->pkey)) ||
((global_role & ROLE_OR_CONNECT_ALL) && !connection_twin_get_by_addr_port(rarray[choice]->addr, rarray[choice]->or_port))) {
/* Same router as last choice, or router twin,
* or no routers with that key are connected to us.
* Try again. */
log(LOG_DEBUG,"new_route(): Picked a router %d that won't work as next hop.",choice);
i--;
continue;
}
log(LOG_DEBUG,"new_route(): Chosen router %u for hop %u.",choice,i);
oldchoice = choice;
route[i] = choice;
}
return route;
}
/* creates a new onion from route, stores it and its length into buf and len respectively */
unsigned char *create_onion(routerinfo_t **rarray, int rarray_len, unsigned int *route, int routelen, int *len, crypt_path_t **cpath)
{
int i,j;
int retval = 0;
onion_layer_t *layer = NULL;
crypt_path_t *hop = NULL;
unsigned char *retbuf = NULL;
unsigned char *buf;
routerinfo_t *router;
unsigned char iv[16];
assert(rarray && route && len && routelen);
/* calculate the size of the onion */
*len = routelen * 28 + 100; /* 28 bytes per layer + 100 bytes padding for the innermost layer */
log(LOG_DEBUG,"create_onion() : Size of the onion is %u.",*len);
/* allocate memory for the onion */
buf = (unsigned char *)malloc(*len);
if (!buf)
{
log(LOG_ERR,"Error allocating memory.");
return NULL;
}
log(LOG_DEBUG,"create_onion() : Allocated memory for the onion.");
for (retval=0; retval<routelen;retval++)
{
log(LOG_DEBUG,"create_onion() : %u : %s:%u, %u/%u",routelen-retval,inet_ntoa(*((struct in_addr *)&((rarray[route[retval]])->addr))),(rarray[route[retval]])->or_port,(rarray[route[retval]])->pkey,crypto_pk_keysize((rarray[route[retval]])->pkey));
}
layer = (onion_layer_t *)(buf + *len - 128); /* pointer to innermost layer */
/* create the onion layer by layer, starting with the innermost */
for (i=0;i<routelen;i++)
{
router = rarray[route[i]];
log(LOG_DEBUG,"create_onion() : %u",router);
log(LOG_DEBUG,"create_onion() : This router is %s:%u",inet_ntoa(*((struct in_addr *)&router->addr)),router->or_port);
log(LOG_DEBUG,"create_onion() : Key pointer = %u.",router->pkey);
log(LOG_DEBUG,"create_onion() : Key size = %u.",crypto_pk_keysize(router->pkey));
/* 0 bit */
layer->zero = 0;
/* version */
layer->version = OR_VERSION;
/* Back F + Forw F both use DES OFB*/
layer->backf = ONION_DEFAULT_CIPHER;
layer->forwf = ONION_DEFAULT_CIPHER;
/* Dest Port */
if (i) /* not last hop */
layer->port = rarray[route[i-1]]->or_port;
else
layer->port = 0;
/* Dest Addr */
if (i) /* not last hop */
layer->addr = rarray[route[i-1]]->addr;
else
layer->addr = 0;
/* Expiration Time */
layer->expire = time(NULL) + 3600; /* NOW + 1 hour */
/* Key Seed Material */
retval = crypto_rand(16, layer->keyseed);
if (retval) /* error */
{
log(LOG_ERR,"Error generating random data.");
free((void *)buf);
if (cpath)
{
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
}
return NULL;
}
log(LOG_DEBUG,"create_onion() : Onion layer %u built : %u, %u, %u, %s, %u.",i+1,layer->zero,layer->backf,layer->forwf,inet_ntoa(*((struct in_addr *)&layer->addr)),layer->port);
/* build up the crypt_path */
if (cpath)
{
cpath[i] = (crypt_path_t *)malloc(sizeof(crypt_path_t));
if (!cpath[i])
{
log(LOG_ERR,"Error allocating memory.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
}
log(LOG_DEBUG,"create_onion() : Building hop %u of crypt path.",i+1);
hop = cpath[i];
/* set crypto functions */
hop->backf = layer->backf;
hop->forwf = layer->forwf;
/* calculate keys */
crypto_SHA_digest(layer->keyseed,16,hop->digest3);
log(LOG_DEBUG,"create_onion() : First SHA pass performed.");
crypto_SHA_digest(hop->digest3,20,hop->digest2);
log(LOG_DEBUG,"create_onion() : Second SHA pass performed.");
crypto_SHA_digest(hop->digest2,20,hop->digest3);
log(LOG_DEBUG,"create_onion() : Third SHA pass performed.");
log(LOG_DEBUG,"create_onion() : Keys generated.");
/* set IV to zero */
memset((void *)iv,0,16);
/* initialize cipher engines */
switch(layer->forwf)
{
case ONION_CIPHER_DES :
hop->f_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_DES);
break;
case ONION_CIPHER_RC4 :
hop->f_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_RC4);
break;
case ONION_CIPHER_IDENTITY :
hop->f_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_IDENTITY);
break;
}
if (!hop->f_crypto) /* cipher initialization failed */
{
log(LOG_ERR,"Could not create a crypto environment.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
return NULL;
}
/* set the key and IV */
if (crypto_cipher_set_key(hop->f_crypto, hop->digest3) ||
crypto_cipher_set_iv(hop->f_crypto, iv)) {
log(LOG_ERR,"Could not initialize the crypto engine.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
return NULL;
}
switch(layer->backf)
{
case ONION_CIPHER_DES :
hop->b_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_DES);
break;
case ONION_CIPHER_RC4 :
hop->b_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_RC4);
break;
case ONION_CIPHER_IDENTITY :
hop->b_crypto = crypto_new_cipher_env(CRYPTO_CIPHER_IDENTITY);
break;
}
if (!hop->b_crypto) /* cipher initialization failed */
{
log(LOG_ERR,"Could not create a crypto environment.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
return NULL;
}
/* set the key and IV */
if (crypto_cipher_set_key(hop->b_crypto, hop->digest2) ||
crypto_cipher_set_iv(hop->b_crypto, iv)) {
log(LOG_ERR,"Could not initialize the crypto engine.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
return NULL;
}
/* initialize */
if (crypto_cipher_encrypt_init_cipher(hop->f_crypto) || crypto_cipher_decrypt_init_cipher(hop->b_crypto)) {
log(LOG_ERR,"Could not initialize the crypto engine.");
free((void *)buf);
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
return NULL;
}
log(LOG_DEBUG,"create_onion() : Built corresponding crypt path hop.");
}
/* padding if this is the innermost layer */
if (!i)
{
retval=crypto_pseudo_rand(100, (unsigned char *)layer + 28);
if (retval) /* error */
{
log(LOG_ERR,"Error generating pseudo-random data.");
free((void *)buf);
if (cpath)
{
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
}
return NULL;
}
log(LOG_DEBUG,"create_onion() : This is the innermost layer. Adding 100 bytes of padding.");
}
/* encrypt */
retbuf = encrypt_onion(layer,128+(i*28),router->pkey);
if (!retbuf)
{
log(LOG_ERR,"Error encrypting onion layer.");
free((void *)buf);
if (cpath)
{
for (j=0;j<i;j++) {
if (cpath[i]->f_crypto)
crypto_free_cipher_env(cpath[i]->f_crypto);
if (cpath[i]->b_crypto)
crypto_free_cipher_env(cpath[i]->b_crypto);
free((void *)cpath[i]);
}
}
return NULL;
}
log(LOG_DEBUG,"create_onion() : Encrypted layer.");
/* calculate pointer to next layer */
layer = (onion_layer_t *)(buf + (routelen-i-2)*sizeof(onion_layer_t));
}
return buf;
}
/* encrypts 128 bytes of the onion with the specified public key, the rest with
* DES OFB with the key as defined in the outter layer */
unsigned char *encrypt_onion(onion_layer_t *onion, uint32_t onionlen, crypto_pk_env_t *pkey)
{
unsigned char *tmpbuf = NULL; /* temporary buffer for crypto operations */
unsigned char digest[20]; /* stores SHA1 output - 160 bits */
unsigned char iv[8];
int retval = 0;
crypto_cipher_env_t *crypt_env; /* crypto environment */
if ( (onion) && (pkey) ) /* valid parameters */
{
memset((void *)iv,0,8);
log(LOG_DEBUG,"Onion layer : %u, %u, %u, %s, %u.",onion->zero,onion->backf,onion->forwf,inet_ntoa(*((struct in_addr *)&onion->addr)),onion->port);
/* allocate space for tmpbuf */
tmpbuf = (unsigned char *)malloc(onionlen);
if (!tmpbuf)
{
log(LOG_ERR,"Could not allocate memory.");
return NULL;
}
log(LOG_DEBUG,"encrypt_onion() : allocated %u bytes of memory for the encrypted onion (at %u).",onionlen,tmpbuf);
/* get key1 = SHA1(KeySeed) */
if (crypto_SHA_digest(((onion_layer_t *)onion)->keyseed,16,digest))
{
log(LOG_ERR,"Error computing SHA1 digest.");
free((void *)tmpbuf);
return NULL;
}
log(LOG_DEBUG,"encrypt_onion() : Computed DES key.");
log(LOG_DEBUG,"encrypt_onion() : Trying to RSA encrypt.");
/* encrypt 128 bytes with RSA *pkey */
retval = crypto_pk_public_encrypt(pkey, (unsigned char *)onion, 128, tmpbuf, RSA_NO_PADDING);
if (retval == -1)
{
log(LOG_ERR,"Error RSA-encrypting data :%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
log(LOG_DEBUG,"encrypt_onion() : RSA encrypted first 128 bytes of the onion.");
/* now encrypt the rest with DES OFB */
crypt_env = crypto_new_cipher_env(CRYPTO_CIPHER_DES);
if (!crypt_env)
{
log(LOG_ERR,"Error creating the crypto environment.");
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_set_key(crypt_env, digest)) /* error */
{
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_set_iv(crypt_env, iv))
{
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_encrypt_init_cipher(crypt_env)) {
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
retval = crypto_cipher_encrypt(crypt_env,(unsigned char *)onion+128, onionlen-128, (unsigned char *)tmpbuf+128);
if (retval) /* error */
{
log(LOG_ERR,"Error performing DES encryption:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
log(LOG_DEBUG,"encrypt_onion() : DES OFB encrypted the rest of the onion.");
crypto_free_cipher_env(crypt_env);
/* now copy tmpbuf to onion */
memcpy((void *)onion,(void *)tmpbuf,onionlen);
log(LOG_DEBUG,"encrypt_onion() : Copied cipher to original onion buffer.");
free((void *)tmpbuf);
return (unsigned char *)onion;
} /* valid parameters */
else
return NULL;
}
/* decrypts the first 128 bytes using RSA and prkey, decrypts the rest with DES OFB with key1 */
unsigned char *decrypt_onion(onion_layer_t *onion, uint32_t onionlen, crypto_pk_env_t *prkey)
{
void *tmpbuf = NULL; /* temporary buffer for crypto operations */
unsigned char digest[20]; /* stores SHA1 output - 160 bits */
unsigned char iv[8];
int retval = 0;
crypto_cipher_env_t *crypt_env; /* crypto environment */
if ( (onion) && (prkey) ) /* valid parameters */
{
memset((void *)iv,0,8);
/* allocate space for tmpbuf */
tmpbuf = malloc(onionlen);
if (!tmpbuf)
{
log(LOG_ERR,"Could not allocate memory.");
return NULL;
}
log(LOG_DEBUG,"decrypt_onion() : Allocated memory for the temporary buffer.");
/* decrypt 128 bytes with RSA *prkey */
retval = crypto_pk_private_decrypt(prkey, (unsigned char*)onion, 128, (unsigned char *)tmpbuf, RSA_NO_PADDING);
if (retval == -1)
{
log(LOG_ERR,"Error RSA-decrypting data :%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
log(LOG_DEBUG,"decrypt_onion() : RSA decryption complete.");
/* get key1 = SHA1(KeySeed) */
retval = crypto_SHA_digest(((onion_layer_t *)tmpbuf)->keyseed,16,digest);
if (retval)
{
log(LOG_ERR,"Error computing SHA1 digest.");
free((void *)tmpbuf);
return NULL;
}
log(LOG_DEBUG,"decrypt_onion() : Computed DES key.");
/* now decrypt the rest with DES OFB */
crypt_env = crypto_new_cipher_env(CRYPTO_CIPHER_DES);
if (!crypt_env)
{
log(LOG_ERR,"Error creating the crypto environment.");
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_set_key(crypt_env, digest)) /* error */
{
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_set_iv(crypt_env, iv))
{
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
if (crypto_cipher_decrypt_init_cipher(crypt_env)) {
log(LOG_ERR,"Error initializing DES engine:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
retval = crypto_cipher_decrypt(crypt_env,(unsigned char *)onion+128, onionlen-128,(unsigned char *)tmpbuf+128);
if (retval) /* error */
{
log(LOG_ERR,"Error performing DES decryption:%s",crypto_perror());
free((void *)tmpbuf);
return NULL;
}
crypto_free_cipher_env(crypt_env);
log(LOG_DEBUG,"decrypt_onion() : DES decryption complete.");
/* now copy tmpbuf to onion */
memcpy((void *)onion,(void *)tmpbuf,onionlen);
free((void *)tmpbuf);
return (unsigned char *)onion;
} /* valid parameters */
else
return NULL;
}
/* delete first n bytes of the onion and pads the end with n bytes of random data */
void pad_onion(unsigned char *onion, uint32_t onionlen, int n)
{
if (onion) /* valid parameter */
{
memmove((void *)onion,(void *)(onion+n),onionlen-n);
crypto_pseudo_rand(n, onion+onionlen-n);
}
}
/* create a new tracked_onion entry */
tracked_onion_t *new_tracked_onion(unsigned char *onion, uint32_t onionlen, tracked_onion_t **tracked_onions, tracked_onion_t **last_tracked_onion)
{
tracked_onion_t *to = NULL;
if (!onion || !tracked_onions || !last_tracked_onion) /* invalid parameters */
return NULL;
to = (tracked_onion_t *)malloc(sizeof(tracked_onion_t));
if (!to)
return NULL;
to->expire = ((onion_layer_t *)onion)->expire; /* set the expiration date */
/* compute the SHA digest */
if (crypto_SHA_digest(onion, onionlen, to->digest))
{
log(LOG_DEBUG,"new_tracked_onion() : Failed to compute a SHA1 digest of the onion.");
free((void *)to);
return NULL;
}
to->next = NULL;
if (!*tracked_onions)
{
to->prev = NULL;
*tracked_onions = to;
}
else
{
to->prev = (void *)*last_tracked_onion;
(*last_tracked_onion)->next = (void *)to;
}
*last_tracked_onion = to;
return to;
}
/* delete a tracked onion entry */
void remove_tracked_onion(tracked_onion_t *to, tracked_onion_t **tracked_onions, tracked_onion_t **last_tracked_onion)
{
if (!*tracked_onions || !*last_tracked_onion || !to)
return;
if (to->prev)
((tracked_onion_t *)to->prev)->next = to->next;
if (to->next)
((tracked_onion_t *)to->next)->prev = to->prev;
if (to == *tracked_onions)
*tracked_onions = (tracked_onion_t *)to->next;
if (to == *last_tracked_onion)
*last_tracked_onion = (tracked_onion_t *)to->prev;
free((void *)to);
return;
}
/* find a tracked onion in the linked list of tracked onions */
tracked_onion_t *id_tracked_onion(unsigned char *onion, uint32_t onionlen, tracked_onion_t *tracked_onions)
{
tracked_onion_t *to = tracked_onions;
unsigned char digest[20];
/* compute the SHA digest of the onion */
crypto_SHA_digest(onion,onionlen, digest);
while(to)
{
if (!memcmp((void *)digest, (void *)to->digest, 20))
return to;
to = (tracked_onion_t *)to->next;
}
return NULL;
}
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