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Fix packet authentication.

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This wasn't working at all, since we didn't do HMAC but just a plain hash.
Also, verification of packets failed because it was checking the whole packet,
not the packet minus the HMAC.
This commit is contained in:
Guus Sliepen 2009-12-18 01:15:25 +01:00
parent 10d609b1f0
commit c845bc109c
6 changed files with 86 additions and 37 deletions
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34
src/gcrypt/digest.c
View file

@ -87,6 +87,7 @@ static bool digest_open(digest_t *digest, int algo, int maclength) {
digest->maclength = maclength;
digest->algo = algo;
digest->hmac = NULL;
return true;
}
@ -118,24 +119,45 @@ bool digest_open_sha1(digest_t *digest, int maclength) {
}
void digest_close(digest_t *digest) {
if(digest->hmac)
gcry_md_close(digest->hmac);
digest->hmac = NULL;
}
bool digest_set_key(digest_t *digest, const void *key, size_t len) {
if(!digest->hmac)
gcry_md_open(&digest->hmac, digest->algo, GCRY_MD_FLAG_HMAC);
if(!digest->hmac)
return false;
return !gcry_md_setkey(digest->hmac, key, len);
}
bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) {
unsigned int len = gcry_md_get_algo_dlen(digest->algo);
char tmpdata[len];
gcry_md_hash_buffer(digest->algo, tmpdata, indata, inlen);
memcpy(outdata, tmpdata, digest->maclength);
if(digest->hmac) {
char *tmpdata;
gcry_md_reset(digest->hmac);
gcry_md_write(digest->hmac, indata, inlen);
tmpdata = gcry_md_read(digest->hmac, digest->algo);
if(!tmpdata)
return false;
memcpy(outdata, tmpdata, digest->maclength);
} else {
char tmpdata[len];
gcry_md_hash_buffer(digest->algo, tmpdata, indata, inlen);
memcpy(outdata, tmpdata, digest->maclength);
}
return true;
}
bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *cmpdata) {
unsigned int len = gcry_md_get_algo_dlen(digest->algo);
unsigned int len = digest->maclength;
char outdata[len];
gcry_md_hash_buffer(digest->algo, outdata, indata, inlen);
return !memcmp(cmpdata, outdata, digest->maclength);
return digest_create(digest, indata, inlen, outdata) && !memcmp(cmpdata, outdata, len);
}
int digest_get_nid(const digest_t *digest) {

2
src/gcrypt/digest.h
View file

@ -28,6 +28,7 @@ typedef struct digest {
int algo;
int nid;
int maclength;
gcry_md_hd_t hmac;
} digest_t;
extern bool digest_open_by_name(struct digest *, const char *name, int maclength);
@ -36,6 +37,7 @@ extern bool digest_open_sha1(struct digest *, int maclength);
extern void digest_close(struct digest *);
extern bool digest_create(struct digest *, const void *indata, size_t inlen, void *outdata);
extern bool digest_verify(struct digest *, const void *indata, size_t inlen, const void *digestdata);
extern bool digest_set_key(struct digest *, const void *key, size_t len);
extern int digest_get_nid(const struct digest *);
extern size_t digest_length(const struct digest *);
extern bool digest_active(const struct digest *);

41
src/net_packet.c
View file

@ -195,7 +195,7 @@ static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
return false;
return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len);
return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
}
static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
@ -222,11 +222,13 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
/* Check the message authentication code */
if(digest_active(&n->indigest) && !digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
return;
if(digest_active(&n->indigest)) {
inpkt->len -= n->indigest.maclength;
if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
ifdebug(TRAFFIC) logger(LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
return;
}
}
/* Decrypt the packet */
if(cipher_active(&n->incipher)) {
@ -501,31 +503,28 @@ void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
splay_node_t *node;
edge_t *e;
node_t *n = NULL;
node_t *n, *found = NULL;
static time_t last_hard_try = 0;
time_t now = time(NULL);
for(node = edge_weight_tree->head; node; node = node->next) {
e = node->data;
if(last_hard_try == now)
return NULL;
else
last_hard_try = now;
if(sockaddrcmp_noport(from, &e->address)) {
if(last_hard_try == now)
continue;
last_hard_try = now;
}
for(node = node_tree->head; node; node = node->next) {
n = node->data;
if(!n)
n = e->to;
if(!try_mac(e->to, pkt))
if(n == myself || !digest_active(&n->indigest))
continue;
n = e->to;
break;
if(try_mac(n, pkt)) {
found = n;
break;
}
}
return n;
return found;
}
void handle_incoming_vpn_data(int sock, short events, void *data) {

33
src/openssl/digest.c
View file

@ -18,8 +18,11 @@
*/
#include "system.h"
#include "utils.h"
#include "xalloc.h"
#include <openssl/err.h>
#include <openssl/hmac.h>
#include "digest.h"
#include "logger.h"
@ -35,6 +38,7 @@ static void set_maclength(digest_t *digest, int maclength) {
bool digest_open_by_name(digest_t *digest, const char *name, int maclength) {
digest->digest = EVP_get_digestbyname(name);
digest->key = NULL;
if(!digest->digest) {
logger(LOG_DEBUG, "Unknown digest name '%s'!", name);
@ -47,6 +51,7 @@ bool digest_open_by_name(digest_t *digest, const char *name, int maclength) {
bool digest_open_by_nid(digest_t *digest, int nid, int maclength) {
digest->digest = EVP_get_digestbynid(nid);
digest->key = NULL;
if(!digest->digest) {
logger(LOG_DEBUG, "Unknown digest nid %d!", nid);
@ -59,25 +64,39 @@ bool digest_open_by_nid(digest_t *digest, int nid, int maclength) {
bool digest_open_sha1(digest_t *digest, int maclength) {
digest->digest = EVP_sha1();
digest->key = NULL;
set_maclength(digest, maclength);
return true;
}
bool digest_set_key(digest_t *digest, const void *key, size_t len) {
digest->key = xrealloc(digest->key, len);
memcpy(digest->key, key, len);
digest->keylength = len;
}
void digest_close(digest_t *digest) {
if(digest->key)
free(digest->key);
digest->key = NULL;
}
bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *outdata) {
size_t len = EVP_MD_size(digest->digest);
unsigned char tmpdata[len];
EVP_MD_CTX ctx;
if(digest->key) {
HMAC(digest->digest, digest->key, digest->keylength, indata, inlen, tmpdata, NULL);
} else {
EVP_MD_CTX ctx;
if(!EVP_DigestInit(&ctx, digest->digest)
|| !EVP_DigestUpdate(&ctx, indata, inlen)
|| !EVP_DigestFinal(&ctx, tmpdata, NULL)) {
logger(LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
return false;
if(!EVP_DigestInit(&ctx, digest->digest)
|| !EVP_DigestUpdate(&ctx, indata, inlen)
|| !EVP_DigestFinal(&ctx, tmpdata, NULL)) {
logger(LOG_DEBUG, "Error creating digest: %s", ERR_error_string(ERR_get_error(), NULL));
return false;
}
}
memcpy(outdata, tmpdata, digest->maclength);
@ -85,7 +104,7 @@ bool digest_create(digest_t *digest, const void *indata, size_t inlen, void *out
}
bool digest_verify(digest_t *digest, const void *indata, size_t inlen, const void *cmpdata) {
size_t len = EVP_MD_size(digest->digest);
size_t len = digest->maclength;
unsigned char outdata[len];
return digest_create(digest, indata, inlen, outdata) && !memcmp(cmpdata, outdata, digest->maclength);

3
src/openssl/digest.h
View file

@ -27,6 +27,8 @@
typedef struct digest {
const EVP_MD *digest;
int maclength;
int keylength;
char *key;
} digest_t;
extern bool digest_open_by_name(struct digest *, const char *name, int maclength);
@ -35,6 +37,7 @@ extern bool digest_open_sha1(struct digest *, int maclength);
extern void digest_close(struct digest *);
extern bool digest_create(struct digest *, const void *indata, size_t inlen, void *outdata);
extern bool digest_verify(struct digest *, const void *indata, size_t inlen, const void *digestdata);
extern bool digest_set_key(struct digest *, const void *key, size_t len);
extern int digest_get_nid(const struct digest *);
extern size_t digest_length(const struct digest *);
extern bool digest_active(const struct digest *);

10
src/protocol_key.c
View file

@ -139,6 +139,7 @@ bool send_ans_key(node_t *to) {
randomize(key, keylen);
cipher_set_key(&to->incipher, key, true);
digest_set_key(&to->indigest, key, keylen);
bin2hex(key, key, keylen);
key[keylen * 2] = '\0';
@ -160,7 +161,7 @@ bool ans_key_h(connection_t *c, char *request) {
char from_name[MAX_STRING_SIZE];
char to_name[MAX_STRING_SIZE];
char key[MAX_STRING_SIZE];
int cipher, digest, maclength, compression;
int cipher, digest, maclength, compression, keylen;
node_t *from, *to;
if(sscanf(request, "%*d "MAX_STRING" "MAX_STRING" "MAX_STRING" %d %d %d %d",
@ -209,7 +210,9 @@ bool ans_key_h(connection_t *c, char *request) {
return false;
}
if(strlen(key) / 2 != cipher_keylength(&from->outcipher)) {
keylen = strlen(key) / 2;
if(keylen != cipher_keylength(&from->outcipher)) {
logger(LOG_ERR, "Node %s (%s) uses wrong keylength!", from->name, from->hostname);
return false;
}
@ -233,8 +236,9 @@ bool ans_key_h(connection_t *c, char *request) {
/* Update our copy of the origin's packet key */
hex2bin(key, key, cipher_keylength(&from->outcipher));
hex2bin(key, key, keylen);
cipher_set_key(&from->outcipher, key, false);
digest_set_key(&from->outdigest, key, keylen);
from->status.validkey = true;
from->status.waitingforkey = false;