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Add MessageAuthenticator support

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To address RadiusBLAST vulnerability.

Fixes #16
This commit is contained in:
Samuel Thibault 2024-10-19 22:31:59 +02:00
parent 42ef80e0b4
commit cc012e18fa
8 changed files with 149 additions and 2 deletions
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99
radius.c
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@ -32,6 +32,10 @@ extern ip_filtert *ip_filters;
static const hasht zero;
static enum {
MAYBE = 0, YES, NO,
} radius_sends_message_authenticator[MAXRADSERVER];
static void calc_auth(const void *buf, size_t len, const uint8_t *in, uint8_t *out)
{
MD5_CTX ctx;
@ -163,7 +167,7 @@ void radiussend(uint16_t r, uint8_t state)
uint8_t b[4096]; // RADIUS packet
char pass[129];
int pl;
uint8_t *p;
uint8_t *p, *ma = NULL;
sessionidt s;
CSTAT(radiussend);
@ -237,6 +241,16 @@ void radiussend(uint16_t r, uint8_t state)
memcpy(b + 4, radius[r].auth, 16);
p = b + 20;
if (state == RADIUSAUTH || state == RADIUSJUSTAUTH)
{
*p = 80; // MessageAuthenticator
p[1] = 18; // length
ma = p+2;
memset(ma, 0, 16); // Zero for the computation
p += p[1];
}
if (s)
{
*p = 1; // user name
@ -464,12 +478,18 @@ void radiussend(uint16_t r, uint8_t state)
// All AVpairs added
*(uint16_t *) (b + 2) = htons(p - b);
if (state != RADIUSAUTH && state != RADIUSJUSTAUTH)
{
// Build auth for accounting packet
calc_auth(b, p - b, zero, b + 4);
memcpy(radius[r].auth, b + 4, 16);
}
// Compute MessageAuthenticator
if (ma)
MD5_Hmac(ma, b, p-b, config->radiussecret, strlen(config->radiussecret));
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
*(uint32_t *) & addr.sin_addr = config->radiusserver[(radius[r].try - 1) % config->numradiusservers];
@ -587,6 +607,83 @@ void processrad(uint8_t *buf, int len, char socket_index)
if (radius[r].state == RADIUSAUTH || radius[r].state == RADIUSJUSTAUTH)
{
// First check MessageAuthenticator
{
uint8_t *p = buf + 20;
uint8_t *e = buf + len;
int seen = 0, want;
for (; p + 2 <= e && p[1] && p + p[1] <= e; p += p[1])
{
if (*p == 80)
{
// MessageAuthenticator
uint8_t auth[16];
uint8_t authcheck[16];
uint8_t vector[16];
/* Set original vector for computation */
memcpy(vector, buf+4, 16);
memcpy(buf+4, radius[r].auth, 16);
/* Set authenticator to zero for computation */
memcpy(auth, p+2, 16);
memset(p+2, 0, 16);
MD5_Hmac(authcheck, buf, len, config->radiussecret, strlen(config->radiussecret));
if (memcmp(auth, authcheck, 16) != 0)
{
LOG(1, 0, 0, "Incorrect MessageAuthenticator in Access reply (wrong secret in radius config?)\n");
return;
}
/* Restore vector */
memcpy(buf+4, vector, 16);
/* Restore authenticator */
memcpy(p+2, auth, 16);
seen = 1;
}
}
if (!strcmp(config->radius_require_message_authenticator, "no"))
want = 0;
else if (!strcmp(config->radius_require_message_authenticator, "yes"))
want = 1;
else
{
if (config->radius_require_message_authenticator[0]
&& strcmp(config->radius_require_message_authenticator, "auto"))
LOG(1, 0, 0, "Unrecognized radius_require_message_authenticator '%s', assuming auto\n",
config->radius_require_message_authenticator);
int num = radius[r].try % config->numradiusservers;
switch (radius_sends_message_authenticator[num]) {
case YES:
want = 1;
break;
case NO:
want = 0;
break;
case MAYBE:
want = seen;
if (seen)
radius_sends_message_authenticator[num] = YES;
else
radius_sends_message_authenticator[num] = NO;
break;
}
}
if (want && !seen)
{
LOG(1, 0, 0, "Missing MessageAuthenticator in Access reply\n");
return;
}
}
// run post-auth plugin
struct param_post_auth packet = {
&tunnel[t],