SGSN: fix FCS calculation for encrypted frames
Change-Id: I352bc9db0c17fff773788831c4389ec0a5a30af8
Related: OS#1582
diff --git a/openbsc/src/gprs/gprs_llc.c b/openbsc/src/gprs/gprs_llc.c
index 23fd2e3..7724ebb 100644
--- a/openbsc/src/gprs/gprs_llc.c
+++ b/openbsc/src/gprs/gprs_llc.c
@@ -357,7 +357,7 @@
return -EINVAL;
/* Compute the 'Input' Paraemeter */
- uint32_t iv = gprs_cipher_gen_input_ui(lle->llme->iov_ui, sapi,
+ uint32_t fcs_calc, iv = gprs_cipher_gen_input_ui(lle->llme->iov_ui, sapi,
nu, oc);
/* Compute gamma that we need to XOR with the data */
int r = gprs_cipher_run(cipher_out, crypt_len, lle->llme->algo,
@@ -371,6 +371,12 @@
}
if (fcs) {
+ /* Mark frame as encrypted and update FCS */
+ data[2] |= 0x02;
+ fcs_calc = gprs_llc_fcs(data, fcs - data);
+ fcs[0] = fcs_calc & 0xff;
+ fcs[1] = (fcs_calc >> 8) & 0xff;
+ fcs[2] = (fcs_calc >> 16) & 0xff;
data += 3;
}
@@ -452,9 +458,6 @@
msgb_free(msg);
return rc;
}
-
- /* Mark frame as encrypted */
- ctrl[1] |= 0x02;
}
/* Identifiers passed down: (BVCI, NSEI) */
@@ -640,6 +643,9 @@
llhp.data);
if (rc < 0)
return rc;
+ llhp.fcs = *(llhp.data + llhp.data_len);
+ llhp.fcs |= *(llhp.data + llhp.data_len + 1) << 8;
+ llhp.fcs |= *(llhp.data + llhp.data_len + 2) << 16;
} else {
LOGP(DLLC, LOGL_NOTICE, "encrypted frame for LLC that "
"has no KC/Algo! Dropping.\n");