SGSN: move cipher application to separate function
Split out generation and application of GEA gamma into separate function which can be used for both encryption and decryption. Change-Id: I442f2ead57e40d9bcd24e7f1b261041371595360 Related: OS#1582
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@ -347,6 +347,40 @@ static int gprs_llc_tx_xid(struct gprs_llc_lle *lle, struct msgb *msg,
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return gprs_llc_tx_u(msg, lle->sapi, command, GPRS_LLC_U_XID, 1);
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}
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/* encrypt information field + FCS, if needed! */
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static int apply_gea(struct gprs_llc_lle *lle, uint16_t crypt_len, uint16_t nu,
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uint32_t oc, uint8_t sapi, uint8_t *fcs, uint8_t *data)
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{
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uint8_t cipher_out[GSM0464_CIPH_MAX_BLOCK];
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if (lle->llme->algo == GPRS_ALGO_GEA0)
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return -EINVAL;
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/* Compute the 'Input' Paraemeter */
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uint32_t iv = gprs_cipher_gen_input_ui(lle->llme->iov_ui, sapi,
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nu, oc);
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/* Compute gamma that we need to XOR with the data */
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int r = gprs_cipher_run(cipher_out, crypt_len, lle->llme->algo,
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lle->llme->kc, iv,
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fcs ? GPRS_CIPH_SGSN2MS : GPRS_CIPH_MS2SGSN);
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if (r < 0) {
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LOGP(DLLC, LOGL_ERROR, "Error producing %s gamma for UI "
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"frame: %d\n", get_value_string(gprs_cipher_names,
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lle->llme->algo), r);
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return -ENOMSG;
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}
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if (fcs) {
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data += 3;
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}
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/* XOR the cipher output with the data */
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for (r = 0; r < crypt_len; r++)
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*(data + r) ^= cipher_out[r];
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return 0;
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}
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/* Transmit a UI frame over the given SAPI:
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'encryptable' indicates whether particular message can be encrypted according
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to 3GPP TS 24.008 § 4.7.1.2
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@ -412,31 +446,13 @@ int gprs_llc_tx_ui(struct msgb *msg, uint8_t sapi, int command,
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fcs[1] = (fcs_calc >> 8) & 0xff;
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fcs[2] = (fcs_calc >> 16) & 0xff;
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/* encrypt information field + FCS, if needed! */
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if (lle->llme->algo != GPRS_ALGO_GEA0 && encryptable) {
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uint32_t iov_ui = 0; /* FIXME: randomly select for TLLI */
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uint16_t crypt_len = (fcs + 3) - (llch + 3);
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uint8_t cipher_out[GSM0464_CIPH_MAX_BLOCK];
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uint32_t iv;
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int rc, i;
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uint8_t *kc = lle->llme->kc;
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/* Compute the 'Input' Paraemeter */
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iv = gprs_cipher_gen_input_ui(iov_ui, sapi, nu, oc);
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/* Compute the keystream that we need to XOR with the data */
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rc = gprs_cipher_run(cipher_out, crypt_len, lle->llme->algo,
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kc, iv, GPRS_CIPH_SGSN2MS);
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int rc = apply_gea(lle, fcs - llch, nu, oc, sapi, fcs, llch);
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if (rc < 0) {
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LOGP(DLLC, LOGL_ERROR, "Error crypting UI frame: %d\n", rc);
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msgb_free(msg);
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return rc;
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}
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/* XOR the cipher output with the information field + FCS */
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for (i = 0; i < crypt_len; i++)
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*(llch + 3 + i) ^= cipher_out[i];
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/* Mark frame as encrypted */
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ctrl[1] |= 0x02;
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}
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@ -618,32 +634,17 @@ int gprs_llc_rcvmsg(struct msgb *msg, struct tlv_parsed *tv)
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/* decrypt information field + FCS, if needed! */
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if (llhp.is_encrypted) {
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uint32_t iov_ui = 0; /* FIXME: randomly select for TLLI */
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uint16_t crypt_len = llhp.data_len + 3;
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uint8_t cipher_out[GSM0464_CIPH_MAX_BLOCK];
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uint32_t iv;
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uint8_t *kc = lle->llme->kc;
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int rc, i;
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if (lle->llme->algo == GPRS_ALGO_GEA0) {
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if (lle->llme->algo != GPRS_ALGO_GEA0) {
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rc = apply_gea(lle, llhp.data_len + 3, llhp.seq_tx,
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lle->oc_ui_recv, lle->sapi, NULL,
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llhp.data);
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if (rc < 0)
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return rc;
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} else {
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LOGP(DLLC, LOGL_NOTICE, "encrypted frame for LLC that "
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"has no KC/Algo! Dropping.\n");
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return 0;
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}
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iv = gprs_cipher_gen_input_ui(iov_ui, lle->sapi, llhp.seq_tx,
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lle->oc_ui_recv);
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rc = gprs_cipher_run(cipher_out, crypt_len, lle->llme->algo,
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kc, iv, GPRS_CIPH_MS2SGSN);
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if (rc < 0) {
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LOGP(DLLC, LOGL_ERROR, "Error decrypting frame: %d\n",
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rc);
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return rc;
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}
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/* XOR the cipher output with the information field + FCS */
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for (i = 0; i < crypt_len; i++)
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*(llhp.data + i) ^= cipher_out[i];
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} else {
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if (lle->llme->algo != GPRS_ALGO_GEA0 &&
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lle->llme->cksn != GSM_KEY_SEQ_INVAL)
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