diff options
Diffstat (limited to 'src/gsm')
| -rw-r--r-- | src/gsm/a5.c | 71 |
1 files changed, 68 insertions, 3 deletions
diff --git a/src/gsm/a5.c b/src/gsm/a5.c index 10a063e2..d0c7c5f5 100644 --- a/src/gsm/a5.c +++ b/src/gsm/a5.c @@ -36,23 +36,80 @@ #include <errno.h> #include <string.h> +#include <stdbool.h> #include <osmocom/gsm/a5.h> +#include <osmocom/gsm/kasumi.h> /* Somme OS (like Nuttx) don't have ENOTSUP */ #ifndef ENOTSUP #define ENOTSUP EINVAL #endif +/* ------------------------------------------------------------------------ */ +/* A5/3&4 */ +/* ------------------------------------------------------------------------ */ + +/*! \brief Generate a GSM A5/4 cipher stream + * \param[in] key 16 byte array for the key (as received from the SIM) + * \param[in] fn Frame number + * \param[out] dl Pointer to array of ubits to return Downlink cipher stream + * \param[out] ul Pointer to array of ubits to return Uplink cipher stream + * \param[in] fn_correct true if fn is a real GSM frame number and thus requires internal conversion + * + * Either (or both) of dl/ul should be NULL if not needed. + * + * Implementation based on specifications from 3GPP TS 55.216, 3GPP TR 55.919 and ETSI TS 135 202 + * with slight simplifications (CE hardcoded to 0). + */ +void +_a5_4(const uint8_t *ck, uint32_t fn, ubit_t *dl, ubit_t *ul, bool fn_correct) +{ + uint8_t i, gamma[32], uplink[15]; + uint32_t fn_count = (fn_correct) ? osmo_a5_fn_count(fn) : fn; + + if (ul) { + _kasumi_kgcore(0xF, 0, fn_count, 0, ck, gamma, 228); + for(i = 0; i < 15; i++) uplink[i] = (gamma[i + 14] << 2) + (gamma[i + 15] >> 6); + osmo_pbit2ubit(ul, uplink, 114); + } + if (dl) { + _kasumi_kgcore(0xF, 0, fn_count, 0, ck, gamma, 114); + osmo_pbit2ubit(dl, gamma, 114); + } +} + +/*! \brief Generate a GSM A5/3 cipher stream + * \param[in] key 8 byte array for the key (as received from the SIM) + * \param[in] fn Frame number + * \param[out] dl Pointer to array of ubits to return Downlink cipher stream + * \param[out] ul Pointer to array of ubits to return Uplink cipher stream + * \param[in] fn_correct true if fn is a real GSM frame number and thus requires internal conversion + * + * Either (or both) of dl/ul should be NULL if not needed. + * + * Implementation based on specifications from 3GPP TS 55.216, 3GPP TR 55.919 and ETSI TS 135 202 + * with slight simplifications (CE hardcoded to 0). + */ +void +_a5_3(const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul, bool fn_correct) +{ + uint8_t ck[16]; + memcpy(ck, key, 8); + memcpy(ck + 8, key, 8); + /* internal function require 128 bit key so we expand by concatenating supplied 64 bit key */ + _a5_4(ck, fn, dl, ul, fn_correct); +} + /*! \brief Main method to generate a A5/x cipher stream * \param[in] n Which A5/x method to use - * \param[in] key 8 byte array for the key (as received from the SIM) + * \param[in] key 8 or 16 (for a5/4) byte array for the key (as received from the SIM) * \param[in] fn Frame number * \param[out] dl Pointer to array of ubits to return Downlink cipher stream * \param[out] ul Pointer to array of ubits to return Uplink cipher stream * \returns 0 for success, -ENOTSUP for invalid cipher selection. * - * Currently A5/[0-2] are supported. + * Currently A5/[0-4] are supported. * Either (or both) of dl/ul can be NULL if not needed. */ int @@ -75,8 +132,16 @@ osmo_a5(int n, const uint8_t *key, uint32_t fn, ubit_t *dl, ubit_t *ul) osmo_a5_2(key, fn, dl, ul); break; + case 3: + _a5_3(key, fn, dl, ul, true); + break; + + case 4: + _a5_4(key, fn, dl, ul, true); + break; + default: - /* a5/[3..7] not supported here/yet */ + /* a5/[5..7] not supported here/yet */ return -ENOTSUP; } |