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pair_homekit.c
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pair_homekit.c
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/*
* Adaption of ap2-sender by ViktoriiaKh:
* <https://github.com/ViktoriiaKh/ap2-sender>
*
* To test, it is useful to try with this receiver:
* <https://github.com/ckdo/airplay2-receiver>
*
* The Secure Remote Password 6a implementation is adapted from:
* - Tom Cocagne
* <https://github.com/cocagne/csrp>
*
* TLV helpers are adapted from ESP homekit:
* <https://github.com/maximkulkin/esp-homekit>
*
* The MIT License (MIT)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is furnished to do
* so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <assert.h>
#include <sodium.h>
#include "pair-internal.h"
#include "pair-tlv.h"
/* ----------------------------- DEFINES ETC ------------------------------- */
#define USERNAME "Pair-Setup"
#define AUTHTAG_LENGTH 16
#define NONCE_LENGTH 12 // 96 bits according to chacha poly1305
#define REQUEST_BUFSIZE 4096
#define ENCRYPTED_LEN_MAX 0x400
// #define DEBUG_SHORT_A 1
enum pair_keys
{
PAIR_SETUP_MSG01 = 0,
PAIR_SETUP_MSG02,
PAIR_SETUP_MSG03,
PAIR_SETUP_MSG04,
PAIR_SETUP_MSG05,
PAIR_SETUP_MSG06,
PAIR_SETUP_CONTROLLER_SIGN,
PAIR_SETUP_ACCESSORY_SIGN,
PAIR_VERIFY_MSG01,
PAIR_VERIFY_MSG02,
PAIR_VERIFY_MSG03,
PAIR_VERIFY_MSG04,
PAIR_CONTROL_WRITE,
PAIR_CONTROL_READ,
PAIR_EVENTS_WRITE,
PAIR_EVENTS_READ,
};
struct pair_keys_map
{
uint8_t state;
const char *salt;
const char *info;
const char nonce[8];
};
static struct pair_keys_map pair_keys_map[] =
{
// Used for /pair-setup
{ 0x01, NULL, NULL, "" },
{ 0x02, NULL, NULL, "" },
{ 0x03, NULL, NULL, "" },
{ 0x04, NULL, NULL, "" },
{ 0x05, "Pair-Setup-Encrypt-Salt", "Pair-Setup-Encrypt-Info", "PS-Msg05" },
{ 0x06, "Pair-Setup-Encrypt-Salt", "Pair-Setup-Encrypt-Info", "PS-Msg06" },
{ 0, "Pair-Setup-Controller-Sign-Salt", "Pair-Setup-Controller-Sign-Info", "" },
{ 0, "Pair-Setup-Accessory-Sign-Salt", "Pair-Setup-Accessory-Sign-Info", "" },
// Used for /pair-verify
{ 0x01, NULL, NULL, "" },
{ 0x02, "Pair-Verify-Encrypt-Salt", "Pair-Verify-Encrypt-Info", "PV-Msg02" },
{ 0x03, "Pair-Verify-Encrypt-Salt", "Pair-Verify-Encrypt-Info", "PV-Msg03" },
{ 0x04, NULL, NULL, "" },
// Encryption/decryption of control channel
{ 0, "Control-Salt", "Control-Write-Encryption-Key", "" },
{ 0, "Control-Salt", "Control-Read-Encryption-Key", "" },
// Encryption/decryption of event channel
{ 0, "Events-Salt", "Events-Write-Encryption-Key", "" },
{ 0, "Events-Salt", "Events-Read-Encryption-Key", "" },
};
enum pair_method {
PairingMethodPairSetup = 0x00,
PairingMethodPairSetupWithAuth = 0x01,
PairingMethodPairVerify = 0x02,
PairingMethodAddPairing = 0x03,
PairingMethodRemovePairing = 0x04,
PairingMethodListPairings = 0x05
};
enum pair_flags {
PairingFlagsTransient = 0x10,
};
// Forwards
const struct pair_definition pair_client_homekit_normal;
const struct pair_definition pair_client_homekit_transient;
const struct pair_definition pair_server_homekit;
/* ---------------------------------- SRP ----------------------------------- */
typedef enum
{
SRP_NG_2048,
SRP_NG_3072,
SRP_NG_CUSTOM
} SRP_NGType;
typedef struct
{
int N_len;
bnum N;
bnum g;
} NGConstant;
struct SRPUser
{
enum hash_alg alg;
NGConstant *ng;
bnum a;
bnum A;
bnum S;
const unsigned char *bytes_A;
int authenticated;
char *username;
unsigned char *password;
int password_len;
unsigned char M [SHA512_DIGEST_LENGTH];
unsigned char H_AMK [SHA512_DIGEST_LENGTH];
unsigned char session_key [SHA512_DIGEST_LENGTH];
int session_key_len;
};
struct SRPVerifier
{
enum hash_alg alg;
NGConstant *ng;
const unsigned char *bytes_B;
int authenticated;
char *username;
unsigned char M [SHA512_DIGEST_LENGTH];
unsigned char H_AMK [SHA512_DIGEST_LENGTH];
unsigned char session_key [SHA512_DIGEST_LENGTH];
int session_key_len;
};
struct NGHex
{
int N_len;
const char *n_hex;
const char *g_hex;
};
// These constants here were pulled from Appendix A of RFC 5054
static struct NGHex global_Ng_constants[] =
{
{ /* 2048 */
256,
"AC6BDB41324A9A9BF166DE5E1389582FAF72B6651987EE07FC3192943DB56050A37329CBB4"
"A099ED8193E0757767A13DD52312AB4B03310DCD7F48A9DA04FD50E8083969EDB767B0CF60"
"95179A163AB3661A05FBD5FAAAE82918A9962F0B93B855F97993EC975EEAA80D740ADBF4FF"
"747359D041D5C33EA71D281E446B14773BCA97B43A23FB801676BD207A436C6481F1D2B907"
"8717461A5B9D32E688F87748544523B524B0D57D5EA77A2775D2ECFA032CFBDBF52FB37861"
"60279004E57AE6AF874E7303CE53299CCC041C7BC308D82A5698F3A8D0C38271AE35F8E9DB"
"FBB694B5C803D89F7AE435DE236D525F54759B65E372FCD68EF20FA7111F9E4AFF73",
"2"
},
{ /* 3072 */
384,
"FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B"
"139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485"
"B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1F"
"E649286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23"
"DCA3AD961C62F356208552BB9ED529077096966D670C354E4ABC9804F1746C08CA18217C32"
"905E462E36CE3BE39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9DE2BCBF69558"
"17183995497CEA956AE515D2261898FA051015728E5A8AAAC42DAD33170D04507A33A85521"
"ABDF1CBA64ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7ABF5AE8CDB0933D7"
"1E8C94E04A25619DCEE3D2261AD2EE6BF12FFA06D98A0864D87602733EC86A64521F2B1817"
"7B200CBBE117577A615D6C770988C0BAD946E208E24FA074E5AB3143DB5BFCE0FD108E4B82"
"D120A93AD2CAFFFFFFFFFFFFFFFF",
"5"
},
{0} /* null sentinel */
};
static NGConstant *
new_ng(SRP_NGType ng_type, const char *n_hex, const char *g_hex)
{
NGConstant *ng = calloc(1, sizeof(NGConstant));
if ( ng_type != SRP_NG_CUSTOM )
{
n_hex = global_Ng_constants[ng_type].n_hex;
g_hex = global_Ng_constants[ng_type].g_hex;
}
bnum_hex2bn(ng->N, n_hex);
bnum_hex2bn(ng->g, g_hex);
ng->N_len = bnum_num_bytes(ng->N);
assert(ng_type == SRP_NG_CUSTOM || ng->N_len == global_Ng_constants[ng_type].N_len);
return ng;
}
static void
free_ng(NGConstant * ng)
{
if (!ng)
return;
bnum_free(ng->N);
bnum_free(ng->g);
free(ng);
}
static int
N_len(SRP_NGType ng_type)
{
if (ng_type == SRP_NG_CUSTOM)
return -1;
return global_Ng_constants[ng_type].N_len;
}
static bnum
calculate_x(enum hash_alg alg, const bnum salt, const char *username, const unsigned char *password, int password_len)
{
unsigned char ucp_hash[SHA512_DIGEST_LENGTH];
HashCTX ctx;
hash_init( alg, &ctx );
hash_update( alg, &ctx, username, strlen(username) );
hash_update( alg, &ctx, ":", 1 );
hash_update( alg, &ctx, password, password_len );
hash_final( alg, &ctx, ucp_hash );
return H_ns( alg, salt, ucp_hash, hash_length(alg) );
}
static void
calculate_M(enum hash_alg alg, NGConstant *ng, unsigned char *dest, const char *I, const bnum s,
const bnum A, const bnum B, const unsigned char *K, int K_len)
{
unsigned char H_N[ SHA512_DIGEST_LENGTH ];
unsigned char H_g[ SHA512_DIGEST_LENGTH ];
unsigned char H_I[ SHA512_DIGEST_LENGTH ];
unsigned char H_xor[ SHA512_DIGEST_LENGTH ];
HashCTX ctx;
int i = 0;
int hash_len = hash_length(alg);
hash_num( alg, ng->N, H_N );
hash_num( alg, ng->g, H_g );
hash(alg, (const unsigned char *)I, strlen(I), H_I);
for (i=0; i < hash_len; i++ )
H_xor[i] = H_N[i] ^ H_g[i];
hash_init( alg, &ctx );
hash_update( alg, &ctx, H_xor, hash_len );
hash_update( alg, &ctx, H_I, hash_len );
update_hash_n( alg, &ctx, s );
update_hash_n( alg, &ctx, A );
update_hash_n( alg, &ctx, B );
hash_update( alg, &ctx, K, K_len );
hash_final( alg, &ctx, dest );
}
static void
calculate_H_AMK(enum hash_alg alg, unsigned char *dest, const bnum A, const unsigned char * M, const unsigned char * K, int K_len)
{
HashCTX ctx;
hash_init( alg, &ctx );
update_hash_n( alg, &ctx, A );
hash_update( alg, &ctx, M, hash_length(alg) );
hash_update( alg, &ctx, K, K_len );
hash_final( alg, &ctx, dest );
}
/* ----------------------- SRP for the client side -------------------------- */
static struct SRPUser *
srp_user_new(enum hash_alg alg, SRP_NGType ng_type, const char *username,
const unsigned char *bytes_password, int len_password,
const char *n_hex, const char *g_hex)
{
struct SRPUser *usr = calloc(1, sizeof(struct SRPUser));
int ulen = strlen(username) + 1;
if (!usr)
goto err_exit;
usr->alg = alg;
usr->ng = new_ng( ng_type, n_hex, g_hex );
bnum_new(usr->a);
bnum_new(usr->A);
bnum_new(usr->S);
if (!usr->ng || !usr->a || !usr->A || !usr->S)
goto err_exit;
usr->username = malloc(ulen);
usr->password = malloc(len_password);
usr->password_len = len_password;
if (!usr->username || !usr->password)
goto err_exit;
memcpy(usr->username, username, ulen);
memcpy(usr->password, bytes_password, len_password);
usr->authenticated = 0;
usr->bytes_A = 0;
return usr;
err_exit:
if (!usr)
return NULL;
bnum_free(usr->a);
bnum_free(usr->A);
bnum_free(usr->S);
free(usr->username);
if (usr->password)
{
memset(usr->password, 0, usr->password_len);
free(usr->password);
}
free(usr);
return NULL;
}
static void
srp_user_free(struct SRPUser *usr)
{
if(!usr)
return;
bnum_free(usr->a);
bnum_free(usr->A);
bnum_free(usr->S);
free_ng(usr->ng);
memset(usr->password, 0, usr->password_len);
free(usr->username);
free(usr->password);
free((char *)usr->bytes_A);
memset(usr, 0, sizeof(*usr));
free(usr);
}
static int
srp_user_is_authenticated(struct SRPUser *usr)
{
return usr->authenticated;
}
static const unsigned char *
srp_user_get_session_key(struct SRPUser *usr, int *key_length)
{
if (key_length)
*key_length = usr->session_key_len;
return usr->session_key;
}
#ifdef DEBUG_SHORT_A
// This value of "a" will yield a 383 byte A
static uint8_t short_a[] = {
0xef, 0xb5, 0x93, 0xf5, 0x03, 0x97, 0x69, 0x8e, 0x15, 0xed, 0xee, 0x5b, 0xf2, 0xf9, 0x23, 0x6c,
0xf0, 0x59, 0x6c, 0xe2, 0x77, 0xf2, 0x14, 0x16, 0xac, 0x99, 0xfa, 0x31, 0xae, 0x2b, 0xd3, 0x41,
};
#endif
/* Output: username, bytes_A, len_A */
static void
srp_user_start_authentication(struct SRPUser *usr, const char **username,
const unsigned char **bytes_A, int *len_A)
{
// BN_hex2bn(&(usr->a), "D929DFB605687233C9E9030C2280156D03BDB9FDCF3CCE3BC27D9CCFCB5FF6A1");
bnum_random(usr->a, 256);
#ifdef DEBUG_SHORT_A
bnum_bin2bn(usr->a, short_a, sizeof(short_a));
#endif
#ifdef DEBUG_PAIR
bnum_dump("Random value of usr->a:\n", usr->a);
#endif
bnum_modexp(usr->A, usr->ng->g, usr->a, usr->ng->N);
*len_A = bnum_num_bytes(usr->A);
*bytes_A = malloc(*len_A);
if (!*bytes_A)
{
*len_A = 0;
*bytes_A = 0;
*username = 0;
return;
}
bnum_bn2bin(usr->A, (unsigned char *) *bytes_A, *len_A);
usr->bytes_A = *bytes_A;
*username = usr->username;
}
/* Output: bytes_M. Buffer length is SHA512_DIGEST_LENGTH */
static void
srp_user_process_challenge(struct SRPUser *usr, const unsigned char *bytes_s, int len_s,
const unsigned char *bytes_B, int len_B,
const unsigned char **bytes_M, int *len_M )
{
bnum s, B, k, v;
bnum tmp1, tmp2, tmp3;
bnum u, x;
*len_M = 0;
*bytes_M = NULL;
bnum_bin2bn(s, bytes_s, len_s);
bnum_bin2bn(B, bytes_B, len_B);
k = H_nn_pad(usr->alg, usr->ng->N, usr->ng->g, usr->ng->N_len);
bnum_new(v);
bnum_new(tmp1);
bnum_new(tmp2);
bnum_new(tmp3);
if (!s || !B || !k || !v || !tmp1 || !tmp2 || !tmp3)
goto cleanup1;
u = H_nn_pad(usr->alg, usr->A, B, usr->ng->N_len);
x = calculate_x(usr->alg, s, usr->username, usr->password, usr->password_len);
if (!u || !x)
goto cleanup2;
// SRP-6a safety check
if (!bnum_is_zero(B) && !bnum_is_zero(u))
{
bnum_modexp(v, usr->ng->g, x, usr->ng->N);
// S = (B - k*(g^x)) ^ (a + ux)
bnum_mul(tmp1, u, x);
bnum_add(tmp2, usr->a, tmp1); // tmp2 = (a + ux)
bnum_modexp(tmp1, usr->ng->g, x, usr->ng->N);
bnum_mul(tmp3, k, tmp1); // tmp3 = k*(g^x)
bnum_sub(tmp1, B, tmp3); // tmp1 = (B - K*(g^x))
bnum_modexp(usr->S, tmp1, tmp2, usr->ng->N);
hash_num(usr->alg, usr->S, usr->session_key);
usr->session_key_len = hash_length(usr->alg);
calculate_M(usr->alg, usr->ng, usr->M, usr->username, s, usr->A, B, usr->session_key, usr->session_key_len);
calculate_H_AMK(usr->alg, usr->H_AMK, usr->A, usr->M, usr->session_key, usr->session_key_len);
*bytes_M = usr->M;
*len_M = hash_length(usr->alg);
}
cleanup2:
bnum_free(x);
bnum_free(u);
cleanup1:
bnum_free(tmp3);
bnum_free(tmp2);
bnum_free(tmp1);
bnum_free(v);
bnum_free(k);
bnum_free(B);
bnum_free(s);
}
static void
srp_user_verify_session(struct SRPUser *usr, const unsigned char *bytes_HAMK)
{
if (memcmp(usr->H_AMK, bytes_HAMK, hash_length(usr->alg)) == 0)
usr->authenticated = 1;
}
/* ----------------------- SRP for the server side -------------------------- */
static int
srp_create_salted_verification_key(enum hash_alg alg,
SRP_NGType ng_type, const char *username,
const unsigned char *password, int len_password,
unsigned char **bytes_s, int *len_s,
unsigned char **bytes_v, int *len_v,
const char *n_hex, const char *g_hex )
{
bnum s, v, x;
NGConstant *ng;
bnum_new(s);
bnum_new(v);
x = NULL;
ng = new_ng(ng_type, n_hex, g_hex);
*bytes_s = NULL;
*bytes_v = NULL;
if (!s || !v || !ng)
goto error;
bnum_random(s, 128); // MODIFIED from csrp's BN_rand(s, 32, -1, 0)
#ifdef DEBUG_PAIR
bnum_dump("Random value of s:\n", s);
#endif
x = calculate_x(alg, s, username, password, len_password);
if (!x)
goto error;
bnum_modexp(v, ng->g, x, ng->N);
*len_s = bnum_num_bytes(s);
*len_v = bnum_num_bytes(v);
*bytes_s = malloc(*len_s);
*bytes_v = malloc(*len_v);
if (!(*bytes_s) || !(*bytes_v))
goto error;
bnum_bn2bin(s, (unsigned char *) *bytes_s, *len_s);
bnum_bn2bin(v, (unsigned char *) *bytes_v, *len_v);
free_ng(ng);
bnum_free(s);
bnum_free(v);
bnum_free(x);
return 0;
error:
free(*bytes_s);
free(*bytes_v);
free_ng(ng);
bnum_free(s);
bnum_free(v);
bnum_free(x);
return -1;
}
static int
srp_verifier_start_authentication(enum hash_alg alg, SRP_NGType ng_type,
const unsigned char *bytes_v, int len_v,
unsigned char **bytes_b, int *len_b,
unsigned char **bytes_B, int *len_B,
const char *n_hex, const char *g_hex)
{
bnum v, k, b, B, tmp1, tmp2;
NGConstant *ng;
v = NULL;
k = NULL;
bnum_new(b);
bnum_new(B);
bnum_new(tmp1);
bnum_new(tmp2);
*len_b = 0;
*bytes_b = NULL;
*len_B = 0;
*bytes_B = NULL;
ng = new_ng(ng_type, n_hex, g_hex);
if (!b || !B || !tmp1 || !tmp2 || !ng)
goto error;
bnum_bin2bn(v, bytes_v, len_v);
bnum_random(b, 256); // MODIFIED from BN_rand(b, 256, -1, 0)
#ifdef DEBUG_PAIR
bnum_dump("Random value of b:\n", b);
#endif
k = H_nn_pad(alg, ng->N, ng->g, ng->N_len); // MODIFIED from H_nn(alg, ng->N, ng->g)
if (!k)
goto error;
// B = kv + g^b
bnum_mul(tmp1, k, v);
bnum_modexp(tmp2, ng->g, b, ng->N);
bnum_modadd(B, tmp1, tmp2, ng->N);
*len_B = bnum_num_bytes(B);
*len_b = bnum_num_bytes(b);
*bytes_B = malloc(*len_B);
*bytes_b = malloc(*len_b);
if (!(*bytes_B) || !(*bytes_b))
goto error;
bnum_bn2bin(B, (unsigned char *) *bytes_B, *len_B);
bnum_bn2bin(b, (unsigned char *) *bytes_b, *len_b);
bnum_free(b);
bnum_free(B);
bnum_free(v);
bnum_free(k);
bnum_free(tmp1);
bnum_free(tmp2);
free_ng(ng);
return 0;
error:
free(*bytes_B);
free(*bytes_b);
bnum_free(b);
bnum_free(B);
bnum_free(v);
bnum_free(k);
bnum_free(tmp1);
bnum_free(tmp2);
free_ng(ng);
return -1;
}
static void
srp_verifier_free(struct SRPVerifier *ver)
{
if (!ver)
return;
free_ng(ver->ng);
free(ver->username);
memset(ver, 0, sizeof(struct SRPVerifier));
free(ver);
}
static struct SRPVerifier *
srp_verifier_new(enum hash_alg alg, SRP_NGType ng_type, const char *username,
const unsigned char *bytes_s, int len_s,
const unsigned char *bytes_v, int len_v,
const unsigned char *bytes_A, int len_A,
const unsigned char *bytes_b, int len_b,
const unsigned char *bytes_B, int len_B,
const char *n_hex, const char *g_hex )
{
struct SRPVerifier *ver = NULL;
bnum s, v, A, b, B, S, tmp1, tmp2, u, k;
NGConstant *ng;
size_t ulen;
bnum_bin2bn(s, bytes_s, len_s);
bnum_bin2bn(v, bytes_v, len_v);
bnum_bin2bn(A, bytes_A, len_A);
bnum_bin2bn(b, bytes_b, len_b);
bnum_bin2bn(B, bytes_B, len_B);
bnum_new(S);
bnum_new(tmp1);
bnum_new(tmp2);
u = NULL;
k = NULL;
ng = new_ng(ng_type, n_hex, g_hex);
if (!s || !v || !A || !B || !S || !b || !tmp1 || !tmp2 || !ng)
goto error;
ver = calloc(1, sizeof(struct SRPVerifier));
if (!ver)
goto error;
ulen = strlen(username) + 1;
ver->alg = alg;
ver->ng = ng;
ver->username = malloc(ulen);
if (!ver->username)
goto error;
memcpy(ver->username, username, ulen);
ver->authenticated = 0;
// SRP-6a safety check
bnum_mod(tmp1, A, ng->N);
if (bnum_is_zero(tmp1))
goto error;
k = H_nn_pad(alg, ng->N, ng->g, ng->N_len); // MODIFIED from H_nn(alg, ng->N, ng->g)
u = H_nn_pad(alg, A, B, ng->N_len); // MODIFIED from H_nn(alg, A, B)
// S = (A *(v^u)) ^ b
bnum_modexp(tmp1, v, u, ng->N);
bnum_mul(tmp2, A, tmp1);
bnum_modexp(S, tmp2, b, ng->N);
hash_num(alg, S, ver->session_key);
ver->session_key_len = hash_length(ver->alg);
calculate_M(alg, ng, ver->M, username, s, A, B, ver->session_key, ver->session_key_len);
calculate_H_AMK(alg, ver->H_AMK, A, ver->M, ver->session_key, ver->session_key_len);
ver->bytes_B = bytes_B;
bnum_free(s);
bnum_free(v);
bnum_free(A);
bnum_free(u);
bnum_free(k);
bnum_free(B);
bnum_free(S);
bnum_free(b);
bnum_free(tmp1);
bnum_free(tmp2);
return ver;
error:
srp_verifier_free(ver);
bnum_free(s);
bnum_free(v);
bnum_free(A);
bnum_free(u);
bnum_free(k);
bnum_free(B);
bnum_free(S);
bnum_free(b);
bnum_free(tmp1);
bnum_free(tmp2);
return NULL;
}
// user_M must be exactly SHA512_DIGEST_LENGTH bytes in size
static void
srp_verifier_verify_session(struct SRPVerifier *ver, const unsigned char *user_M, const unsigned char **bytes_HAMK)
{
if (memcmp(ver->M, user_M, hash_length(ver->alg)) == 0)
{
ver->authenticated = 1;
*bytes_HAMK = ver->H_AMK;
}
else
*bytes_HAMK = NULL;
}
static const unsigned char *
srp_verifier_get_session_key(struct SRPVerifier *ver, int *key_length)
{
if (key_length)
*key_length = hash_length(ver->alg);
return ver->session_key;
}
/* -------------------------------- HELPERS --------------------------------- */
static void
hexread(uint8_t *out, size_t out_len, const char *in)
{
char hex[] = { 0, 0, 0 };
int i;
for (i = 0; i < out_len; i++, in+=2)
{
hex[0] = in[0];
hex[1] = in[1];
out[i] = strtol(hex, NULL, 16);
}
}
static pair_tlv_values_t *
message_process(const uint8_t *data, size_t data_len, const char **errmsg)
{
pair_tlv_values_t *response;
pair_tlv_t *error;
int ret;
response = pair_tlv_new();
if (!response)
{
*errmsg = "Out of memory\n";
return NULL;
}
ret = pair_tlv_parse(data, data_len, response);
if (ret < 0)
{
*errmsg = "Could not parse TLV\n";
goto error;
}
#ifdef DEBUG_PAIR
pair_tlv_debug(response);
#endif
error = pair_tlv_get_value(response, TLVType_Error);
if (error)
{
if (error->value[0] == TLVError_Authentication)
*errmsg = "Device returned an authentication failure";
else if (error->value[0] == TLVError_Backoff)
*errmsg = "Device told us to back off pairing attempts\n";
else if (error->value[0] == TLVError_MaxPeers)
*errmsg = "Max peers trying to connect to device\n";
else if (error->value[0] == TLVError_MaxTries)
*errmsg = "Max pairing attemps reached\n";
else if (error->value[0] == TLVError_Unavailable)
*errmsg = "Device is unuavailble at this time\n";
else
*errmsg = "Device is busy/returned unknown error\n";
goto error;
}
return response;
error:
pair_tlv_free(response);
return NULL;
}
/* Executes SHA512 RFC 5869 extract + expand, writing a derived key to okm
hkdfExtract(SHA512, salt, salt_len, ikm, ikm_len, prk);
hkdfExpand(SHA512, prk, SHA512_LEN, info, info_len, okm, okm_len);
*/
static int
hkdf_extract_expand(uint8_t *okm, size_t okm_len, const uint8_t *ikm, size_t ikm_len, enum pair_keys pair_key)
{
#ifdef CONFIG_OPENSSL
#include <openssl/kdf.h>
EVP_PKEY_CTX *pctx;
if (okm_len > SHA512_DIGEST_LENGTH)
return -1;
if (! (pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL)))
return -1;
if (EVP_PKEY_derive_init(pctx) <= 0)
goto error;
if (EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha512()) <= 0)
goto error;
if (EVP_PKEY_CTX_set1_hkdf_salt(pctx, (const unsigned char *)pair_keys_map[pair_key].salt, strlen(pair_keys_map[pair_key].salt)) <= 0)
goto error;
if (EVP_PKEY_CTX_set1_hkdf_key(pctx, ikm, ikm_len) <= 0)
goto error;
if (EVP_PKEY_CTX_add1_hkdf_info(pctx, (const unsigned char *)pair_keys_map[pair_key].info, strlen(pair_keys_map[pair_key].info)) <= 0)
goto error;
if (EVP_PKEY_derive(pctx, okm, &okm_len) <= 0)
goto error;
EVP_PKEY_CTX_free(pctx);
return 0;
error:
EVP_PKEY_CTX_free(pctx);
return -1;
#elif CONFIG_GCRYPT
uint8_t prk[SHA512_DIGEST_LENGTH];
gcry_md_hd_t hmac_handle;
if (okm_len > SHA512_DIGEST_LENGTH)
return -1; // Below calculation not valid if output is larger than hash size
if (gcry_md_open(&hmac_handle, GCRY_MD_SHA512, GCRY_MD_FLAG_HMAC) != GPG_ERR_NO_ERROR)
return -1;
if (gcry_md_setkey(hmac_handle, (const unsigned char *)pair_keys_map[pair_key].salt, strlen(pair_keys_map[pair_key].salt)) != GPG_ERR_NO_ERROR)
goto error;
gcry_md_write(hmac_handle, ikm, ikm_len);
memcpy(prk, gcry_md_read(hmac_handle, 0), sizeof(prk));
gcry_md_reset(hmac_handle);
if (gcry_md_setkey(hmac_handle, prk, sizeof(prk)) != GPG_ERR_NO_ERROR)
goto error;
gcry_md_write(hmac_handle, (const unsigned char *)pair_keys_map[pair_key].info, strlen(pair_keys_map[pair_key].info));
gcry_md_putc(hmac_handle, 1);
memcpy(okm, gcry_md_read(hmac_handle, 0), okm_len);
gcry_md_close(hmac_handle);
return 0;
error:
gcry_md_close(hmac_handle);
return -1;
#else
return -1;
#endif
}
static int
encrypt_chacha(uint8_t *cipher, const uint8_t *plain, size_t plain_len, const uint8_t *key, size_t key_len, const void *ad, size_t ad_len, uint8_t *tag, size_t tag_len, const uint8_t nonce[NONCE_LENGTH])
{
#ifdef CONFIG_OPENSSL
EVP_CIPHER_CTX *ctx;
int len;
if (! (ctx = EVP_CIPHER_CTX_new()))
return -1;
if (EVP_EncryptInit_ex(ctx, EVP_chacha20_poly1305(), NULL, key, nonce) != 1)
goto error;
if (EVP_CIPHER_CTX_set_padding(ctx, 0) != 1) // Maybe not necessary
goto error;
if (ad_len > 0 && EVP_EncryptUpdate(ctx, NULL, &len, ad, ad_len) != 1)
goto error;
if (EVP_EncryptUpdate(ctx, cipher, &len, plain, plain_len) != 1)
goto error;
assert(len == plain_len);
if (EVP_EncryptFinal_ex(ctx, NULL, &len) != 1)
goto error;
if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, tag_len, tag) != 1)
goto error;
EVP_CIPHER_CTX_free(ctx);
return 0;
error:
EVP_CIPHER_CTX_free(ctx);
return -1;
#elif CONFIG_GCRYPT
gcry_cipher_hd_t hd;
if (gcry_cipher_open(&hd, GCRY_CIPHER_CHACHA20, GCRY_CIPHER_MODE_POLY1305, 0) != GPG_ERR_NO_ERROR)
return -1;
if (gcry_cipher_setkey(hd, key, key_len) != GPG_ERR_NO_ERROR)
goto error;
if (gcry_cipher_setiv(hd, nonce, NONCE_LENGTH) != GPG_ERR_NO_ERROR)
goto error;
if (ad_len > 0 && gcry_cipher_authenticate(hd, ad, ad_len) != GPG_ERR_NO_ERROR)
goto error;
if (gcry_cipher_encrypt(hd, cipher, plain_len, plain, plain_len) != GPG_ERR_NO_ERROR)
goto error;
if (gcry_cipher_gettag(hd, tag, tag_len) != GPG_ERR_NO_ERROR)
goto error;