| James Kuszmaul | 82f6c04 | 2021-01-17 11:30:16 -0800 | [diff] [blame^] | 1 | /** |
| 2 | * @file srtp/misc.c SRTP functions |
| 3 | * |
| 4 | * Copyright (C) 2010 Creytiv.com |
| 5 | */ |
| 6 | #include <string.h> |
| 7 | #include <re_types.h> |
| 8 | #include <re_mem.h> |
| 9 | #include <re_mbuf.h> |
| 10 | #include <re_list.h> |
| 11 | #include <re_aes.h> |
| 12 | #include <re_sa.h> |
| 13 | #include <re_srtp.h> |
| 14 | #include "srtp.h" |
| 15 | |
| 16 | |
| 17 | /* |
| 18 | * Appendix A: Pseudocode for Index Determination |
| 19 | * |
| 20 | * In the following, signed arithmetic is assumed. |
| 21 | */ |
| 22 | uint64_t srtp_get_index(uint32_t roc, uint16_t s_l, uint16_t seq) |
| 23 | { |
| 24 | int v; |
| 25 | |
| 26 | if (s_l < 32768) { |
| 27 | |
| 28 | if ((int)seq - (int)s_l > 32768) |
| 29 | v = (roc-1) & 0xffffffffu; |
| 30 | else |
| 31 | v = roc; |
| 32 | } |
| 33 | else { |
| 34 | if ((int)s_l - 32768 > seq) |
| 35 | v = (roc+1) & 0xffffffffu; |
| 36 | else |
| 37 | v = roc; |
| 38 | } |
| 39 | |
| 40 | return seq + v*65536; |
| 41 | } |
| 42 | |
| 43 | |
| 44 | int srtp_derive(uint8_t *out, size_t out_len, uint8_t label, |
| 45 | const uint8_t *master_key, size_t key_bytes, |
| 46 | const uint8_t *master_salt, size_t salt_bytes) |
| 47 | { |
| 48 | uint8_t x[AES_BLOCK_SIZE] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; |
| 49 | static const uint8_t null[AES_BLOCK_SIZE * 2]; |
| 50 | struct aes *aes; |
| 51 | int err; |
| 52 | |
| 53 | if (!out || !master_key || !master_salt) |
| 54 | return EINVAL; |
| 55 | |
| 56 | if (out_len > sizeof(null) || salt_bytes > sizeof(x)) |
| 57 | return EINVAL; |
| 58 | |
| 59 | memcpy(x, master_salt, salt_bytes); |
| 60 | x[7] ^= label; |
| 61 | |
| 62 | /* NOTE: Counter Mode is used for both CTR and GCM */ |
| 63 | err = aes_alloc(&aes, AES_MODE_CTR, master_key, key_bytes*8, x); |
| 64 | if (err) |
| 65 | return err; |
| 66 | |
| 67 | err = aes_encr(aes, out, null, out_len); |
| 68 | |
| 69 | mem_deref(aes); |
| 70 | |
| 71 | return err; |
| 72 | |
| 73 | } |
| 74 | |
| 75 | |
| 76 | void srtp_iv_calc(union vect128 *iv, const union vect128 *k_s, |
| 77 | uint32_t ssrc, uint64_t ix) |
| 78 | { |
| 79 | if (!iv || !k_s) |
| 80 | return; |
| 81 | |
| 82 | iv->u32[0] = k_s->u32[0]; |
| 83 | iv->u32[1] = k_s->u32[1] ^ htonl(ssrc); |
| 84 | iv->u32[2] = k_s->u32[2] ^ htonl((uint32_t)(ix>>16)); |
| 85 | iv->u16[6] = k_s->u16[6] ^ htons((uint16_t)ix); |
| 86 | iv->u16[7] = 0; |
| 87 | } |
| 88 | |
| 89 | |
| 90 | /* |
| 91 | * NOTE: The IV for AES-GCM is 12 bytes |
| 92 | */ |
| 93 | void srtp_iv_calc_gcm(union vect128 *iv, const union vect128 *k_s, |
| 94 | uint32_t ssrc, uint64_t ix) |
| 95 | { |
| 96 | if (!iv || !k_s) |
| 97 | return; |
| 98 | |
| 99 | iv->u16[0] = k_s->u16[0]; |
| 100 | iv->u16[1] = k_s->u16[1] ^ htons(ssrc >> 16); |
| 101 | iv->u16[2] = k_s->u16[2] ^ htons(ssrc & 0xffff); |
| 102 | iv->u16[3] = k_s->u16[3] ^ htons((ix >> 32) & 0xffff); |
| 103 | iv->u16[4] = k_s->u16[4] ^ htons((ix >> 16) & 0xffff); |
| 104 | iv->u16[5] = k_s->u16[5] ^ htons(ix & 0xffff); |
| 105 | } |
| 106 | |
| 107 | |
| 108 | const char *srtp_suite_name(enum srtp_suite suite) |
| 109 | { |
| 110 | switch (suite) { |
| 111 | |
| 112 | case SRTP_AES_CM_128_HMAC_SHA1_32: return "AES_CM_128_HMAC_SHA1_32"; |
| 113 | case SRTP_AES_CM_128_HMAC_SHA1_80: return "AES_CM_128_HMAC_SHA1_80"; |
| 114 | case SRTP_AES_256_CM_HMAC_SHA1_32: return "AES_256_CM_HMAC_SHA1_32"; |
| 115 | case SRTP_AES_256_CM_HMAC_SHA1_80: return "AES_256_CM_HMAC_SHA1_80"; |
| 116 | case SRTP_AES_128_GCM: return "AEAD_AES_128_GCM"; |
| 117 | case SRTP_AES_256_GCM: return "AEAD_AES_256_GCM"; |
| 118 | default: return "?"; |
| 119 | } |
| 120 | } |