1: /* Copyright (c) 2012-2020 Simon Kelley
2:
3: This program is free software; you can redistribute it and/or modify
4: it under the terms of the GNU General Public License as published by
5: the Free Software Foundation; version 2 dated June, 1991, or
6: (at your option) version 3 dated 29 June, 2007.
7:
8: This program is distributed in the hope that it will be useful,
9: but WITHOUT ANY WARRANTY; without even the implied warranty of
10: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11: GNU General Public License for more details.
12:
13: You should have received a copy of the GNU General Public License
14: along with this program. If not, see <http://www.gnu.org/licenses/>.
15: */
16:
17:
18: /* Hash the question section. This is used to safely detect query
19: retransmission and to detect answers to questions we didn't ask, which
20: might be poisoning attacks. Note that we decode the name rather
21: than CRC the raw bytes, since replies might be compressed differently.
22: We ignore case in the names for the same reason.
23:
24: The hash used is SHA-256. If we're building with DNSSEC support,
25: we use the Nettle cypto library. If not, we prefer not to
26: add a dependency on Nettle, and use a stand-alone implementation.
27: */
28:
29: #include "dnsmasq.h"
30:
31: #if defined(HAVE_DNSSEC) || defined(HAVE_CRYPTOHASH)
32:
33: static const struct nettle_hash *hash;
34: static void *ctx;
35: static unsigned char *digest;
36:
37: void hash_questions_init(void)
38: {
39: if (!(hash = hash_find("sha256")))
40: die(_("Failed to create SHA-256 hash object"), NULL, EC_MISC);
41:
42: ctx = safe_malloc(hash->context_size);
43: digest = safe_malloc(hash->digest_size);
44: }
45:
46: unsigned char *hash_questions(struct dns_header *header, size_t plen, char *name)
47: {
48: int q;
49: unsigned char *p = (unsigned char *)(header+1);
50:
51: hash->init(ctx);
52:
53: for (q = ntohs(header->qdcount); q != 0; q--)
54: {
55: char *cp, c;
56:
57: if (!extract_name(header, plen, &p, name, 1, 4))
58: return NULL; /* bad packet */
59:
60: for (cp = name; (c = *cp); cp++)
61: if (c >= 'A' && c <= 'Z')
62: *cp += 'a' - 'A';
63:
64: hash->update(ctx, cp - name, (unsigned char *)name);
65: /* CRC the class and type as well */
66: hash->update(ctx, 4, p);
67:
68: p += 4;
69: if (!CHECK_LEN(header, p, plen, 0))
70: return NULL; /* bad packet */
71: }
72:
73: hash->digest(ctx, hash->digest_size, digest);
74: return digest;
75: }
76:
77: #else /* HAVE_DNSSEC || HAVE_CRYPTOHASH */
78:
79: #define SHA256_BLOCK_SIZE 32 /* SHA256 outputs a 32 byte digest */
80: typedef unsigned char BYTE; /* 8-bit byte */
81: typedef unsigned int WORD; /* 32-bit word, change to "long" for 16-bit machines */
82:
83: typedef struct {
84: BYTE data[64];
85: WORD datalen;
86: unsigned long long bitlen;
87: WORD state[8];
88: } SHA256_CTX;
89:
90: static void sha256_init(SHA256_CTX *ctx);
91: static void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len);
92: static void sha256_final(SHA256_CTX *ctx, BYTE hash[]);
93:
94: void hash_questions_init(void)
95: {
96: }
97:
98: unsigned char *hash_questions(struct dns_header *header, size_t plen, char *name)
99: {
100: int q;
101: unsigned char *p = (unsigned char *)(header+1);
102: SHA256_CTX ctx;
103: static BYTE digest[SHA256_BLOCK_SIZE];
104:
105: sha256_init(&ctx);
106:
107: for (q = ntohs(header->qdcount); q != 0; q--)
108: {
109: char *cp, c;
110:
111: if (!extract_name(header, plen, &p, name, 1, 4))
112: return NULL; /* bad packet */
113:
114: for (cp = name; (c = *cp); cp++)
115: if (c >= 'A' && c <= 'Z')
116: *cp += 'a' - 'A';
117:
118: sha256_update(&ctx, (BYTE *)name, cp - name);
119: /* CRC the class and type as well */
120: sha256_update(&ctx, (BYTE *)p, 4);
121:
122: p += 4;
123: if (!CHECK_LEN(header, p, plen, 0))
124: return NULL; /* bad packet */
125: }
126:
127: sha256_final(&ctx, digest);
128: return (unsigned char *)digest;
129: }
130:
131: /* Code from here onwards comes from https://github.com/B-Con/crypto-algorithms
132: and was written by Brad Conte (brad@bradconte.com), to whom all credit is given.
133:
134: This code is in the public domain, and the copyright notice at the head of this
135: file does not apply to it.
136: */
137:
138:
139: /****************************** MACROS ******************************/
140: #define ROTLEFT(a,b) (((a) << (b)) | ((a) >> (32-(b))))
141: #define ROTRIGHT(a,b) (((a) >> (b)) | ((a) << (32-(b))))
142:
143: #define CH(x,y,z) (((x) & (y)) ^ (~(x) & (z)))
144: #define MAJ(x,y,z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
145: #define EP0(x) (ROTRIGHT(x,2) ^ ROTRIGHT(x,13) ^ ROTRIGHT(x,22))
146: #define EP1(x) (ROTRIGHT(x,6) ^ ROTRIGHT(x,11) ^ ROTRIGHT(x,25))
147: #define SIG0(x) (ROTRIGHT(x,7) ^ ROTRIGHT(x,18) ^ ((x) >> 3))
148: #define SIG1(x) (ROTRIGHT(x,17) ^ ROTRIGHT(x,19) ^ ((x) >> 10))
149:
150: /**************************** VARIABLES *****************************/
151: static const WORD k[64] = {
152: 0x428a2f98,0x71374491,0xb5c0fbcf,0xe9b5dba5,0x3956c25b,0x59f111f1,0x923f82a4,0xab1c5ed5,
153: 0xd807aa98,0x12835b01,0x243185be,0x550c7dc3,0x72be5d74,0x80deb1fe,0x9bdc06a7,0xc19bf174,
154: 0xe49b69c1,0xefbe4786,0x0fc19dc6,0x240ca1cc,0x2de92c6f,0x4a7484aa,0x5cb0a9dc,0x76f988da,
155: 0x983e5152,0xa831c66d,0xb00327c8,0xbf597fc7,0xc6e00bf3,0xd5a79147,0x06ca6351,0x14292967,
156: 0x27b70a85,0x2e1b2138,0x4d2c6dfc,0x53380d13,0x650a7354,0x766a0abb,0x81c2c92e,0x92722c85,
157: 0xa2bfe8a1,0xa81a664b,0xc24b8b70,0xc76c51a3,0xd192e819,0xd6990624,0xf40e3585,0x106aa070,
158: 0x19a4c116,0x1e376c08,0x2748774c,0x34b0bcb5,0x391c0cb3,0x4ed8aa4a,0x5b9cca4f,0x682e6ff3,
159: 0x748f82ee,0x78a5636f,0x84c87814,0x8cc70208,0x90befffa,0xa4506ceb,0xbef9a3f7,0xc67178f2
160: };
161:
162: /*********************** FUNCTION DEFINITIONS ***********************/
163: static void sha256_transform(SHA256_CTX *ctx, const BYTE data[])
164: {
165: WORD a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
166:
167: for (i = 0, j = 0; i < 16; ++i, j += 4)
168: m[i] = (data[j] << 24) | (data[j + 1] << 16) | (data[j + 2] << 8) | (data[j + 3]);
169: for ( ; i < 64; ++i)
170: m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
171:
172: a = ctx->state[0];
173: b = ctx->state[1];
174: c = ctx->state[2];
175: d = ctx->state[3];
176: e = ctx->state[4];
177: f = ctx->state[5];
178: g = ctx->state[6];
179: h = ctx->state[7];
180:
181: for (i = 0; i < 64; ++i)
182: {
183: t1 = h + EP1(e) + CH(e,f,g) + k[i] + m[i];
184: t2 = EP0(a) + MAJ(a,b,c);
185: h = g;
186: g = f;
187: f = e;
188: e = d + t1;
189: d = c;
190: c = b;
191: b = a;
192: a = t1 + t2;
193: }
194:
195: ctx->state[0] += a;
196: ctx->state[1] += b;
197: ctx->state[2] += c;
198: ctx->state[3] += d;
199: ctx->state[4] += e;
200: ctx->state[5] += f;
201: ctx->state[6] += g;
202: ctx->state[7] += h;
203: }
204:
205: static void sha256_init(SHA256_CTX *ctx)
206: {
207: ctx->datalen = 0;
208: ctx->bitlen = 0;
209: ctx->state[0] = 0x6a09e667;
210: ctx->state[1] = 0xbb67ae85;
211: ctx->state[2] = 0x3c6ef372;
212: ctx->state[3] = 0xa54ff53a;
213: ctx->state[4] = 0x510e527f;
214: ctx->state[5] = 0x9b05688c;
215: ctx->state[6] = 0x1f83d9ab;
216: ctx->state[7] = 0x5be0cd19;
217: }
218:
219: static void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len)
220: {
221: WORD i;
222:
223: for (i = 0; i < len; ++i)
224: {
225: ctx->data[ctx->datalen] = data[i];
226: ctx->datalen++;
227: if (ctx->datalen == 64) {
228: sha256_transform(ctx, ctx->data);
229: ctx->bitlen += 512;
230: ctx->datalen = 0;
231: }
232: }
233: }
234:
235: static void sha256_final(SHA256_CTX *ctx, BYTE hash[])
236: {
237: WORD i;
238:
239: i = ctx->datalen;
240:
241: /* Pad whatever data is left in the buffer. */
242: if (ctx->datalen < 56)
243: {
244: ctx->data[i++] = 0x80;
245: while (i < 56)
246: ctx->data[i++] = 0x00;
247: }
248: else
249: {
250: ctx->data[i++] = 0x80;
251: while (i < 64)
252: ctx->data[i++] = 0x00;
253: sha256_transform(ctx, ctx->data);
254: memset(ctx->data, 0, 56);
255: }
256:
257: /* Append to the padding the total message's length in bits and transform. */
258: ctx->bitlen += ctx->datalen * 8;
259: ctx->data[63] = ctx->bitlen;
260: ctx->data[62] = ctx->bitlen >> 8;
261: ctx->data[61] = ctx->bitlen >> 16;
262: ctx->data[60] = ctx->bitlen >> 24;
263: ctx->data[59] = ctx->bitlen >> 32;
264: ctx->data[58] = ctx->bitlen >> 40;
265: ctx->data[57] = ctx->bitlen >> 48;
266: ctx->data[56] = ctx->bitlen >> 56;
267: sha256_transform(ctx, ctx->data);
268:
269: /* Since this implementation uses little endian byte ordering and SHA uses big endian,
270: reverse all the bytes when copying the final state to the output hash. */
271: for (i = 0; i < 4; ++i)
272: {
273: hash[i] = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
274: hash[i + 4] = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
275: hash[i + 8] = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
276: hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
277: hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
278: hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
279: hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
280: hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
281: }
282: }
283:
284: #endif
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