[efi] Implement the EFI_PXE_BASE_CODE_PROTOCOL
[ipxe.git] / src / crypto / hash_df.c
1 /*
2 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
3 *
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License as
6 * published by the Free Software Foundation; either version 2 of the
7 * License, or any later version.
8 *
9 * This program is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
17 * 02110-1301, USA.
18 *
19 * You can also choose to distribute this program under the terms of
20 * the Unmodified Binary Distribution Licence (as given in the file
21 * COPYING.UBDL), provided that you have satisfied its requirements.
22 */
23
24 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
25
26 /** @file
27 *
28 * Hash-based derivation function (Hash_df)
29 *
30 * This algorithm is designed to comply with ANS X9.82 Part 3-2007
31 * Section 10.5.2. This standard is not freely available, but most of
32 * the text appears to be shared with NIST SP 800-90, which can be
33 * downloaded from
34 *
35 * http://csrc.nist.gov/publications/nistpubs/800-90/SP800-90revised_March2007.pdf
36 *
37 * Where possible, references are given to both documents. In the
38 * case of any disagreement, ANS X9.82 takes priority over NIST SP
39 * 800-90. (In particular, note that some algorithms that are
40 * Approved by NIST SP 800-90 are not Approved by ANS X9.82.)
41 */
42
43 #include <stdint.h>
44 #include <string.h>
45 #include <assert.h>
46 #include <byteswap.h>
47 #include <ipxe/crypto.h>
48 #include <ipxe/hash_df.h>
49
50 /**
51 * Distribute entropy throughout a buffer
52 *
53 * @v hash Underlying hash algorithm
54 * @v input Input data
55 * @v input_len Length of input data, in bytes
56 * @v output Output buffer
57 * @v output_len Length of output buffer, in bytes
58 *
59 * This is the Hash_df function defined in ANS X9.82 Part 3-2007
60 * Section 10.5.2 (NIST SP 800-90 Section 10.4.1).
61 *
62 * The number of bits requested is implicit in the length of the
63 * output buffer. Requests must be for an integral number of bytes.
64 *
65 * The output buffer is filled incrementally with each iteration of
66 * the central loop, rather than constructing an overall "temp" and
67 * then taking the leftmost(no_of_bits_to_return) bits.
68 *
69 * There is no way for the Hash_df function to fail. The returned
70 * status SUCCESS is implicit.
71 */
72 void hash_df ( struct digest_algorithm *hash, const void *input,
73 size_t input_len, void *output, size_t output_len ) {
74 uint8_t context[hash->ctxsize];
75 uint8_t digest[hash->digestsize];
76 size_t frag_len;
77 struct {
78 uint8_t pad[3];
79 uint8_t counter;
80 uint32_t no_of_bits_to_return;
81 } __attribute__ (( packed )) prefix;
82 void *temp;
83 size_t remaining;
84
85 DBGC ( &hash_df, "HASH_DF input:\n" );
86 DBGC_HDA ( &hash_df, 0, input, input_len );
87
88 /* Sanity checks */
89 assert ( input != NULL );
90 assert ( output != NULL );
91
92 /* 1. temp = the Null string
93 * 2. len = ceil ( no_of_bits_to_return / outlen )
94 *
95 * (Nothing to do. We fill the output buffer incrementally,
96 * rather than constructing the complete "temp" in-memory.
97 * "len" is implicit in the number of iterations required to
98 * fill the output buffer, and so is not calculated
99 * explicitly.)
100 */
101
102 /* 3. counter = an 8-bit binary value representing the integer "1" */
103 prefix.counter = 1;
104
105 /* 4. For i = 1 to len do */
106 for ( temp = output, remaining = output_len ; remaining > 0 ; ) {
107
108 /* Comment: in step 5.1 (sic), no_of_bits_to_return is
109 * used as a 32-bit string.
110 *
111 * 4.1 temp = temp || Hash ( counter || no_of_bits_to_return
112 * || input_string )
113 */
114 prefix.no_of_bits_to_return = htonl ( output_len * 8 );
115 digest_init ( hash, context );
116 digest_update ( hash, context, &prefix.counter,
117 ( sizeof ( prefix ) -
118 offsetof ( typeof ( prefix ), counter ) ) );
119 digest_update ( hash, context, input, input_len );
120 digest_final ( hash, context, digest );
121
122 /* 4.2 counter = counter + 1 */
123 prefix.counter++;
124
125 /* 5. requested_bits = Leftmost ( no_of_bits_to_return )
126 * of temp
127 *
128 * (We fill the output buffer incrementally.)
129 */
130 frag_len = sizeof ( digest );
131 if ( frag_len > remaining )
132 frag_len = remaining;
133 memcpy ( temp, digest, frag_len );
134 temp += frag_len;
135 remaining -= frag_len;
136 }
137
138 /* 6. Return SUCCESS and requested_bits */
139 DBGC ( &hash_df, "HASH_DF output:\n" );
140 DBGC_HDA ( &hash_df, 0, output, output_len );
141 return;
142 }