1// Copyright 2015 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package pkcs12
6
7import (
8	"bytes"
9	"crypto/sha1"
10	"math/big"
11)
12
13var (
14	one = big.NewInt(1)
15)
16
17// sha1Sum returns the SHA-1 hash of in.
18func sha1Sum(in []byte) []byte {
19	sum := sha1.Sum(in)
20	return sum[:]
21}
22
23// fillWithRepeats returns v*ceiling(len(pattern) / v) bytes consisting of
24// repeats of pattern.
25func fillWithRepeats(pattern []byte, v int) []byte {
26	if len(pattern) == 0 {
27		return nil
28	}
29	outputLen := v * ((len(pattern) + v - 1) / v)
30	return bytes.Repeat(pattern, (outputLen+len(pattern)-1)/len(pattern))[:outputLen]
31}
32
33func pbkdf(hash func([]byte) []byte, u, v int, salt, password []byte, r int, ID byte, size int) (key []byte) {
34	// implementation of https://tools.ietf.org/html/rfc7292#appendix-B.2 , RFC text verbatim in comments
35
36	//    Let H be a hash function built around a compression function f:
37
38	//       Z_2^u x Z_2^v -> Z_2^u
39
40	//    (that is, H has a chaining variable and output of length u bits, and
41	//    the message input to the compression function of H is v bits).  The
42	//    values for u and v are as follows:
43
44	//            HASH FUNCTION     VALUE u        VALUE v
45	//              MD2, MD5          128            512
46	//                SHA-1           160            512
47	//               SHA-224          224            512
48	//               SHA-256          256            512
49	//               SHA-384          384            1024
50	//               SHA-512          512            1024
51	//             SHA-512/224        224            1024
52	//             SHA-512/256        256            1024
53
54	//    Furthermore, let r be the iteration count.
55
56	//    We assume here that u and v are both multiples of 8, as are the
57	//    lengths of the password and salt strings (which we denote by p and s,
58	//    respectively) and the number n of pseudorandom bits required.  In
59	//    addition, u and v are of course non-zero.
60
61	//    For information on security considerations for MD5 [19], see [25] and
62	//    [1], and on those for MD2, see [18].
63
64	//    The following procedure can be used to produce pseudorandom bits for
65	//    a particular "purpose" that is identified by a byte called "ID".
66	//    This standard specifies 3 different values for the ID byte:
67
68	//    1.  If ID=1, then the pseudorandom bits being produced are to be used
69	//        as key material for performing encryption or decryption.
70
71	//    2.  If ID=2, then the pseudorandom bits being produced are to be used
72	//        as an IV (Initial Value) for encryption or decryption.
73
74	//    3.  If ID=3, then the pseudorandom bits being produced are to be used
75	//        as an integrity key for MACing.
76
77	//    1.  Construct a string, D (the "diversifier"), by concatenating v/8
78	//        copies of ID.
79	var D []byte
80	for i := 0; i < v; i++ {
81		D = append(D, ID)
82	}
83
84	//    2.  Concatenate copies of the salt together to create a string S of
85	//        length v(ceiling(s/v)) bits (the final copy of the salt may be
86	//        truncated to create S).  Note that if the salt is the empty
87	//        string, then so is S.
88
89	S := fillWithRepeats(salt, v)
90
91	//    3.  Concatenate copies of the password together to create a string P
92	//        of length v(ceiling(p/v)) bits (the final copy of the password
93	//        may be truncated to create P).  Note that if the password is the
94	//        empty string, then so is P.
95
96	P := fillWithRepeats(password, v)
97
98	//    4.  Set I=S||P to be the concatenation of S and P.
99	I := append(S, P...)
100
101	//    5.  Set c=ceiling(n/u).
102	c := (size + u - 1) / u
103
104	//    6.  For i=1, 2, ..., c, do the following:
105	A := make([]byte, c*20)
106	var IjBuf []byte
107	for i := 0; i < c; i++ {
108		//        A.  Set A2=H^r(D||I). (i.e., the r-th hash of D||1,
109		//            H(H(H(... H(D||I))))
110		Ai := hash(append(D, I...))
111		for j := 1; j < r; j++ {
112			Ai = hash(Ai)
113		}
114		copy(A[i*20:], Ai[:])
115
116		if i < c-1 { // skip on last iteration
117			// B.  Concatenate copies of Ai to create a string B of length v
118			//     bits (the final copy of Ai may be truncated to create B).
119			var B []byte
120			for len(B) < v {
121				B = append(B, Ai[:]...)
122			}
123			B = B[:v]
124
125			// C.  Treating I as a concatenation I_0, I_1, ..., I_(k-1) of v-bit
126			//     blocks, where k=ceiling(s/v)+ceiling(p/v), modify I by
127			//     setting I_j=(I_j+B+1) mod 2^v for each j.
128			{
129				Bbi := new(big.Int).SetBytes(B)
130				Ij := new(big.Int)
131
132				for j := 0; j < len(I)/v; j++ {
133					Ij.SetBytes(I[j*v : (j+1)*v])
134					Ij.Add(Ij, Bbi)
135					Ij.Add(Ij, one)
136					Ijb := Ij.Bytes()
137					// We expect Ijb to be exactly v bytes,
138					// if it is longer or shorter we must
139					// adjust it accordingly.
140					if len(Ijb) > v {
141						Ijb = Ijb[len(Ijb)-v:]
142					}
143					if len(Ijb) < v {
144						if IjBuf == nil {
145							IjBuf = make([]byte, v)
146						}
147						bytesShort := v - len(Ijb)
148						for i := 0; i < bytesShort; i++ {
149							IjBuf[i] = 0
150						}
151						copy(IjBuf[bytesShort:], Ijb)
152						Ijb = IjBuf
153					}
154					copy(I[j*v:(j+1)*v], Ijb)
155				}
156			}
157		}
158	}
159	//    7.  Concatenate A_1, A_2, ..., A_c together to form a pseudorandom
160	//        bit string, A.
161
162	//    8.  Use the first n bits of A as the output of this entire process.
163	return A[:size]
164
165	//    If the above process is being used to generate a DES key, the process
166	//    should be used to create 64 random bits, and the key's parity bits
167	//    should be set after the 64 bits have been produced.  Similar concerns
168	//    hold for 2-key and 3-key triple-DES keys, for CDMF keys, and for any
169	//    similar keys with parity bits "built into them".
170}
171