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1 | /*************************************************************************** |
2 | * | |
3 | * Part II Project, "A secure, private IP network" | |
4 | * Stephen Early <sde1000@cam.ac.uk> | |
5 | * | |
6 | * | |
7 | * $RCSfile: dh.c,v $ | |
8 | * | |
9 | * Description: Diffie-Hellman implementation | |
10 | * | |
11 | * Copyright: (C) Stephen Early 1995 | |
12 | * | |
13 | * $Revision: 1.3 $ | |
14 | * | |
15 | * $Date: 1996/05/16 18:38:54 $ | |
16 | * | |
17 | * $State: Exp $ | |
18 | * | |
19 | ***************************************************************************/ | |
20 | ||
21 | /* | |
22 | * $Log: dh.c,v $ | |
23 | * Revision 1.3 1996/05/16 18:38:54 sde1000 | |
24 | * Removed unused hexdigits variable. | |
25 | * | |
26 | * Revision 1.2 1996/04/14 16:33:52 sde1000 | |
27 | * Moved mpbin/mpstring functions into util.c | |
28 | * | |
29 | * Revision 1.1 1996/04/14 16:21:47 sde1000 | |
30 | * Initial revision | |
31 | * | |
32 | */ | |
33 | ||
34 | #include <stdio.h> | |
35 | #include <gmp.h> | |
36 | ||
37 | #include "secnet.h" | |
38 | #include "util.h" | |
39 | ||
40 | struct dh { | |
41 | closure_t cl; | |
42 | struct dh_if ops; | |
43 | struct cloc loc; | |
44 | MP_INT p,g; /* prime modulus and generator */ | |
45 | }; | |
46 | ||
47 | static string_t dh_makepublic(void *sst, uint8_t *secret, uint32_t secretlen) | |
48 | { | |
49 | struct dh *st=sst; | |
50 | string_t r; | |
51 | MP_INT a, b; /* a is secret key, b is public key */ | |
52 | ||
53 | mpz_init(&a); | |
54 | mpz_init(&b); | |
55 | ||
56 | read_mpbin(&a, secret, secretlen); | |
57 | ||
58 | mpz_powm(&b, &st->g, &a, &st->p); | |
59 | ||
60 | r=write_mpstring(&b); | |
61 | ||
62 | mpz_clear(&a); | |
63 | mpz_clear(&b); | |
64 | return r; | |
65 | } | |
66 | ||
67 | static void dh_makeshared(void *sst, uint8_t *secret, uint32_t secretlen, | |
68 | string_t rempublic, uint8_t *sharedsecret, | |
69 | uint32_t buflen) | |
70 | { | |
71 | struct dh *st=sst; | |
72 | MP_INT a, b, c; | |
73 | ||
74 | mpz_init(&a); | |
75 | mpz_init(&b); | |
76 | mpz_init(&c); | |
77 | ||
78 | read_mpbin(&a, secret, secretlen); | |
79 | mpz_set_str(&b, rempublic, 16); | |
80 | ||
81 | mpz_powm(&c, &b, &a, &st->p); | |
82 | ||
83 | write_mpbin(&c,sharedsecret,buflen); | |
84 | ||
85 | mpz_clear(&a); | |
86 | mpz_clear(&b); | |
87 | mpz_clear(&c); | |
88 | } | |
89 | ||
90 | static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context, | |
91 | list_t *args) | |
92 | { | |
93 | struct dh *st; | |
94 | string_t p,g; | |
95 | item_t *i; | |
96 | ||
97 | st=safe_malloc(sizeof(*st),"dh_apply"); | |
98 | st->cl.description="dh"; | |
99 | st->cl.type=CL_DH; | |
100 | st->cl.apply=NULL; | |
101 | st->cl.interface=&st->ops; | |
102 | st->ops.st=st; | |
103 | st->ops.makepublic=dh_makepublic; | |
104 | st->ops.makeshared=dh_makeshared; | |
105 | st->loc=loc; | |
106 | /* We have two string arguments: the first is the modulus, and the | |
107 | second is the generator. Both are in hex. */ | |
108 | i=list_elem(args,0); | |
109 | if (i) { | |
110 | if (i->type!=t_string) { | |
111 | cfgfatal(i->loc,"diffie-hellman","first argument must be a " | |
112 | "string\n"); | |
113 | } | |
114 | p=i->data.string; | |
115 | if (mpz_init_set_str(&st->p,p,16)!=0) { | |
116 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
117 | "string\n",p); | |
118 | } | |
119 | } else { | |
120 | cfgfatal(loc,"diffie-hellman","you must provide a prime modulus\n"); | |
121 | } | |
122 | ||
123 | i=list_elem(args,1); | |
124 | if (i) { | |
125 | if (i->type!=t_string) { | |
126 | cfgfatal(i->loc,"diffie-hellman","second argument must be a " | |
127 | "string\n"); | |
128 | } | |
129 | g=i->data.string; | |
130 | if (mpz_init_set_str(&st->g,g,16)!=0) { | |
131 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
132 | "string\n",g); | |
133 | } | |
134 | } else { | |
135 | cfgfatal(loc,"diffie-hellman","you must provide a generator\n"); | |
136 | } | |
137 | ||
138 | /* Test that the modulus is really prime */ | |
139 | if (mpz_probab_prime_p(&st->p,5)==0) { | |
140 | cfgfatal(loc,"diffie-hellman","modulus must be a prime\n"); | |
141 | } | |
142 | st->ops.len=mpz_sizeinbase(&st->p,2)/8; | |
143 | ||
144 | return new_closure(&st->cl); | |
145 | } | |
146 | ||
147 | init_module dh_module; | |
148 | void dh_module(dict_t *dict) | |
149 | { | |
150 | add_closure(dict,"diffie-hellman",dh_apply); | |
151 | } |