Commit | Line | Data |
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2fe58dfd SE |
1 | #include <stdio.h> |
2 | #include <gmp.h> | |
59230b9b | 3 | #include <limits.h> |
2fe58dfd SE |
4 | |
5 | #include "secnet.h" | |
6 | #include "util.h" | |
7 | ||
8 | struct dh { | |
9 | closure_t cl; | |
10 | struct dh_if ops; | |
11 | struct cloc loc; | |
12 | MP_INT p,g; /* prime modulus and generator */ | |
13 | }; | |
14 | ||
1caa23ff | 15 | static string_t dh_makepublic(void *sst, uint8_t *secret, int32_t secretlen) |
2fe58dfd SE |
16 | { |
17 | struct dh *st=sst; | |
18 | string_t r; | |
19 | MP_INT a, b; /* a is secret key, b is public key */ | |
20 | ||
21 | mpz_init(&a); | |
22 | mpz_init(&b); | |
23 | ||
24 | read_mpbin(&a, secret, secretlen); | |
25 | ||
26 | mpz_powm(&b, &st->g, &a, &st->p); | |
27 | ||
28 | r=write_mpstring(&b); | |
29 | ||
30 | mpz_clear(&a); | |
31 | mpz_clear(&b); | |
32 | return r; | |
33 | } | |
34 | ||
fe5e9cc4 | 35 | static dh_makeshared_fn dh_makeshared; |
1caa23ff | 36 | static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen, |
fe5e9cc4 | 37 | cstring_t rempublic, uint8_t *sharedsecret, |
1caa23ff | 38 | int32_t buflen) |
2fe58dfd SE |
39 | { |
40 | struct dh *st=sst; | |
41 | MP_INT a, b, c; | |
42 | ||
43 | mpz_init(&a); | |
44 | mpz_init(&b); | |
45 | mpz_init(&c); | |
46 | ||
47 | read_mpbin(&a, secret, secretlen); | |
48 | mpz_set_str(&b, rempublic, 16); | |
49 | ||
50 | mpz_powm(&c, &b, &a, &st->p); | |
51 | ||
52 | write_mpbin(&c,sharedsecret,buflen); | |
53 | ||
54 | mpz_clear(&a); | |
55 | mpz_clear(&b); | |
56 | mpz_clear(&c); | |
57 | } | |
58 | ||
59 | static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context, | |
60 | list_t *args) | |
61 | { | |
62 | struct dh *st; | |
63 | string_t p,g; | |
64 | item_t *i; | |
65 | ||
66 | st=safe_malloc(sizeof(*st),"dh_apply"); | |
67 | st->cl.description="dh"; | |
68 | st->cl.type=CL_DH; | |
69 | st->cl.apply=NULL; | |
70 | st->cl.interface=&st->ops; | |
71 | st->ops.st=st; | |
72 | st->ops.makepublic=dh_makepublic; | |
73 | st->ops.makeshared=dh_makeshared; | |
74 | st->loc=loc; | |
75 | /* We have two string arguments: the first is the modulus, and the | |
76 | second is the generator. Both are in hex. */ | |
77 | i=list_elem(args,0); | |
78 | if (i) { | |
79 | if (i->type!=t_string) { | |
80 | cfgfatal(i->loc,"diffie-hellman","first argument must be a " | |
81 | "string\n"); | |
82 | } | |
83 | p=i->data.string; | |
84 | if (mpz_init_set_str(&st->p,p,16)!=0) { | |
85 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
86 | "string\n",p); | |
87 | } | |
88 | } else { | |
89 | cfgfatal(loc,"diffie-hellman","you must provide a prime modulus\n"); | |
90 | } | |
91 | ||
92 | i=list_elem(args,1); | |
93 | if (i) { | |
94 | if (i->type!=t_string) { | |
95 | cfgfatal(i->loc,"diffie-hellman","second argument must be a " | |
96 | "string\n"); | |
97 | } | |
98 | g=i->data.string; | |
99 | if (mpz_init_set_str(&st->g,g,16)!=0) { | |
100 | cfgfatal(i->loc,"diffie-hellman","\"%s\" is not a hex number " | |
101 | "string\n",g); | |
102 | } | |
103 | } else { | |
104 | cfgfatal(loc,"diffie-hellman","you must provide a generator\n"); | |
105 | } | |
106 | ||
70dc107b SE |
107 | i=list_elem(args,2); |
108 | if (i && i->type==t_bool && i->data.bool==False) { | |
109 | Message(M_INFO,"diffie-hellman (%s:%d): skipping modulus " | |
110 | "primality check\n",loc.file,loc.line); | |
111 | } else { | |
112 | /* Test that the modulus is really prime */ | |
113 | if (mpz_probab_prime_p(&st->p,5)==0) { | |
114 | cfgfatal(loc,"diffie-hellman","modulus must be a prime\n"); | |
115 | } | |
2fe58dfd | 116 | } |
59230b9b IJ |
117 | |
118 | size_t sz=mpz_sizeinbase(&st->p,2)/8; | |
119 | if (sz>INT_MAX) { | |
120 | cfgfatal(loc,"diffie-hellman","modulus far too large\n"); | |
121 | } | |
122 | if (mpz_cmp(&st->g,&st->p) >= 0) { | |
123 | cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n"); | |
124 | } | |
125 | ||
126 | st->ops.len=sz; | |
2fe58dfd | 127 | |
7c9ca4bd IJ |
128 | st->ops.ceil_len=(mpz_sizeinbase(&st->p,2)+7)/8; |
129 | /* According to the docs, mpz_sizeinbase(,256) is allowed to return | |
130 | * an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */ | |
131 | ||
2fe58dfd SE |
132 | return new_closure(&st->cl); |
133 | } | |
134 | ||
2fe58dfd SE |
135 | void dh_module(dict_t *dict) |
136 | { | |
137 | add_closure(dict,"diffie-hellman",dh_apply); | |
138 | } |