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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: rsa.c,v $ | |
8 | * | |
9 | * Description: RSA signature making and checking functions | |
10 | * | |
11 | * Copyright: (C) Stephen Early 1995 | |
12 | * | |
13 | * $Revision: 1.1 $ | |
14 | * | |
15 | * $Date: 1996/05/16 18:40:14 $ | |
16 | * | |
17 | * $State: Exp $ | |
18 | * | |
19 | ***************************************************************************/ | |
20 | ||
21 | /* $Log: rsa.c,v $ | |
22 | * Revision 1.1 1996/05/16 18:40:14 sde1000 | |
23 | * Initial revision | |
24 | * | |
25 | */ | |
26 | ||
27 | #include <stdio.h> | |
28 | #include <gmp.h> | |
29 | #include "secnet.h" | |
30 | #include "util.h" | |
31 | ||
32 | #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n" | |
33 | ||
34 | struct rsapriv { | |
35 | closure_t cl; | |
36 | struct rsaprivkey_if ops; | |
37 | struct cloc loc; | |
38 | MP_INT d; | |
39 | MP_INT n; | |
40 | }; | |
41 | struct rsapub { | |
42 | closure_t cl; | |
43 | struct rsapubkey_if ops; | |
44 | struct cloc loc; | |
45 | MP_INT e; | |
46 | MP_INT n; | |
47 | }; | |
48 | /* Sign data. NB data must be smaller than modulus */ | |
49 | ||
50 | static char *hexchars="0123456789abcdef"; | |
51 | ||
52 | static string_t rsa_sign(void *sst, uint8_t *data, uint32_t datalen) | |
53 | { | |
54 | struct rsapriv *st=sst; | |
55 | MP_INT a, b; | |
56 | char buff[2048]; | |
57 | int msize, i; | |
58 | string_t signature; | |
59 | ||
60 | mpz_init(&a); | |
61 | mpz_init(&b); | |
62 | ||
63 | msize=mpz_sizeinbase(&st->n, 16); | |
64 | ||
65 | strcpy(buff,"0001"); | |
66 | ||
67 | for (i=0; i<datalen; i++) { | |
68 | buff[4+i*2]=hexchars[(data[i]&0xf0)>>4]; | |
69 | buff[5+i*2]=hexchars[data[i]&0xf]; | |
70 | } | |
71 | buff[4+datalen*2]=0; | |
72 | ||
73 | for (i=datalen*2+4; i<msize; i++) | |
74 | buff[i]='f'; | |
75 | ||
76 | buff[msize]=0; | |
77 | ||
78 | mpz_set_str(&a, buff, 16); | |
79 | ||
80 | mpz_powm(&b, &a, &st->d, &st->n); | |
81 | ||
82 | signature=write_mpstring(&b); | |
83 | ||
84 | mpz_clear(&b); | |
85 | mpz_clear(&a); | |
86 | return signature; | |
87 | } | |
88 | ||
89 | static bool_t rsa_sig_check(void *sst, uint8_t *data, uint32_t datalen, | |
90 | string_t signature) | |
91 | { | |
92 | struct rsapub *st=sst; | |
93 | MP_INT a, b, c; | |
94 | char buff[2048]; | |
95 | int msize, i; | |
96 | bool_t ok; | |
97 | ||
98 | mpz_init(&a); | |
99 | mpz_init(&b); | |
100 | mpz_init(&c); | |
101 | ||
102 | msize=mpz_sizeinbase(&st->n, 16); | |
103 | ||
104 | strcpy(buff,"0001"); | |
105 | ||
106 | for (i=0; i<datalen; i++) { | |
107 | buff[4+i*2]=hexchars[(data[i]&0xf0)>>4]; | |
108 | buff[5+i*2]=hexchars[data[i]&0xf]; | |
109 | } | |
110 | buff[4+datalen*2]=0; | |
111 | ||
112 | for (i=datalen*2+4; i<msize; i++) | |
113 | buff[i]='f'; | |
114 | ||
115 | buff[msize]=0; | |
116 | ||
117 | mpz_set_str(&a, buff, 16); | |
118 | ||
119 | mpz_set_str(&b, signature, 16); | |
120 | ||
121 | mpz_powm(&c, &b, &st->e, &st->n); | |
122 | ||
123 | ok=(mpz_cmp(&a, &c)==0); | |
124 | ||
125 | mpz_clear(&c); | |
126 | mpz_clear(&b); | |
127 | mpz_clear(&a); | |
128 | ||
129 | return ok; | |
130 | } | |
131 | ||
132 | static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context, | |
133 | list_t *args) | |
134 | { | |
135 | struct rsapub *st; | |
136 | item_t *i; | |
137 | string_t e,n; | |
138 | ||
139 | st=safe_malloc(sizeof(*st),"rsapub_apply"); | |
140 | st->cl.description="rsapub"; | |
141 | st->cl.type=CL_RSAPUBKEY; | |
142 | st->cl.apply=NULL; | |
143 | st->cl.interface=&st->ops; | |
144 | st->ops.st=st; | |
145 | st->ops.check=rsa_sig_check; | |
146 | st->loc=loc; | |
147 | ||
148 | i=list_elem(args,0); | |
149 | if (i) { | |
150 | if (i->type!=t_string) { | |
151 | cfgfatal(i->loc,"rsa-public","first argument must be a string"); | |
152 | } | |
153 | e=i->data.string; | |
154 | if (mpz_init_set_str(&st->e,e,10)!=0) { | |
155 | cfgfatal(i->loc,"rsa-public","encryption key \"%s\" is not a " | |
156 | "decimal number string\n",e); | |
157 | } | |
158 | } else { | |
159 | cfgfatal(loc,"rsa-public","you must provide an encryption key\n"); | |
160 | } | |
161 | ||
162 | i=list_elem(args,1); | |
163 | if (i) { | |
164 | if (i->type!=t_string) { | |
165 | cfgfatal(i->loc,"rsa-public","second argument must be a string"); | |
166 | } | |
167 | n=i->data.string; | |
168 | if (mpz_init_set_str(&st->n,n,10)!=0) { | |
169 | cfgfatal(i->loc,"rsa-public","modulus \"%s\" is not a decimal " | |
170 | "number string\n",n); | |
171 | } | |
172 | } else { | |
173 | cfgfatal(loc,"rsa-public","you must provide a modulus\n"); | |
174 | } | |
175 | return new_closure(&st->cl); | |
176 | } | |
177 | ||
178 | static uint32_t keyfile_get_int(FILE *f) | |
179 | { | |
180 | uint32_t r; | |
181 | r=fgetc(f)<<24; | |
182 | r|=fgetc(f)<<16; | |
183 | r|=fgetc(f)<<8; | |
184 | r|=fgetc(f); | |
185 | return r; | |
186 | } | |
187 | ||
188 | static uint16_t keyfile_get_short(FILE *f) | |
189 | { | |
190 | uint16_t r; | |
191 | r=fgetc(f)<<8; | |
192 | r|=fgetc(f); | |
193 | return r; | |
194 | } | |
195 | ||
196 | static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, | |
197 | list_t *args) | |
198 | { | |
199 | struct rsapriv *st; | |
200 | FILE *f; | |
201 | string_t filename; | |
202 | item_t *i; | |
203 | long length; | |
204 | uint8_t *b, *c; | |
205 | int cipher_type; | |
206 | MP_INT e,sig,plain,check; | |
207 | ||
208 | st=safe_malloc(sizeof(*st),"rsapriv_apply"); | |
209 | st->cl.description="rsapriv"; | |
210 | st->cl.type=CL_RSAPRIVKEY; | |
211 | st->cl.apply=NULL; | |
212 | st->cl.interface=&st->ops; | |
213 | st->ops.st=st; | |
214 | st->ops.sign=rsa_sign; | |
215 | st->loc=loc; | |
216 | ||
217 | /* Argument is filename pointing to SSH1 private key file */ | |
218 | i=list_elem(args,0); | |
219 | if (i) { | |
220 | if (i->type!=t_string) { | |
221 | cfgfatal(i->loc,"rsa-public","first argument must be a string"); | |
222 | } | |
223 | filename=i->data.string; | |
224 | } else { | |
225 | filename=""; /* Make compiler happy */ | |
226 | cfgfatal(loc,"rsa-private","you must provide a filename\n"); | |
227 | } | |
228 | ||
229 | f=fopen(filename,"rb"); | |
230 | if (!f) { | |
baa06aeb SE |
231 | if (just_check_config) { |
232 | Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile " | |
233 | "\"%s\"; assuming it's valid while we check the " | |
234 | "rest of the configuration\n",loc.file,loc.line,filename); | |
235 | goto assume_valid; | |
236 | } else { | |
237 | fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"", | |
238 | loc.file,loc.line,filename); | |
239 | } | |
2fe58dfd SE |
240 | } |
241 | ||
242 | /* Check that the ID string is correct */ | |
243 | length=strlen(AUTHFILE_ID_STRING)+1; | |
244 | b=safe_malloc(length,"rsapriv_apply"); | |
245 | if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) { | |
246 | cfgfatal(loc,"rsa-private","file \"%s\" is not a " | |
247 | "SSH1 private keyfile\n",filename); | |
248 | } | |
249 | free(b); | |
250 | ||
251 | cipher_type=fgetc(f); | |
252 | keyfile_get_int(f); /* "Reserved data" */ | |
253 | if (cipher_type != 0) { | |
254 | cfgfatal(loc,"rsa-private","we don't support encrypted keyfiles\n"); | |
255 | } | |
256 | ||
257 | /* Read the public key */ | |
258 | keyfile_get_int(f); /* Not sure what this is */ | |
259 | length=(keyfile_get_short(f)+7)/8; | |
260 | if (length>1024) { | |
261 | cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n", | |
262 | length); | |
263 | } | |
264 | b=safe_malloc(length,"rsapriv_apply"); | |
265 | if (fread(b,length,1,f) != 1) { | |
266 | cfgfatal(loc,"rsa-private","error reading modulus\n"); | |
267 | } | |
268 | mpz_init(&st->n); | |
269 | read_mpbin(&st->n,b,length); | |
270 | free(b); | |
271 | length=(keyfile_get_short(f)+7)/8; | |
272 | if (length>1024) { | |
273 | cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length); | |
274 | } | |
275 | b=safe_malloc(length,"rsapriv_apply"); | |
276 | if (fread(b,length,1,f)!=1) { | |
277 | cfgfatal(loc,"rsa-private","error reading e\n"); | |
278 | } | |
279 | mpz_init(&e); | |
280 | read_mpbin(&e,b,length); | |
281 | free(b); | |
282 | ||
283 | length=keyfile_get_int(f); | |
284 | if (length>1024) { | |
285 | cfgfatal(loc,"rsa-private","implausibly long (%ld) key comment\n", | |
286 | length); | |
287 | } | |
288 | c=safe_malloc(length+1,"rsapriv_apply"); | |
289 | if (fread(c,length,1,f)!=1) { | |
290 | cfgfatal(loc,"rsa-private","error reading key comment\n"); | |
291 | } | |
292 | c[length]=0; | |
293 | ||
294 | /* Check that the next two pairs of characters are identical - the | |
295 | keyfile is not encrypted, so they should be */ | |
296 | if (keyfile_get_short(f) != keyfile_get_short(f)) { | |
297 | cfgfatal(loc,"rsa-private","corrupt keyfile\n"); | |
298 | } | |
299 | ||
300 | /* Read d */ | |
301 | length=(keyfile_get_short(f)+7)/8; | |
302 | if (length>1024) { | |
303 | cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n", | |
304 | length); | |
305 | } | |
306 | b=safe_malloc(length,"rsapriv_apply"); | |
307 | if (fread(b,length,1,f)!=1) { | |
308 | cfgfatal(loc,"rsa-private","error reading decryption key\n"); | |
309 | } | |
310 | mpz_init(&st->d); | |
311 | read_mpbin(&st->d,b,length); | |
312 | free(b); | |
313 | ||
314 | if (fclose(f)!=0) { | |
315 | fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line); | |
316 | } | |
317 | ||
318 | /* Now do trial signature/check to make sure it's a real keypair: | |
319 | sign the comment string! */ | |
70dc107b SE |
320 | i=list_elem(args,1); |
321 | if (i && i->type==t_bool && i->data.bool==False) { | |
322 | Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity " | |
323 | "check\n",loc.file,loc.line); | |
324 | } else { | |
325 | mpz_init(&sig); | |
326 | mpz_init(&plain); | |
327 | mpz_init(&check); | |
328 | read_mpbin(&plain,c,strlen(c)); | |
329 | mpz_powm(&sig, &plain, &st->d, &st->n); | |
330 | mpz_powm(&check, &sig, &e, &st->n); | |
331 | if (mpz_cmp(&plain,&check)!=0) { | |
332 | cfgfatal(loc,"rsa-private","file \"%s\" does not contain a " | |
333 | "valid RSA key!\n",filename); | |
334 | } | |
335 | mpz_clear(&sig); | |
336 | mpz_clear(&plain); | |
337 | mpz_clear(&check); | |
2fe58dfd | 338 | } |
2fe58dfd SE |
339 | |
340 | free(c); | |
341 | mpz_clear(&e); | |
342 | ||
baa06aeb | 343 | assume_valid: |
2fe58dfd SE |
344 | return new_closure(&st->cl); |
345 | } | |
346 | ||
347 | init_module rsa_module; | |
348 | void rsa_module(dict_t *dict) | |
349 | { | |
350 | add_closure(dict,"rsa-private",rsapriv_apply); | |
351 | add_closure(dict,"rsa-public",rsapub_apply); | |
352 | } |