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2fe58dfd SE |
1 | #include <stdio.h> |
2 | #include <gmp.h> | |
3 | #include "secnet.h" | |
4 | #include "util.h" | |
5 | ||
6 | #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n" | |
7 | ||
8 | struct rsapriv { | |
9 | closure_t cl; | |
10 | struct rsaprivkey_if ops; | |
11 | struct cloc loc; | |
12 | MP_INT d; | |
13 | MP_INT n; | |
14 | }; | |
15 | struct rsapub { | |
16 | closure_t cl; | |
17 | struct rsapubkey_if ops; | |
18 | struct cloc loc; | |
19 | MP_INT e; | |
20 | MP_INT n; | |
21 | }; | |
22 | /* Sign data. NB data must be smaller than modulus */ | |
23 | ||
24 | static char *hexchars="0123456789abcdef"; | |
25 | ||
26 | static string_t rsa_sign(void *sst, uint8_t *data, uint32_t datalen) | |
27 | { | |
28 | struct rsapriv *st=sst; | |
29 | MP_INT a, b; | |
30 | char buff[2048]; | |
31 | int msize, i; | |
32 | string_t signature; | |
33 | ||
34 | mpz_init(&a); | |
35 | mpz_init(&b); | |
36 | ||
37 | msize=mpz_sizeinbase(&st->n, 16); | |
38 | ||
3454dce4 SE |
39 | if (datalen*2+4>=msize) { |
40 | fatal("rsa_sign: message too big\n"); | |
41 | } | |
42 | ||
2fe58dfd SE |
43 | strcpy(buff,"0001"); |
44 | ||
45 | for (i=0; i<datalen; i++) { | |
46 | buff[4+i*2]=hexchars[(data[i]&0xf0)>>4]; | |
47 | buff[5+i*2]=hexchars[data[i]&0xf]; | |
48 | } | |
49 | buff[4+datalen*2]=0; | |
3454dce4 | 50 | |
2fe58dfd SE |
51 | for (i=datalen*2+4; i<msize; i++) |
52 | buff[i]='f'; | |
53 | ||
54 | buff[msize]=0; | |
55 | ||
56 | mpz_set_str(&a, buff, 16); | |
57 | ||
58 | mpz_powm(&b, &a, &st->d, &st->n); | |
59 | ||
60 | signature=write_mpstring(&b); | |
61 | ||
62 | mpz_clear(&b); | |
63 | mpz_clear(&a); | |
64 | return signature; | |
65 | } | |
66 | ||
67 | static bool_t rsa_sig_check(void *sst, uint8_t *data, uint32_t datalen, | |
68 | string_t signature) | |
69 | { | |
70 | struct rsapub *st=sst; | |
71 | MP_INT a, b, c; | |
72 | char buff[2048]; | |
73 | int msize, i; | |
74 | bool_t ok; | |
75 | ||
76 | mpz_init(&a); | |
77 | mpz_init(&b); | |
78 | mpz_init(&c); | |
79 | ||
80 | msize=mpz_sizeinbase(&st->n, 16); | |
81 | ||
82 | strcpy(buff,"0001"); | |
83 | ||
84 | for (i=0; i<datalen; i++) { | |
85 | buff[4+i*2]=hexchars[(data[i]&0xf0)>>4]; | |
86 | buff[5+i*2]=hexchars[data[i]&0xf]; | |
87 | } | |
88 | buff[4+datalen*2]=0; | |
89 | ||
90 | for (i=datalen*2+4; i<msize; i++) | |
91 | buff[i]='f'; | |
92 | ||
93 | buff[msize]=0; | |
94 | ||
95 | mpz_set_str(&a, buff, 16); | |
96 | ||
97 | mpz_set_str(&b, signature, 16); | |
98 | ||
99 | mpz_powm(&c, &b, &st->e, &st->n); | |
100 | ||
101 | ok=(mpz_cmp(&a, &c)==0); | |
102 | ||
103 | mpz_clear(&c); | |
104 | mpz_clear(&b); | |
105 | mpz_clear(&a); | |
106 | ||
107 | return ok; | |
108 | } | |
109 | ||
110 | static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context, | |
111 | list_t *args) | |
112 | { | |
113 | struct rsapub *st; | |
114 | item_t *i; | |
115 | string_t e,n; | |
116 | ||
117 | st=safe_malloc(sizeof(*st),"rsapub_apply"); | |
118 | st->cl.description="rsapub"; | |
119 | st->cl.type=CL_RSAPUBKEY; | |
120 | st->cl.apply=NULL; | |
121 | st->cl.interface=&st->ops; | |
122 | st->ops.st=st; | |
123 | st->ops.check=rsa_sig_check; | |
124 | st->loc=loc; | |
125 | ||
126 | i=list_elem(args,0); | |
127 | if (i) { | |
128 | if (i->type!=t_string) { | |
129 | cfgfatal(i->loc,"rsa-public","first argument must be a string"); | |
130 | } | |
131 | e=i->data.string; | |
132 | if (mpz_init_set_str(&st->e,e,10)!=0) { | |
133 | cfgfatal(i->loc,"rsa-public","encryption key \"%s\" is not a " | |
134 | "decimal number string\n",e); | |
135 | } | |
136 | } else { | |
137 | cfgfatal(loc,"rsa-public","you must provide an encryption key\n"); | |
138 | } | |
139 | ||
140 | i=list_elem(args,1); | |
141 | if (i) { | |
142 | if (i->type!=t_string) { | |
143 | cfgfatal(i->loc,"rsa-public","second argument must be a string"); | |
144 | } | |
145 | n=i->data.string; | |
146 | if (mpz_init_set_str(&st->n,n,10)!=0) { | |
147 | cfgfatal(i->loc,"rsa-public","modulus \"%s\" is not a decimal " | |
148 | "number string\n",n); | |
149 | } | |
150 | } else { | |
151 | cfgfatal(loc,"rsa-public","you must provide a modulus\n"); | |
152 | } | |
153 | return new_closure(&st->cl); | |
154 | } | |
155 | ||
156 | static uint32_t keyfile_get_int(FILE *f) | |
157 | { | |
158 | uint32_t r; | |
159 | r=fgetc(f)<<24; | |
160 | r|=fgetc(f)<<16; | |
161 | r|=fgetc(f)<<8; | |
162 | r|=fgetc(f); | |
163 | return r; | |
164 | } | |
165 | ||
166 | static uint16_t keyfile_get_short(FILE *f) | |
167 | { | |
168 | uint16_t r; | |
169 | r=fgetc(f)<<8; | |
170 | r|=fgetc(f); | |
171 | return r; | |
172 | } | |
173 | ||
174 | static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context, | |
175 | list_t *args) | |
176 | { | |
177 | struct rsapriv *st; | |
178 | FILE *f; | |
179 | string_t filename; | |
180 | item_t *i; | |
181 | long length; | |
182 | uint8_t *b, *c; | |
183 | int cipher_type; | |
184 | MP_INT e,sig,plain,check; | |
185 | ||
186 | st=safe_malloc(sizeof(*st),"rsapriv_apply"); | |
187 | st->cl.description="rsapriv"; | |
188 | st->cl.type=CL_RSAPRIVKEY; | |
189 | st->cl.apply=NULL; | |
190 | st->cl.interface=&st->ops; | |
191 | st->ops.st=st; | |
192 | st->ops.sign=rsa_sign; | |
193 | st->loc=loc; | |
194 | ||
195 | /* Argument is filename pointing to SSH1 private key file */ | |
196 | i=list_elem(args,0); | |
197 | if (i) { | |
198 | if (i->type!=t_string) { | |
199 | cfgfatal(i->loc,"rsa-public","first argument must be a string"); | |
200 | } | |
201 | filename=i->data.string; | |
202 | } else { | |
203 | filename=""; /* Make compiler happy */ | |
204 | cfgfatal(loc,"rsa-private","you must provide a filename\n"); | |
205 | } | |
206 | ||
207 | f=fopen(filename,"rb"); | |
208 | if (!f) { | |
baa06aeb SE |
209 | if (just_check_config) { |
210 | Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile " | |
211 | "\"%s\"; assuming it's valid while we check the " | |
212 | "rest of the configuration\n",loc.file,loc.line,filename); | |
213 | goto assume_valid; | |
214 | } else { | |
215 | fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"", | |
216 | loc.file,loc.line,filename); | |
217 | } | |
2fe58dfd SE |
218 | } |
219 | ||
220 | /* Check that the ID string is correct */ | |
221 | length=strlen(AUTHFILE_ID_STRING)+1; | |
222 | b=safe_malloc(length,"rsapriv_apply"); | |
223 | if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) { | |
224 | cfgfatal(loc,"rsa-private","file \"%s\" is not a " | |
225 | "SSH1 private keyfile\n",filename); | |
226 | } | |
227 | free(b); | |
228 | ||
229 | cipher_type=fgetc(f); | |
230 | keyfile_get_int(f); /* "Reserved data" */ | |
231 | if (cipher_type != 0) { | |
232 | cfgfatal(loc,"rsa-private","we don't support encrypted keyfiles\n"); | |
233 | } | |
234 | ||
235 | /* Read the public key */ | |
236 | keyfile_get_int(f); /* Not sure what this is */ | |
237 | length=(keyfile_get_short(f)+7)/8; | |
238 | if (length>1024) { | |
239 | cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n", | |
240 | length); | |
241 | } | |
242 | b=safe_malloc(length,"rsapriv_apply"); | |
243 | if (fread(b,length,1,f) != 1) { | |
244 | cfgfatal(loc,"rsa-private","error reading modulus\n"); | |
245 | } | |
246 | mpz_init(&st->n); | |
247 | read_mpbin(&st->n,b,length); | |
248 | free(b); | |
249 | length=(keyfile_get_short(f)+7)/8; | |
250 | if (length>1024) { | |
251 | cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length); | |
252 | } | |
253 | b=safe_malloc(length,"rsapriv_apply"); | |
254 | if (fread(b,length,1,f)!=1) { | |
255 | cfgfatal(loc,"rsa-private","error reading e\n"); | |
256 | } | |
257 | mpz_init(&e); | |
258 | read_mpbin(&e,b,length); | |
259 | free(b); | |
260 | ||
261 | length=keyfile_get_int(f); | |
262 | if (length>1024) { | |
263 | cfgfatal(loc,"rsa-private","implausibly long (%ld) key comment\n", | |
264 | length); | |
265 | } | |
266 | c=safe_malloc(length+1,"rsapriv_apply"); | |
267 | if (fread(c,length,1,f)!=1) { | |
268 | cfgfatal(loc,"rsa-private","error reading key comment\n"); | |
269 | } | |
270 | c[length]=0; | |
271 | ||
272 | /* Check that the next two pairs of characters are identical - the | |
273 | keyfile is not encrypted, so they should be */ | |
274 | if (keyfile_get_short(f) != keyfile_get_short(f)) { | |
275 | cfgfatal(loc,"rsa-private","corrupt keyfile\n"); | |
276 | } | |
277 | ||
278 | /* Read d */ | |
279 | length=(keyfile_get_short(f)+7)/8; | |
280 | if (length>1024) { | |
281 | cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n", | |
282 | length); | |
283 | } | |
284 | b=safe_malloc(length,"rsapriv_apply"); | |
285 | if (fread(b,length,1,f)!=1) { | |
286 | cfgfatal(loc,"rsa-private","error reading decryption key\n"); | |
287 | } | |
288 | mpz_init(&st->d); | |
289 | read_mpbin(&st->d,b,length); | |
290 | free(b); | |
291 | ||
292 | if (fclose(f)!=0) { | |
293 | fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line); | |
294 | } | |
295 | ||
296 | /* Now do trial signature/check to make sure it's a real keypair: | |
297 | sign the comment string! */ | |
70dc107b SE |
298 | i=list_elem(args,1); |
299 | if (i && i->type==t_bool && i->data.bool==False) { | |
300 | Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity " | |
301 | "check\n",loc.file,loc.line); | |
302 | } else { | |
303 | mpz_init(&sig); | |
304 | mpz_init(&plain); | |
305 | mpz_init(&check); | |
306 | read_mpbin(&plain,c,strlen(c)); | |
307 | mpz_powm(&sig, &plain, &st->d, &st->n); | |
308 | mpz_powm(&check, &sig, &e, &st->n); | |
309 | if (mpz_cmp(&plain,&check)!=0) { | |
310 | cfgfatal(loc,"rsa-private","file \"%s\" does not contain a " | |
311 | "valid RSA key!\n",filename); | |
312 | } | |
313 | mpz_clear(&sig); | |
314 | mpz_clear(&plain); | |
315 | mpz_clear(&check); | |
2fe58dfd | 316 | } |
2fe58dfd SE |
317 | |
318 | free(c); | |
319 | mpz_clear(&e); | |
320 | ||
baa06aeb | 321 | assume_valid: |
2fe58dfd SE |
322 | return new_closure(&st->cl); |
323 | } | |
324 | ||
325 | init_module rsa_module; | |
326 | void rsa_module(dict_t *dict) | |
327 | { | |
328 | add_closure(dict,"rsa-private",rsapriv_apply); | |
329 | add_closure(dict,"rsa-public",rsapub_apply); | |
330 | } |