1 /* This file is part of secnet, and is distributed under the terms of
2 the GNU General Public License version 2 or later.
4 Copyright (C) 1995-2002 Stephen Early
5 Copyright (C) 2001 Simon Tatham
6 Copyright (C) 2002 Ian Jackson
15 #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
17 #define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
21 struct rsaprivkey_if ops;
30 struct rsapubkey_if ops;
35 /* Sign data. NB data must be smaller than modulus */
37 #define RSA_MAX_MODBYTES 2048
38 /* The largest modulus I've seen is 15360 bits, which works out at 1920
39 * bytes. Using keys this big is quite implausible, but it doesn't cost us
40 * much to support them.
43 static const char *hexchars="0123456789abcdef";
45 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
46 const uint8_t *data, int32_t datalen)
48 char buff[2*RSA_MAX_MODBYTES + 1];
51 /* RSA PKCS#1 v1.5 signature padding:
53 * <------------ msize hex digits ---------->
55 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
59 * = datalen*2 hex digits
61 * NB that according to PKCS#1 v1.5 we're supposed to include a
62 * hash function OID in the data. We don't do that (because we
63 * don't have the hash function OID to hand here), thus violating
64 * the spec in a way that affects interop but not security.
69 msize=mpz_sizeinbase(n, 16);
71 if (datalen*2+6>=msize) {
72 fatal("rsa_sign: message too big");
77 for (i=0; i<datalen; i++) {
78 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
79 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
82 buff[msize-datalen*2-2]= '0';
83 buff[msize-datalen*2-1]= '0';
85 for (i=4; i<msize-datalen*2-2; i++)
90 mpz_set_str(m, buff, 16);
93 static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
95 struct rsapriv *st=sst;
96 MP_INT a, b, u, v, tmp, tmp2;
102 /* Construct the message representative. */
103 emsa_pkcs1(&st->n, &a, data, datalen);
106 * Produce an RSA signature (a^d mod n) using the Chinese
107 * Remainder Theorem. We compute:
109 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
110 * v = a^dq mod q (== a^d mod q, similarly)
112 * We also know w == iqmp * q, which has the property that w ==
113 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
114 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
116 * b = w * u + (1-w) * v
119 * so that b is congruent to a^d both mod p and mod q. Hence b,
120 * reduced mod n, is the required signature.
127 mpz_powm(&u, &a, &st->dp, &st->p);
128 mpz_powm(&v, &a, &st->dq, &st->q);
129 mpz_sub(&tmp, &u, &v);
130 mpz_mul(&tmp2, &tmp, &st->w);
131 mpz_add(&tmp, &tmp2, &v);
132 mpz_mod(&b, &tmp, &st->n);
139 signature=write_mpstring(&b);
146 static rsa_checksig_fn rsa_sig_check;
147 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
150 struct rsapub *st=sst;
158 emsa_pkcs1(&st->n, &a, data, datalen);
160 mpz_set_str(&b, signature, 16);
162 mpz_powm(&c, &b, &st->e, &st->n);
164 ok=(mpz_cmp(&a, &c)==0);
173 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
180 st=safe_malloc(sizeof(*st),"rsapub_apply");
181 st->cl.description="rsapub";
182 st->cl.type=CL_RSAPUBKEY;
184 st->cl.interface=&st->ops;
186 st->ops.check=rsa_sig_check;
191 if (i->type!=t_string) {
192 cfgfatal(i->loc,"rsa-public","first argument must be a string\n");
195 if (mpz_init_set_str(&st->e,e,10)!=0) {
196 cfgfatal(i->loc,"rsa-public","encryption key \"%s\" is not a "
197 "decimal number string\n",e);
200 cfgfatal(loc,"rsa-public","you must provide an encryption key\n");
202 if (mpz_sizeinbase(&st->e, 256) > RSA_MAX_MODBYTES) {
203 cfgfatal(loc, "rsa-public", "implausibly large public exponent\n");
208 if (i->type!=t_string) {
209 cfgfatal(i->loc,"rsa-public","second argument must be a string\n");
212 if (mpz_init_set_str(&st->n,n,10)!=0) {
213 cfgfatal(i->loc,"rsa-public","modulus \"%s\" is not a decimal "
214 "number string\n",n);
217 cfgfatal(loc,"rsa-public","you must provide a modulus\n");
219 if (mpz_sizeinbase(&st->n, 256) > RSA_MAX_MODBYTES) {
220 cfgfatal(loc, "rsa-public", "implausibly large modulus\n");
222 return new_closure(&st->cl);
225 static uint32_t keyfile_get_int(struct cloc loc, FILE *f)
232 cfgfile_postreadcheck(loc,f);
236 static uint16_t keyfile_get_short(struct cloc loc, FILE *f)
241 cfgfile_postreadcheck(loc,f);
245 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
255 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
258 st=safe_malloc(sizeof(*st),"rsapriv_apply");
259 st->cl.description="rsapriv";
260 st->cl.type=CL_RSAPRIVKEY;
262 st->cl.interface=&st->ops;
264 st->ops.sign=rsa_sign;
267 /* Argument is filename pointing to SSH1 private key file */
270 if (i->type!=t_string) {
271 cfgfatal(i->loc,"rsa-public","first argument must be a string\n");
273 filename=i->data.string;
275 filename=NULL; /* Make compiler happy */
276 cfgfatal(loc,"rsa-private","you must provide a filename\n");
279 f=fopen(filename,"rb");
281 if (just_check_config) {
282 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
283 "\"%s\"; assuming it's valid while we check the "
284 "rest of the configuration\n",loc.file,loc.line,filename);
287 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
288 loc.file,loc.line,filename);
292 /* Check that the ID string is correct */
293 length=strlen(AUTHFILE_ID_STRING)+1;
294 b=safe_malloc(length,"rsapriv_apply");
295 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
296 cfgfatal_maybefile(f,loc,"rsa-private","failed to read magic ID"
297 " string from SSH1 private keyfile \"%s\"\n",
302 cipher_type=fgetc(f);
303 keyfile_get_int(loc,f); /* "Reserved data" */
304 if (cipher_type != 0) {
305 cfgfatal(loc,"rsa-private","we don't support encrypted keyfiles\n");
308 /* Read the public key */
309 keyfile_get_int(loc,f); /* Not sure what this is */
310 length=(keyfile_get_short(loc,f)+7)/8;
311 if (length>RSA_MAX_MODBYTES) {
312 cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n",
315 b=safe_malloc(length,"rsapriv_apply");
316 if (fread(b,length,1,f) != 1) {
317 cfgfatal_maybefile(f,loc,"rsa-private","error reading modulus\n");
320 read_mpbin(&st->n,b,length);
322 length=(keyfile_get_short(loc,f)+7)/8;
323 if (length>RSA_MAX_MODBYTES) {
324 cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length);
326 b=safe_malloc(length,"rsapriv_apply");
327 if (fread(b,length,1,f)!=1) {
328 cfgfatal_maybefile(f,loc,"rsa-private","error reading e\n");
331 read_mpbin(&e,b,length);
334 length=keyfile_get_int(loc,f);
336 cfgfatal(loc,"rsa-private","implausibly long (%ld) key comment\n",
339 c=safe_malloc(length+1,"rsapriv_apply");
340 if (fread(c,length,1,f)!=1) {
341 cfgfatal_maybefile(f,loc,"rsa-private","error reading key comment\n");
345 /* Check that the next two pairs of characters are identical - the
346 keyfile is not encrypted, so they should be */
348 if (keyfile_get_short(loc,f) != keyfile_get_short(loc,f)) {
349 cfgfatal(loc,"rsa-private","corrupt keyfile\n");
353 length=(keyfile_get_short(loc,f)+7)/8;
354 if (length>RSA_MAX_MODBYTES) {
355 cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n",
358 b=safe_malloc(length,"rsapriv_apply");
359 if (fread(b,length,1,f)!=1) {
360 cfgfatal_maybefile(f,loc,"rsa-private",
361 "error reading decryption key\n");
364 read_mpbin(&d,b,length);
366 /* Read iqmp (inverse of q mod p) */
367 length=(keyfile_get_short(loc,f)+7)/8;
368 if (length>RSA_MAX_MODBYTES) {
369 cfgfatal(loc,"rsa-private","implausibly long (%ld)"
370 " iqmp auxiliary value\n", length);
372 b=safe_malloc(length,"rsapriv_apply");
373 if (fread(b,length,1,f)!=1) {
374 cfgfatal_maybefile(f,loc,"rsa-private",
375 "error reading decryption key\n");
378 read_mpbin(&iqmp,b,length);
380 /* Read q (the smaller of the two primes) */
381 length=(keyfile_get_short(loc,f)+7)/8;
382 if (length>RSA_MAX_MODBYTES) {
383 cfgfatal(loc,"rsa-private","implausibly long (%ld) q value\n",
386 b=safe_malloc(length,"rsapriv_apply");
387 if (fread(b,length,1,f)!=1) {
388 cfgfatal_maybefile(f,loc,"rsa-private",
389 "error reading q value\n");
392 read_mpbin(&st->q,b,length);
394 /* Read p (the larger of the two primes) */
395 length=(keyfile_get_short(loc,f)+7)/8;
396 if (length>RSA_MAX_MODBYTES) {
397 cfgfatal(loc,"rsa-private","implausibly long (%ld) p value\n",
400 b=safe_malloc(length,"rsapriv_apply");
401 if (fread(b,length,1,f)!=1) {
402 cfgfatal_maybefile(f,loc,"rsa-private",
403 "error reading p value\n");
406 read_mpbin(&st->p,b,length);
410 fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line);
414 * Now verify the validity of the key, and set up the auxiliary
415 * values for fast CRT signing.
422 if (i && i->type==t_bool && i->data.bool==False) {
423 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
424 "check\n",loc.file,loc.line);
426 /* Verify that p*q is equal to n. */
427 mpz_mul(&tmp, &st->p, &st->q);
428 if (mpz_cmp(&tmp, &st->n) != 0)
432 * Verify that d*e is congruent to 1 mod (p-1), and mod
433 * (q-1). This is equivalent to it being congruent to 1 mod
434 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
435 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
436 * actually necessary.
438 mpz_mul(&tmp, &d, &e);
439 mpz_sub_ui(&tmp2, &st->p, 1);
440 mpz_mod(&tmp3, &tmp, &tmp2);
441 if (mpz_cmp_si(&tmp3, 1) != 0)
443 mpz_sub_ui(&tmp2, &st->q, 1);
444 mpz_mod(&tmp3, &tmp, &tmp2);
445 if (mpz_cmp_si(&tmp3, 1) != 0)
448 /* Verify that q*iqmp is congruent to 1 mod p. */
449 mpz_mul(&tmp, &st->q, &iqmp);
450 mpz_mod(&tmp2, &tmp, &st->p);
451 if (mpz_cmp_si(&tmp2, 1) != 0)
454 /* Now we know the key is valid (or we don't care). */
458 * Now we compute auxiliary values dp, dq and w to allow us
459 * to use the CRT optimisation when signing.
461 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
462 * dq == d mod (q-1) similarly mod q
463 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
468 mpz_sub_ui(&tmp, &st->p, 1);
469 mpz_mod(&st->dp, &d, &tmp);
470 mpz_sub_ui(&tmp, &st->q, 1);
471 mpz_mod(&st->dq, &d, &tmp);
472 mpz_mul(&st->w, &iqmp, &st->q);
476 cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
477 "valid RSA key!\n",filename);
489 return new_closure(&st->cl);
492 void rsa_module(dict_t *dict)
494 add_closure(dict,"rsa-private",rsapriv_apply);
495 add_closure(dict,"rsa-public",rsapub_apply);