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 static const char *hexchars="0123456789abcdef";
39 static string_t rsa_sign(void *sst, uint8_t *data, int32_t datalen)
41 struct rsapriv *st=sst;
42 MP_INT a, b, u, v, tmp, tmp2;
50 /* RSA PKCS#1 v1.5 signature padding:
52 * <------------ msize hex digits ---------->
54 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
58 * = datalen*2 hex digits
60 * NB that according to PKCS#1 v1.5 we're supposed to include a
61 * hash function OID in the data. We don't do that (because we
62 * don't have the hash function OID to hand here), thus violating
63 * the spec in a way that affects interop but not security.
68 msize=mpz_sizeinbase(&st->n, 16);
70 if (datalen*2+6>=msize) {
71 fatal("rsa_sign: message too big");
76 for (i=0; i<datalen; i++) {
77 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
78 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
81 buff[msize-datalen*2-2]= '0';
82 buff[msize-datalen*2-1]= '0';
84 for (i=4; i<msize-datalen*2-2; i++)
89 mpz_set_str(&a, buff, 16);
92 * Produce an RSA signature (a^d mod n) using the Chinese
93 * Remainder Theorem. We compute:
95 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
96 * v = a^dq mod q (== a^d mod q, similarly)
98 * We also know w == iqmp * q, which has the property that w ==
99 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
100 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
102 * b = w * u + (1-w) * v
105 * so that b is congruent to a^d both mod p and mod q. Hence b,
106 * reduced mod n, is the required signature.
113 mpz_powm(&u, &a, &st->dp, &st->p);
114 mpz_powm(&v, &a, &st->dq, &st->q);
115 mpz_sub(&tmp, &u, &v);
116 mpz_mul(&tmp2, &tmp, &st->w);
117 mpz_add(&tmp, &tmp2, &v);
118 mpz_mod(&b, &tmp, &st->n);
125 signature=write_mpstring(&b);
132 static rsa_checksig_fn rsa_sig_check;
133 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
136 struct rsapub *st=sst;
146 msize=mpz_sizeinbase(&st->n, 16);
150 for (i=0; i<datalen; i++) {
151 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
152 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
155 buff[msize-datalen*2-2]= '0';
156 buff[msize-datalen*2-1]= '0';
158 for (i=4; i<msize-datalen*2-2; i++)
163 mpz_set_str(&a, buff, 16);
165 mpz_set_str(&b, signature, 16);
167 mpz_powm(&c, &b, &st->e, &st->n);
169 ok=(mpz_cmp(&a, &c)==0);
178 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
185 st=safe_malloc(sizeof(*st),"rsapub_apply");
186 st->cl.description="rsapub";
187 st->cl.type=CL_RSAPUBKEY;
189 st->cl.interface=&st->ops;
191 st->ops.check=rsa_sig_check;
196 if (i->type!=t_string) {
197 cfgfatal(i->loc,"rsa-public","first argument must be a string");
200 if (mpz_init_set_str(&st->e,e,10)!=0) {
201 cfgfatal(i->loc,"rsa-public","encryption key \"%s\" is not a "
202 "decimal number string\n",e);
205 cfgfatal(loc,"rsa-public","you must provide an encryption key\n");
210 if (i->type!=t_string) {
211 cfgfatal(i->loc,"rsa-public","second argument must be a string");
214 if (mpz_init_set_str(&st->n,n,10)!=0) {
215 cfgfatal(i->loc,"rsa-public","modulus \"%s\" is not a decimal "
216 "number string\n",n);
219 cfgfatal(loc,"rsa-public","you must provide a modulus\n");
221 return new_closure(&st->cl);
224 static uint32_t keyfile_get_int(struct cloc loc, FILE *f)
231 cfgfile_postreadcheck(loc,f);
235 static uint16_t keyfile_get_short(struct cloc loc, FILE *f)
240 cfgfile_postreadcheck(loc,f);
244 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
254 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
257 st=safe_malloc(sizeof(*st),"rsapriv_apply");
258 st->cl.description="rsapriv";
259 st->cl.type=CL_RSAPRIVKEY;
261 st->cl.interface=&st->ops;
263 st->ops.sign=rsa_sign;
266 /* Argument is filename pointing to SSH1 private key file */
269 if (i->type!=t_string) {
270 cfgfatal(i->loc,"rsa-public","first argument must be a string");
272 filename=i->data.string;
274 filename=NULL; /* Make compiler happy */
275 cfgfatal(loc,"rsa-private","you must provide a filename\n");
278 f=fopen(filename,"rb");
280 if (just_check_config) {
281 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
282 "\"%s\"; assuming it's valid while we check the "
283 "rest of the configuration\n",loc.file,loc.line,filename);
286 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
287 loc.file,loc.line,filename);
291 /* Check that the ID string is correct */
292 length=strlen(AUTHFILE_ID_STRING)+1;
293 b=safe_malloc(length,"rsapriv_apply");
294 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
295 cfgfatal_maybefile(f,loc,"rsa-private","failed to read magic ID"
296 " string from SSH1 private keyfile \"%s\"\n",
301 cipher_type=fgetc(f);
302 keyfile_get_int(loc,f); /* "Reserved data" */
303 if (cipher_type != 0) {
304 cfgfatal(loc,"rsa-private","we don't support encrypted keyfiles\n");
307 /* Read the public key */
308 keyfile_get_int(loc,f); /* Not sure what this is */
309 length=(keyfile_get_short(loc,f)+7)/8;
311 cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n",
314 b=safe_malloc(length,"rsapriv_apply");
315 if (fread(b,length,1,f) != 1) {
316 cfgfatal_maybefile(f,loc,"rsa-private","error reading modulus");
319 read_mpbin(&st->n,b,length);
321 length=(keyfile_get_short(loc,f)+7)/8;
323 cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length);
325 b=safe_malloc(length,"rsapriv_apply");
326 if (fread(b,length,1,f)!=1) {
327 cfgfatal_maybefile(f,loc,"rsa-private","error reading e\n");
330 read_mpbin(&e,b,length);
333 length=keyfile_get_int(loc,f);
335 cfgfatal(loc,"rsa-private","implausibly long (%ld) key comment\n",
338 c=safe_malloc(length+1,"rsapriv_apply");
339 if (fread(c,length,1,f)!=1) {
340 cfgfatal_maybefile(f,loc,"rsa-private","error reading key comment\n");
344 /* Check that the next two pairs of characters are identical - the
345 keyfile is not encrypted, so they should be */
347 if (keyfile_get_short(loc,f) != keyfile_get_short(loc,f)) {
348 cfgfatal(loc,"rsa-private","corrupt keyfile\n");
352 length=(keyfile_get_short(loc,f)+7)/8;
354 cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n",
357 b=safe_malloc(length,"rsapriv_apply");
358 if (fread(b,length,1,f)!=1) {
359 cfgfatal_maybefile(f,loc,"rsa-private",
360 "error reading decryption key\n");
363 read_mpbin(&d,b,length);
365 /* Read iqmp (inverse of q mod p) */
366 length=(keyfile_get_short(loc,f)+7)/8;
368 cfgfatal(loc,"rsa-private","implausibly long (%ld)"
369 " iqmp auxiliary value\n", length);
371 b=safe_malloc(length,"rsapriv_apply");
372 if (fread(b,length,1,f)!=1) {
373 cfgfatal_maybefile(f,loc,"rsa-private",
374 "error reading decryption key\n");
377 read_mpbin(&iqmp,b,length);
379 /* Read q (the smaller of the two primes) */
380 length=(keyfile_get_short(loc,f)+7)/8;
382 cfgfatal(loc,"rsa-private","implausibly long (%ld) q value\n",
385 b=safe_malloc(length,"rsapriv_apply");
386 if (fread(b,length,1,f)!=1) {
387 cfgfatal_maybefile(f,loc,"rsa-private",
388 "error reading q value\n");
391 read_mpbin(&st->q,b,length);
393 /* Read p (the larger of the two primes) */
394 length=(keyfile_get_short(loc,f)+7)/8;
396 cfgfatal(loc,"rsa-private","implausibly long (%ld) p value\n",
399 b=safe_malloc(length,"rsapriv_apply");
400 if (fread(b,length,1,f)!=1) {
401 cfgfatal_maybefile(f,loc,"rsa-private",
402 "error reading p value\n");
405 read_mpbin(&st->p,b,length);
409 fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line);
413 * Now verify the validity of the key, and set up the auxiliary
414 * values for fast CRT signing.
421 if (i && i->type==t_bool && i->data.bool==False) {
422 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
423 "check\n",loc.file,loc.line);
425 /* Verify that p*q is equal to n. */
426 mpz_mul(&tmp, &st->p, &st->q);
427 if (mpz_cmp(&tmp, &st->n) != 0)
431 * Verify that d*e is congruent to 1 mod (p-1), and mod
432 * (q-1). This is equivalent to it being congruent to 1 mod
433 * lcm(p-1,q-1), i.e. congruent to 1 mod phi(n). Note that
434 * phi(n) is _not_ simply (p-1)*(q-1).
436 mpz_mul(&tmp, &d, &e);
437 mpz_sub_ui(&tmp2, &st->p, 1);
438 mpz_mod(&tmp3, &tmp, &tmp2);
439 if (mpz_cmp_si(&tmp3, 1) != 0)
441 mpz_sub_ui(&tmp2, &st->q, 1);
442 mpz_mod(&tmp3, &tmp, &tmp2);
443 if (mpz_cmp_si(&tmp3, 1) != 0)
446 /* Verify that q*iqmp is congruent to 1 mod p. */
447 mpz_mul(&tmp, &st->q, &iqmp);
448 mpz_mod(&tmp2, &tmp, &st->p);
449 if (mpz_cmp_si(&tmp2, 1) != 0)
452 /* Now we know the key is valid (or we don't care). */
456 * Now we compute auxiliary values dp, dq and w to allow us
457 * to use the CRT optimisation when signing.
459 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
460 * dq == d mod (q-1) similarly mod q
461 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
466 mpz_sub_ui(&tmp, &st->p, 1);
467 mpz_mod(&st->dp, &d, &tmp);
468 mpz_sub_ui(&tmp, &st->q, 1);
469 mpz_mod(&st->dq, &d, &tmp);
470 mpz_mul(&st->w, &iqmp, &st->q);
474 cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
475 "valid RSA key!\n",filename);
487 return new_closure(&st->cl);
490 void rsa_module(dict_t *dict)
492 add_closure(dict,"rsa-private",rsapriv_apply);
493 add_closure(dict,"rsa-public",rsapub_apply);