1 /* CRT work by Simon Tatham */
8 #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
10 #define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
14 struct rsaprivkey_if ops;
23 struct rsapubkey_if ops;
28 /* Sign data. NB data must be smaller than modulus */
30 static const char *hexchars="0123456789abcdef";
32 static string_t rsa_sign(void *sst, uint8_t *data, uint32_t datalen)
34 struct rsapriv *st=sst;
35 MP_INT a, b, u, v, tmp, tmp2;
43 msize=mpz_sizeinbase(&st->n, 16);
45 if (datalen*2+4>=msize) {
46 fatal("rsa_sign: message too big");
51 for (i=0; i<datalen; i++) {
52 buff[4+i*2]=hexchars[(data[i]&0xf0)>>4];
53 buff[5+i*2]=hexchars[data[i]&0xf];
57 for (i=datalen*2+4; i<msize; i++)
62 mpz_set_str(&a, buff, 16);
65 * Produce an RSA signature (a^d mod n) using the Chinese
66 * Remainder Theorem. We compute:
68 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
69 * v = a^dq mod q (== a^d mod q, similarly)
71 * We also know w == iqmp * q, which has the property that w ==
72 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
73 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
75 * b = w * u + (1-w) * v
78 * so that b is congruent to a^d both mod p and mod q. Hence b,
79 * reduced mod n, is the required signature.
86 mpz_powm(&u, &a, &st->dp, &st->p);
87 mpz_powm(&v, &a, &st->dq, &st->q);
88 mpz_sub(&tmp, &u, &v);
89 mpz_mul(&tmp2, &tmp, &st->w);
90 mpz_add(&tmp, &tmp2, &v);
91 mpz_mod(&b, &tmp, &st->n);
98 signature=write_mpstring(&b);
105 static rsa_checksig_fn rsa_sig_check;
106 static bool_t rsa_sig_check(void *sst, uint8_t *data, uint32_t datalen,
109 struct rsapub *st=sst;
119 msize=mpz_sizeinbase(&st->n, 16);
123 for (i=0; i<datalen; i++) {
124 buff[4+i*2]=hexchars[(data[i]&0xf0)>>4];
125 buff[5+i*2]=hexchars[data[i]&0xf];
129 for (i=datalen*2+4; i<msize; i++)
134 mpz_set_str(&a, buff, 16);
136 mpz_set_str(&b, signature, 16);
138 mpz_powm(&c, &b, &st->e, &st->n);
140 ok=(mpz_cmp(&a, &c)==0);
149 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
156 st=safe_malloc(sizeof(*st),"rsapub_apply");
157 st->cl.description="rsapub";
158 st->cl.type=CL_RSAPUBKEY;
160 st->cl.interface=&st->ops;
162 st->ops.check=rsa_sig_check;
167 if (i->type!=t_string) {
168 cfgfatal(i->loc,"rsa-public","first argument must be a string");
171 if (mpz_init_set_str(&st->e,e,10)!=0) {
172 cfgfatal(i->loc,"rsa-public","encryption key \"%s\" is not a "
173 "decimal number string\n",e);
176 cfgfatal(loc,"rsa-public","you must provide an encryption key\n");
181 if (i->type!=t_string) {
182 cfgfatal(i->loc,"rsa-public","second argument must be a string");
185 if (mpz_init_set_str(&st->n,n,10)!=0) {
186 cfgfatal(i->loc,"rsa-public","modulus \"%s\" is not a decimal "
187 "number string\n",n);
190 cfgfatal(loc,"rsa-public","you must provide a modulus\n");
192 return new_closure(&st->cl);
195 static uint32_t keyfile_get_int(struct cloc loc, FILE *f)
202 cfgfile_postreadcheck(loc,f);
206 static uint16_t keyfile_get_short(struct cloc loc, FILE *f)
211 cfgfile_postreadcheck(loc,f);
215 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
225 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
227 st=safe_malloc(sizeof(*st),"rsapriv_apply");
228 st->cl.description="rsapriv";
229 st->cl.type=CL_RSAPRIVKEY;
231 st->cl.interface=&st->ops;
233 st->ops.sign=rsa_sign;
236 /* Argument is filename pointing to SSH1 private key file */
239 if (i->type!=t_string) {
240 cfgfatal(i->loc,"rsa-public","first argument must be a string");
242 filename=i->data.string;
244 filename=NULL; /* Make compiler happy */
245 cfgfatal(loc,"rsa-private","you must provide a filename\n");
248 f=fopen(filename,"rb");
250 if (just_check_config) {
251 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
252 "\"%s\"; assuming it's valid while we check the "
253 "rest of the configuration\n",loc.file,loc.line,filename);
256 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
257 loc.file,loc.line,filename);
261 /* Check that the ID string is correct */
262 length=strlen(AUTHFILE_ID_STRING)+1;
263 b=safe_malloc(length,"rsapriv_apply");
264 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
265 cfgfatal_maybefile(f,loc,"rsa-private","failed to read magic ID"
266 " string from SSH1 private keyfile \"%s\"\n",
271 cipher_type=fgetc(f);
272 keyfile_get_int(loc,f); /* "Reserved data" */
273 if (cipher_type != 0) {
274 cfgfatal(loc,"rsa-private","we don't support encrypted keyfiles\n");
277 /* Read the public key */
278 keyfile_get_int(loc,f); /* Not sure what this is */
279 length=(keyfile_get_short(loc,f)+7)/8;
281 cfgfatal(loc,"rsa-private","implausible length %ld for modulus\n",
284 b=safe_malloc(length,"rsapriv_apply");
285 if (fread(b,length,1,f) != 1) {
286 cfgfatal_maybefile(f,loc,"rsa-private","error reading modulus");
289 read_mpbin(&st->n,b,length);
291 length=(keyfile_get_short(loc,f)+7)/8;
293 cfgfatal(loc,"rsa-private","implausible length %ld for e\n",length);
295 b=safe_malloc(length,"rsapriv_apply");
296 if (fread(b,length,1,f)!=1) {
297 cfgfatal_maybefile(f,loc,"rsa-private","error reading e\n");
300 read_mpbin(&e,b,length);
303 length=keyfile_get_int(loc,f);
305 cfgfatal(loc,"rsa-private","implausibly long (%ld) key comment\n",
308 c=safe_malloc(length+1,"rsapriv_apply");
309 if (fread(c,length,1,f)!=1) {
310 cfgfatal_maybefile(f,loc,"rsa-private","error reading key comment\n");
314 /* Check that the next two pairs of characters are identical - the
315 keyfile is not encrypted, so they should be */
317 if (keyfile_get_short(loc,f) != keyfile_get_short(loc,f)) {
318 cfgfatal(loc,"rsa-private","corrupt keyfile\n");
322 length=(keyfile_get_short(loc,f)+7)/8;
324 cfgfatal(loc,"rsa-private","implausibly long (%ld) decryption key\n",
327 b=safe_malloc(length,"rsapriv_apply");
328 if (fread(b,length,1,f)!=1) {
329 cfgfatal_maybefile(f,loc,"rsa-private",
330 "error reading decryption key\n");
333 read_mpbin(&d,b,length);
335 /* Read iqmp (inverse of q mod p) */
336 length=(keyfile_get_short(loc,f)+7)/8;
338 cfgfatal(loc,"rsa-private","implausibly long (%ld)"
339 " iqmp auxiliary value\n", length);
341 b=safe_malloc(length,"rsapriv_apply");
342 if (fread(b,length,1,f)!=1) {
343 cfgfatal_maybefile(f,loc,"rsa-private",
344 "error reading decryption key\n");
347 read_mpbin(&iqmp,b,length);
349 /* Read q (the smaller of the two primes) */
350 length=(keyfile_get_short(loc,f)+7)/8;
352 cfgfatal(loc,"rsa-private","implausibly long (%ld) q value\n",
355 b=safe_malloc(length,"rsapriv_apply");
356 if (fread(b,length,1,f)!=1) {
357 cfgfatal_maybefile(f,loc,"rsa-private",
358 "error reading q value\n");
361 read_mpbin(&st->q,b,length);
363 /* Read p (the larger of the two primes) */
364 length=(keyfile_get_short(loc,f)+7)/8;
366 cfgfatal(loc,"rsa-private","implausibly long (%ld) p value\n",
369 b=safe_malloc(length,"rsapriv_apply");
370 if (fread(b,length,1,f)!=1) {
371 cfgfatal_maybefile(f,loc,"rsa-private",
372 "error reading p value\n");
375 read_mpbin(&st->p,b,length);
379 fatal_perror("rsa-private (%s:%d): fclose",loc.file,loc.line);
383 * Now verify the validity of the key, and set up the auxiliary
384 * values for fast CRT signing.
387 if (i && i->type==t_bool && i->data.bool==False) {
388 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
389 "check\n",loc.file,loc.line);
396 /* Verify that p*q is equal to n. */
397 mpz_mul(&tmp, &st->p, &st->q);
398 if (mpz_cmp(&tmp, &st->n) != 0)
402 * Verify that d*e is congruent to 1 mod (p-1), and mod
403 * (q-1). This is equivalent to it being congruent to 1 mod
404 * lcm(p-1,q-1), i.e. congruent to 1 mod phi(n). Note that
405 * phi(n) is _not_ simply (p-1)*(q-1).
407 mpz_mul(&tmp, &d, &e);
408 mpz_sub_ui(&tmp2, &st->p, 1);
409 mpz_mod(&tmp3, &tmp, &tmp2);
410 if (mpz_cmp_si(&tmp3, 1) != 0)
412 mpz_sub_ui(&tmp2, &st->q, 1);
413 mpz_mod(&tmp3, &tmp, &tmp2);
414 if (mpz_cmp_si(&tmp3, 1) != 0)
417 /* Verify that q*iqmp is congruent to 1 mod p. */
418 mpz_mul(&tmp, &st->q, &iqmp);
419 mpz_mod(&tmp2, &tmp, &st->p);
420 if (mpz_cmp_si(&tmp2, 1) != 0)
423 /* Now we know the key is valid. */
427 * Now we compute auxiliary values dp, dq and w to allow us
428 * to use the CRT optimisation when signing.
430 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
431 * dq == d mod (q-1) similarly mod q
432 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
434 mpz_sub_ui(&tmp, &st->p, 1);
435 mpz_mod(&st->dp, &d, &tmp);
436 mpz_sub_ui(&tmp, &st->q, 1);
437 mpz_mod(&st->dq, &d, &tmp);
438 mpz_mul(&st->w, &iqmp, &st->q);
442 cfgfatal(loc,"rsa-private","file \"%s\" does not contain a "
443 "valid RSA key!\n",filename);
456 return new_closure(&st->cl);
459 init_module rsa_module;
460 void rsa_module(dict_t *dict)
462 add_closure(dict,"rsa-private",rsapriv_apply);
463 add_closure(dict,"rsa-public",rsapub_apply);