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
);