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
);