2 * rsa.c: implementation of RSA with PKCS#1 padding
5 * This file is Free Software. It was originally written for secnet.
7 * Copyright 1995-2003 Stephen Early
8 * Copyright 2002-2014 Ian Jackson
9 * Copyright 2001 Simon Tatham
10 * Copyright 2013 Mark Wooding
12 * You may redistribute secnet as a whole and/or modify it under the
13 * terms of the GNU General Public License as published by the Free
14 * Software Foundation; either version 3, or (at your option) any
17 * You may redistribute this file and/or modify it under the terms of
18 * the GNU General Public License as published by the Free Software
19 * Foundation; either version 2, or (at your option) any later
22 * This software is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
27 * You should have received a copy of the GNU General Public License
28 * along with this software; if not, see
29 * https://www.gnu.org/licenses/gpl.html.
38 #include "unaligned.h"
40 #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
42 #define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
48 #define FREE(b) ({ free((b)); (b)=0; })
51 void (*verror)(struct load_ctx *l, struct cloc loc,
53 const char *message, va_list args);
54 bool_t (*postreadcheck)(struct load_ctx *l, FILE *f);
56 dict_t *deprdict; /* used only to look up hash */
65 static void load_err(struct load_ctx *l,
66 const struct cloc *maybe_loc, FILE *maybe_f,
71 l->verror(l, maybe_loc ? *maybe_loc : l->loc, maybe_f,fmt,al);
76 static void verror_tryload(struct load_ctx *l, struct cloc loc,
78 const char *message, va_list args)
81 slilog_part(l->u.tryload.log,class,"%s: ",l->what);
82 vslilog(l->u.tryload.log,class,message,args);
85 static void verror_cfgfatal(struct load_ctx *l, struct cloc loc,
87 const char *message, va_list args)
89 vcfgfatal_maybefile(maybe_f,l->loc,l->what,message,args,"");
94 struct sigprivkey_if ops;
96 struct rsacommon common;
103 #define RSAPUB_BNS(each) \
104 each(0,e,"public exponent") \
107 #define RSAPUB_LOADCORE_PASSBN(ix,en,what) \
110 #define RSAPUB_INIT_ST_BN( ix,en,what) mpz_init (&st->en);
111 #define RSAPUB_CLEAR_ST_BN(ix,en,what) mpz_clear(&st->en);
115 struct sigpubkey_if ops;
117 struct rsacommon common;
121 /* Sign data. NB data must be smaller than modulus */
123 #define RSA_MAX_MODBYTES 2048
124 /* The largest modulus I've seen is 15360 bits, which works out at 1920
125 * bytes. Using keys this big is quite implausible, but it doesn't cost us
126 * much to support them.
129 static const char *hexchars="0123456789abcdef";
131 static void rsa_sethash(struct load_ctx *l,
133 const struct hash_if **in_ops)
135 struct hash_if *hash=0;
137 hash=find_cl_if(l->deprdict,"hash",CL_HASH,False,"site",l->loc);
140 c->hashbuf=safe_malloc(hash->hlen, "generate_msg");
144 static void rsacommon_dispose(struct rsacommon *c)
149 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
150 const uint8_t *data, int32_t datalen)
152 char buff[2*RSA_MAX_MODBYTES + 1];
155 /* RSA PKCS#1 v1.5 signature padding:
157 * <------------ msize hex digits ---------->
159 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
163 * = datalen*2 hex digits
165 * NB that according to PKCS#1 v1.5 we're supposed to include a
166 * hash function OID in the data. We don't do that (because we
167 * don't have the hash function OID to hand here), thus violating
168 * the spec in a way that affects interop but not security.
173 msize=mpz_sizeinbase(n, 16);
175 if (datalen*2+6>=msize) {
176 fatal("rsa: message too big");
181 for (i=0; i<datalen; i++) {
182 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
183 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
186 buff[msize-datalen*2-2]= '0';
187 buff[msize-datalen*2-1]= '0';
189 for (i=4; i<msize-datalen*2-2; i++)
194 mpz_set_str(m, buff, 16);
197 static bool_t rsa_sign(void *sst, uint8_t *data, int32_t datalen,
198 struct buffer_if *msg)
200 struct rsapriv *st=sst;
201 MP_INT a, b, u, v, tmp, tmp2;
202 string_t signature = 0;
208 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
209 /* Construct the message representative. */
210 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
213 * Produce an RSA signature (a^d mod n) using the Chinese
214 * Remainder Theorem. We compute:
216 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
217 * v = a^dq mod q (== a^d mod q, similarly)
219 * We also know w == iqmp * q, which has the property that w ==
220 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
221 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
223 * b = w * u + (1-w) * v
226 * so that b is congruent to a^d both mod p and mod q. Hence b,
227 * reduced mod n, is the required signature.
234 mpz_powm_sec(&u, &a, &st->dp, &st->p);
235 mpz_powm_sec(&v, &a, &st->dq, &st->q);
236 mpz_sub(&tmp, &u, &v);
237 mpz_mul(&tmp2, &tmp, &st->w);
238 mpz_add(&tmp, &tmp2, &v);
239 mpz_mod(&b, &tmp, &st->n);
246 signature=write_mpstring(&b);
248 uint8_t *op = buf_append(msg,2);
249 if (!op) { ok=False; goto out; }
250 size_t l = strlen(signature);
253 op = buf_append(msg,l);
254 if (!op) { ok=False; goto out; }
255 memcpy(op, signature, l);
266 static bool_t rsa_sig_unpick(void *sst, struct buffer_if *msg,
267 struct alg_msg_data *sig)
269 uint8_t *lp = buf_unprepend(msg, 2);
270 if (!lp) return False;
271 sig->len = get_uint16(lp);
272 sig->start = buf_unprepend(msg, sig->len);
273 if (!sig->start) return False;
275 /* In `rsa_sig_check' below, we assume that we can write a nul
276 * terminator following the signature. Make sure there's enough space.
278 if (msg->start >= msg->base + msg->alloclen)
284 static sig_checksig_fn rsa_sig_check;
285 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
286 const struct alg_msg_data *sig)
288 struct rsapub *st=sst;
296 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
297 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
299 /* Terminate signature with a '0' - already checked that this will fit */
300 int save = sig->start[sig->len];
301 sig->start[sig->len] = 0;
302 mpz_set_str(&b, sig->start, 16);
303 sig->start[sig->len] = save;
305 mpz_powm(&c, &b, &st->e, &st->n);
307 ok=(mpz_cmp(&a, &c)==0);
316 static void rsapub_dispose(void *sst) {
317 struct rsapub *st=sst;
320 RSAPUB_BNS(RSAPUB_CLEAR_ST_BN)
321 rsacommon_dispose(&st->common);
325 #define RSAPUB_LOADCORE_DEFBN(ix,en,what) \
326 const char *en##s, struct cloc en##_loc,
328 #define LDPUBFATAL(lc,...) ({ \
329 load_err(l,(lc),0,__VA_ARGS__); \
333 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
339 st->cl.description="rsapub";
340 st->cl.type=CL_SIGPUBKEY;
342 st->cl.interface=&st->ops;
344 st->common.hashbuf=NULL;
345 st->ops.unpick=rsa_sig_unpick;
346 st->ops.check=rsa_sig_check;
348 st->ops.dispose=rsapub_dispose;
350 RSAPUB_BNS(RSAPUB_INIT_ST_BN)
352 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
353 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
354 LDPUBFATAL(&en##_loc, what " \"%s\" is not a " \
355 "decimal number string",en##s); \
357 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
358 LDPUBFATAL(&en##_loc, "implausibly large " what); \
361 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
363 rsa_sethash(l,&st->common,&st->ops.hash);
372 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
375 struct load_ctx l[1];
376 l->verror=verror_cfgfatal;
378 l->what="rsa-public";
382 #define RSAPUB_APPLY_GETBN(ix,en,what) \
385 en##i=list_elem(args,ix); \
387 cfgfatal(loc,"rsa-public", \
388 "you must provide an encryption key\n"); \
389 struct cloc en##_loc=en##i->loc; \
390 if (en##i->type!=t_string) \
391 cfgfatal(en##_loc,"rsa-public", \
392 "first argument must be a string\n"); \
393 en##s=en##i->data.string;
395 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
397 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
400 return new_closure(&st->cl);
403 bool_t rsa1_loadpub(const struct sigscheme_info *algo,
404 struct buffer_if *pubkeydata,
405 struct sigpubkey_if **sigpub_r,
406 closure_t **closure_r,
407 struct log_if *log, struct cloc loc)
411 struct load_ctx l[1];
412 l->verror=verror_tryload;
414 l->what="rsa1_loadpub";
417 l->u.tryload.log=log;
419 char *nul=buf_append(pubkeydata,1);
420 if (!nul) LDPUBFATAL(0,"rsa1 public key data too long for extra nul");
423 const char *delim=" \t\n";
425 /*unused*/ strtok_r(pubkeydata->start,delim,&saveptr);
427 #define RSAPUB_TRYLOAD_GETBN(ix,en,what) \
428 struct cloc en##_loc=loc; \
429 const char *en##s=strtok_r(0,delim,&saveptr); \
430 if (!en##s) LDPUBFATAL(0,"end of pubkey data looking for " what);
432 RSAPUB_BNS(RSAPUB_TRYLOAD_GETBN);
434 st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN) l);
435 if (!st) goto error_out;
446 #define LDFATAL(...) ({ load_err(l,0,0,__VA_ARGS__); goto error_out; })
447 #define LDFATAL_FILE(...) ({ load_err(l,0,f,__VA_ARGS__); goto error_out; })
448 #define KEYFILE_GET(is) ({ \
449 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
450 if (!l->postreadcheck(l,f)) goto error_out; \
454 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
464 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
472 static void rsapriv_dispose(void *sst)
474 struct rsapriv *st=sst;
476 mpz_clear(&st->p); mpz_clear(&st->dp);
477 mpz_clear(&st->q); mpz_clear(&st->dq);
479 rsacommon_dispose(&st->common);
483 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
484 FILE *f, struct cloc loc,
485 bool_t do_validity_check)
487 struct rsapriv *st=0;
491 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
502 st->cl.description="rsapriv";
503 st->cl.type=CL_SIGPRIVKEY;
505 st->cl.interface=&st->ops;
507 st->common.hashbuf=NULL;
508 st->ops.sign=rsa_sign;
510 st->ops.dispose=rsapriv_dispose;
520 assert(just_check_config);
524 /* Check that the ID string is correct */
525 length=strlen(AUTHFILE_ID_STRING)+1;
526 b=safe_malloc(length,"rsapriv_apply");
527 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
528 LDFATAL_FILE("failed to read magic ID"
529 " string from SSH1 private keyfile\n");
533 cipher_type=fgetc(f);
534 KEYFILE_GET(32); /* "Reserved data" */
535 if (cipher_type != 0) {
536 LDFATAL("we don't support encrypted keyfiles\n");
539 /* Read the public key */
540 KEYFILE_GET(32); /* Not sure what this is */
541 length=(KEYFILE_GET(16)+7)/8;
542 if (length>RSA_MAX_MODBYTES) {
543 LDFATAL("implausible length %ld for modulus\n",
546 b=safe_malloc(length,"rsapriv_apply");
547 if (fread(b,length,1,f) != 1) {
548 LDFATAL_FILE("error reading modulus\n");
550 read_mpbin(&st->n,b,length);
552 length=(KEYFILE_GET(16)+7)/8;
553 if (length>RSA_MAX_MODBYTES) {
554 LDFATAL("implausible length %ld for e\n",length);
556 b=safe_malloc(length,"rsapriv_apply");
557 if (fread(b,length,1,f)!=1) {
558 LDFATAL_FILE("error reading e\n");
560 read_mpbin(&e,b,length);
563 length=KEYFILE_GET(32);
565 LDFATAL("implausibly long (%ld) key comment\n",
568 c=safe_malloc(length+1,"rsapriv_apply");
569 if (fread(c,length,1,f)!=1) {
570 LDFATAL_FILE("error reading key comment\n");
574 /* Check that the next two pairs of characters are identical - the
575 keyfile is not encrypted, so they should be */
577 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
578 LDFATAL("corrupt keyfile\n");
582 length=(KEYFILE_GET(16)+7)/8;
583 if (length>RSA_MAX_MODBYTES) {
584 LDFATAL("implausibly long (%ld) decryption key\n",
587 b=safe_malloc(length,"rsapriv_apply");
588 if (fread(b,length,1,f)!=1) {
589 LDFATAL_FILE("error reading decryption key\n");
591 read_mpbin(&d,b,length);
593 /* Read iqmp (inverse of q mod p) */
594 length=(KEYFILE_GET(16)+7)/8;
595 if (length>RSA_MAX_MODBYTES) {
596 LDFATAL("implausibly long (%ld)"
597 " iqmp auxiliary value\n", length);
599 b=safe_malloc(length,"rsapriv_apply");
600 if (fread(b,length,1,f)!=1) {
601 LDFATAL_FILE("error reading decryption key\n");
603 read_mpbin(&iqmp,b,length);
605 /* Read q (the smaller of the two primes) */
606 length=(KEYFILE_GET(16)+7)/8;
607 if (length>RSA_MAX_MODBYTES) {
608 LDFATAL("implausibly long (%ld) q value\n",
611 b=safe_malloc(length,"rsapriv_apply");
612 if (fread(b,length,1,f)!=1) {
613 LDFATAL_FILE("error reading q value\n");
615 read_mpbin(&st->q,b,length);
617 /* Read p (the larger of the two primes) */
618 length=(KEYFILE_GET(16)+7)/8;
619 if (length>RSA_MAX_MODBYTES) {
620 LDFATAL("implausibly long (%ld) p value\n",
623 b=safe_malloc(length,"rsapriv_apply");
624 if (fread(b,length,1,f)!=1) {
625 LDFATAL_FILE("error reading p value\n");
627 read_mpbin(&st->p,b,length);
631 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
634 rsa_sethash(l,&st->common,&st->ops.hash);
637 * Now verify the validity of the key, and set up the auxiliary
638 * values for fast CRT signing.
641 if (do_validity_check) {
642 /* Verify that p*q is equal to n. */
643 mpz_mul(&tmp, &st->p, &st->q);
644 if (mpz_cmp(&tmp, &st->n) != 0)
648 * Verify that d*e is congruent to 1 mod (p-1), and mod
649 * (q-1). This is equivalent to it being congruent to 1 mod
650 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
651 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
652 * actually necessary.
654 mpz_mul(&tmp, &d, &e);
655 mpz_sub_ui(&tmp2, &st->p, 1);
656 mpz_mod(&tmp3, &tmp, &tmp2);
657 if (mpz_cmp_si(&tmp3, 1) != 0)
659 mpz_sub_ui(&tmp2, &st->q, 1);
660 mpz_mod(&tmp3, &tmp, &tmp2);
661 if (mpz_cmp_si(&tmp3, 1) != 0)
664 /* Verify that q*iqmp is congruent to 1 mod p. */
665 mpz_mul(&tmp, &st->q, &iqmp);
666 mpz_mod(&tmp2, &tmp, &st->p);
667 if (mpz_cmp_si(&tmp2, 1) != 0)
670 /* Now we know the key is valid (or we don't care). */
674 * Now we compute auxiliary values dp, dq and w to allow us
675 * to use the CRT optimisation when signing.
677 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
678 * dq == d mod (q-1) similarly mod q
679 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
681 mpz_sub_ui(&tmp, &st->p, 1);
682 mpz_mod(&st->dp, &d, &tmp);
683 mpz_sub_ui(&tmp, &st->q, 1);
684 mpz_mod(&st->dq, &d, &tmp);
685 mpz_mul(&st->w, &iqmp, &st->q);
689 LDFATAL("file does not contain a "
708 if (st) rsapriv_dispose(st);
713 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
716 if (feof(f)) { load_err(l,0,0,"eof mid-integer"); return False; }
720 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
721 struct buffer_if *privkeydata,
722 struct sigprivkey_if **sigpriv_r,
723 closure_t **closure_r,
724 struct log_if *log, struct cloc loc)
727 struct rsapriv *st=0;
729 f=fmemopen(privkeydata->start,privkeydata->size,"r");
731 slilog(log,M_ERR,"failed to fmemopen private key file\n");
735 struct load_ctx l[1];
736 l->what="rsa1priv load";
737 l->verror=verror_tryload;
738 l->postreadcheck=postreadcheck_tryload;
741 l->u.tryload.log=log;
743 st=rsa_loadpriv_core(l,f,loc,False);
744 if (!st) goto error_out;
751 if (!st) return False;
757 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
759 cfgfile_postreadcheck(l->loc,f);
763 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
770 struct load_ctx l[1];
772 l->what="rsa-private";
773 l->verror=verror_cfgfatal;
774 l->postreadcheck=postreadcheck_apply;
778 /* Argument is filename pointing to SSH1 private key file */
781 if (i->type!=t_string) {
782 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
784 filename=i->data.string;
786 filename=NULL; /* Make compiler happy */
787 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
790 f=fopen(filename,"rb");
792 if (just_check_config) {
793 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
794 "\"%s\"; assuming it's valid while we check the "
795 "rest of the configuration\n",loc.file,loc.line,filename);
797 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
798 loc.file,loc.line,filename);
802 bool_t do_validity_check=True;
804 if (i && i->type==t_bool && i->data.bool==False) {
805 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
806 "check\n",loc.file,loc.line);
807 do_validity_check=False;
810 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
812 return new_closure(&st->cl);
815 void rsa_module(dict_t *dict)
817 add_closure(dict,"rsa-private",rsapriv_apply);
818 add_closure(dict,"rsa-public",rsapub_apply);