blob: 95545f931a2decbdc5a249e3bfbdc39dc5f5c39c [file] [log] [blame]
#include "std.h"
#include "dat.h"
/*
* RSA authentication.
*
* Encrypt/Decrypt:
* start n=xxx ek=xxx
* write msg
* read encrypt/decrypt(msg)
*
* Sign (PKCS #1 using hash=sha1 or hash=md5)
* start n=xxx ek=xxx
* write hash(msg)
* read signature(hash(msg))
*
* Verify:
* start n=xxx ek=xxx
* write hash(msg)
* write signature(hash(msg))
* read ok or fail
*
* all numbers are hexadecimal biginits parsable with strtomp.
* must be lower case for attribute matching in start.
*/
static int
xrsadecrypt(Conv *c)
{
char *txt, buf[4096], *role;
int n, ret;
mpint *m, *mm;
Key *k;
RSApriv *key;
ret = -1;
txt = nil;
m = nil;
mm = nil;
/* fetch key */
c->state = "keylookup";
k = keylookup("%A", c->attr);
if(k == nil)
goto out;
key = k->priv;
/* make sure have private half if needed */
role = strfindattr(c->attr, "role");
if(strcmp(role, "decrypt") == 0 && !key->c2){
werrstr("missing private half of key -- cannot decrypt");
goto out;
}
/* read text */
c->state = "read";
if((n=convreadm(c, &txt)) < 0)
goto out;
if(n < 32){
convprint(c, "data too short");
goto out;
}
/* encrypt/decrypt */
m = betomp((uchar*)txt, n, nil);
if(m == nil)
goto out;
if(strcmp(role, "decrypt") == 0)
mm = rsadecrypt(key, m, nil);
else
mm = rsaencrypt(&key->pub, m, nil);
if(mm == nil)
goto out;
n = mptobe(mm, (uchar*)buf, sizeof buf, nil);
/* send response */
c->state = "write";
convwrite(c, buf, n);
ret = 0;
out:
mpfree(m);
mpfree(mm);
keyclose(k);
free(txt);
return ret;
}
static int
xrsasign(Conv *c)
{
char *hash, *role;
int dlen, n, ret;
DigestAlg *hashfn;
Key *k;
RSApriv *key;
uchar sig[1024], digest[64];
char *sig2;
ret = -1;
/* fetch key */
c->state = "keylookup";
k = keylookup("%A", c->attr);
if(k == nil)
goto out;
/* make sure have private half if needed */
key = k->priv;
role = strfindattr(c->attr, "role");
if(strcmp(role, "sign") == 0 && !key->c2){
werrstr("missing private half of key -- cannot sign");
goto out;
}
/* get hash type from key */
hash = strfindattr(k->attr, "hash");
if(hash == nil)
hash = "sha1";
if(strcmp(hash, "sha1") == 0){
hashfn = sha1;
dlen = SHA1dlen;
}else if(strcmp(hash, "md5") == 0){
hashfn = md5;
dlen = MD5dlen;
}else{
werrstr("unknown hash function %s", hash);
goto out;
}
/* read hash */
c->state = "read hash";
if((n=convread(c, digest, dlen)) < 0)
goto out;
if(strcmp(role, "sign") == 0){
/* sign */
if((n=rsasign(key, hashfn, digest, dlen, sig, sizeof sig)) < 0)
goto out;
/* write */
convwrite(c, sig, n);
}else{
/* read signature */
if((n = convreadm(c, &sig2)) < 0)
goto out;
/* verify */
if(rsaverify(&key->pub, hashfn, digest, dlen, (uchar*)sig2, n) == 0)
convprint(c, "ok");
else
convprint(c, "signature does not verify");
free(sig2);
}
ret = 0;
out:
keyclose(k);
return ret;
}
/*
* convert to canonical form (lower case)
* for use in attribute matches.
*/
static void
strlwr(char *a)
{
for(; *a; a++){
if('A' <= *a && *a <= 'Z')
*a += 'a' - 'A';
}
}
static RSApriv*
readrsapriv(Key *k)
{
char *a;
RSApriv *priv;
priv = rsaprivalloc();
if((a=strfindattr(k->attr, "ek"))==nil
|| (priv->pub.ek=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if((a=strfindattr(k->attr, "n"))==nil
|| (priv->pub.n=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if(k->privattr == nil) /* only public half */
return priv;
if((a=strfindattr(k->privattr, "!p"))==nil
|| (priv->p=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if((a=strfindattr(k->privattr, "!q"))==nil
|| (priv->q=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if(!probably_prime(priv->p, 20) || !probably_prime(priv->q, 20)) {
werrstr("rsa: p or q not prime");
goto Error;
}
if((a=strfindattr(k->privattr, "!kp"))==nil
|| (priv->kp=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if((a=strfindattr(k->privattr, "!kq"))==nil
|| (priv->kq=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if((a=strfindattr(k->privattr, "!c2"))==nil
|| (priv->c2=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
if((a=strfindattr(k->privattr, "!dk"))==nil
|| (priv->dk=strtomp(a, nil, 16, nil))==nil)
goto Error;
strlwr(a);
return priv;
Error:
rsaprivfree(priv);
return nil;
}
static int
rsacheck(Key *k)
{
static int first = 1;
if(first){
fmtinstall('B', mpfmt);
first = 0;
}
if((k->priv = readrsapriv(k)) == nil){
werrstr("malformed key data");
return -1;
}
return 0;
}
static void
rsaclose(Key *k)
{
rsaprivfree(k->priv);
k->priv = nil;
}
static Role
rsaroles[] =
{
"sign", xrsasign,
"verify", xrsasign, /* public operation */
"decrypt", xrsadecrypt,
"encrypt", xrsadecrypt, /* public operation */
0
};
Proto rsa = {
"rsa",
rsaroles,
nil,
rsacheck,
rsaclose
};