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#include "std.h"
#include "dat.h"
/*
* RSA authentication.
*
* Client:
* start n=xxx ek=xxx
* write msg
* read decrypt(msg)
*
* Sign (PKCS #1 using hash=sha1 or hash=md5)
* start n=xxx ek=xxx
* write hash(msg)
* read signature(hash(msg))
*
* all numbers are hexadecimal biginits parsable with strtomp.
* must be lower case for attribute matching in start.
*/
static int
rsaclient(Conv *c)
{
char *chal;
mpint *m;
Key *k;
k = keylookup("%A", c->attr);
if(k == nil)
return -1;
c->state = "read challenge";
if(convreadm(c, &chal) < 0){
keyclose(k);
return -1;
}
if(strlen(chal) < 32){
badchal:
free(chal);
convprint(c, "bad challenge");
keyclose(k);
return -1;
}
m = strtomp(chal, nil, 16, nil);
if(m == nil)
goto badchal;
free(chal);
m = rsadecrypt(k->priv, m, m);
convprint(c, "%B", m);
mpfree(m);
keyclose(k);
return 0;
}
static int
xrsasign(Conv *c)
{
char *hash;
int dlen, n;
DigestAlg *hashfn;
Key *k;
uchar sig[1024], digest[64];
k = keylookup("%A", c->attr);
if(k == nil)
return -1;
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);
return -1;
}
c->state = "read data";
if((n=convread(c, digest, dlen)) < 0){
keyclose(k);
return -1;
}
memset(sig, 0xAA, sizeof sig);
n = rsasign(k->priv, hashfn, digest, dlen, sig, sizeof sig);
keyclose(k);
if(n < 0)
return -1;
convwrite(c, sig, n);
return 0;
}
/*
* 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((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((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[] =
{
"client", rsaclient,
"sign", xrsasign,
0
};
Proto rsa = {
"rsa",
rsaroles,
nil,
rsacheck,
rsaclose
};
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