factotum: update rsa for ssh2 (sync with sources)
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cinap_lenrek
parent
95c865a497
commit
43eed8d824
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@ -1,13 +1,22 @@
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/*
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* SSH RSA authentication.
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*
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* Client protocol:
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* RSA authentication.
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*
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* Old ssh client protocol:
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* read public key
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* if you don't like it, read another, repeat
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* write challenge
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* read response
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*
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* all numbers are hexadecimal biginits parsable with strtomp.
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*
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* Sign (PKCS #1 using hash=sha1 or hash=md5)
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* write hash(msg)
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* read signature(hash(msg))
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*
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* Verify:
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* write hash(msg)
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* write signature(hash(msg))
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* read ok or fail
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*/
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#include "dat.h"
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@ -15,13 +24,22 @@
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enum {
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CHavePub,
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CHaveResp,
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VNeedHash,
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VNeedSig,
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VHaveResp,
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SNeedHash,
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SHaveResp,
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Maxphase,
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};
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static char *phasenames[] = {
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[CHavePub] "CHavePub",
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[CHaveResp] "CHaveResp",
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[VNeedHash] "VNeedHash",
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[VNeedSig] "VNeedSig",
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[VHaveResp] "VHaveResp",
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[SNeedHash] "SNeedHash",
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[SHaveResp] "SHaveResp",
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};
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struct State
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@ -30,8 +48,12 @@ struct State
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mpint *resp;
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int off;
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Key *key;
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mpint *digest;
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int sigresp;
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};
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static mpint* mkdigest(RSApub *key, char *hashalg, uchar *hash, uint dlen);
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static RSApriv*
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readrsapriv(Key *k)
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{
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@ -44,6 +66,8 @@ readrsapriv(Key *k)
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goto Error;
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if((a=_strfindattr(k->attr, "n"))==nil || (priv->pub.n=strtomp(a, nil, 16, nil))==nil)
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goto Error;
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if(k->privattr == nil) /* only public half */
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return priv;
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if((a=_strfindattr(k->privattr, "!p"))==nil || (priv->p=strtomp(a, nil, 16, nil))==nil)
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goto Error;
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if((a=_strfindattr(k->privattr, "!q"))==nil || (priv->q=strtomp(a, nil, 16, nil))==nil)
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@ -66,19 +90,37 @@ Error:
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static int
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rsainit(Proto*, Fsstate *fss)
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{
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int iscli;
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Keyinfo ki;
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State *s;
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char *role;
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if((iscli = isclient(_strfindattr(fss->attr, "role"))) < 0)
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return failure(fss, nil);
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if(iscli==0)
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return failure(fss, "rsa server unimplemented");
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if((role = _strfindattr(fss->attr, "role")) == nil)
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return failure(fss, "rsa role not specified");
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if(strcmp(role, "client") == 0)
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fss->phase = CHavePub;
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else if(strcmp(role, "sign") == 0)
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fss->phase = SNeedHash;
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else if(strcmp(role, "verify") == 0)
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fss->phase = VNeedHash;
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else
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return failure(fss, "rsa role %s unimplemented", role);
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s = emalloc(sizeof *s);
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fss->phasename = phasenames;
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fss->maxphase = Maxphase;
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fss->phase = CHavePub;
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fss->ps = s;
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switch(fss->phase){
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case SNeedHash:
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case VNeedHash:
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mkkeyinfo(&ki, fss, nil);
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if(findkey(&s->key, &ki, nil) != RpcOk)
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return failure(fss, nil);
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/* signing needs private key */
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if(fss->phase == SNeedHash && s->key->privattr == nil)
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return failure(fss,
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"missing private half of key -- cannot sign");
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}
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return RpcOk;
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}
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@ -87,7 +129,9 @@ rsaread(Fsstate *fss, void *va, uint *n)
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{
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RSApriv *priv;
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State *s;
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mpint *m;
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Keyinfo ki;
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int len, r;
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s = fss->ps;
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switch(fss->phase){
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@ -111,14 +155,37 @@ rsaread(Fsstate *fss, void *va, uint *n)
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*n = snprint(va, *n, "%B", s->resp);
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fss->phase = Established;
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return RpcOk;
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case SHaveResp:
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priv = s->key->priv;
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len = (mpsignif(priv->pub.n)+7)/8;
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if(len > *n)
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return failure(fss, "signature buffer too short");
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m = rsadecrypt(priv, s->digest, nil);
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r = mptobe(m, (uchar*)va, len, nil);
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if(r < len){
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memmove((uchar*)va+len-r, va, r);
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memset(va, 0, len-r);
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}
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*n = len;
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mpfree(m);
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fss->phase = Established;
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return RpcOk;
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case VHaveResp:
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*n = snprint(va, *n, "%s", s->sigresp == 0? "ok":
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"signature does not verify");
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fss->phase = Established;
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return RpcOk;
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}
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}
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static int
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rsawrite(Fsstate *fss, void *va, uint)
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rsawrite(Fsstate *fss, void *va, uint n)
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{
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mpint *m;
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RSApriv *priv;
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mpint *m, *mm;
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State *s;
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char *hash;
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int dlen;
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s = fss->ps;
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switch(fss->phase){
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@ -142,6 +209,39 @@ rsawrite(Fsstate *fss, void *va, uint)
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s->resp = m;
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fss->phase = CHaveResp;
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return RpcOk;
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case SNeedHash:
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case VNeedHash:
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/* get hash type from key */
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hash = _strfindattr(s->key->attr, "hash");
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if(hash == nil)
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hash = "sha1";
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if(strcmp(hash, "sha1") == 0)
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dlen = SHA1dlen;
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else if(strcmp(hash, "md5") == 0)
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dlen = MD5dlen;
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else
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return failure(fss, "unknown hash function %s", hash);
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if(n != dlen)
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return failure(fss, "hash length %d should be %d",
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n, dlen);
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priv = s->key->priv;
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s->digest = mkdigest(&priv->pub, hash, (uchar *)va, n);
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if(s->digest == nil)
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return failure(fss, nil);
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if(fss->phase == VNeedHash)
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fss->phase = VNeedSig;
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else
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fss->phase = SHaveResp;
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return RpcOk;
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case VNeedSig:
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priv = s->key->priv;
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m = betomp((uchar*)va, n, nil);
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mm = rsaencrypt(&priv->pub, m, nil);
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s->sigresp = mpcmp(s->digest, mm);
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mpfree(m);
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mpfree(mm);
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fss->phase = VHaveResp;
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return RpcOk;
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}
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}
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@ -155,6 +255,8 @@ rsaclose(Fsstate *fss)
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closekey(s->key);
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if(s->resp)
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mpfree(s->resp);
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if(s->digest)
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mpfree(s->digest);
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free(s);
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}
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@ -185,3 +287,116 @@ Proto rsa = {
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.addkey= rsaaddkey,
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.closekey= rsaclosekey,
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};
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/*
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* Simple ASN.1 encodings.
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* Lengths < 128 are encoded as 1-bytes constants,
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* making our life easy.
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*/
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/*
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* Hash OIDs
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*
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* SHA1 = 1.3.14.3.2.26
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* MDx = 1.2.840.113549.2.x
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*/
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#define O0(a,b) ((a)*40+(b))
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#define O2(x) \
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(((x)>> 7)&0x7F)|0x80, \
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((x)&0x7F)
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#define O3(x) \
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(((x)>>14)&0x7F)|0x80, \
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(((x)>> 7)&0x7F)|0x80, \
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((x)&0x7F)
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uchar oidsha1[] = { O0(1, 3), 14, 3, 2, 26 };
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uchar oidmd2[] = { O0(1, 2), O2(840), O3(113549), 2, 2 };
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uchar oidmd5[] = { O0(1, 2), O2(840), O3(113549), 2, 5 };
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/*
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* DigestInfo ::= SEQUENCE {
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* digestAlgorithm AlgorithmIdentifier,
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* digest OCTET STRING
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* }
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*
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* except that OpenSSL seems to sign
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*
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* DigestInfo ::= SEQUENCE {
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* SEQUENCE{ digestAlgorithm AlgorithmIdentifier, NULL }
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* digest OCTET STRING
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* }
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*
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* instead. Sigh.
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*/
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static int
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mkasn1(uchar *asn1, char *alg, uchar *d, uint dlen)
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{
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uchar *obj, *p;
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uint olen;
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if(strcmp(alg, "sha1") == 0){
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obj = oidsha1;
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olen = sizeof(oidsha1);
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}else if(strcmp(alg, "md5") == 0){
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obj = oidmd5;
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olen = sizeof(oidmd5);
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}else{
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sysfatal("bad alg in mkasn1");
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return -1;
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}
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p = asn1;
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*p++ = 0x30; /* sequence */
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p++;
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*p++ = 0x30; /* another sequence */
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p++;
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*p++ = 0x06; /* object id */
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*p++ = olen;
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memmove(p, obj, olen);
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p += olen;
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*p++ = 0x05; /* null */
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*p++ = 0;
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asn1[3] = p - (asn1+4); /* end of inner sequence */
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*p++ = 0x04; /* octet string */
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*p++ = dlen;
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memmove(p, d, dlen);
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p += dlen;
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asn1[1] = p - (asn1+2); /* end of outer sequence */
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return p - asn1;
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}
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static mpint*
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mkdigest(RSApub *key, char *hashalg, uchar *hash, uint dlen)
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{
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mpint *m;
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uchar asn1[512], *buf;
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int len, n, pad;
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/*
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* Create ASN.1
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*/
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n = mkasn1(asn1, hashalg, hash, dlen);
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/*
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* PKCS#1 padding
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*/
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len = (mpsignif(key->n)+7)/8 - 1;
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if(len < n+2){
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werrstr("rsa key too short");
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return nil;
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}
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pad = len - (n+2);
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buf = emalloc(len);
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buf[0] = 0x01;
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memset(buf+1, 0xFF, pad);
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buf[1+pad] = 0x00;
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memmove(buf+1+pad+1, asn1, n);
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m = betomp(buf, len, nil);
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free(buf);
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return m;
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}
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