ssh: use RSA/SHA-256 instead of RSA/SHA-1 as the public key algorithm
openssh now disables RSA/SHA-1 by default, so using RSA/SHA-1 will eventually cause us problems: https://undeadly.org/cgi?action=article;sid=20210830113413 in addition, github will disable RSA/SHA-1 for recently added RSA keys: https://github.blog/2021-09-01-improving-git-protocol-security-github/ this patch modifies ssh.c to use RSA/SHA-256 (aka rsa-sha2-256) instead of RSA/SHA-1 (aka ssh-rsa) as the public key algorithm. NOTE: public rsa keys and thumbprints are ***NOT AFFECTED*** by this patch. while we're here, remove the workaround for github.com. it seems that github has fixed their implementation, and does not look into macalgs when we're using an aead cipher. ---
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@ -398,14 +398,16 @@ ssh2rsapub(uchar *data, int len)
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return pub;
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}
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static char rsasha256[] = "rsa-sha2-256";
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int
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rsasig2ssh(RSApub *pub, mpint *S, uchar *data, int len)
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{
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int l = (mpsignif(pub->n)+7)/8;
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if(4+7+4+l > len)
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if(4+12+4+l > len)
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return -1;
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mptober(S, data+4+7+4, l);
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return pack(data, len, "ss", sshrsa, sizeof(sshrsa)-1, data+4+7+4, l);
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mptober(S, data+4+12+4, l);
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return pack(data, len, "ss", rsasha256, sizeof(rsasha256)-1, data+4+12+4, l);
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}
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mpint*
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@ -417,7 +419,7 @@ ssh2rsasig(uchar *data, int len)
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m = mpnew(0);
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if(unpack(data, len, "sm", &s, &n, m) < 0
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|| n != sizeof(sshrsa)-1 || memcmp(s, sshrsa, n) != 0){
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|| n != sizeof(rsasha256)-1 || memcmp(s, rsasha256, n) != 0){
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mpfree(m);
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return nil;
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}
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@ -427,10 +429,10 @@ ssh2rsasig(uchar *data, int len)
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mpint*
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pkcs1digest(uchar *data, int len, RSApub *pub)
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{
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uchar digest[SHA1dlen], buf[256];
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uchar digest[SHA2_256dlen], buf[256];
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sha1(data, len, digest, nil);
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return pkcs1padbuf(buf, asn1encodedigest(sha1, digest, buf, sizeof(buf)), pub->n, 1);
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sha2_256(data, len, digest, nil);
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return pkcs1padbuf(buf, asn1encodedigest(sha2_256, digest, buf, sizeof(buf)), pub->n, 1);
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}
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int
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@ -489,7 +491,7 @@ kex(int gotkexinit)
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static char kexalgs[] = "curve25519-sha256,curve25519-sha256@libssh.org";
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static char cipheralgs[] = "chacha20-poly1305@openssh.com";
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static char zipalgs[] = "none";
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static char macalgs[] = "hmac-sha1"; /* work around for github.com */
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static char macalgs[] = "";
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static char langs[] = "";
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uchar cookie[16], x[32], yc[32], z[32], k[32+1], h[SHA2_256dlen], *ys, *ks, *sig;
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@ -506,7 +508,7 @@ kex(int gotkexinit)
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sendpkt("b[ssssssssssbu", MSG_KEXINIT,
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cookie, sizeof(cookie),
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kexalgs, sizeof(kexalgs)-1,
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sshrsa, sizeof(sshrsa)-1,
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rsasha256, sizeof(rsasha256)-1,
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cipheralgs, sizeof(cipheralgs)-1,
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cipheralgs, sizeof(cipheralgs)-1,
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macalgs, sizeof(macalgs)-1,
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@ -744,7 +746,7 @@ pubkeyauth(void)
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service, strlen(service),
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authmeth, sizeof(authmeth)-1,
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0,
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sshrsa, sizeof(sshrsa)-1,
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rsasha256, sizeof(rsasha256)-1,
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pk, npk);
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Next1: switch(recvpkt()){
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default:
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@ -767,7 +769,7 @@ Next1: switch(recvpkt()){
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service, strlen(service),
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authmeth, sizeof(authmeth)-1,
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1,
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sshrsa, sizeof(sshrsa)-1,
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rsasha256, sizeof(rsasha256)-1,
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pk, npk);
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S = pkcs1digest(send.b, n, pub);
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n = snprint((char*)send.b, sizeof(send.b), "%B", S);
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@ -788,7 +790,7 @@ Next1: switch(recvpkt()){
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service, strlen(service),
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authmeth, sizeof(authmeth)-1,
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1,
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sshrsa, sizeof(sshrsa)-1,
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rsasha256, sizeof(rsasha256)-1,
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pk, npk,
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sig, nsig);
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Next2: switch(recvpkt()){
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