# HG changeset patch
# User Matt Johnston <matt@ucc.asn.au>
# Date 1586186306 -28800
# Node ID ba6fc7afe1c56c7a4714bd0d9f575368d1c75d57
# Parent  49cb3cf4bd6f1b989e91e54b64aa101b2a87456b
use sigtype where appropriate

diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 algo.h
--- a/algo.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/algo.h	Mon Apr 06 23:18:26 2020 +0800
@@ -112,7 +112,6 @@
 	const struct ltc_hash_descriptor *hash_desc;
 };
 
-int have_algo(const char* algo, size_t algolen, const algo_type algos[]);
 void buf_put_algolist(buffer * buf, const algo_type localalgos[]);
 
 enum kexguess2_used {
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 cli-authpubkey.c
--- a/cli-authpubkey.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/cli-authpubkey.c	Mon Apr 06 23:18:26 2020 +0800
@@ -33,7 +33,7 @@
 #include "agentfwd.h"
 
 #if DROPBEAR_CLI_PUBKEY_AUTH
-static void send_msg_userauth_pubkey(sign_key *key, int type, int realsign);
+static void send_msg_userauth_pubkey(sign_key *key, enum signkey_type sigtype, int realsign);
 
 /* Called when we receive a SSH_MSG_USERAUTH_FAILURE for a pubkey request.
  * We use it to remove the key we tried from the list */
@@ -58,14 +58,15 @@
 	buffer* keybuf = NULL;
 	char* algotype = NULL;
 	unsigned int algolen;
-	enum signkey_type keytype;
+	enum signkey_type sigtype, keytype;
 	unsigned int remotelen;
 
 	TRACE(("enter recv_msg_userauth_pk_ok"))
 
 	algotype = buf_getstring(ses.payload, &algolen);
-	keytype = signkey_type_from_name(algotype, algolen);
-	TRACE(("recv_msg_userauth_pk_ok: type %d", keytype))
+	sigtype = signature_type_from_name(algotype, algolen);
+	keytype = signkey_type_from_signature(sigtype);
+	TRACE(("recv_msg_userauth_pk_ok: type %d", sigtype))
 	m_free(algotype);
 
 	keybuf = buf_new(MAX_PUBKEY_SIZE);
@@ -120,9 +121,10 @@
 	TRACE(("leave recv_msg_userauth_pk_ok"))
 }
 
-void cli_buf_put_sign(buffer* buf, sign_key *key, int type, 
+static void cli_buf_put_sign(buffer* buf, sign_key *key, enum signkey_type sigtype,
 			const buffer *data_buf) {
 #if DROPBEAR_CLI_AGENTFWD
+	// TODO: rsa-sha256 agent
 	if (key->source == SIGNKEY_SOURCE_AGENT) {
 		/* Format the agent signature ourselves, as buf_put_sign would. */
 		buffer *sigblob;
@@ -133,16 +135,16 @@
 	} else 
 #endif /* DROPBEAR_CLI_AGENTFWD */
 	{
-		buf_put_sign(buf, key, type, data_buf);
+		buf_put_sign(buf, key, sigtype, data_buf);
 	}
 }
 
-/* TODO: make it take an agent reference to use as well */
-static void send_msg_userauth_pubkey(sign_key *key, int type, int realsign) {
+static void send_msg_userauth_pubkey(sign_key *key, enum signkey_type sigtype, int realsign) {
 
 	const char *algoname = NULL;
 	unsigned int algolen;
 	buffer* sigbuf = NULL;
+	enum signkey_type keytype = signkey_type_from_signature(sigtype);
 
 	TRACE(("enter send_msg_userauth_pubkey"))
 	CHECKCLEARTOWRITE();
@@ -160,10 +162,9 @@
 
 	buf_putbyte(ses.writepayload, realsign);
 
-	algoname = signkey_name_from_type(type, &algolen);
-
+	algoname = signature_name_from_type(sigtype, &algolen);
 	buf_putstring(ses.writepayload, algoname, algolen);
-	buf_put_pub_key(ses.writepayload, key, type);
+	buf_put_pub_key(ses.writepayload, key, keytype);
 
 	if (realsign) {
 		TRACE(("realsign"))
@@ -172,7 +173,7 @@
 		sigbuf = buf_new(4 + ses.session_id->len + ses.writepayload->len);
 		buf_putbufstring(sigbuf, ses.session_id);
 		buf_putbytes(sigbuf, ses.writepayload->data, ses.writepayload->len);
-		cli_buf_put_sign(ses.writepayload, key, type, sigbuf);
+		cli_buf_put_sign(ses.writepayload, key, sigtype, sigbuf);
 		buf_free(sigbuf); /* Nothing confidential in the buffer */
 	}
 
@@ -195,8 +196,15 @@
 
 	if (cli_opts.privkeys->first) {
 		sign_key * key = (sign_key*)cli_opts.privkeys->first->item;
+		enum signkey_type sigtype = key->type;
 		/* Send a trial request */
-		send_msg_userauth_pubkey(key, key->type, 0);
+#if DROPBEAR_RSA && DROPBEAR_RSA_SHA256
+		// TODO: use ext-info to choose rsa kind
+		if (sigtype == DROPBEAR_SIGNKEY_RSA) {
+			sigtype = DROPBEAR_SIGNKEY_RSA_SHA256;
+		}
+#endif
+		send_msg_userauth_pubkey(key, sigtype, 0);
 		cli_ses.lastprivkey = key;
 		TRACE(("leave cli_auth_pubkey-success"))
 		return 1;
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 cli-kex.c
--- a/cli-kex.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/cli-kex.c	Mon Apr 06 23:18:26 2020 +0800
@@ -94,7 +94,7 @@
 void recv_msg_kexdh_reply() {
 
 	sign_key *hostkey = NULL;
-	unsigned int type, keybloblen;
+	unsigned int keytype, keybloblen;
 	unsigned char* keyblob = NULL;
 
 	TRACE(("enter recv_msg_kexdh_reply"))
@@ -102,8 +102,8 @@
 	if (cli_ses.kex_state != KEXDH_INIT_SENT) {
 		dropbear_exit("Received out-of-order kexdhreply");
 	}
-	type = ses.newkeys->algo_hostkey;
-	TRACE(("type is %d", type))
+	keytype = ses.newkeys->algo_hostkey;
+	TRACE(("keytype is %d", keytype))
 
 	hostkey = new_sign_key();
 	keybloblen = buf_getint(ses.payload);
@@ -114,7 +114,7 @@
 		checkhostkey(keyblob, keybloblen);
 	}
 
-	if (buf_get_pub_key(ses.payload, hostkey, &type) != DROPBEAR_SUCCESS) {
+	if (buf_get_pub_key(ses.payload, hostkey, &keytype) != DROPBEAR_SUCCESS) {
 		TRACE(("failed getting pubkey"))
 		dropbear_exit("Bad KEX packet");
 	}
@@ -173,7 +173,8 @@
 #endif
 
 	cli_ses.param_kex_algo = NULL;
-	if (buf_verify(ses.payload, hostkey, ses.hash) != DROPBEAR_SUCCESS) {
+	if (buf_verify(ses.payload, hostkey, ses.newkeys->algo_signature, 
+			ses.hash) != DROPBEAR_SUCCESS) {
 		dropbear_exit("Bad hostkey signature");
 	}
 
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 common-algo.c
--- a/common-algo.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/common-algo.c	Mon Apr 06 23:18:26 2020 +0800
@@ -237,8 +237,13 @@
 #endif
 #endif
 #if DROPBEAR_RSA
+#if DROPBEAR_RSA_SHA256
+	{"rsa-sha2-256", DROPBEAR_SIGNKEY_RSA_SHA256, NULL, 1, NULL},
+#endif
+#if DROPBEAR_RSA_SHA1
 	{"ssh-rsa", DROPBEAR_SIGNKEY_RSA, NULL, 1, NULL},
 #endif
+#endif
 #if DROPBEAR_DSS
 	{"ssh-dss", DROPBEAR_SIGNKEY_DSS, NULL, 1, NULL},
 #endif
@@ -311,24 +316,6 @@
 	{NULL, 0, NULL, 0, NULL}
 };
 
-/* algolen specifies the length of algo, algos is our local list to match
- * against.
- * Returns DROPBEAR_SUCCESS if we have a match for algo, DROPBEAR_FAILURE
- * otherwise */
-int have_algo(const char* algo, size_t algolen, const algo_type algos[]) {
-
-	int i;
-
-	for (i = 0; algos[i].name != NULL; i++) {
-		if (strlen(algos[i].name) == algolen
-				&& (strncmp(algos[i].name, algo, algolen) == 0)) {
-			return DROPBEAR_SUCCESS;
-		}
-	}
-
-	return DROPBEAR_FAILURE;
-}
-
 /* Output a comma separated list of algorithms to a buffer */
 void buf_put_algolist(buffer * buf, const algo_type localalgos[]) {
 
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 common-kex.c
--- a/common-kex.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/common-kex.c	Mon Apr 06 23:18:26 2020 +0800
@@ -111,7 +111,8 @@
 
 	if (ses.send_kex_first_guess) {
 		ses.newkeys->algo_kex = sshkex[0].data;
-		ses.newkeys->algo_hostkey = sshhostkey[0].val;
+		ses.newkeys->algo_signature = sshhostkey[0].val;
+		ses.newkeys->algo_hostkey = signkey_type_from_signature(ses.newkeys->algo_signature);
 		ses.send_kex_first_guess();
 	}
 
@@ -152,6 +153,7 @@
 		TRACE(("switch_keys done"))
 		ses.keys->algo_kex = ses.newkeys->algo_kex;
 		ses.keys->algo_hostkey = ses.newkeys->algo_hostkey;
+		ses.keys->algo_signature = ses.newkeys->algo_signature;
 		ses.keys->allow_compress = 0;
 		m_free(ses.newkeys);
 		ses.newkeys = NULL;
@@ -847,8 +849,9 @@
 		erralgo = "hostkey";
 		goto error;
 	}
-	TRACE(("hostkey algo %s", algo->name))
-	ses.newkeys->algo_hostkey = algo->val;
+	TRACE(("signature algo %s", algo->name))
+	ses.newkeys->algo_signature = algo->val;
+	ses.newkeys->algo_hostkey = signkey_type_from_signature(ses.newkeys->algo_signature);
 
 	/* encryption_algorithms_client_to_server */
 	c2s_cipher_algo = buf_match_algo(ses.payload, sshciphers, NULL, NULL);
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 dss.h
--- a/dss.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/dss.h	Mon Apr 06 23:18:26 2020 +0800
@@ -30,7 +30,7 @@
 
 #if DROPBEAR_DSS 
 
-typedef struct {
+typedef struct dropbear_DSS_Key {
 
 	mp_int* p;
 	mp_int* q;
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 ed25519.h
--- a/ed25519.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/ed25519.h	Mon Apr 06 23:18:26 2020 +0800
@@ -32,7 +32,7 @@
 
 #define CURVE25519_LEN 32
 
-typedef struct {
+typedef struct dropbear_ED25519_Key {
 
 	unsigned char priv[CURVE25519_LEN];
 	unsigned char pub[CURVE25519_LEN];
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 fuzzer-pubkey.c
--- a/fuzzer-pubkey.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/fuzzer-pubkey.c	Mon Apr 06 23:18:26 2020 +0800
@@ -27,7 +27,7 @@
 		unsigned int algolen;
 		char* algoname = buf_getstring(keyblob, &algolen);
 
-		if (have_algo(algoname, algolen, sshhostkey) == DROPBEAR_FAILURE) {
+		if (signature_type_from_name(algoname, algolen) == DROPBEAR_SIGNKEY_NONE) {
 			dropbear_exit("fuzzer imagined a bogus algorithm");
 		}
 
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 keyimport.c
--- a/keyimport.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/keyimport.c	Mon Apr 06 23:18:26 2020 +0800
@@ -36,6 +36,9 @@
 #include "dbutil.h"
 #include "ecc.h"
 #include "ssh.h"
+#include "rsa.h"
+#include "dss.h"
+#include "ed25519.h"
 
 static const unsigned char OSSH_PKEY_BLOB[] =
 	"openssh-key-v1\0"			/* AUTH_MAGIC */
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 rsa.c
--- a/rsa.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/rsa.c	Mon Apr 06 23:18:26 2020 +0800
@@ -35,11 +35,16 @@
 #include "buffer.h"
 #include "ssh.h"
 #include "dbrandom.h"
+#include "signkey.h"
 
 #if DROPBEAR_RSA 
 
+#if !(DROPBEAR_RSA_SHA1 || DROPBEAR_RSA_SHA256)
+#error Somehow RSA was enabled with neither DROPBEAR_RSA_SHA1 nor DROPBEAR_RSA_SHA256
+#endif
+
 static void rsa_pad_em(const dropbear_rsa_key * key,
-	const buffer *data_buf, mp_int * rsa_em);
+	const buffer *data_buf, mp_int * rsa_em, enum signkey_type sigtype);
 
 /* Load a public rsa key from a buffer, initialising the values.
  * The key will have the same format as buf_put_rsa_key.
@@ -191,7 +196,8 @@
 #if DROPBEAR_SIGNKEY_VERIFY
 /* Verify a signature in buf, made on data by the key given.
  * Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE */
-int buf_rsa_verify(buffer * buf, const dropbear_rsa_key *key, const buffer *data_buf) {
+int buf_rsa_verify(buffer * buf, const dropbear_rsa_key *key, 
+		enum signkey_type sigtype, const buffer *data_buf) {
 	unsigned int slen;
 	DEF_MP_INT(rsa_s);
 	DEF_MP_INT(rsa_mdash);
@@ -223,7 +229,7 @@
 	}
 
 	/* create the magic PKCS padded value */
-	rsa_pad_em(key, data_buf, &rsa_em);
+	rsa_pad_em(key, data_buf, &rsa_em, sigtype);
 
 	if (mp_exptmod(&rsa_s, key->e, key->n, &rsa_mdash) != MP_OKAY) {
 		TRACE(("failed exptmod rsa_s"))
@@ -246,8 +252,10 @@
 
 /* Sign the data presented with key, writing the signature contents
  * to the buffer */
-void buf_put_rsa_sign(buffer* buf, const dropbear_rsa_key *key, const buffer *data_buf) {
-	unsigned int nsize, ssize;
+void buf_put_rsa_sign(buffer* buf, const dropbear_rsa_key *key, 
+		enum signkey_type sigtype, const buffer *data_buf) {
+	const char *name = NULL;
+	unsigned int nsize, ssize, namelen = 0;
 	unsigned int i;
 	DEF_MP_INT(rsa_s);
 	DEF_MP_INT(rsa_tmp1);
@@ -259,7 +267,7 @@
 
 	m_mp_init_multi(&rsa_s, &rsa_tmp1, &rsa_tmp2, &rsa_tmp3, NULL);
 
-	rsa_pad_em(key, data_buf, &rsa_tmp1);
+	rsa_pad_em(key, data_buf, &rsa_tmp1, sigtype);
 
 	/* the actual signing of the padded data */
 
@@ -311,7 +319,8 @@
 	mp_clear_multi(&rsa_tmp1, &rsa_tmp2, &rsa_tmp3, NULL);
 	
 	/* create the signature to return */
-	buf_putstring(buf, SSH_SIGNKEY_RSA, SSH_SIGNKEY_RSA_LEN);
+	name = signature_name_from_type(sigtype, &namelen);
+	buf_putstring(buf, name, namelen);
 
 	nsize = mp_unsigned_bin_size(key->n);
 
@@ -340,51 +349,73 @@
 	TRACE(("leave buf_put_rsa_sign"))
 }
 
-/* Creates the message value as expected by PKCS, see rfc2437 etc */
-/* format to be padded to is:
- * EM = 01 | FF* | 00 | prefix | hash
- *
- * where FF is repeated enough times to make EM one byte
- * shorter than the size of key->n
- *
- * prefix is the ASN1 designator prefix,
- * hex 30 21 30 09 06 05 2B 0E 03 02 1A 05 00 04 14
- *
- * rsa_em must be a pointer to an initialised mp_int.
- */
+/* Creates the message value as expected by PKCS, 
+   see rfc8017 section 9.2 */
 static void rsa_pad_em(const dropbear_rsa_key * key,
-	const buffer *data_buf, mp_int * rsa_em) {
+	const buffer *data_buf, mp_int * rsa_em, enum signkey_type sigtype) {
+    /* EM = 0x00 || 0x01 || PS || 0x00 || T 
+	   PS is padding of 0xff to make EM the size of key->n
+
+	   T is the DER encoding of the hash alg (sha1 or sha256)
+	*/
 
-	/* ASN1 designator (including the 0x00 preceding) */
-	const unsigned char rsa_asn1_magic[] = 
-		{0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 
+	/* From rfc8017 page 46 */
+#if DROPBEAR_RSA_SHA1
+	const unsigned char T_sha1[] =
+		{0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b,
 		 0x0e, 0x03, 0x02, 0x1a, 0x05, 0x00, 0x04, 0x14};
-	const unsigned int RSA_ASN1_MAGIC_LEN = 16;
+#endif
+#if DROPBEAR_RSA_SHA256
+	const unsigned char T_sha256[] =
+		{0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60, 0x86, 0x48, 0x01,
+		 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20};
+#endif
 
+    int Tlen = 0;
+    const unsigned char *T = NULL;
+	const struct ltc_hash_descriptor *hash_desc = NULL;
 	buffer * rsa_EM = NULL;
 	hash_state hs;
 	unsigned int nsize;
+
+	switch (sigtype) {
+#if DROPBEAR_RSA_SHA1
+		case DROPBEAR_SIGNKEY_RSA:
+			Tlen = sizeof(T_sha1);
+			T = T_sha1;
+			hash_desc = &sha1_desc;
+			break;
+#endif
+#if DROPBEAR_RSA_SHA256
+		case DROPBEAR_SIGNKEY_RSA_SHA256:
+			Tlen = sizeof(T_sha256);
+			T = T_sha256;
+			hash_desc = &sha256_desc;
+			break;
+#endif
+		default:
+			assert(0);
+	}
 	
-	dropbear_assert(key != NULL);
 	nsize = mp_unsigned_bin_size(key->n);
 
-	rsa_EM = buf_new(nsize-1);
+	rsa_EM = buf_new(nsize);
 	/* type byte */
+	buf_putbyte(rsa_EM, 0x00);
 	buf_putbyte(rsa_EM, 0x01);
-	/* Padding with 0xFF bytes */
-	while(rsa_EM->pos != rsa_EM->size - RSA_ASN1_MAGIC_LEN - SHA1_HASH_SIZE) {
+	/* Padding with PS 0xFF bytes */
+	while(rsa_EM->pos != rsa_EM->size - (1 + Tlen + hash_desc->hashsize)) {
 		buf_putbyte(rsa_EM, 0xff);
 	}
+	buf_putbyte(rsa_EM, 0x00);
 	/* Magic ASN1 stuff */
-	memcpy(buf_getwriteptr(rsa_EM, RSA_ASN1_MAGIC_LEN),
-			rsa_asn1_magic, RSA_ASN1_MAGIC_LEN);
-	buf_incrwritepos(rsa_EM, RSA_ASN1_MAGIC_LEN);
+	buf_putbytes(rsa_EM, T, Tlen);
 
 	/* The hash of the data */
-	sha1_init(&hs);
-	sha1_process(&hs, data_buf->data, data_buf->len);
-	sha1_done(&hs, buf_getwriteptr(rsa_EM, SHA1_HASH_SIZE));
-	buf_incrwritepos(rsa_EM, SHA1_HASH_SIZE);
+	hash_desc->init(&hs);
+	hash_desc->process(&hs, data_buf->data, data_buf->len);
+	hash_desc->done(&hs, buf_getwriteptr(rsa_EM, hash_desc->hashsize));
+	buf_incrwritepos(rsa_EM, hash_desc->hashsize);
 
 	dropbear_assert(rsa_EM->pos == rsa_EM->size);
 
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 rsa.h
--- a/rsa.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/rsa.h	Mon Apr 06 23:18:26 2020 +0800
@@ -26,13 +26,12 @@
 #define DROPBEAR_RSA_H_
 
 #include "includes.h"
+#include "signkey.h"
 #include "buffer.h"
 
 #if DROPBEAR_RSA 
 
-#define RSA_SIGNATURE_SIZE (4+7+4+40)
-
-typedef struct {
+typedef struct dropbear_RSA_Key {
 
 	mp_int* n;
 	mp_int* e;
@@ -43,9 +42,11 @@
 
 } dropbear_rsa_key;
 
-void buf_put_rsa_sign(buffer* buf, const dropbear_rsa_key *key, const buffer *data_buf);
+void buf_put_rsa_sign(buffer* buf, const dropbear_rsa_key *key, 
+        enum signkey_type sigtype, const buffer *data_buf);
 #if DROPBEAR_SIGNKEY_VERIFY
-int buf_rsa_verify(buffer * buf, const dropbear_rsa_key *key, const buffer *data_buf);
+int buf_rsa_verify(buffer * buf, const dropbear_rsa_key *key, 
+        enum signkey_type sigtype, const buffer *data_buf);
 #endif
 int buf_get_rsa_pub_key(buffer* buf, dropbear_rsa_key *key);
 int buf_get_rsa_priv_key(buffer* buf, dropbear_rsa_key *key);
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 session.h
--- a/session.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/session.h	Mon Apr 06 23:18:26 2020 +0800
@@ -92,7 +92,8 @@
 	struct key_context_directional trans;
 
 	const struct dropbear_kex *algo_kex;
-	int algo_hostkey;
+	int algo_hostkey; /* server key type */
+	int algo_signature; /* server signature type */
 
 	int allow_compress; /* whether compression has started (useful in 
 							zlib@openssh.com delayed compression case) */
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 signkey.c
--- a/signkey.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/signkey.c	Mon Apr 06 23:18:26 2020 +0800
@@ -28,6 +28,9 @@
 #include "buffer.h"
 #include "ssh.h"
 #include "ecdsa.h"
+#include "rsa.h"
+#include "dss.h"
+#include "ed25519.h"
 
 static const char * const signkey_names[DROPBEAR_SIGNKEY_NUM_NAMED] = {
 #if DROPBEAR_RSA
@@ -44,6 +47,7 @@
 #if DROPBEAR_ED25519
 	"ssh-ed25519",
 #endif /* DROPBEAR_ED25519 */
+	/* "rsa-sha2-256" is special-cased below since it is only a signature name, not key type */
 };
 
 /* malloc a new sign_key and set the dss and rsa keys to NULL */
@@ -105,6 +109,38 @@
 	return DROPBEAR_SIGNKEY_NONE;
 }
 
+/* Special case for rsa-sha2-256. This could be generalised if more 
+   signature names are added that aren't 1-1 with public key names */
+const char* signature_name_from_type(enum signkey_type type, unsigned int *namelen) {
+#if DROPBEAR_RSA_SHA256
+	if (type == DROPBEAR_SIGNKEY_RSA_SHA256) {
+		*namelen = strlen(SSH_SIGNKEY_RSA_SHA256);
+		return SSH_SIGNKEY_RSA_SHA256;
+	}
+#endif
+	return signkey_name_from_type(type, namelen);
+}
+
+enum signkey_type signature_type_from_name(const char* name, unsigned int namelen) {
+#if DROPBEAR_RSA_SHA256
+	if (namelen == strlen(SSH_SIGNKEY_RSA_SHA256) 
+		&& memcmp(name, SSH_SIGNKEY_RSA_SHA256, namelen) == 0) {
+		return DROPBEAR_SIGNKEY_RSA_SHA256;
+	}
+#endif
+	return signkey_type_from_name(name, namelen);
+}
+
+enum signkey_type signkey_type_from_signature(enum signkey_type sigtype) {
+#if DROPBEAR_RSA_SHA256
+	if (sigtype == DROPBEAR_SIGNKEY_RSA_SHA256) {
+		return DROPBEAR_SIGNKEY_RSA;
+	}
+#endif
+	assert(sigtype < DROPBEAR_SIGNKEY_NUM_NAMED);
+	return sigtype;
+}
+
 /* Returns a pointer to the key part specific to "type".
 Be sure to check both (ret != NULL) and (*ret != NULL) */
 void **
@@ -526,31 +562,31 @@
 #endif
 }
 
-void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type type, 
+void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type sigtype, 
 	const buffer *data_buf) {
-	buffer *sigblob;
-	sigblob = buf_new(MAX_PUBKEY_SIZE);
+	buffer *sigblob = buf_new(MAX_PUBKEY_SIZE);
+	enum signkey_type keytype = signkey_type_from_signature(sigtype);
 
 #if DROPBEAR_DSS
-	if (type == DROPBEAR_SIGNKEY_DSS) {
+	if (keytype == DROPBEAR_SIGNKEY_DSS) {
 		buf_put_dss_sign(sigblob, key->dsskey, data_buf);
 	}
 #endif
 #if DROPBEAR_RSA
-	if (type == DROPBEAR_SIGNKEY_RSA) {
-		buf_put_rsa_sign(sigblob, key->rsakey, data_buf);
+	if (keytype == DROPBEAR_SIGNKEY_RSA) {
+		buf_put_rsa_sign(sigblob, key->rsakey, sigtype, data_buf);
 	}
 #endif
 #if DROPBEAR_ECDSA
-	if (signkey_is_ecdsa(type)) {
-		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
+	if (signkey_is_ecdsa(keytype)) {
+		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, keytype);
 		if (eck && *eck) {
 			buf_put_ecdsa_sign(sigblob, *eck, data_buf);
 		}
 	}
 #endif
 #if DROPBEAR_ED25519
-	if (type == DROPBEAR_SIGNKEY_ED25519) {
+	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
 		buf_put_ed25519_sign(sigblob, key->ed25519key, data_buf);
 	}
 #endif
@@ -567,21 +603,27 @@
  * If FAILURE is returned, the position of
  * buf is undefined. If SUCCESS is returned, buf will be positioned after the
  * signature blob */
-int buf_verify(buffer * buf, sign_key *key, const buffer *data_buf) {
+int buf_verify(buffer * buf, sign_key *key, enum signkey_type expect_sigtype, const buffer *data_buf) {
 	
 	char *type_name = NULL;
 	unsigned int type_name_len = 0;
-	enum signkey_type type;
+	enum signkey_type sigtype, keytype;
 
 	TRACE(("enter buf_verify"))
 
 	buf_getint(buf); /* blob length */
 	type_name = buf_getstring(buf, &type_name_len);
-	type = signkey_type_from_name(type_name, type_name_len);
+	sigtype = signature_type_from_name(type_name, type_name_len);
 	m_free(type_name);
 
+	if (expect_sigtype != DROPBEAR_SIGNKEY_ANY
+		&& expect_sigtype != sigtype) {
+			dropbear_exit("Non-matching signing type");
+	}
+
+	keytype = signkey_type_from_signature(sigtype);
 #if DROPBEAR_DSS
-	if (type == DROPBEAR_SIGNKEY_DSS) {
+	if (keytype == DROPBEAR_SIGNKEY_DSS) {
 		if (key->dsskey == NULL) {
 			dropbear_exit("No DSS key to verify signature");
 		}
@@ -590,23 +632,23 @@
 #endif
 
 #if DROPBEAR_RSA
-	if (type == DROPBEAR_SIGNKEY_RSA) {
+	if (keytype == DROPBEAR_SIGNKEY_RSA) {
 		if (key->rsakey == NULL) {
 			dropbear_exit("No RSA key to verify signature");
 		}
-		return buf_rsa_verify(buf, key->rsakey, data_buf);
+		return buf_rsa_verify(buf, key->rsakey, sigtype, data_buf);
 	}
 #endif
 #if DROPBEAR_ECDSA
-	if (signkey_is_ecdsa(type)) {
-		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, type);
+	if (signkey_is_ecdsa(keytype)) {
+		ecc_key **eck = (ecc_key**)signkey_key_ptr(key, keytype);
 		if (eck && *eck) {
 			return buf_ecdsa_verify(buf, *eck, data_buf);
 		}
 	}
 #endif
 #if DROPBEAR_ED25519
-	if (type == DROPBEAR_SIGNKEY_ED25519) {
+	if (keytype == DROPBEAR_SIGNKEY_ED25519) {
 		if (key->ed25519key == NULL) {
 			dropbear_exit("No Ed25519 key to verify signature");
 		}
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 signkey.h
--- a/signkey.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/signkey.h	Mon Apr 06 23:18:26 2020 +0800
@@ -26,9 +26,11 @@
 #define DROPBEAR_SIGNKEY_H_
 
 #include "buffer.h"
-#include "dss.h"
-#include "rsa.h"
-#include "ed25519.h"
+
+/* Forward declarations */
+struct dropbear_DSS_Key;
+struct dropbear_RSA_Key;
+struct dropbear_ED25519_Key;
 
 enum signkey_type {
 #if DROPBEAR_RSA
@@ -47,6 +49,9 @@
 #endif
 	DROPBEAR_SIGNKEY_NUM_NAMED,
 	DROPBEAR_SIGNKEY_ECDSA_KEYGEN = 70, /* just "ecdsa" for keygen */
+#if DROPBEAR_RSA_SHA256
+	DROPBEAR_SIGNKEY_RSA_SHA256, /* rsa-sha2-256 signature. has a ssh-rsa key */
+#endif
 	DROPBEAR_SIGNKEY_ANY = 80,
 	DROPBEAR_SIGNKEY_NONE = 90,
 };
@@ -66,10 +71,10 @@
 	char *filename;
 
 #if DROPBEAR_DSS
-	dropbear_dss_key * dsskey;
+	struct dropbear_DSS_Key * dsskey;
 #endif
 #if DROPBEAR_RSA
-	dropbear_rsa_key * rsakey;
+	struct dropbear_RSA_Key * rsakey;
 #endif
 #if DROPBEAR_ECDSA
 #if DROPBEAR_ECC_256
@@ -83,7 +88,7 @@
 #endif
 #endif
 #if DROPBEAR_ED25519
-	dropbear_ed25519_key * ed25519key;
+	struct dropbear_ED25519_Key * ed25519key;
 #endif
 };
 
@@ -92,14 +97,17 @@
 sign_key * new_sign_key(void);
 const char* signkey_name_from_type(enum signkey_type type, unsigned int *namelen);
 enum signkey_type signkey_type_from_name(const char* name, unsigned int namelen);
+const char* signature_name_from_type(enum signkey_type type, unsigned int *namelen);
+enum signkey_type signature_type_from_name(const char* name, unsigned int namelen);
+enum signkey_type signkey_type_from_signature(enum signkey_type sigtype);
 int buf_get_pub_key(buffer *buf, sign_key *key, enum signkey_type *type);
 int buf_get_priv_key(buffer* buf, sign_key *key, enum signkey_type *type);
 void buf_put_pub_key(buffer* buf, sign_key *key, enum signkey_type type);
 void buf_put_priv_key(buffer* buf, sign_key *key, enum signkey_type type);
 void sign_key_free(sign_key *key);
-void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type type, const buffer *data_buf);
+void buf_put_sign(buffer* buf, sign_key *key, enum signkey_type sigtype, const buffer *data_buf);
 #if DROPBEAR_SIGNKEY_VERIFY
-int buf_verify(buffer * buf, sign_key *key, const buffer *data_buf);
+int buf_verify(buffer * buf, sign_key *key, enum signkey_type type, const buffer *data_buf);
 char * sign_key_fingerprint(const unsigned char* keyblob, unsigned int keybloblen);
 #endif
 int cmp_base64_key(const unsigned char* keyblob, unsigned int keybloblen, 
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 ssh.h
--- a/ssh.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/ssh.h	Mon Apr 06 23:18:26 2020 +0800
@@ -100,13 +100,15 @@
 #define SSH_SERVICE_CONNECTION "ssh-connection"
 #define SSH_SERVICE_CONNECTION_LEN 14
 
-/* public key types */
+/* public/signature key types */
 #define SSH_SIGNKEY_DSS "ssh-dss"
 #define SSH_SIGNKEY_DSS_LEN 7
 #define SSH_SIGNKEY_RSA "ssh-rsa"
 #define SSH_SIGNKEY_RSA_LEN 7
 #define SSH_SIGNKEY_ED25519 "ssh-ed25519"
 #define SSH_SIGNKEY_ED25519_LEN 11
+/* signature type */
+#define SSH_SIGNKEY_RSA_SHA256 "rsa-sha2-256"
 
 /* Agent commands. These aren't part of the spec, and are defined
  * only on the openssh implementation. */
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 svr-authpubkey.c
--- a/svr-authpubkey.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/svr-authpubkey.c	Mon Apr 06 23:18:26 2020 +0800
@@ -70,10 +70,10 @@
 #define MIN_AUTHKEYS_LINE 10 /* "ssh-rsa AB" - short but doesn't matter */
 #define MAX_AUTHKEYS_LINE 4200 /* max length of a line in authkeys */
 
-static int checkpubkey(const char* algo, unsigned int algolen,
+static int checkpubkey(const char* keyalgo, unsigned int keyalgolen,
 		const unsigned char* keyblob, unsigned int keybloblen);
 static int checkpubkeyperms(void);
-static void send_msg_userauth_pk_ok(const char* algo, unsigned int algolen,
+static void send_msg_userauth_pk_ok(const char* sigalgo, unsigned int sigalgolen,
 		const unsigned char* keyblob, unsigned int keybloblen);
 static int checkfileperm(char * filename);
 
@@ -82,16 +82,18 @@
 void svr_auth_pubkey(int valid_user) {
 
 	unsigned char testkey; /* whether we're just checking if a key is usable */
-	char* algo = NULL; /* pubkey algo */
-	unsigned int algolen;
+	char* sigalgo = NULL;
+	unsigned int sigalgolen;
+	const char* keyalgo;
+	unsigned int keyalgolen;
 	unsigned char* keyblob = NULL;
 	unsigned int keybloblen;
 	unsigned int sign_payload_length;
 	buffer * signbuf = NULL;
 	sign_key * key = NULL;
 	char* fp = NULL;
-	enum signkey_type type = -1;
-        int auth_failure = 1;
+	enum signkey_type sigtype, keytype;
+    int auth_failure = 1;
 
 	TRACE(("enter pubkeyauth"))
 
@@ -99,7 +101,11 @@
 	 * actual attempt*/
 	testkey = (buf_getbool(ses.payload) == 0);
 
-	algo = buf_getstring(ses.payload, &algolen);
+	sigalgo = buf_getstring(ses.payload, &sigalgolen);
+	sigtype = signature_type_from_name(sigalgo, sigalgolen);
+	keytype = signkey_type_from_signature(sigtype);
+	keyalgo = signkey_name_from_type(keytype, &keyalgolen);
+
 	keybloblen = buf_getint(ses.payload);
 	keyblob = buf_getptr(ses.payload, keybloblen);
 
@@ -117,8 +123,8 @@
             if (svr_ses.plugin_instance->checkpubkey(
                         svr_ses.plugin_instance,
                         &ses.plugin_session,
-                        algo, 
-                        algolen, 
+                        keyalgo, 
+                        keyalgolen, 
                         keyblob, 
                         keybloblen,
                         ses.authstate.username) == DROPBEAR_SUCCESS) {
@@ -146,7 +152,7 @@
 #endif
 	/* check if the key is valid */
         if (auth_failure) {
-            auth_failure = checkpubkey(algo, algolen, keyblob, keybloblen) == DROPBEAR_FAILURE;
+            auth_failure = checkpubkey(keyalgo, keyalgolen, keyblob, keybloblen) == DROPBEAR_FAILURE;
         }
 
         if (auth_failure) {
@@ -156,7 +162,7 @@
 
 	/* let them know that the key is ok to use */
 	if (testkey) {
-		send_msg_userauth_pk_ok(algo, algolen, keyblob, keybloblen);
+		send_msg_userauth_pk_ok(sigalgo, sigalgolen, keyblob, keybloblen);
 		goto out;
 	}
 
@@ -164,8 +170,7 @@
 	
 	/* get the key */
 	key = new_sign_key();
-	type = DROPBEAR_SIGNKEY_ANY;
-	if (buf_get_pub_key(ses.payload, key, &type) == DROPBEAR_FAILURE) {
+	if (buf_get_pub_key(ses.payload, key, &keytype) == DROPBEAR_FAILURE) {
 		send_msg_userauth_failure(0, 1);
 		goto out;
 	}
@@ -188,7 +193,7 @@
 
 	/* ... and finally verify the signature */
 	fp = sign_key_fingerprint(keyblob, keybloblen);
-	if (buf_verify(ses.payload, key, signbuf) == DROPBEAR_SUCCESS) {
+	if (buf_verify(ses.payload, key, sigtype, signbuf) == DROPBEAR_SUCCESS) {
 		dropbear_log(LOG_NOTICE,
 				"Pubkey auth succeeded for '%s' with key %s from %s",
 				ses.authstate.pw_name, fp, svr_ses.addrstring);
@@ -213,8 +218,8 @@
 	if (signbuf) {
 		buf_free(signbuf);
 	}
-	if (algo) {
-		m_free(algo);
+	if (sigalgo) {
+		m_free(sigalgo);
 	}
 	if (key) {
 		sign_key_free(key);
@@ -230,14 +235,14 @@
 /* Reply that the key is valid for auth, this is sent when the user sends
  * a straight copy of their pubkey to test, to avoid having to perform
  * expensive signing operations with a worthless key */
-static void send_msg_userauth_pk_ok(const char* algo, unsigned int algolen,
+static void send_msg_userauth_pk_ok(const char* sigalgo, unsigned int sigalgolen,
 		const unsigned char* keyblob, unsigned int keybloblen) {
 
 	TRACE(("enter send_msg_userauth_pk_ok"))
 	CHECKCLEARTOWRITE();
 
 	buf_putbyte(ses.writepayload, SSH_MSG_USERAUTH_PK_OK);
-	buf_putstring(ses.writepayload, algo, algolen);
+	buf_putstring(ses.writepayload, sigalgo, sigalgolen);
 	buf_putstring(ses.writepayload, (const char*)keyblob, keybloblen);
 
 	encrypt_packet();
@@ -354,7 +359,7 @@
 /* Checks whether a specified publickey (and associated algorithm) is an
  * acceptable key for authentication */
 /* Returns DROPBEAR_SUCCESS if key is ok for auth, DROPBEAR_FAILURE otherwise */
-static int checkpubkey(const char* algo, unsigned int algolen,
+static int checkpubkey(const char* keyalgo, unsigned int keyalgolen,
 		const unsigned char* keyblob, unsigned int keybloblen) {
 
 	FILE * authfile = NULL;
@@ -368,14 +373,6 @@
 
 	TRACE(("enter checkpubkey"))
 
-	/* check that we can use the algo */
-	if (have_algo(algo, algolen, sshhostkey) == DROPBEAR_FAILURE) {
-		dropbear_log(LOG_WARNING,
-				"Pubkey auth attempt with unknown algo for '%s' from %s",
-				ses.authstate.pw_name, svr_ses.addrstring);
-		goto out;
-	}
-
 	/* check file permissions, also whether file exists */
 	if (checkpubkeyperms() == DROPBEAR_FAILURE) {
 		TRACE(("bad authorized_keys permissions, or file doesn't exist"))
@@ -427,7 +424,7 @@
 		}
 		line_num++;
 
-		ret = checkpubkey_line(line, line_num, filename, algo, algolen, keyblob, keybloblen);
+		ret = checkpubkey_line(line, line_num, filename, keyalgo, keyalgolen, keyblob, keybloblen);
 		if (ret == DROPBEAR_SUCCESS) {
 			break;
 		}
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 svr-kex.c
--- a/svr-kex.c	Fri Mar 27 23:23:11 2020 +0800
+++ b/svr-kex.c	Mon Apr 06 23:18:26 2020 +0800
@@ -234,7 +234,7 @@
 
 	/* calc the signature */
 	buf_put_sign(ses.writepayload, svr_opts.hostkey, 
-			ses.newkeys->algo_hostkey, ses.hash);
+			ses.newkeys->algo_signature, ses.hash);
 
 	/* the SSH_MSG_KEXDH_REPLY is done */
 	encrypt_packet();
diff -r 49cb3cf4bd6f -r ba6fc7afe1c5 sysoptions.h
--- a/sysoptions.h	Fri Mar 27 23:23:11 2020 +0800
+++ b/sysoptions.h	Mon Apr 06 23:18:26 2020 +0800
@@ -139,9 +139,17 @@
  * signing operations slightly slower. */
 #define DROPBEAR_RSA_BLINDING 1
 
+#ifndef DROPBEAR_RSA_SHA1
+#define DROPBEAR_RSA_SHA1 DROPBEAR_RSA
+#endif
+#ifndef DROPBEAR_RSA_SHA256
+#define DROPBEAR_RSA_SHA256 DROPBEAR_RSA
+#endif
+
 /* hashes which will be linked and registered */
-#define DROPBEAR_SHA256 ((DROPBEAR_SHA2_256_HMAC) || (DROPBEAR_ECC_256)  \
- 			|| (DROPBEAR_CURVE25519) || (DROPBEAR_DH_GROUP14_SHA256))
+#define DROPBEAR_SHA256 ((DROPBEAR_SHA2_256_HMAC) || (DROPBEAR_ECC_256) \
+ 			|| (DROPBEAR_CURVE25519) || (DROPBEAR_DH_GROUP14_SHA256) \
+			|| (DROPBEAR_RSA_SHA256))
 #define DROPBEAR_SHA384 (DROPBEAR_ECC_384)
 /* LTC SHA384 depends on SHA512 */
 #define DROPBEAR_SHA512 ((DROPBEAR_SHA2_512_HMAC) || (DROPBEAR_ECC_521) \