Attachment 3104 Details for Bug 2799 – check signature type at verification time

[patch] check signature type at verification time

bz2799-2.diff (text/plain), 11.68 KB, created by Damien Miller on 2017-12-08 17:56:11 AEDT

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Creator: Damien Miller

Created: 2017-12-08 17:56:11 AEDT

Size: 11.68 KB

patch

obsolete

>diff --git a/auth2-hostbased.c b/auth2-hostbased.c
>index 3ea8311..cc2927e 100644
>--- a/auth2-hostbased.c
>+++ b/auth2-hostbased.c
>@@ -143,7 +143,7 @@ userauth_hostbased(struct ssh *ssh)
> 	authenticated = 0;
> 	if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
> 	    PRIVSEP(sshkey_verify(key, sig, slen,
>-	    sshbuf_ptr(b), sshbuf_len(b), ssh->compat)) == 0)
>+	    sshbuf_ptr(b), sshbuf_len(b), pkalg, ssh->compat)) == 0)
> 		authenticated = 1;
> 
> 	auth2_record_key(authctxt, authenticated, key);
>diff --git a/auth2-pubkey.c b/auth2-pubkey.c
>index 73cc2ed..e7907ed 100644
>--- a/auth2-pubkey.c
>+++ b/auth2-pubkey.c
>@@ -195,7 +195,7 @@ userauth_pubkey(struct ssh *ssh)
> 		authenticated = 0;
> 		if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) &&
> 		    PRIVSEP(sshkey_verify(key, sig, slen, sshbuf_ptr(b),
>-		    sshbuf_len(b), ssh->compat)) == 0) {
>+		    sshbuf_len(b), pkalg, ssh->compat)) == 0) {
> 			authenticated = 1;
> 		}
> 		sshbuf_free(b);
>diff --git a/clientloop.c b/clientloop.c
>index be13321..609ca4b 100644
>--- a/clientloop.c
>+++ b/clientloop.c
>@@ -1919,7 +1919,8 @@ client_global_hostkeys_private_confirm(struct ssh *ssh, int type,
> 			goto out;
> 		}
> 		if ((r = sshkey_verify(ctx->keys[i], sig, siglen,
>-		    sshbuf_ptr(signdata), sshbuf_len(signdata), 0)) != 0) {
>+		    sshbuf_ptr(signdata), sshbuf_len(signdata),
>+		    ssh->kex->hostkey_alg, 0)) != 0) {
> 			error("%s: server gave bad signature for %s key %zu",
> 			    __func__, sshkey_type(ctx->keys[i]), i);
> 			goto out;
>diff --git a/kexc25519c.c b/kexc25519c.c
>index 5661d21..5fe8efc 100644
>--- a/kexc25519c.c
>+++ b/kexc25519c.c
>@@ -139,7 +139,7 @@ input_kex_c25519_reply(int type, u_int32_t seq, struct ssh *ssh)
> 		goto out;
> 
> 	if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
>-	    ssh->compat)) != 0)
>+	    kex->hostkey_alg, ssh->compat)) != 0)
> 		goto out;
> 
> 	/* save session id */
>diff --git a/kexdhc.c b/kexdhc.c
>index efc2772..e145a75 100644
>--- a/kexdhc.c
>+++ b/kexdhc.c
>@@ -178,7 +178,7 @@ input_kex_dh(int type, u_int32_t seq, struct ssh *ssh)
> 		goto out;
> 
> 	if ((r = sshkey_verify(server_host_key, signature, slen, hash, hashlen,
>-	    ssh->compat)) != 0)
>+	    kex->hostkey_alg, ssh->compat)) != 0)
> 		goto out;
> 
> 	/* save session id */
>diff --git a/kexecdhc.c b/kexecdhc.c
>index 3222803..23b7232 100644
>--- a/kexecdhc.c
>+++ b/kexecdhc.c
>@@ -184,7 +184,7 @@ input_kex_ecdh_reply(int type, u_int32_t seq, struct ssh *ssh)
> 		goto out;
> 
> 	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
>-	    hashlen, ssh->compat)) != 0)
>+	    hashlen, kex->hostkey_alg, ssh->compat)) != 0)
> 		goto out;
> 
> 	/* save session id */
>diff --git a/kexgexc.c b/kexgexc.c
>index 6107486..9cc91cd 100644
>--- a/kexgexc.c
>+++ b/kexgexc.c
>@@ -225,7 +225,7 @@ input_kex_dh_gex_reply(int type, u_int32_t seq, struct ssh *ssh)
> 		goto out;
> 
> 	if ((r = sshkey_verify(server_host_key, signature, slen, hash,
>-	    hashlen, ssh->compat)) != 0)
>+	    hashlen, kex->hostkey_alg, ssh->compat)) != 0)
> 		goto out;
> 
> 	/* save session id */
>diff --git a/key.c b/key.c
>index 921a9b5..19175cf 100644
>--- a/key.c
>+++ b/key.c
>@@ -93,21 +93,6 @@ key_sign(const Key *key, u_char **sigp, u_int *lenp,
> 	return 0;
> }
> 
>-int
>-key_verify(const Key *key, const u_char *signature, u_int signaturelen,
>-    const u_char *data, u_int datalen)
>-{
>-	int r;
>-
>-	if ((r = sshkey_verify(key, signature, signaturelen,
>-	    data, datalen, datafellows)) != 0) {
>-		fatal_on_fatal_errors(r, __func__, 0);
>-		error("%s: %s", __func__, ssh_err(r));
>-		return r == SSH_ERR_SIGNATURE_INVALID ? 0 : -1;
>-	}
>-	return 1;
>-}
>-
> Key *
> key_demote(const Key *k)
> {
>diff --git a/key.h b/key.h
>index a14f370..8589755 100644
>--- a/key.h
>+++ b/key.h
>@@ -58,7 +58,6 @@ int	 key_to_blob(const Key *, u_char **, u_int *);
> 
> int	 key_sign(const Key *, u_char **, u_int *, const u_char *, u_int,
>     const char *);
>-int	 key_verify(const Key *, const u_char *, u_int, const u_char *, u_int);
> 
> /* authfile.c */
> Key	*key_load_cert(const char *);
>diff --git a/krl.c b/krl.c
>index cb7f728..33be352 100644
>--- a/krl.c
>+++ b/krl.c
>@@ -1012,7 +1012,7 @@ ssh_krl_from_blob(struct sshbuf *buf, struct ssh_krl **krlp,
> 		}
> 		/* Check signature over entire KRL up to this point */
> 		if ((r = sshkey_verify(key, blob, blen,
>-		    sshbuf_ptr(buf), sig_off, 0)) != 0)
>+		    sshbuf_ptr(buf), sig_off, NULL, 0)) != 0)
> 			goto out;
> 		/* Check if this key has already signed this KRL */
> 		for (i = 0; i < nca_used; i++) {
>diff --git a/monitor.c b/monitor.c
>index a6d5087..4995627 100644
>--- a/monitor.c
>+++ b/monitor.c
>@@ -1048,12 +1048,14 @@ mm_answer_keyverify(int sock, struct sshbuf *m)
> {
> 	struct sshkey *key;
> 	u_char *signature, *data, *blob;
>+	char *sigalg;
> 	size_t signaturelen, datalen, bloblen;
> 	int r, ret, valid_data = 0, encoded_ret;
> 
> 	if ((r = sshbuf_get_string(m, &blob, &bloblen)) != 0 ||
> 	    (r = sshbuf_get_string(m, &signature, &signaturelen)) != 0 ||
>-	    (r = sshbuf_get_string(m, &data, &datalen)) != 0)
>+	    (r = sshbuf_get_string(m, &data, &datalen)) != 0 ||
>+	    (r = sshbuf_get_cstring(m, &sigalg, NULL)) != 0)
> 		fatal("%s: buffer error: %s", __func__, ssh_err(r));
> 
> 	if (hostbased_cuser == NULL || hostbased_chost == NULL ||
>@@ -1082,7 +1084,7 @@ mm_answer_keyverify(int sock, struct sshbuf *m)
> 		fatal("%s: bad signature data blob", __func__);
> 
> 	ret = sshkey_verify(key, signature, signaturelen, data, datalen,
>-	    active_state->compat);
>+	    sigalg, active_state->compat);
> 	debug3("%s: %s %p signature %s", __func__, auth_method, key,
> 	    (ret == 0) ? "verified" : "unverified");
> 	auth2_record_key(authctxt, ret == 0, key);
>diff --git a/monitor_wrap.c b/monitor_wrap.c
>index 11fc243..c123ba7 100644
>--- a/monitor_wrap.c
>+++ b/monitor_wrap.c
>@@ -423,7 +423,7 @@ mm_key_allowed(enum mm_keytype type, const char *user, const char *host,
> 
> int
> mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
>-    const u_char *data, size_t datalen, u_int compat)
>+    const u_char *data, size_t datalen, const char *sigalg, u_int compat)
> {
> 	Buffer m;
> 	u_char *blob;
>@@ -440,6 +440,7 @@ mm_sshkey_verify(const struct sshkey *key, const u_char *sig, size_t siglen,
> 	buffer_put_string(&m, blob, len);
> 	buffer_put_string(&m, sig, siglen);
> 	buffer_put_string(&m, data, datalen);
>+	buffer_put_cstring(&m, sigalg);
> 	free(blob);
> 
> 	mm_request_send(pmonitor->m_recvfd, MONITOR_REQ_KEYVERIFY, &m);
>diff --git a/monitor_wrap.h b/monitor_wrap.h
>index f484b37..575450f 100644
>--- a/monitor_wrap.h
>+++ b/monitor_wrap.h
>@@ -51,7 +51,7 @@ int mm_user_key_allowed(struct passwd *, struct sshkey *, int);
> int mm_hostbased_key_allowed(struct passwd *, const char *,
>     const char *, struct sshkey *);
> int mm_sshkey_verify(const struct sshkey *, const u_char *, size_t,
>-    const u_char *, size_t, u_int);
>+    const u_char *, size_t, const char *, u_int);
> 
> #ifdef GSSAPI
> OM_uint32 mm_ssh_gssapi_server_ctx(Gssctxt **, gss_OID);
>diff --git a/serverloop.c b/serverloop.c
>index 955656e..688f0c8 100644
>--- a/serverloop.c
>+++ b/serverloop.c
>@@ -702,7 +702,8 @@ server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
> 		    ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
> 		    (r = sshkey_puts(key, sigbuf)) != 0 ||
> 		    (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
>-		    sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), NULL, 0)) != 0 ||
>+		    sshbuf_ptr(sigbuf), sshbuf_len(sigbuf),
>+		    ssh->kex->hostkey_alg, 0)) != 0 ||
> 		    (r = sshbuf_put_string(resp, sig, slen)) != 0) {
> 			error("%s: couldn't prepare signature: %s",
> 			    __func__, ssh_err(r));
>diff --git a/ssh-keygen.c b/ssh-keygen.c
>index 282324f..8b2df24 100644
>--- a/ssh-keygen.c
>+++ b/ssh-keygen.c
>@@ -529,7 +529,7 @@ do_convert_private_ssh2_from_blob(u_char *blob, u_int blen)
> 
> 	/* try the key */
> 	if (sshkey_sign(key, &sig, &slen, data, sizeof(data), NULL, 0) != 0 ||
>-	    sshkey_verify(key, sig, slen, data, sizeof(data), 0) != 0) {
>+	    sshkey_verify(key, sig, slen, data, sizeof(data), NULL, 0) != 0) {
> 		sshkey_free(key);
> 		free(sig);
> 		return NULL;
>diff --git a/ssh-rsa.c b/ssh-rsa.c
>index fa9d7f0..076b25e 100644
>--- a/ssh-rsa.c
>+++ b/ssh-rsa.c
>@@ -193,9 +193,10 @@ ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
> 
> int
> ssh_rsa_verify(const struct sshkey *key,
>-    const u_char *sig, size_t siglen, const u_char *data, size_t datalen)
>+    const u_char *sig, size_t siglen, const u_char *data, size_t datalen,
>+    const char *alg)
> {
>-	char *ktype = NULL;
>+	char *sigtype = NULL;
> 	int hash_alg, ret = SSH_ERR_INTERNAL_ERROR;
> 	size_t len, diff, modlen, dlen;
> 	struct sshbuf *b = NULL;
>@@ -210,11 +211,17 @@ ssh_rsa_verify(const struct sshkey *key,
> 
> 	if ((b = sshbuf_from(sig, siglen)) == NULL)
> 		return SSH_ERR_ALLOC_FAIL;
>-	if (sshbuf_get_cstring(b, &ktype, NULL) != 0) {
>+	if (sshbuf_get_cstring(b, &sigtype, NULL) != 0) {
> 		ret = SSH_ERR_INVALID_FORMAT;
> 		goto out;
> 	}
>-	if ((hash_alg = rsa_hash_alg_from_ident(ktype)) == -1) {
>+	/* XXX djm: need cert types that reliably yield SHA-2 signatures */
>+	if (alg != NULL && strcmp(alg, sigtype) != 0 &&
>+	    strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) {
>+		ret = SSH_ERR_SIGNATURE_INVALID;
>+		goto out;
>+	}
>+	if ((hash_alg = rsa_hash_alg_from_ident(sigtype)) == -1) {
> 		ret = SSH_ERR_KEY_TYPE_MISMATCH;
> 		goto out;
> 	}
>@@ -258,7 +265,7 @@ ssh_rsa_verify(const struct sshkey *key,
> 		explicit_bzero(sigblob, len);
> 		free(sigblob);
> 	}
>-	free(ktype);
>+	free(sigtype);
> 	sshbuf_free(b);
> 	explicit_bzero(digest, sizeof(digest));
> 	return ret;
>diff --git a/sshkey.c b/sshkey.c
>index ed4b54e..e8c33ef 100644
>--- a/sshkey.c
>+++ b/sshkey.c
>@@ -1778,7 +1778,7 @@ cert_parse(struct sshbuf *b, struct sshkey *key, struct sshbuf *certbuf)
> 		goto out;
> 	}
> 	if ((ret = sshkey_verify(key->cert->signature_key, sig, slen,
>-	    sshbuf_ptr(key->cert->certblob), signed_len, 0)) != 0)
>+	    sshbuf_ptr(key->cert->certblob), signed_len, NULL, 0)) != 0)
> 		goto out;
> 
> 	/* Success */
>@@ -2067,13 +2067,16 @@ sshkey_sign(const struct sshkey *key,
> 	}
> }
> 
>+#include "log.h"
>+
> /*
>  * ssh_key_verify returns 0 for a correct signature  and < 0 on error.
>+ * If "alg" specified, then the signature must use that algorithm.
>  */
> int
> sshkey_verify(const struct sshkey *key,
>     const u_char *sig, size_t siglen,
>-    const u_char *data, size_t dlen, u_int compat)
>+    const u_char *data, size_t dlen, const char *alg, u_int compat)
> {
> 	if (siglen == 0 || dlen > SSH_KEY_MAX_SIGN_DATA_SIZE)
> 		return SSH_ERR_INVALID_ARGUMENT;
>@@ -2087,7 +2090,7 @@ sshkey_verify(const struct sshkey *key,
> 		return ssh_ecdsa_verify(key, sig, siglen, data, dlen, compat);
> 	case KEY_RSA_CERT:
> 	case KEY_RSA:
>-		return ssh_rsa_verify(key, sig, siglen, data, dlen);
>+		return ssh_rsa_verify(key, sig, siglen, data, dlen, alg);
> #endif /* WITH_OPENSSL */
> 	case KEY_ED25519:
> 	case KEY_ED25519_CERT:
>diff --git a/sshkey.h b/sshkey.h
>index b81cf8f..b45c683 100644
>--- a/sshkey.h
>+++ b/sshkey.h
>@@ -172,7 +172,7 @@ int	 sshkey_sigtype(const u_char *, size_t, char **);
> int	 sshkey_sign(const struct sshkey *, u_char **, size_t *,
>     const u_char *, size_t, const char *, u_int);
> int	 sshkey_verify(const struct sshkey *, const u_char *, size_t,
>-    const u_char *, size_t, u_int);
>+    const u_char *, size_t, const char *, u_int);
> 
> /* for debug */
> void	sshkey_dump_ec_point(const EC_GROUP *, const EC_POINT *);
>@@ -199,7 +199,8 @@ int ssh_rsa_sign(const struct sshkey *key,
>     u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
>     const char *ident);
> int ssh_rsa_verify(const struct sshkey *key,
>-    const u_char *sig, size_t siglen, const u_char *data, size_t datalen);
>+    const u_char *sig, size_t siglen, const u_char *data, size_t datalen,
>+    const char *alg);
> int ssh_dss_sign(const struct sshkey *key, u_char **sigp, size_t *lenp,
>     const u_char *data, size_t datalen, u_int compat);
> int ssh_dss_verify(const struct sshkey *key,

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Attachments on bug 2799: 3090 | 3092 | 3100 | 3104 | 3135