Attachment 3264 Details for Bug 2995 – Use SSH KDF from OpenSSL

Use SSH KDF from OpenSSL

file_2995.txt (text/plain), 3.23 KB, created by Jakub Jelen on 2019-04-17 19:29:51 AEST

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Creator: Jakub Jelen

Created: 2019-04-17 19:29:51 AEST

Size: 3.23 KB

patch

obsolete

>commit 2c3ef499bfffce3cfd315edeebf202850ba4e00a
>Author: Jakub Jelen <jjelen@redhat.com>
>Date:   Tue Apr 16 15:35:18 2019 +0200
>
>    Use the new OpenSSL KDF
>
>diff --git a/configure.ac b/configure.ac
>index 2a455e4e..e01c3d43 100644
>--- a/configure.ac
>+++ b/configure.ac
>@@ -2712,6 +2712,7 @@ if test "x$openssl" = "xyes" ; then
> 		HMAC_CTX_init \
> 		RSA_generate_key_ex \
> 		RSA_get_default_method \
>+		EVP_KDF_CTX_new_id \
> 	])
> 
> 	# OpenSSL_add_all_algorithms may be a macro.
>diff --git a/kex.c b/kex.c
>index b6f041f4..1fbce2bb 100644
>--- a/kex.c
>+++ b/kex.c
>@@ -38,6 +38,9 @@
> #ifdef WITH_OPENSSL
> #include <openssl/crypto.h>
> #include <openssl/dh.h>
>+# ifdef HAVE_EVP_KDF_CTX_NEW_ID
>+# include <openssl/kdf.h>
>+# endif
> #endif
> 
> #include "ssh.h"
>@@ -942,6 +945,95 @@ kex_choose_conf(struct ssh *ssh)
> 	return r;
> }
> 
>+#ifdef HAVE_EVP_KDF_CTX_NEW_ID
>+static const EVP_MD *
>+digest_to_md(int digest_type)
>+{
>+	switch (digest_type) {
>+	case SSH_DIGEST_SHA1:
>+		return EVP_sha1();
>+	case SSH_DIGEST_SHA256:
>+		return EVP_sha256();
>+	case SSH_DIGEST_SHA384:
>+		return EVP_sha384();
>+	case SSH_DIGEST_SHA512:
>+		return EVP_sha512();
>+	}
>+	return NULL;
>+}
>+
>+static int
>+derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
>+    const struct sshbuf *shared_secret, u_char **keyp)
>+{
>+	struct kex *kex = ssh->kex;
>+	EVP_KDF_CTX *ctx = NULL;
>+	u_char *key = NULL;
>+	int r, key_len;
>+
>+	if ((key_len = ssh_digest_bytes(kex->hash_alg)) == 0)
>+		return SSH_ERR_INVALID_ARGUMENT;
>+	key_len = ROUNDUP(need, key_len);
>+	if ((key = calloc(1, key_len)) == NULL) {
>+		r = SSH_ERR_ALLOC_FAIL;
>+		goto out;
>+	}
>+
>+	ctx = EVP_KDF_CTX_new_id(EVP_KDF_SSHKDF);
>+	if (!ctx) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+
>+	r = EVP_KDF_ctrl(ctx, EVP_KDF_CTRL_SET_MD, digest_to_md(kex->hash_alg));
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+	r = EVP_KDF_ctrl(ctx, EVP_KDF_CTRL_SET_KEY,
>+	    sshbuf_ptr(shared_secret), sshbuf_len(shared_secret));
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+	r = EVP_KDF_ctrl(ctx, EVP_KDF_CTRL_SET_SSHKDF_XCGHASH, hash, hashlen);
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+	r = EVP_KDF_ctrl(ctx, EVP_KDF_CTRL_SET_SSHKDF_TYPE, id);
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+	r = EVP_KDF_ctrl(ctx, EVP_KDF_CTRL_SET_SSHKDF_SESSION_ID,
>+	    kex->session_id, kex->session_id_len);
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+	r = EVP_KDF_derive(ctx, key, key_len);
>+	if (r != 1) {
>+		r = SSH_ERR_LIBCRYPTO_ERROR;
>+		goto out;
>+	}
>+#ifdef DEBUG_KEX
>+	fprintf(stderr, "key '%c'== ", id);
>+	dump_digest("key", key, key_len);
>+#endif
>+	*keyp = key;
>+	key = NULL;
>+	r = 0;
>+
>+out:
>+	free (key);
>+	EVP_KDF_CTX_free(ctx);
>+	if (r < 0) {
>+		return r;
>+	}
>+	return 0;
>+}
>+#else
> static int
> derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
>     const struct sshbuf *shared_secret, u_char **keyp)
>@@ -1004,6 +1096,7 @@ derive_key(struct ssh *ssh, int id, u_int need, u_char *hash, u_int hashlen,
> 	ssh_digest_free(hashctx);
> 	return r;
> }
>+#endif /* HAVE_OPENSSL_EVP_KDF_CTX_NEW_ID */
> 
> #define NKEYS	6
> int

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