1 files changed, 166 insertions, 0 deletions

diff --git a/ssh-ed25519-sk.c b/ssh-ed25519-sk.c
new file mode 100644
index 000000000..b6f28c09a
--- /dev/null
+++ b/ssh-ed25519-sk.c
@@ -0,0 +1,166 @@
+/* $OpenBSD: ssh-ed25519-sk.c,v 1.4 2019/11/26 03:04:27 djm Exp $ */
+/*
+ * Copyright (c) 2019 Markus Friedl.  All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/* #define DEBUG_SK 1 */
+
+#include "includes.h"
+
+#define SSHKEY_INTERNAL
+#include <sys/types.h>
+#include <limits.h>
+
+#include "crypto_api.h"
+
+#include <string.h>
+#include <stdarg.h>
+
+#include "log.h"
+#include "sshbuf.h"
+#include "sshkey.h"
+#include "ssherr.h"
+#include "ssh.h"
+#include "digest.h"
+
+int
+ssh_ed25519_sk_verify(const struct sshkey *key,
+    const u_char *signature, size_t signaturelen,
+    const u_char *data, size_t datalen, u_int compat,
+    struct sshkey_sig_details **detailsp)
+{
+        struct sshbuf *b = NULL;
+        struct sshbuf *encoded = NULL;
+        char *ktype = NULL;
+        const u_char *sigblob;
+        const u_char *sm;
+        u_char *m = NULL;
+        u_char apphash[32];
+        u_char msghash[32];
+        u_char sig_flags;
+        u_int sig_counter;
+        size_t len;
+        unsigned long long smlen = 0, mlen = 0;
+        int r = SSH_ERR_INTERNAL_ERROR;
+        int ret;
+        struct sshkey_sig_details *details = NULL;
+
+        if (detailsp != NULL)
+                *detailsp = NULL;
+
+        if (key == NULL ||
+            sshkey_type_plain(key->type) != KEY_ED25519_SK ||
+            key->ed25519_pk == NULL ||
+            signature == NULL || signaturelen == 0)
+                return SSH_ERR_INVALID_ARGUMENT;
+
+        if ((b = sshbuf_from(signature, signaturelen)) == NULL)
+                return SSH_ERR_ALLOC_FAIL;
+        if (sshbuf_get_cstring(b, &ktype, NULL) != 0 ||
+            sshbuf_get_string_direct(b, &sigblob, &len) != 0 ||
+            sshbuf_get_u8(b, &sig_flags) != 0 ||
+            sshbuf_get_u32(b, &sig_counter) != 0) {
+                r = SSH_ERR_INVALID_FORMAT;
+                goto out;
+        }
+#ifdef DEBUG_SK
+        fprintf(stderr, "%s: data:\n", __func__);
+        /* sshbuf_dump_data(data, datalen, stderr); */
+        fprintf(stderr, "%s: sigblob:\n", __func__);
+        sshbuf_dump_data(sigblob, len, stderr);
+        fprintf(stderr, "%s: sig_flags = 0x%02x, sig_counter = %u\n",
+            __func__, sig_flags, sig_counter);
+#endif
+        if (strcmp(sshkey_ssh_name_plain(key), ktype) != 0) {
+                r = SSH_ERR_KEY_TYPE_MISMATCH;
+                goto out;
+        }
+        if (sshbuf_len(b) != 0) {
+                r = SSH_ERR_UNEXPECTED_TRAILING_DATA;
+                goto out;
+        }
+        if (len > crypto_sign_ed25519_BYTES) {
+                r = SSH_ERR_INVALID_FORMAT;
+                goto out;
+        }
+        if (ssh_digest_memory(SSH_DIGEST_SHA256, key->sk_application,
+            strlen(key->sk_application), apphash, sizeof(apphash)) != 0 ||
+            ssh_digest_memory(SSH_DIGEST_SHA256, data, datalen,
+            msghash, sizeof(msghash)) != 0) {
+                r = SSH_ERR_INVALID_ARGUMENT;
+                goto out;
+        }
+#ifdef DEBUG_SK
+        fprintf(stderr, "%s: hashed application:\n", __func__);
+        sshbuf_dump_data(apphash, sizeof(apphash), stderr);
+        fprintf(stderr, "%s: hashed message:\n", __func__);
+        sshbuf_dump_data(msghash, sizeof(msghash), stderr);
+#endif
+        if ((details = calloc(1, sizeof(*details))) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        details->sk_counter = sig_counter;
+        details->sk_flags = sig_flags;
+        if ((encoded = sshbuf_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if (sshbuf_put(encoded, sigblob, len) != 0 ||
+            sshbuf_put(encoded, apphash, sizeof(apphash)) != 0 ||
+            sshbuf_put_u8(encoded, sig_flags) != 0 ||
+            sshbuf_put_u32(encoded, sig_counter) != 0 ||
+            sshbuf_put(encoded, msghash, sizeof(msghash)) != 0) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+#ifdef DEBUG_SK
+        fprintf(stderr, "%s: signed buf:\n", __func__);
+        sshbuf_dump(encoded, stderr);
+#endif
+        sm = sshbuf_ptr(encoded);
+        smlen = sshbuf_len(encoded);
+        mlen = smlen;
+        if ((m = malloc(smlen)) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((ret = crypto_sign_ed25519_open(m, &mlen, sm, smlen,
+            key->ed25519_pk)) != 0) {
+                debug2("%s: crypto_sign_ed25519_open failed: %d",
+                    __func__, ret);
+        }
+        if (ret != 0 || mlen != smlen - len) {
+                r = SSH_ERR_SIGNATURE_INVALID;
+                goto out;
+        }
+        /* XXX compare 'm' and 'sm + len' ? */
+        /* success */
+        r = 0;
+        if (detailsp != NULL) {
+                *detailsp = details;
+                details = NULL;
+        }
+ out:
+        if (m != NULL) {
+                explicit_bzero(m, smlen); /* NB mlen may be invalid if r != 0 */
+                free(m);
+        }
+        sshkey_sig_details_free(details);
+        sshbuf_free(b);
+        sshbuf_free(encoded);
+        free(ktype);
+        return r;
+}