Provide tls_peer_cert_hash() which returns a hash of the raw certificate

that was presented by the peer. The hash used is currently SHA256, however
since we prefix the result with the hash name, we can change this in the
future as the need arises.

The same output can be generated by using:

 h=$(openssl x509 -outform der -in mycert.crt | sha256)
 printf "SHA256:${h}\n"

ok beck@

3 files changed, 92 insertions, 2 deletions

diff --git a/src/lib/libtls/Makefile b/src/lib/libtls/Makefile
index 4b6b34c283..0e3329589e 100644
--- a/src/lib/libtls/Makefile
+++ b/src/lib/libtls/Makefile
@@ -1,4 +1,4 @@
-#       $OpenBSD: Makefile,v 1.14 2015/09/11 07:07:23 jmc Exp $
+#       $OpenBSD: Makefile,v 1.15 2015/09/11 11:28:01 jsing Exp $
 
 CFLAGS+= -Wall -Werror -Wimplicit
 CFLAGS+= -DLIBRESSL_INTERNAL
@@ -15,6 +15,7 @@ HDRS=	tls.h
 SRCS=   tls.c \
         tls_client.c \
         tls_config.c \
+        tls_peer.c \
         tls_server.c \
         tls_util.c \
         tls_verify.c
diff --git a/src/lib/libtls/tls.h b/src/lib/libtls/tls.h
index f7c12920e0..3cb24f0ee5 100644
--- a/src/lib/libtls/tls.h
+++ b/src/lib/libtls/tls.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls.h,v 1.18 2015/09/10 10:26:49 beck Exp $ */
+/* $OpenBSD: tls.h,v 1.19 2015/09/11 11:28:01 jsing Exp $ */
 /*
  * Copyright (c) 2014 Joel Sing <jsing@openbsd.org>
  *
@@ -99,6 +99,8 @@ ssize_t tls_read(struct tls *_ctx, void *_buf, size_t _buflen);
 ssize_t tls_write(struct tls *_ctx, const void *_buf, size_t _buflen);
 int tls_close(struct tls *_ctx);
 
+int tls_peer_cert_hash(struct tls *_ctx, char **_hash);
+
 uint8_t *tls_load_file(const char *_file, size_t *_len, char *_password);
 
 #ifdef __cplusplus
diff --git a/src/lib/libtls/tls_peer.c b/src/lib/libtls/tls_peer.c
new file mode 100644
index 0000000000..e2a2c7b141
--- /dev/null
+++ b/src/lib/libtls/tls_peer.c
@@ -0,0 +1,87 @@
+/* $OpenBSD: tls_peer.c,v 1.1 2015/09/11 11:28:01 jsing Exp $ */
+/*
+ * Copyright (c) 2015 Joel Sing <jsing@openbsd.org>
+ *
+ * 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.
+ */
+
+#include <stdio.h>
+
+#include <openssl/x509.h>
+
+#include <tls.h>
+#include "tls_internal.h"
+
+static int
+tls_hex_string(const unsigned char *in, size_t inlen, char **out,
+    size_t *outlen)
+{
+        static const char hex[] = "0123456789abcdef";
+        size_t i, len;
+        char *p;
+
+        if (outlen != NULL)
+                *outlen = 0;
+
+        if (inlen >= SIZE_MAX)
+                return (-1);
+        if ((*out = reallocarray(NULL, inlen + 1, 2)) == NULL)
+                return (-1);
+
+        p = *out;
+        len = 0;
+        for (i = 0; i < inlen; i++) {
+                p[len++] = hex[(in[i] >> 4) & 0x0f];
+                p[len++] = hex[in[i] & 0x0f];
+        }
+        p[len++] = 0;
+
+        if (outlen != NULL)
+                *outlen = len;
+
+        return (0);
+}
+
+int
+tls_peer_cert_hash(struct tls *ctx, char **hash)
+{
+        char d[EVP_MAX_MD_SIZE], *dhex = NULL;
+        int dlen, rv = -1;
+
+        *hash = NULL;
+        if (ctx->ssl_peer_cert == NULL)
+                return (0);
+
+        if (X509_digest(ctx->ssl_peer_cert, EVP_sha256(), d, &dlen) != 1) {
+                tls_set_errorx(ctx, "digest failed");
+                goto err;
+        }
+
+        if (tls_hex_string(d, dlen, &dhex, NULL) != 0) {
+                tls_set_errorx(ctx, "digest hex string failed");
+                goto err;
+        }
+
+        if (asprintf(hash, "SHA256:%s", dhex) == -1) {
+                tls_set_errorx(ctx, "out of memory");
+                *hash = NULL;
+                goto err;
+        }
+
+        rv = 0;
+
+err:
+        free(dhex);
+
+        return (rv);
+}