1 files changed, 140 insertions, 0 deletions

diff --git a/src/lib/libcrypto/ct/ct_vfy.c b/src/lib/libcrypto/ct/ct_vfy.c
new file mode 100644
index 0000000000..74fd34f415
--- /dev/null
+++ b/src/lib/libcrypto/ct/ct_vfy.c
@@ -0,0 +1,140 @@
+/*
+ * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <string.h>
+
+#include <openssl/ct.h>
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/x509.h>
+
+#include "ct_local.h"
+
+typedef enum sct_signature_type_t {
+    SIGNATURE_TYPE_NOT_SET = -1,
+    SIGNATURE_TYPE_CERT_TIMESTAMP,
+    SIGNATURE_TYPE_TREE_HASH
+} SCT_SIGNATURE_TYPE;
+
+/*
+ * Update encoding for SCT signature verification/generation to supplied
+ * EVP_MD_CTX.
+ */
+static int sct_ctx_update(EVP_MD_CTX *ctx, const SCT_CTX *sctx, const SCT *sct)
+{
+    unsigned char tmpbuf[12];
+    unsigned char *p, *der;
+    size_t derlen;
+    /*+
+     * digitally-signed struct {
+     *   (1 byte) Version sct_version;
+     *   (1 byte) SignatureType signature_type = certificate_timestamp;
+     *   (8 bytes) uint64 timestamp;
+     *   (2 bytes) LogEntryType entry_type;
+     *   (? bytes) select(entry_type) {
+     *     case x509_entry: ASN.1Cert;
+     *     case precert_entry: PreCert;
+     *   } signed_entry;
+     *   (2 bytes + sct->ext_len) CtExtensions extensions;
+     * }
+     */
+    if (sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET)
+        return 0;
+    if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)
+        return 0;
+
+    p = tmpbuf;
+    *p++ = sct->version;
+    *p++ = SIGNATURE_TYPE_CERT_TIMESTAMP;
+    l2n8(sct->timestamp, p);
+    s2n(sct->entry_type, p);
+
+    if (!EVP_DigestUpdate(ctx, tmpbuf, p - tmpbuf))
+        return 0;
+
+    if (sct->entry_type == CT_LOG_ENTRY_TYPE_X509) {
+        der = sctx->certder;
+        derlen = sctx->certderlen;
+    } else {
+        if (!EVP_DigestUpdate(ctx, sctx->ihash, sctx->ihashlen))
+            return 0;
+        der = sctx->preder;
+        derlen = sctx->prederlen;
+    }
+
+    /* If no encoding available, fatal error */
+    if (der == NULL)
+        return 0;
+
+    /* Include length first */
+    p = tmpbuf;
+    l2n3(derlen, p);
+
+    if (!EVP_DigestUpdate(ctx, tmpbuf, 3))
+        return 0;
+    if (!EVP_DigestUpdate(ctx, der, derlen))
+        return 0;
+
+    /* Add any extensions */
+    p = tmpbuf;
+    s2n(sct->ext_len, p);
+    if (!EVP_DigestUpdate(ctx, tmpbuf, 2))
+        return 0;
+
+    if (sct->ext_len && !EVP_DigestUpdate(ctx, sct->ext, sct->ext_len))
+        return 0;
+
+    return 1;
+}
+
+int SCT_CTX_verify(const SCT_CTX *sctx, const SCT *sct)
+{
+    EVP_MD_CTX *ctx = NULL;
+    int ret = 0;
+
+    if (!SCT_is_complete(sct) || sctx->pkey == NULL ||
+        sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET ||
+        (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)) {
+        CTerr(CT_F_SCT_CTX_VERIFY, CT_R_SCT_NOT_SET);
+        return 0;
+    }
+    if (sct->version != SCT_VERSION_V1) {
+        CTerr(CT_F_SCT_CTX_VERIFY, CT_R_SCT_UNSUPPORTED_VERSION);
+        return 0;
+    }
+    if (sct->log_id_len != sctx->pkeyhashlen ||
+        memcmp(sct->log_id, sctx->pkeyhash, sctx->pkeyhashlen) != 0) {
+        CTerr(CT_F_SCT_CTX_VERIFY, CT_R_SCT_LOG_ID_MISMATCH);
+        return 0;
+    }
+    if (sct->timestamp > sctx->epoch_time_in_ms) {
+        CTerr(CT_F_SCT_CTX_VERIFY, CT_R_SCT_FUTURE_TIMESTAMP);
+        return 0;
+    }
+
+    ctx = EVP_MD_CTX_new();
+    if (ctx == NULL)
+        goto end;
+
+    if (!EVP_DigestVerifyInit(ctx, NULL, EVP_sha256(), NULL, sctx->pkey))
+        goto end;
+
+    if (!sct_ctx_update(ctx, sctx, sct))
+        goto end;
+
+    /* Verify signature */
+    ret = EVP_DigestVerifyFinal(ctx, sct->sig, sct->sig_len);
+    /* If ret < 0 some other error: fall through without setting error */
+    if (ret == 0)
+        CTerr(CT_F_SCT_CTX_VERIFY, CT_R_SCT_INVALID_SIGNATURE);
+
+end:
+    EVP_MD_CTX_free(ctx);
+    return ret;
+}