Convert SCT verification to CBB.

ok inoguchi@ tb@

diff --git a/lib/libcrypto/ct/ct_vfy.c b/lib/libcrypto/ct/ct_vfy.c
index e88f939..4241172 100644 (file)
--- a/lib/libcrypto/ct/ct_vfy.c
+++ b/lib/libcrypto/ct/ct_vfy.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ct_vfy.c,v 1.5 2021/12/18 16:34:52 tb Exp $ */
+/*     $OpenBSD: ct_vfy.c,v 1.6 2022/01/06 14:34:40 jsing Exp $ */
 /*
  * Written by Rob Stradling (rob@comodo.com) and Stephen Henson
  * (steve@openssl.org) for the OpenSSL project 2014.
@@ -79,70 +79,72 @@ typedef enum sct_signature_type_t {
 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;
-        * }
-        */
+       CBB cbb, entry, extensions;
+       uint8_t *data = NULL;
+       size_t data_len;
+       int ret = 0;
+
+       memset(&cbb, 0, sizeof(cbb));
+
        if (sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET)
-               return 0;
+               goto err;
        if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)
-               return 0;
+               goto err;
 
-       p = tmpbuf;
-       *p++ = sct->version;
-       *p++ = SIGNATURE_TYPE_CERT_TIMESTAMP;
-       l2n8(sct->timestamp, p);
-       s2n(sct->entry_type, p);
+       if (!CBB_init(&cbb, 0))
+               goto err;
 
-       if (!EVP_DigestUpdate(ctx, tmpbuf, p - tmpbuf))
-               return 0;
+       /*
+        * Build the digitally-signed struct per RFC 6962 section 3.2.
+        */
+       if (!CBB_add_u8(&cbb, sct->version))
+               goto err;
+       if (!CBB_add_u8(&cbb, SIGNATURE_TYPE_CERT_TIMESTAMP))
+               goto err;
+       if (!CBB_add_u64(&cbb, sct->timestamp))
+               goto err;
+       if (!CBB_add_u16(&cbb, sct->entry_type))
+               goto err;
+
+       if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT) {
+               if (!CBB_add_bytes(&cbb, sctx->ihash, sctx->ihashlen))
+                       goto err;
+       }
 
-       if (sct->entry_type == CT_LOG_ENTRY_TYPE_X509) {
-               der = sctx->certder;
-               derlen = sctx->certderlen;
+       if (!CBB_add_u24_length_prefixed(&cbb, &entry))
+               goto err;
+       if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT) {
+               if (sctx->preder == NULL)
+                       goto err;
+               if (!CBB_add_bytes(&entry, sctx->preder, sctx->prederlen))
+                       goto err;
        } else {
-               if (!EVP_DigestUpdate(ctx, sctx->ihash, sctx->ihashlen))
-                       return 0;
-               der = sctx->preder;
-               derlen = sctx->prederlen;
+               if (sctx->certder == NULL)
+                       goto err;
+               if (!CBB_add_bytes(&entry, sctx->certder, sctx->certderlen))
+                       goto err;
        }
 
-       /* If no encoding available, fatal error */
-       if (der == NULL)
-               return 0;
+       if (!CBB_add_u16_length_prefixed(&cbb, &extensions))
+               goto err;
+       if (sct->ext_len > 0) {
+               if (!CBB_add_bytes(&extensions, sct->ext, sct->ext_len))
+                       goto err;
+       }
 
-       /* Include length first */
-       p = tmpbuf;
-       l2n3(derlen, p);
+       if (!CBB_finish(&cbb, &data, &data_len))
+               goto err;
 
-       if (!EVP_DigestUpdate(ctx, tmpbuf, 3))
-               return 0;
-       if (!EVP_DigestUpdate(ctx, der, derlen))
-               return 0;
+       if (!EVP_DigestUpdate(ctx, data, data_len))
+               goto err;
 
-       /* Add any extensions */
-       p = tmpbuf;
-       s2n(sct->ext_len, p);
-       if (!EVP_DigestUpdate(ctx, tmpbuf, 2))
-               return 0;
+       ret = 1;
 
-       if (sct->ext_len && !EVP_DigestUpdate(ctx, sct->ext, sct->ext_len))
-               return 0;
+ err:
+       CBB_cleanup(&cbb);
+       free(data);
 
-       return 1;
+       return ret;
 }
 
 int
@@ -172,8 +174,7 @@ SCT_CTX_verify(const SCT_CTX *sctx, const SCT *sct)
                return 0;
        }
 
-       ctx = EVP_MD_CTX_new();
-       if (ctx == NULL)
+       if ((ctx = EVP_MD_CTX_new()) == NULL)
                goto end;
 
        if (!EVP_DigestVerifyInit(ctx, NULL, EVP_sha256(), NULL, sctx->pkey))
@@ -183,12 +184,12 @@ SCT_CTX_verify(const SCT_CTX *sctx, const SCT *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)
+       if ((ret = EVP_DigestVerifyFinal(ctx, sct->sig, sct->sig_len)) == 0)
                CTerror(CT_R_SCT_INVALID_SIGNATURE);
 
  end:
        EVP_MD_CTX_free(ctx);
+
        return ret;
 }