Convert SCT verification to CBB.

ok inoguchi@ tb@

1 files changed, 57 insertions, 56 deletions

diff --git a/src/lib/libcrypto/ct/ct_vfy.c b/src/lib/libcrypto/ct/ct_vfy.c
index e88f9394b8..424117263a 100644
--- a/src/lib/libcrypto/ct/ct_vfy.c
+++ b/src/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;
 }