From c8b2f3749e953b254b4d6ac1ea047451eb771953 Mon Sep 17 00:00:00 2001
From: Jeremy Harris <jgh146exb@wizmail.org>
Date: Sat, 22 Dec 2018 13:36:07 +0000
Subject: [PATCH] DKIM: better debug for key/signature size mismatch

---
 src/src/pdkim/signing.c | 42 ++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/src/pdkim/signing.c b/src/src/pdkim/signing.c
index 2a086b1e2..a47f824b8 100644
--- a/src/src/pdkim/signing.c
+++ b/src/src/pdkim/signing.c
@@ -831,7 +831,6 @@ const uschar *
 exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig)
 {
 const EVP_MD * md;
-const uschar * where;
 
 switch (hash)
   {
@@ -847,38 +846,39 @@ if (!md)
   {
   EVP_MD_CTX * ctx;
 
-  if (  (ctx = EVP_MD_CTX_new())
-     && EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0
-     && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0
-     )
-    { EVP_MD_CTX_free(ctx); return NULL; }
-
-  if (ctx) EVP_MD_CTX_free(ctx);
+  if ((ctx = EVP_MD_CTX_new()))
+    {
+    if (  EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0
+       && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0
+       )
+      { EVP_MD_CTX_free(ctx); return NULL; }
+    EVP_MD_CTX_free(ctx);
+    }
   }
 else
 #endif
   {
   EVP_PKEY_CTX * ctx;
 
-  if ((where = US"EVP_PKEY_CTX_new",
-	   (ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL))))
+  if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)))
     {
-    if (  (where = US"EVP_PKEY_verify_init",
-		      EVP_PKEY_verify_init(ctx) > 0)
-       && (where = US"EVP_PKEY_CTX_set_rsa_padding",
-		      EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0)
-       && (where = US"EVP_PKEY_CTX_set_signature_md",
-		      EVP_PKEY_CTX_set_signature_md(ctx, md) > 0)
-       && (where = US"EVP_PKEY_verify",
-		      EVP_PKEY_verify(ctx, sig->data, sig->len,
-				      data->data, data->len) == 1)
+    if (  EVP_PKEY_verify_init(ctx) > 0
+       && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0
+       && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0
+       && EVP_PKEY_verify(ctx, sig->data, sig->len,
+				      data->data, data->len) == 1
        )
       { EVP_PKEY_CTX_free(ctx); return NULL; }
-
     EVP_PKEY_CTX_free(ctx);
+
+    DEBUG(D_tls)
+      if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0)
+	debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n",
+	 (int) sig->len, EVP_PKEY_size(verify_ctx->key));
     }
   }
-return string_sprintf("%s: %s", where, ERR_error_string(ERR_get_error(), NULL));
+
+return US ERR_error_string(ERR_get_error(), NULL);
 }
 
 
-- 
2.25.1