DKIM: more info on verify errors under OpenSSL

diff --git a/src/src/pdkim/signing.c b/src/src/pdkim/signing.c
index 7b8a6a0df5e44f11e6393f8e080595627d02913f..d7491565f97d89b083e5e8c8598f9ebcc3abd1be 100644 (file)
--- a/src/src/pdkim/signing.c
+++ b/src/src/pdkim/signing.c
@@ -831,6 +831,7 @@ const uschar *
 exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig)
 {
 const EVP_MD * md;
+const uschar * where;
 
 switch (hash)
   {
@@ -859,18 +860,23 @@ else
   {
   EVP_PKEY_CTX * ctx;
 
-  if (  (ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL))
-     && 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
+  if (  (where = US"EVP_PKEY_CTX_new",
+            (ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)))
+     && (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)
      )
     { EVP_PKEY_CTX_free(ctx); return NULL; }
 
   if (ctx) EVP_PKEY_CTX_free(ctx);
   }
-return US ERR_error_string(ERR_get_error(), NULL);
+return string_sprintf("%s: %s", where, ERR_error_string(ERR_get_error(), NULL));
 }