DKIM: fix $dkim_key_length in verify

6 files changed, 22 insertions, 14 deletions

diff --git a/src/src/arc.c b/src/src/arc.c
index b453e171c..578c95c89 100644
--- a/src/src/arc.c
+++ b/src/src/arc.c
@@ -735,7 +735,7 @@ arc_get_verify_hhash(ctx, ams, &hhash);
 
 /* Setup the interface to the signing library */
 
-if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
+if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx, NULL)))
   {
   DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
   as->ams_verify_done = arc_state_reason = US"internal sigverify init error";
@@ -964,7 +964,7 @@ if (!(p = arc_line_to_pubkey(hdr_as)))
 /* We know the b-tag blob is of a nul-term string, so safe as a string */
 pdkim_decode_base64(hdr_as->b.data, &sighash);
 
-if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx)))
+if ((errstr = exim_dkim_verify_init(&p->key, KEYFMT_DER, &vctx, NULL)))
   {
   DEBUG(D_acl) debug_printf("ARC verify init: %s\n", errstr);
   return US"fail";
diff --git a/src/src/dkim.c b/src/src/dkim.c
index 031372720..9c8458b87 100644
--- a/src/src/dkim.c
+++ b/src/src/dkim.c
@@ -406,7 +406,7 @@ for (pdkim_signature * sig = dkim_signatures; sig; sig = sig->next)
     dkim_cur_sig = sig;
     dkim_signing_domain = US sig->domain;
     dkim_signing_selector = US sig->selector;
-    dkim_key_length = sig->sighash.len * 8;
+    dkim_key_length = sig->keybits;
 
     /* These two return static strings, so we can compare the addr
     later to see if the ACL overwrote them.  Check that when logging */
diff --git a/src/src/pdkim/pdkim.c b/src/src/pdkim/pdkim.c
index 7fcfbc76a..0d2674f50 100644
--- a/src/src/pdkim/pdkim.c
+++ b/src/src/pdkim/pdkim.c
@@ -1430,7 +1430,7 @@ if (sig->keytype == KEYTYPE_ED25519)
 
 if ((*errstr = exim_dkim_verify_init(&p->key,
 	    sig->keytype == KEYTYPE_ED25519 ? KEYFMT_ED25519_BARE : KEYFMT_DER,
-	    vctx)))
+	    vctx, &sig->keybits)))
   {
   DEBUG(D_acl) debug_printf("verify_init: %s\n", *errstr);
   sig->verify_status =      PDKIM_VERIFY_INVALID;
diff --git a/src/src/pdkim/pdkim.h b/src/src/pdkim/pdkim.h
index 5ae0f7f45..0b21df8ab 100644
--- a/src/src/pdkim/pdkim.h
+++ b/src/src/pdkim/pdkim.h
@@ -149,8 +149,9 @@ typedef struct pdkim_signature {
   int version;
 
   /* (a=) The signature algorithm. */
-  int keytype;	/* pdkim_keytypes index */
-  int hashtype;	/* pdkim_hashes index */
+  int		keytype;	/* pdkim_keytypes index */
+  unsigned	keybits;	/* size of the key */
+  int		hashtype;	/* pdkim_hashes index */
 
   /* (c=x/) Header canonicalization method. Either PDKIM_CANON_SIMPLE
      or PDKIM_CANON_RELAXED */
diff --git a/src/src/pdkim/signing.c b/src/src/pdkim/signing.c
index 102e7bf51..b55bd9f5f 100644
--- a/src/src/pdkim/signing.c
+++ b/src/src/pdkim/signing.c
@@ -155,7 +155,8 @@ return NULL;
 Return: NULL for success, or an error string */
 
 const uschar *
-exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+  unsigned * bits)
 {
 gnutls_datum_t k;
 int rc;
@@ -182,6 +183,7 @@ switch(fmt)
     ret = US"pubkey format not handled";
     break;
   }
+if (!ret && bits) gnutls_pubkey_get_pk_algorithm(verify_ctx->key, bits);
 return ret;
 }
 
@@ -552,7 +554,8 @@ return NULL;
 Return: NULL for success, or an error string */
 
 const uschar *
-exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+  unsigned * bits)
 {
 /*
 in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
@@ -560,6 +563,7 @@ in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
 uschar tag_class;
 int taglen;
 long alen;
+unsigned nbits;
 int rc;
 uschar * errstr;
 gcry_error_t gerr;
@@ -608,10 +612,10 @@ if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
 
 /* read two integers */
 DEBUG(D_acl) stage = US"MPI";
-if (  (errstr = as_mpi(pubkey, &verify_ctx->n))
-   || (errstr = as_mpi(pubkey, &verify_ctx->e))
-   )
-  return errstr;
+nbits = pubkey->len;
+if ((errstr = as_mpi(pubkey, &verify_ctx->n))) return errstr;
+nbits = (nbits - pubkey->len) * 8;
+if ((errstr = as_mpi(pubkey, &verify_ctx->e))) return errstr;
 
 #ifdef extreme_debug
 DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n");
@@ -624,6 +628,7 @@ DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n");
 	}
 
 #endif
+if (bits) *bits = nbits;
 return NULL;
 
 asn_err:
@@ -794,7 +799,8 @@ return US ERR_error_string(ERR_get_error(), NULL);
 Return: NULL for success, or an error string */
 
 const uschar *
-exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
+  unsigned * bits)
 {
 const uschar * s = pubkey->data;
 uschar * ret = NULL;
@@ -818,6 +824,7 @@ switch(fmt)
     break;
   }
 
+if (!ret && bits) *bits = EVP_PKEY_bits(verify_ctx->key);
 return ret;
 }
 
diff --git a/src/src/pdkim/signing.h b/src/src/pdkim/signing.h
index 96a0720fd..6ecde7537 100644
--- a/src/src/pdkim/signing.h
+++ b/src/src/pdkim/signing.h
@@ -90,7 +90,7 @@ extern gstring * exim_dkim_data_append(gstring *, uschar *);
 
 extern const uschar * exim_dkim_signing_init(const uschar *, es_ctx *);
 extern const uschar * exim_dkim_sign(es_ctx *, hashmethod, blob *, blob *);
-extern const uschar * exim_dkim_verify_init(blob *, keyformat, ev_ctx *);
+extern const uschar * exim_dkim_verify_init(blob *, keyformat, ev_ctx *, unsigned *);
 extern const uschar * exim_dkim_verify(ev_ctx *, hashmethod, blob *, blob *);
 
 #endif	/*DISABLE_DKIM*/