Adding upstream version 4.92.upstream/4.92upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 891 insertions, 0 deletions

diff --git a/src/pdkim/signing.c b/src/pdkim/signing.c
new file mode 100644
index 0000000..a47f824
--- /dev/null
+++ b/src/pdkim/signing.c
@@ -0,0 +1,891 @@
+/*
+ *  PDKIM - a RFC4871 (DKIM) implementation
+ *
+ *  Copyright (C) 1995 - 2018  Exim maintainers
+ *
+ *  signing/verification interface
+ */
+
+#include "../exim.h"
+#include "crypt_ver.h"
+#include "signing.h"
+
+
+#ifdef MACRO_PREDEF
+# include "../macro_predef.h"
+
+void
+features_crypto(void)
+{
+# ifdef SIGN_HAVE_ED25519
+  builtin_macro_create(US"_CRYPTO_SIGN_ED25519");
+# endif
+# ifdef EXIM_HAVE_SHA3
+  builtin_macro_create(US"_CRYPTO_HASH_SHA3");
+# endif
+}
+#else
+
+#ifndef DISABLE_DKIM	/* rest of file */
+
+#ifndef SUPPORT_TLS
+# error Need SUPPORT_TLS for DKIM
+#endif
+
+
+/******************************************************************************/
+#ifdef SIGN_GNUTLS
+# define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3
+
+
+/* Logging function which can be registered with
+ *   gnutls_global_set_log_function()
+ *   gnutls_global_set_log_level() 0..9
+ */
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+static void
+exim_gnutls_logger_cb(int level, const char *message)
+{
+size_t len = strlen(message);
+if (len < 1)
+  {
+  DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level);
+  return;
+  }
+DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message,
+    message[len-1] == '\n' ? "" : "\n");
+}
+#endif
+
+
+
+void
+exim_dkim_init(void)
+{
+#if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0
+DEBUG(D_tls)
+  {
+  gnutls_global_set_log_function(exim_gnutls_logger_cb);
+  /* arbitrarily chosen level; bump upto 9 for more */
+  gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL);
+  }
+#endif
+}
+
+
+/* accumulate data (gnutls-only).  String to be appended must be nul-terminated. */
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return string_cat(g, s);
+}
+
+
+
+/* import private key from PEM string in memory.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+gnutls_datum_t k = { .data = (void *)privkey_pem, .size = Ustrlen(privkey_pem) };
+gnutls_x509_privkey_t x509_key;
+const uschar * where;
+int rc;
+
+if (  (where = US"internal init", rc = gnutls_x509_privkey_init(&x509_key))
+   || (rc = gnutls_privkey_init(&sign_ctx->key))
+   || (where = US"privkey PEM-block import",
+       rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM))
+   || (where = US"internal privkey transfer",
+       rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0))
+   )
+  return string_sprintf("%s: %s", where, gnutls_strerror(rc));
+
+switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL))
+  {
+  case GNUTLS_PK_RSA:		sign_ctx->keytype = KEYTYPE_RSA;     break;
+#ifdef SIGN_HAVE_ED25519
+  case GNUTLS_PK_EDDSA_ED25519:	sign_ctx->keytype = KEYTYPE_ED25519; break;
+#endif
+  default: return rc < 0
+    ? CUS gnutls_strerror(rc)
+    : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc));
+  }
+
+return NULL;
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* hash & sign data.   No way to do incremental.
+
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+gnutls_datum_t k_data = { .data = data->data, .size = data->len };
+gnutls_digest_algorithm_t dig;
+gnutls_datum_t k_sig;
+int rc;
+
+switch (hash)
+  {
+  case HASH_SHA1:	dig = GNUTLS_DIG_SHA1; break;
+  case HASH_SHA2_256:	dig = GNUTLS_DIG_SHA256; break;
+  case HASH_SHA2_512:	dig = GNUTLS_DIG_SHA512; break;
+  default:		return US"nonhandled hash type";
+  }
+
+if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig)))
+  return CUS gnutls_strerror(rc);
+
+/* Don't care about deinit for the key; shortlived process */
+
+sig->data = k_sig.data;
+sig->len = k_sig.size;
+return NULL;
+}
+
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+{
+gnutls_datum_t k;
+int rc;
+const uschar * ret = NULL;
+
+gnutls_pubkey_init(&verify_ctx->key);
+k.data = pubkey->data;
+k.size = pubkey->len;
+
+switch(fmt)
+  {
+  case KEYFMT_DER:
+    if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER)))
+      ret = US gnutls_strerror(rc);
+    break;
+#ifdef SIGN_HAVE_ED25519
+  case KEYFMT_ED25519_BARE:
+    if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key,
+					  GNUTLS_ECC_CURVE_ED25519, &k, NULL)))
+      ret = US gnutls_strerror(rc);
+    break;
+#endif
+  default:
+    ret = US"pubkey format not handled";
+    break;
+  }
+return ret;
+}
+
+
+/* verify signature (of hash if RSA sig, of data if EC sig.  No way to do incremental)
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
+{
+gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len };
+gnutls_datum_t s = { .data = sig->data,       .size = sig->len };
+int rc;
+const uschar * ret = NULL;
+
+#ifdef SIGN_HAVE_ED25519
+if (verify_ctx->keytype == KEYTYPE_ED25519)
+  {
+  if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key,
+				      GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0)
+    ret = US gnutls_strerror(rc);
+  }
+else
+#endif
+  {
+  gnutls_sign_algorithm_t algo;
+  switch (hash)
+    {
+    case HASH_SHA1:	algo = GNUTLS_SIGN_RSA_SHA1;   break;
+    case HASH_SHA2_256:	algo = GNUTLS_SIGN_RSA_SHA256; break;
+    case HASH_SHA2_512:	algo = GNUTLS_SIGN_RSA_SHA512; break;
+    default:		return US"nonhandled hash type";
+    }
+
+  if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, 0, &k, &s)) < 0)
+    ret = US gnutls_strerror(rc);
+  }
+
+gnutls_pubkey_deinit(verify_ctx->key);
+return ret;
+}
+
+
+
+
+#elif defined(SIGN_GCRYPT)
+/******************************************************************************/
+/* This variant is used under pre-3.0.0 GnuTLS.  Only rsa-sha1 and rsa-sha256 */
+
+
+/* Internal service routine:
+Read and move past an asn.1 header, checking class & tag,
+optionally returning the data-length */
+
+static int
+as_tag(blob * der, uschar req_cls, long req_tag, long * alen)
+{
+int rc;
+uschar tag_class;
+int taglen;
+long tag, len;
+
+debug_printf_indent("as_tag: %02x %02x %02x %02x\n",
+	der->data[0], der->data[1], der->data[2], der->data[3]);
+
+if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag))
+    != ASN1_SUCCESS)
+  return rc;
+
+if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND;
+
+if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0)
+  return ASN1_DER_ERROR;
+if (alen) *alen = len;
+
+/* debug_printf_indent("as_tag:  tlen %d dlen %d\n", taglen, (int)len); */
+
+der->data += taglen;
+der->len -= taglen;
+return rc;
+}
+
+/* Internal service routine:
+Read and move over an asn.1 integer, setting an MPI to the value
+*/
+
+static uschar *
+as_mpi(blob * der, gcry_mpi_t * mpi)
+{
+long alen;
+int rc;
+gcry_error_t gerr;
+
+debug_printf_indent("%s\n", __FUNCTION__);
+
+/* integer; move past the header */
+if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
+  return US asn1_strerror(rc);
+
+/* read to an MPI */
+if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL)))
+  return US gcry_strerror(gerr);
+
+/* move over the data */
+der->data += alen; der->len -= alen;
+return NULL;
+}
+
+
+
+void
+exim_dkim_init(void)
+{
+/* Version check should be the very first call because it
+makes sure that important subsystems are initialized. */
+if (!gcry_check_version (GCRYPT_VERSION))
+  {
+  fputs ("libgcrypt version mismatch\n", stderr);
+  exit (2);
+  }
+
+/* We don't want to see any warnings, e.g. because we have not yet
+parsed program options which might be used to suppress such
+warnings. */
+gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN);
+
+/* ... If required, other initialization goes here.  Note that the
+process might still be running with increased privileges and that
+the secure memory has not been initialized.  */
+
+/* Allocate a pool of 16k secure memory.  This make the secure memory
+available and also drops privileges where needed.  */
+gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0);
+
+/* It is now okay to let Libgcrypt complain when there was/is
+a problem with the secure memory. */
+gcry_control (GCRYCTL_RESUME_SECMEM_WARN);
+
+/* ... If required, other initialization goes here.  */
+
+/* Tell Libgcrypt that initialization has completed. */
+gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
+
+return;
+}
+
+
+
+
+/* Accumulate data (gnutls-only).
+String to be appended must be nul-terminated. */
+
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return g;	/*dummy*/
+}
+
+
+
+/* import private key from PEM string in memory.
+Only handles RSA keys.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+uschar * s1, * s2;
+blob der;
+long alen;
+int rc;
+
+/*XXX will need extension to _spot_ as well as handle a
+non-RSA key?  I think...
+So... this is not a PrivateKeyInfo - which would have a field
+identifying the keytype - PrivateKeyAlgorithmIdentifier -
+but a plain RSAPrivateKey (wrapped in PEM-headers.  Can we
+use those as a type tag?  What forms are there?  "BEGIN EC PRIVATE KEY" (cf. ec(1ssl))
+
+How does OpenSSL PEM_read_bio_PrivateKey() deal with it?
+gnutls_x509_privkey_import() ?
+*/
+
+/*
+ *  RSAPrivateKey ::= SEQUENCE
+ *      version           Version,
+ *      modulus           INTEGER,  -- n
+ *      publicExponent    INTEGER,  -- e
+ *      privateExponent   INTEGER,  -- d
+ *      prime1            INTEGER,  -- p
+ *      prime2            INTEGER,  -- q
+ *      exponent1         INTEGER,  -- d mod (p-1)
+ *      exponent2         INTEGER,  -- d mod (q-1)
+ *      coefficient       INTEGER,  -- (inverse of q) mod p
+ *      otherPrimeInfos   OtherPrimeInfos OPTIONAL
+
+ * ECPrivateKey ::= SEQUENCE {
+ *     version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
+ *     privateKey     OCTET STRING,
+ *     parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
+ *     publicKey  [1] BIT STRING OPTIONAL
+ *   }
+ * Hmm, only 1 useful item, and not even an integer?  Wonder how we might use it...
+
+- actually, gnutls_x509_privkey_import() appears to require a curve name parameter
+	value for that is an OID? a local-only integer (it's an enum in GnuTLS)?
+
+
+Useful cmds:
+  ssh-keygen -t ecdsa -f foo.privkey
+  ssh-keygen -t ecdsa -b384 -f foo.privkey
+  ssh-keygen -t ecdsa -b521 -f foo.privkey
+  ssh-keygen -t ed25519 -f foo.privkey
+
+  < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x
+
+  openssl asn1parse -in foo -inform PEM -dump
+  openssl asn1parse -in foo -inform PEM -dump -stroffset 24    (??)
+(not good for ed25519)
+
+ */
+
+if (  !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----"))
+   || !(s2 = Ustrstr(CS (s1+=31),    "-----END RSA PRIVATE KEY-----" ))
+   )
+  return US"Bad PEM wrapper";
+
+*s2 = '\0';
+
+if ((der.len = b64decode(s1, &der.data)) < 0)
+  return US"Bad PEM-DER b64 decode";
+
+/* untangle asn.1 */
+
+/* sequence; just move past the header */
+if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+   != ASN1_SUCCESS) goto asn_err;
+
+/* integer version; move past the header, check is zero */
+if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
+  goto asn_err;
+if (alen != 1 || *der.data != 0)
+  return US"Bad version number";
+der.data++; der.len--;
+
+if (  (s1 = as_mpi(&der, &sign_ctx->n))
+   || (s1 = as_mpi(&der, &sign_ctx->e))
+   || (s1 = as_mpi(&der, &sign_ctx->d))
+   || (s1 = as_mpi(&der, &sign_ctx->p))
+   || (s1 = as_mpi(&der, &sign_ctx->q))
+   || (s1 = as_mpi(&der, &sign_ctx->dp))
+   || (s1 = as_mpi(&der, &sign_ctx->dq))
+   || (s1 = as_mpi(&der, &sign_ctx->qp))
+   )
+  return s1;
+
+#ifdef extreme_debug
+DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n");
+  {
+  uschar * s;
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n);
+  debug_printf_indent(" N : %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e);
+  debug_printf_indent(" E : %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d);
+  debug_printf_indent(" D : %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p);
+  debug_printf_indent(" P : %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q);
+  debug_printf_indent(" Q : %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp);
+  debug_printf_indent(" DP: %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq);
+  debug_printf_indent(" DQ: %s\n", s);
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp);
+  debug_printf_indent(" QP: %s\n", s);
+  }
+#endif
+
+sign_ctx->keytype = KEYTYPE_RSA;
+return NULL;
+
+asn_err: return US asn1_strerror(rc);
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* sign already-hashed data.
+
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+char * sexp_hash;
+gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL;
+gcry_mpi_t m_sig;
+uschar * errstr;
+gcry_error_t gerr;
+
+/*XXX will need extension for hash types (though, possibly, should
+be re-specced to not rehash but take an already-hashed value? Actually
+current impl looks WRONG - it _is_ given a hash so should not be
+re-hashing.  Has this been tested?
+
+Will need extension for non-RSA sugning algos. */
+
+switch (hash)
+  {
+  case HASH_SHA1:	sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
+  case HASH_SHA2_256:	sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
+  default:		return US"nonhandled hash type";
+  }
+
+#define SIGSPACE 128
+sig->data = store_get(SIGSPACE);
+
+if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0)
+  {
+  gcry_mpi_swap (sign_ctx->p, sign_ctx->q);
+  gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q);
+  }
+
+if (  (gerr = gcry_sexp_build (&s_key, NULL,
+		"(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))",
+		sign_ctx->n, sign_ctx->e,
+		sign_ctx->d, sign_ctx->p,
+		sign_ctx->q, sign_ctx->qp))
+   || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
+		(int) data->len, CS data->data))
+   ||  (gerr = gcry_pk_sign (&s_sig, s_hash, s_key))
+   )
+  return US gcry_strerror(gerr);
+
+/* gcry_sexp_dump(s_sig); */
+
+if (  !(s_sig = gcry_sexp_find_token(s_sig, "s", 0))
+   )
+  return US"no sig result";
+
+m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG);
+
+#ifdef extreme_debug
+DEBUG(D_acl)
+  {
+  uschar * s;
+  gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig);
+  debug_printf_indent(" SG: %s\n", s);
+  }
+#endif
+
+gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig);
+if (gerr)
+  {
+  debug_printf_indent("signature conversion from MPI to buffer failed\n");
+  return US gcry_strerror(gerr);
+  }
+#undef SIGSPACE
+
+return NULL;
+}
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+{
+/*
+in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
+*/
+uschar tag_class;
+int taglen;
+long alen;
+int rc;
+uschar * errstr;
+gcry_error_t gerr;
+uschar * stage = US"S1";
+
+if (fmt != KEYFMT_DER) return US"pubkey format not handled";
+
+/*
+sequence
+ sequence
+  OBJECT:rsaEncryption
+  NULL
+ BIT STRING:RSAPublicKey
+  sequence
+   INTEGER:Public modulus
+   INTEGER:Public exponent
+
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head;
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump;
+openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22;
+*/
+
+/* sequence; just move past the header */
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+   != ASN1_SUCCESS) goto asn_err;
+
+/* sequence; skip the entire thing */
+DEBUG(D_acl) stage = US"S2";
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen))
+   != ASN1_SUCCESS) goto asn_err;
+pubkey->data += alen; pubkey->len -= alen;
+
+
+/* bitstring: limit range to size of bitstring;
+move over header + content wrapper */
+DEBUG(D_acl) stage = US"BS";
+if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS)
+  goto asn_err;
+pubkey->len = alen;
+pubkey->data++; pubkey->len--;
+
+/* sequence; just move past the header */
+DEBUG(D_acl) stage = US"S3";
+if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
+   != ASN1_SUCCESS) goto asn_err;
+
+/* 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;
+
+#ifdef extreme_debug
+DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n");
+	{
+	uschar * s;
+	gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n);
+	debug_printf_indent(" N : %s\n", s);
+	gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e);
+	debug_printf_indent(" E : %s\n", s);
+	}
+
+#endif
+return NULL;
+
+asn_err:
+DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc));
+	     return US asn1_strerror(rc);
+}
+
+
+/* verify signature (of hash)
+XXX though we appear to be doing a hash, too!
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
+{
+/*
+cf. libgnutls 2.8.5 _wrap_gcry_pk_verify()
+*/
+char * sexp_hash;
+gcry_mpi_t m_sig;
+gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL;
+gcry_error_t gerr;
+uschar * stage;
+
+/*XXX needs extension for SHA512 */
+switch (hash)
+  {
+  case HASH_SHA1:     sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
+  case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
+  default:	      return US"nonhandled hash type";
+  }
+
+if (  (stage = US"pkey sexp build",
+       gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))",
+		        verify_ctx->n, verify_ctx->e))
+   || (stage = US"data sexp build",
+       gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
+		(int) data_hash->len, CS data_hash->data))
+   || (stage = US"sig mpi scan",
+       gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL))
+   || (stage = US"sig sexp build",
+       gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig))
+   || (stage = US"verify",
+       gerr = gcry_pk_verify (s_sig, s_hash, s_pkey))
+   )
+  {
+  DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage);
+  return US gcry_strerror(gerr);
+  }
+
+if (s_sig) gcry_sexp_release (s_sig);
+if (s_hash) gcry_sexp_release (s_hash);
+if (s_pkey) gcry_sexp_release (s_pkey);
+gcry_mpi_release (m_sig);
+gcry_mpi_release (verify_ctx->n);
+gcry_mpi_release (verify_ctx->e);
+
+return NULL;
+}
+
+
+
+
+#elif defined(SIGN_OPENSSL)
+/******************************************************************************/
+
+void
+exim_dkim_init(void)
+{
+ERR_load_crypto_strings();
+}
+
+
+/* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too
+because now using hash-and-sign interface) */
+gstring *
+exim_dkim_data_append(gstring * g, uschar * s)
+{
+return string_cat(g, s);
+}
+
+
+/* import private key from PEM string in memory.
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
+{
+BIO * bp = BIO_new_mem_buf(privkey_pem, -1);
+
+if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL)))
+  return string_sprintf("privkey PEM-block import: %s",
+		       	ERR_error_string(ERR_get_error(), NULL));
+
+sign_ctx->keytype =
+#ifdef SIGN_HAVE_ED25519
+	EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519
+	  ? KEYTYPE_ED25519 : KEYTYPE_RSA;
+#else
+	KEYTYPE_RSA;
+#endif
+return NULL;
+}
+
+
+
+/* allocate mem for signature (when signing) */
+/* hash & sign data.  Incremental not supported.
+
+Return: NULL for success with the signaature in the sig blob, or an error string */
+
+const uschar *
+exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
+{
+const EVP_MD * md;
+EVP_MD_CTX * ctx;
+size_t siglen;
+
+switch (hash)
+  {
+  case HASH_NULL:	md = NULL;	   break;	/* Ed25519 signing */
+  case HASH_SHA1:	md = EVP_sha1();   break;
+  case HASH_SHA2_256:	md = EVP_sha256(); break;
+  case HASH_SHA2_512:	md = EVP_sha512(); break;
+  default:		return US"nonhandled hash type";
+  }
+
+#ifdef SIGN_HAVE_ED25519
+if (  (ctx = EVP_MD_CTX_new())
+   && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
+   && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0
+   && (sig->data = store_get(siglen))
+
+   /* Obtain the signature (slen could change here!) */
+   && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0
+   )
+  {
+  EVP_MD_CTX_destroy(ctx);
+  sig->len = siglen;
+  return NULL;
+  }
+#else
+/*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */
+if (  (ctx = EVP_MD_CTX_create())
+   && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
+   && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0
+   && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0
+   && (sig->data = store_get(siglen))
+ 
+   /* Obtain the signature (slen could change here!) */
+   && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0
+   )
+  {
+  EVP_MD_CTX_destroy(ctx);
+  sig->len = siglen;
+  return NULL;
+  }
+#endif
+
+if (ctx) EVP_MD_CTX_destroy(ctx);
+return US ERR_error_string(ERR_get_error(), NULL);
+}
+
+
+
+/* import public key (from blob in memory)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx)
+{
+const uschar * s = pubkey->data;
+uschar * ret = NULL;
+
+switch(fmt)
+  {
+  case KEYFMT_DER:
+    /*XXX hmm, we never free this */
+    if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len)))
+      ret = US ERR_error_string(ERR_get_error(), NULL);
+    break;
+#ifdef SIGN_HAVE_ED25519
+  case KEYFMT_ED25519_BARE:
+    if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL,
+							s, pubkey->len)))
+      ret = US ERR_error_string(ERR_get_error(), NULL);
+    break;
+#endif
+  default:
+    ret = US"pubkey format not handled";
+    break;
+  }
+
+return ret;
+}
+
+
+
+
+/* verify signature (of hash, except Ed25519 where of-data)
+(given pubkey & alleged sig)
+Return: NULL for success, or an error string */
+
+const uschar *
+exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig)
+{
+const EVP_MD * md;
+
+switch (hash)
+  {
+  case HASH_NULL:	md = NULL;	   break;
+  case HASH_SHA1:	md = EVP_sha1();   break;
+  case HASH_SHA2_256:	md = EVP_sha256(); break;
+  case HASH_SHA2_512:	md = EVP_sha512(); break;
+  default:		return US"nonhandled hash type";
+  }
+
+#ifdef SIGN_HAVE_ED25519
+if (!md)
+  {
+  EVP_MD_CTX * 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 ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)))
+    {
+    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 US ERR_error_string(ERR_get_error(), NULL);
+}
+
+
+
+#endif
+/******************************************************************************/
+
+#endif	/*DISABLE_DKIM*/
+#endif	/*MACRO_PREDEF*/
+/* End of File */