Signature support: decouple mupdf from the pkcs7 implementation

The mupdf build included an implimentation of the pkcs7 functions that
are needed for signing documents and verifying signatures, the
implementation being either an openssl-based one, or a stub that returned
errors. This commit removes the pkcs7 functions from the main mupdf
library.

For the sake of verification, there wasn't really a need for the pkcs7
functions to be part of mupdf. It was only the checking function that used
them. The checking function is now provided as a helper, outside of the
main build. The openssl-based pkcs7 functions area also supplied as a
helper. Users wishing to verify signatures can either use the checking
function directly, or use the source on which to base their own.

Document signing requires more integration between mupdf and pkcs7
because part of the process is performed at time of signing and part when
saving the document. Mupdf already had a pdf_pkcs7_signer object that
kept information between the two phases. That object has now been extended
to include the pkcs7 functions involved in signing, and the signing
function now requires such an object, rather than a file path to a
certificate. The openssl-based pkcs7 helper provides a function that, given
the path to a certificate, will return a pdf_pkcs7_signer object.

The intention is that different implementations can be produced for
different platforms, based on cryptographic routines built into the
operationg system. In each case, for the sake of document signing, the
routines would be wrapped up as a pdf_pkcs7_signer object.

6 files changed, 282 insertions, 311 deletions

diff --git a/source/helpers/pkcs7/pkcs7-check.c b/source/helpers/pkcs7/pkcs7-check.c
new file mode 100644
index 00000000..72b6af90
--- /dev/null
+++ b/source/helpers/pkcs7/pkcs7-check.c
@@ -0,0 +1,128 @@
+#include "mupdf/fitz.h"
+#include "mupdf/pdf.h"
+#include "mupdf/helpers/pkcs7-openssl.h"
+#include "mupdf/helpers/pkcs7-check.h"
+
+#include <string.h>
+
+
+static void pdf_print_designated_name(pdf_pkcs7_designated_name *name, char *buf, int buflen)
+{
+	int i, n;
+	const char *part[] = {
+		"/CN=", name->cn,
+		"/O=", name->o,
+		"/OU=", name->ou,
+		"/emailAddress=", name->email,
+		"/C=", name->c};
+
+	if (buflen)
+		buf[0] = 0;
+
+	n = sizeof(part)/sizeof(*part);
+	for (i = 0; i < n; i++)
+		if (part[i])
+			fz_strlcat(buf, part[i], buflen);
+}
+
+int pdf_check_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget, char *ebuf, int ebufsize)
+{
+	fz_stream *bytes = NULL;
+	char *contents = NULL;
+	int contents_len;
+	int res = 0;
+
+	if (pdf_xref_obj_is_unsaved_signature(doc, ((pdf_annot *)widget)->obj))
+	{
+		fz_strlcpy(ebuf, "Signed but document yet to be saved", ebufsize);
+		if (ebufsize > 0)
+			ebuf[ebufsize-1] = 0;
+		return 0;
+	}
+
+	fz_var(bytes);
+	fz_var(res);
+	fz_try(ctx)
+	{
+		contents_len = pdf_signature_widget_contents(ctx, doc, widget, &contents);
+		if (contents)
+		{
+			SignatureError err;
+
+			bytes = pdf_signature_widget_hash_bytes(ctx, doc, widget);
+			err = pkcs7_openssl_check_digest(ctx, bytes, contents, contents_len);
+			if (err == SignatureError_Okay)
+				err = pkcs7_openssl_check_certificate(contents, contents_len);
+			switch (err)
+			{
+			case SignatureError_Okay:
+				ebuf[0] = 0;
+				res = 1;
+				break;
+			case SignatureError_NoSignatures:
+				fz_strlcpy(ebuf, "No signatures", ebufsize);
+				break;
+			case SignatureError_NoCertificate:
+				fz_strlcpy(ebuf, "No certificate", ebufsize);
+				break;
+			case SignatureError_DocumentChanged:
+				fz_strlcpy(ebuf, "Document changed since signing", ebufsize);
+				break;
+			case SignatureError_SelfSigned:
+				fz_strlcpy(ebuf, "Self-signed certificate", ebufsize);
+				break;
+			case SignatureError_SelfSignedInChain:
+				fz_strlcpy(ebuf, "Self-signed certificate in chain", ebufsize);
+				break;
+			case SignatureError_NotTrusted:
+				fz_strlcpy(ebuf, "Certificate not trusted", ebufsize);
+				break;
+			default:
+			case SignatureError_Unknown:
+				fz_strlcpy(ebuf, "Unknown error", ebufsize);
+				break;
+			}
+
+			switch (err)
+			{
+			case SignatureError_SelfSigned:
+			case SignatureError_SelfSignedInChain:
+			case SignatureError_NotTrusted:
+				{
+					pdf_pkcs7_designated_name *name = pkcs7_openssl_designated_name(ctx, contents, contents_len);
+					if (name)
+					{
+						int len;
+
+						fz_strlcat(ebuf, ": ", ebufsize);
+						len = strlen(ebuf);
+						pdf_print_designated_name(name, ebuf + len, ebufsize - len);
+						pkcs7_opensll_drop_designated_name(ctx, name);
+					}
+				}
+				break;
+			default:
+				break;
+			}
+		}
+		else
+		{
+			res = 0;
+			fz_strlcpy(ebuf, "Not signed", ebufsize);
+		}
+	}
+	fz_always(ctx)
+	{
+		fz_drop_stream(ctx, bytes);
+	}
+	fz_catch(ctx)
+	{
+		res = 0;
+		fz_strlcpy(ebuf, fz_caught_message(ctx), ebufsize);
+	}
+
+	if (ebufsize > 0)
+		ebuf[ebufsize-1] = 0;
+
+	return res;
+}
diff --git a/source/pdf/pdf-pkcs7.c b/source/helpers/pkcs7/pkcs7-openssl.c
index 7f4e15b1..c0ca9093 100644
--- a/source/pdf/pdf-pkcs7.c
+++ b/source/helpers/pkcs7/pkcs7-openssl.c
@@ -1,11 +1,10 @@
 #include "mupdf/fitz.h"
 #include "mupdf/pdf.h"
-#include "../fitz/fitz-imp.h"
+#include "../../fitz/fitz-imp.h"
+#include "mupdf/helpers/pkcs7-openssl.h"
 
 #include <string.h>
 
-#ifdef HAVE_LIBCRYPTO
-
 /* Generated from resources/certs/AdobeCA.p7c */
 static const char AdobeCA_p7c[] = {
 48,130,4,208,6,9,42,134,72,134,247,13,1,7,2,160,130,4,193,48,130,4,189,2,
@@ -285,12 +284,14 @@ exit:
 
 static SignatureError pk7_verify_cert(X509_STORE *cert_store, PKCS7 *p7)
 {
-	int res = SignatureError_Unknown;
+	int res = SignatureError_Okay;
 	int i;
 	STACK_OF(PKCS7_SIGNER_INFO) *sk;
 	X509_STORE_CTX *ctx;
 
 	ctx = X509_STORE_CTX_new();
+	if (!ctx)
+		return SignatureError_Unknown;
 
 	ERR_clear_error();
 
@@ -333,31 +334,35 @@ static SignatureError pk7_verify_cert(X509_STORE *cert_store, PKCS7 *p7)
 
 		if (!X509_STORE_CTX_init(ctx, cert_store, cert, certs))
 		{
-			res = 0;
-			PKCS7err(PKCS7_F_PKCS7_DATAVERIFY, ERR_R_X509_LIB);
+			res = SignatureError_Unknown;
 			goto exit;
 		}
 
-		X509_STORE_CTX_set_purpose(ctx, X509_PURPOSE_SMIME_SIGN);
+		if (!X509_STORE_CTX_set_purpose(ctx, X509_PURPOSE_SMIME_SIGN))
+		{
+			res = SignatureError_Unknown;
+			goto exit;
+		}
 
+		/* X509_verify_cert may return an error, but in all such cases
+		 * it sets a context error */
 		X509_verify_cert(ctx);
 		X509_STORE_CTX_cleanup(ctx);
 		ctx_err = X509_STORE_CTX_get_error(ctx);
 		switch (ctx_err)
 		{
 		case X509_V_OK:
-			res = SignatureError_Okay;
 			break;
 		case X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT:
 			res = SignatureError_SelfSigned;
-			break;
+			goto exit;
 		case X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN:
 			res = SignatureError_SelfSignedInChain;
-			break;
+			goto exit;
 		default:
-			break;
+			res = SignatureError_Unknown;
+			goto exit;
 		}
-		goto exit;
 	}
 
 exit:
@@ -367,12 +372,11 @@ exit:
 	return res;
 }
 
-SignatureError pdf_pkcs7_check_digest(fz_context *ctx, fz_stream *stm, char *sig, int sig_len)
+SignatureError pkcs7_openssl_check_digest(fz_context *ctx, fz_stream *stm, char *sig, int sig_len)
 {
 	PKCS7 *pk7sig = NULL;
 	BIO *bsig = NULL;
 	BIO *bdata = NULL;
-	STACK_OF(X509) *certs = NULL;
 	int res = SignatureError_Unknown;
 
 	bsig = BIO_new_mem_buf(sig, sig_len);
@@ -394,7 +398,7 @@ exit:
 	return res;
 }
 
-SignatureError pdf_pkcs7_check_certificate(char *sig, int sig_len)
+SignatureError pkcs7_openssl_check_certificate(char *sig, int sig_len)
 {
 	PKCS7 *pk7sig = NULL;
 	PKCS7 *pk7cert = NULL;
@@ -451,16 +455,24 @@ typedef struct pdf_pkcs7_designated_name_openssl_s
 	char buf[8192];
 } pdf_pkcs7_designated_name_openssl;
 
-struct pdf_pkcs7_signer_s
+void pkcs7_opensll_drop_designated_name(fz_context *ctx, pdf_pkcs7_designated_name *dn)
 {
+	fz_free(ctx, dn);
+}
+
+typedef struct
+{
+	pdf_pkcs7_signer base;
+	fz_context *ctx;
 	int refs;
 	X509 *x509;
 	EVP_PKEY *pkey;
-};
+} openssl_signer;
 
-void pdf_pkcs7_drop_designated_name(fz_context *ctx, pdf_pkcs7_designated_name *dn)
+static void signer_drop_designated_name(pdf_pkcs7_signer *signer, pdf_pkcs7_designated_name *dn)
 {
-	fz_free(ctx, dn);
+	openssl_signer *osigner = (openssl_signer *)signer;
+	fz_free(osigner->ctx, dn);
 }
 
 static void add_from_bags(X509 **pX509, EVP_PKEY **pPkey, const STACK_OF(PKCS12_SAFEBAG) *bags, const char *pw);
@@ -524,104 +536,20 @@ static void add_from_bags(X509 **pX509, EVP_PKEY **pPkey, const STACK_OF(PKCS12_
 		add_from_bag(pX509, pPkey, sk_PKCS12_SAFEBAG_value(bags, i), pw);
 }
 
-pdf_pkcs7_signer *pdf_pkcs7_read_pfx(fz_context *ctx, const char *pfile, const char *pw)
+static pdf_pkcs7_signer *keep_signer(pdf_pkcs7_signer *signer)
 {
-	BIO *pfxbio = NULL;
-	PKCS12 *p12 = NULL;
-	STACK_OF(PKCS7) *asafes;
-	pdf_pkcs7_signer *signer = NULL;
-	int i;
-
-	fz_var(pfxbio);
-	fz_var(p12);
-	fz_var(signer);
-	fz_try(ctx)
-	{
-		signer = fz_malloc_struct(ctx, pdf_pkcs7_signer);
-		signer->refs = 1;
-
-		OpenSSL_add_all_algorithms();
-
-		EVP_add_digest(EVP_md5());
-		EVP_add_digest(EVP_sha1());
-
-		ERR_load_crypto_strings();
-
-		ERR_clear_error();
-
-		pfxbio = BIO_new_file(pfile, "rb");
-		if (pfxbio == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Can't open pfx file: %s", pfile);
-
-		p12 = d2i_PKCS12_bio(pfxbio, NULL);
-		if (p12 == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid pfx file: %s", pfile);
-
-		asafes = PKCS12_unpack_authsafes(p12);
-		if (asafes == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid pfx file: %s", pfile);
-
-		/* Nothing in this for loop can fz_throw */
-		for (i = 0; i < sk_PKCS7_num(asafes); i++)
-		{
-			PKCS7 *p7;
-			STACK_OF(PKCS12_SAFEBAG) *bags;
-			int bagnid;
-
-			p7 = sk_PKCS7_value(asafes, i);
-			bagnid = OBJ_obj2nid(p7->type);
-			switch (bagnid)
-			{
-			case NID_pkcs7_data:
-				bags = PKCS12_unpack_p7data(p7);
-				break;
-			case NID_pkcs7_encrypted:
-				bags = PKCS12_unpack_p7encdata(p7, pw, (int)strlen(pw));
-				break;
-			default:
-				continue;
-			}
-
-			if (bags)
-			{
-				add_from_bags(&signer->x509, &signer->pkey, bags, pw);
-				sk_PKCS12_SAFEBAG_pop_free(bags, PKCS12_SAFEBAG_free);
-			}
-		}
-		sk_PKCS7_pop_free (asafes, PKCS7_free);
-
-		if (signer->pkey == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to obtain public key");
-
-		if (signer->x509 == NULL)
-			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to obtain certificate");
-	}
-	fz_always(ctx)
-	{
-		BIO_free(pfxbio);
-		PKCS12_free(p12);
-	}
-	fz_catch(ctx)
-	{
-		pdf_pkcs7_drop_signer(ctx, signer);
-		fz_rethrow(ctx);
-	}
-
-	return signer;
+	openssl_signer *osigner = (openssl_signer *)signer;
+	return fz_keep_imp(osigner->ctx, osigner, &osigner->refs);
 }
 
-pdf_pkcs7_signer *pdf_pkcs7_keep_signer(fz_context *ctx, pdf_pkcs7_signer *signer)
+static void drop_signer(pdf_pkcs7_signer *signer)
 {
-	return fz_keep_imp(ctx, signer, &signer->refs);
-}
-
-void pdf_pkcs7_drop_signer(fz_context *ctx, pdf_pkcs7_signer *signer)
-{
-	if (fz_drop_imp(ctx, signer, &signer->refs))
+	openssl_signer *osigner = (openssl_signer *)signer;
+	if (fz_drop_imp(osigner->ctx, osigner, &osigner->refs))
 	{
-		X509_free(signer->x509);
-		EVP_PKEY_free(signer->pkey);
-		fz_free(ctx, signer);
+		X509_free(osigner->x509);
+		EVP_PKEY_free(osigner->pkey);
+		fz_free(osigner->ctx, osigner);
 	}
 }
 
@@ -649,13 +577,16 @@ static pdf_pkcs7_designated_name *x509_designated_name(fz_context *ctx, X509 *x5
 	return (pdf_pkcs7_designated_name *)dn;
 }
 
-pdf_pkcs7_designated_name *pdf_pkcs7_signer_designated_name(fz_context *ctx, pdf_pkcs7_signer *signer)
+static pdf_pkcs7_designated_name *signer_designated_name(pdf_pkcs7_signer *signer)
 {
-	return x509_designated_name(ctx, signer->x509);
+	openssl_signer *osigner = (openssl_signer *)signer;
+	return x509_designated_name(osigner->ctx, osigner->x509);
 }
 
-int pdf_pkcs7_create_digest(fz_context *ctx, fz_stream *in, pdf_pkcs7_signer *signer, unsigned char *digest, int *digest_len)
+static int signer_create_digest(pdf_pkcs7_signer *signer, fz_stream *in, unsigned char *digest, int *digest_len)
 {
+	openssl_signer *osigner = (openssl_signer *)signer;
+	fz_context *ctx = osigner->ctx;
 	int res = 0;
 	BIO *bdata = NULL;
 	BIO *bp7in = NULL;
@@ -676,12 +607,12 @@ int pdf_pkcs7_create_digest(fz_context *ctx, fz_stream *in, pdf_pkcs7_signer *si
 		goto exit;
 
 	PKCS7_set_type(p7, NID_pkcs7_signed);
-	si = PKCS7_add_signature(p7, signer->x509, signer->pkey, EVP_sha1());
+	si = PKCS7_add_signature(p7, osigner->x509, osigner->pkey, EVP_sha1());
 	if (si == NULL)
 		goto exit;
 
 	PKCS7_add_signed_attribute(si, NID_pkcs9_contentType, V_ASN1_OBJECT, OBJ_nid2obj(NID_pkcs7_data));
-	PKCS7_add_certificate(p7, signer->x509);
+	PKCS7_add_certificate(p7, osigner->x509);
 
 	PKCS7_content_new(p7, NID_pkcs7_data);
 	PKCS7_set_detached(p7, 1);
@@ -725,7 +656,100 @@ exit:
 	return res;
 }
 
-pdf_pkcs7_designated_name *pdf_cert_designated_name(fz_context *ctx, char *sig, int sig_len)
+pdf_pkcs7_signer *pkcs7_openssl_read_pfx(fz_context *ctx, const char *pfile, const char *pw)
+{
+	BIO *pfxbio = NULL;
+	PKCS12 *p12 = NULL;
+	STACK_OF(PKCS7) *asafes;
+	openssl_signer *signer = NULL;
+	int i;
+
+	fz_var(pfxbio);
+	fz_var(p12);
+	fz_var(signer);
+	fz_try(ctx)
+	{
+		signer = fz_malloc_struct(ctx, openssl_signer);
+		signer->refs = 1;
+
+		OpenSSL_add_all_algorithms();
+
+		EVP_add_digest(EVP_md5());
+		EVP_add_digest(EVP_sha1());
+
+		ERR_load_crypto_strings();
+
+		ERR_clear_error();
+
+		pfxbio = BIO_new_file(pfile, "rb");
+		if (pfxbio == NULL)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "Can't open pfx file: %s", pfile);
+
+		p12 = d2i_PKCS12_bio(pfxbio, NULL);
+		if (p12 == NULL)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid pfx file: %s", pfile);
+
+		asafes = PKCS12_unpack_authsafes(p12);
+		if (asafes == NULL)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "Invalid pfx file: %s", pfile);
+
+		/* Nothing in this for loop can fz_throw */
+		for (i = 0; i < sk_PKCS7_num(asafes); i++)
+		{
+			PKCS7 *p7;
+			STACK_OF(PKCS12_SAFEBAG) *bags;
+			int bagnid;
+
+			p7 = sk_PKCS7_value(asafes, i);
+			bagnid = OBJ_obj2nid(p7->type);
+			switch (bagnid)
+			{
+			case NID_pkcs7_data:
+				bags = PKCS12_unpack_p7data(p7);
+				break;
+			case NID_pkcs7_encrypted:
+				bags = PKCS12_unpack_p7encdata(p7, pw, (int)strlen(pw));
+				break;
+			default:
+				continue;
+			}
+
+			if (bags)
+			{
+				add_from_bags(&signer->x509, &signer->pkey, bags, pw);
+				sk_PKCS12_SAFEBAG_pop_free(bags, PKCS12_SAFEBAG_free);
+			}
+		}
+		sk_PKCS7_pop_free (asafes, PKCS7_free);
+
+		if (signer->pkey == NULL)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to obtain public key");
+
+		if (signer->x509 == NULL)
+			fz_throw(ctx, FZ_ERROR_GENERIC, "Failed to obtain certificate");
+
+		signer->ctx = ctx;
+		signer->base.keep = keep_signer;
+		signer->base.drop = drop_signer;
+		signer->base.designated_name = signer_designated_name;
+		signer->base.drop_designated_name = signer_drop_designated_name;
+		signer->base.create_digest = signer_create_digest;
+	}
+	fz_always(ctx)
+	{
+		BIO_free(pfxbio);
+		PKCS12_free(p12);
+	}
+	fz_catch(ctx)
+	{
+		drop_signer(&signer->base);
+		fz_rethrow(ctx);
+	}
+
+	return &signer->base;
+}
+
+pdf_pkcs7_designated_name *pkcs7_openssl_designated_name(fz_context *ctx, char *sig, int sig_len)
 {
 	pdf_pkcs7_designated_name *name = NULL;
 	PKCS7 *pk7sig = NULL;
@@ -752,61 +776,3 @@ exit:
 
 	return name;
 }
-
-
-int pdf_pkcs7_supported(fz_context *ctx)
-{
-	return 1;
-}
-
-#else /* HAVE_LIBCRYPTO */
-
-SignatureError pdf_pkcs7_check_digest(fz_context *ctx, fz_stream *stm, char *sig, int sig_len)
-{
-	return SignatureError_Unknown;
-}
-
-SignatureError pdf_pkcs7_check_certificate(char *sig, int sig_len)
-{
-	return SignatureError_Unknown;
-}
-
-pdf_pkcs7_designated_name *pdf_cert_designated_name(fz_context *ctx, char *sig, int sig_len)
-{
-	return NULL;
-}
-
-void pdf_pkcs7_drop_designated_name(fz_context *ctx, pdf_pkcs7_designated_name *dn)
-{
-}
-
-pdf_pkcs7_signer *pdf_pkcs7_read_pfx(fz_context *ctx, const char *pfile, const char *pw)
-{
-	return NULL;
-}
-
-pdf_pkcs7_signer *pdf_pkcs7_keep_signer(fz_context *ctx, pdf_pkcs7_signer *signer)
-{
-	return NULL;
-}
-
-void pdf_pkcs7_drop_signer(fz_context *ctx, pdf_pkcs7_signer *signer)
-{
-}
-
-pdf_pkcs7_designated_name *pdf_pkcs7_signer_designated_name(fz_context *ctx, pdf_pkcs7_signer *signer)
-{
-	return NULL;
-}
-
-int pdf_pkcs7_create_digest(fz_context *ctx, fz_stream *in, pdf_pkcs7_signer *signer, unsigned char *digest, int *digest_len)
-{
-	return 0;
-}
-
-int pdf_pkcs7_supported(fz_context *ctx)
-{
-	return 0;
-}
-
-#endif /* HAVE_LIBCRYPTO */
diff --git a/source/pdf/pdf-signature.c b/source/pdf/pdf-signature.c
index 3d96a261..3c882f54 100644
--- a/source/pdf/pdf-signature.c
+++ b/source/pdf/pdf-signature.c
@@ -5,25 +5,6 @@
 #include <string.h>
 
 
-static void pdf_print_designated_name(pdf_pkcs7_designated_name *name, char *buf, int buflen)
-{
-	int i, n;
-	const char *part[] = {
-		"/CN=", name->cn,
-		"/O=", name->o,
-		"/OU=", name->ou,
-		"/emailAddress=", name->email,
-		"/C=", name->c};
-
-	if (buflen)
-		buf[0] = 0;
-
-	n = sizeof(part)/sizeof(*part);
-	for (i = 0; i < n; i++)
-		if (part[i])
-			fz_strlcat(buf, part[i], buflen);
-}
-
 void pdf_write_digest(fz_context *ctx, fz_output *out, pdf_obj *byte_range, int hexdigest_offset, int hexdigest_length, pdf_pkcs7_signer *signer)
 {
 	fz_stream *in = NULL;
@@ -53,7 +34,7 @@ void pdf_write_digest(fz_context *ctx, fz_output *out, pdf_obj *byte_range, int
 
 		digest_len = (hexdigest_length - 2) / 2;
 		digest = fz_malloc(ctx, digest_len);
-		res = pdf_pkcs7_create_digest(ctx, in, signer, digest, &digest_len);
+		res = signer->create_digest(signer, in, digest, &digest_len);
 		if (!res)
 			fz_throw(ctx, FZ_ERROR_GENERIC, "pdf_pkcs7_create_digest failed");
 
@@ -77,111 +58,8 @@ void pdf_write_digest(fz_context *ctx, fz_output *out, pdf_obj *byte_range, int
 	}
 }
 
-int pdf_check_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget, char *ebuf, int ebufsize)
-{
-	fz_stream *bytes = NULL;
-	char *contents = NULL;
-	int contents_len;
-	int res = 0;
-
-	if (pdf_xref_obj_is_unsaved_signature(doc, ((pdf_annot *)widget)->obj))
-	{
-		fz_strlcpy(ebuf, "Signed but document yet to be saved", ebufsize);
-		if (ebufsize > 0)
-			ebuf[ebufsize-1] = 0;
-		return 0;
-	}
-
-	fz_var(bytes);
-	fz_var(res);
-	fz_try(ctx)
-	{
-		contents_len = pdf_signature_widget_contents(ctx, doc, widget, &contents);
-		if (contents)
-		{
-			SignatureError err;
-
-			bytes = pdf_signature_widget_hash_bytes(ctx, doc, widget);
-			err = pdf_pkcs7_check_digest(ctx, bytes, contents, contents_len);
-			if (err == SignatureError_Okay)
-				err = pdf_pkcs7_check_certificate(contents, contents_len);
-			switch (err)
-			{
-			case SignatureError_Okay:
-				ebuf[0] = 0;
-				res = 1;
-				break;
-			case SignatureError_NoSignatures:
-				fz_strlcpy(ebuf, "No signatures", ebufsize);
-				break;
-			case SignatureError_NoCertificate:
-				fz_strlcpy(ebuf, "No certificate", ebufsize);
-				break;
-			case SignatureError_DocumentChanged:
-				fz_strlcpy(ebuf, "Document changed since signing", ebufsize);
-				break;
-			case SignatureError_SelfSigned:
-				fz_strlcpy(ebuf, "Self-signed certificate", ebufsize);
-				break;
-			case SignatureError_SelfSignedInChain:
-				fz_strlcpy(ebuf, "Self-signed certificate in chain", ebufsize);
-				break;
-			case SignatureError_NotTrusted:
-				fz_strlcpy(ebuf, "Certificate not trusted", ebufsize);
-				break;
-			default:
-			case SignatureError_Unknown:
-				fz_strlcpy(ebuf, "Unknown error", ebufsize);
-				break;
-			}
-
-			switch (err)
-			{
-			case SignatureError_SelfSigned:
-			case SignatureError_SelfSignedInChain:
-			case SignatureError_NotTrusted:
-				{
-					pdf_pkcs7_designated_name *name = pdf_cert_designated_name(ctx, contents, contents_len);
-					if (name)
-					{
-						int len;
-
-						fz_strlcat(ebuf, ": ", ebufsize);
-						len = strlen(ebuf);
-						pdf_print_designated_name(name, ebuf + len, ebufsize - len);
-						pdf_pkcs7_drop_designated_name(ctx, name);
-					}
-				}
-				break;
-			default:
-				break;
-			}
-		}
-		else
-		{
-			res = 0;
-			fz_strlcpy(ebuf, "Not signed", ebufsize);
-		}
-	}
-	fz_always(ctx)
-	{
-		fz_drop_stream(ctx, bytes);
-	}
-	fz_catch(ctx)
-	{
-		res = 0;
-		fz_strlcpy(ebuf, fz_caught_message(ctx), ebufsize);
-	}
-
-	if (ebufsize > 0)
-		ebuf[ebufsize-1] = 0;
-
-	return res;
-}
-
-void pdf_sign_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget, const char *sigfile, const char *password)
+void pdf_sign_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget, pdf_pkcs7_signer *signer)
 {
-	pdf_pkcs7_signer *signer = pdf_pkcs7_read_pfx(ctx, sigfile, password);
 	pdf_pkcs7_designated_name *dn = NULL;
 	fz_buffer *fzbuf = NULL;
 
@@ -197,7 +75,7 @@ void pdf_sign_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget,
 		/* Create an appearance stream only if the signature is intended to be visible */
 		if (!fz_is_empty_rect(&rect))
 		{
-			dn = pdf_pkcs7_signer_designated_name(ctx, signer);
+			dn = signer->designated_name(signer);
 			fzbuf = fz_new_buffer(ctx, 256);
 			if (!dn->cn)
 				fz_throw(ctx, FZ_ERROR_GENERIC, "Certificate has no common name");
@@ -222,8 +100,7 @@ void pdf_sign_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget,
 	}
 	fz_always(ctx)
 	{
-		pdf_pkcs7_drop_signer(ctx, signer);
-		pdf_pkcs7_drop_designated_name(ctx, dn);
+		signer->drop_designated_name(signer, dn);
 		fz_drop_buffer(ctx, fzbuf);
 	}
 	fz_catch(ctx)
@@ -231,8 +108,3 @@ void pdf_sign_signature(fz_context *ctx, pdf_document *doc, pdf_widget *widget,
 		fz_rethrow(ctx);
 	}
 }
-
-int pdf_signatures_supported(fz_context *ctx)
-{
-	return pdf_pkcs7_supported(ctx);
-}
diff --git a/source/pdf/pdf-write.c b/source/pdf/pdf-write.c
index 0ab76a35..7b163813 100644
--- a/source/pdf/pdf-write.c
+++ b/source/pdf/pdf-write.c
@@ -2708,7 +2708,7 @@ static void complete_signatures(fz_context *ctx, pdf_document *doc, pdf_write_st
 				{
 					xref->unsaved_sigs = usig->next;
 					pdf_drop_obj(ctx, usig->field);
-					pdf_pkcs7_drop_signer(ctx, usig->signer);
+					usig->signer->drop(usig->signer);
 					fz_free(ctx, usig);
 				}
 			}
diff --git a/source/pdf/pdf-xref.c b/source/pdf/pdf-xref.c
index 1dc3b7d8..7e38706b 100644
--- a/source/pdf/pdf-xref.c
+++ b/source/pdf/pdf-xref.c
@@ -59,7 +59,7 @@ static void pdf_drop_xref_sections_imp(fz_context *ctx, pdf_document *doc, pdf_x
 		{
 			xref->unsaved_sigs = usig->next;
 			pdf_drop_obj(ctx, usig->field);
-			pdf_pkcs7_drop_signer(ctx, usig->signer);
+			usig->signer->drop(usig->signer);
 			fz_free(ctx, usig);
 		}
 	}
@@ -418,7 +418,7 @@ void pdf_xref_store_unsaved_signature(fz_context *ctx, pdf_document *doc, pdf_ob
 	 * saving time */
 	unsaved_sig = fz_malloc_struct(ctx, pdf_unsaved_sig);
 	unsaved_sig->field = pdf_keep_obj(ctx, field);
-	unsaved_sig->signer = pdf_pkcs7_keep_signer(ctx, signer);
+	unsaved_sig->signer = signer->keep(signer);
 	unsaved_sig->next = NULL;
 	if (xref->unsaved_sigs_end == NULL)
 		xref->unsaved_sigs_end = &xref->unsaved_sigs;
diff --git a/source/tools/pdfsign.c b/source/tools/pdfsign.c
index bc14be41..434c9332 100644
--- a/source/tools/pdfsign.c
+++ b/source/tools/pdfsign.c
@@ -4,6 +4,7 @@
 
 #include "mupdf/fitz.h"
 #include "mupdf/pdf.h"
+#include "mupdf/helpers/pkcs7-check.h"
 
 #include <string.h>
 #include <stdlib.h>
@@ -22,10 +23,14 @@ static void usage(void)
 
 void verify_signature(fz_context *ctx, pdf_document *doc, int n, pdf_widget *widget)
 {
+#ifdef HAVE_LIBCRYPTO
 	char msg[256];
 	printf("verifying signature on page %d\n", n+1);
 	pdf_check_signature(ctx, doc, widget, msg, sizeof msg);
 	printf("  result: '%s'\n", msg);
+#else
+	printf("No signature support in this build\n");
+#endif
 }
 
 void verify_page(fz_context *ctx, pdf_document *doc, int n, pdf_page *page)