[PATCH v4 09/14] efi_loader: Make the pkcs7 header parsing function an extern

[Sughosh Ganu <sughosh.ganu@linaro.org>]

The pkcs7 header parsing functionality is pretty generic, and can be
used by other features like capsule authentication. Make the function
an extern, also changing it's name to efi_parse_pkcs7_header

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
---

Changes since V3: None

 include/efi_loader.h           |  4 ++
 lib/efi_loader/efi_signature.c | 85 +++++++++++++++++++++++++++++++
 lib/efi_loader/efi_variable.c  | 93 ++--------------------------------
 3 files changed, 93 insertions(+), 89 deletions(-)

diff --git a/include/efi_loader.h b/include/efi_loader.h
index 365f3d01dc..8807fcd913 100644
--- a/include/efi_loader.h
+++ b/include/efi_loader.h
@@ -818,6 +818,10 @@ bool efi_secure_boot_enabled(void);
 bool efi_image_parse(void *efi, size_t len, struct efi_image_regions **regp,
 		     WIN_CERTIFICATE **auth, size_t *auth_len);
 
+struct pkcs7_message *efi_parse_pkcs7_header(const void *buf,
+					     size_t buflen,
+					     u8 **tmpbuf);
+
 /* runtime implementation of memcpy() */
 void efi_memcpy_runtime(void *dest, const void *src, size_t n);
 
diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
index 79dee27421..9ab071b611 100644
--- a/lib/efi_loader/efi_signature.c
+++ b/lib/efi_loader/efi_signature.c
@@ -27,6 +27,91 @@ const efi_guid_t efi_guid_cert_x509_sha256 = EFI_CERT_X509_SHA256_GUID;
 const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
 
 #ifdef CONFIG_EFI_SECURE_BOOT
+static u8 pkcs7_hdr[] = {
+	/* SEQUENCE */
+	0x30, 0x82, 0x05, 0xc7,
+	/* OID: pkcs7-signedData */
+	0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02,
+	/* Context Structured? */
+	0xa0, 0x82, 0x05, 0xb8,
+};
+
+/**
+ * efi_parse_pkcs7_header - parse a signature in payload
+ * @buf:	Pointer to payload's value
+ * @buflen:	Length of @buf
+ * @tmpbuf:	Pointer to temporary buffer
+ *
+ * Parse a signature embedded in payload's value and instantiate
+ * a pkcs7_message structure. Since pkcs7_parse_message() accepts only
+ * pkcs7's signedData, some header needed be prepended for correctly
+ * parsing authentication data
+ * A temporary buffer will be allocated if needed, and it should be
+ * kept valid during the authentication because some data in the buffer
+ * will be referenced by efi_signature_verify().
+ *
+ * Return:	Pointer to pkcs7_message structure on success, NULL on error
+ */
+struct pkcs7_message *efi_parse_pkcs7_header(const void *buf,
+					     size_t buflen,
+					     u8 **tmpbuf)
+{
+	u8 *ebuf;
+	size_t ebuflen, len;
+	struct pkcs7_message *msg;
+
+	/*
+	 * This is the best assumption to check if the binary is
+	 * already in a form of pkcs7's signedData.
+	 */
+	if (buflen > sizeof(pkcs7_hdr) &&
+	    !memcmp(&((u8 *)buf)[4], &pkcs7_hdr[4], 11)) {
+		msg = pkcs7_parse_message(buf, buflen);
+		if (IS_ERR(msg))
+			return NULL;
+		return msg;
+	}
+
+	/*
+	 * Otherwise, we should add a dummy prefix sequence for pkcs7
+	 * message parser to be able to process.
+	 * NOTE: EDK2 also uses similar hack in WrapPkcs7Data()
+	 * in CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyCommon.c
+	 * TODO:
+	 * The header should be composed in a more refined manner.
+	 */
+	EFI_PRINT("Makeshift prefix added to authentication data\n");
+	ebuflen = sizeof(pkcs7_hdr) + buflen;
+	if (ebuflen <= 0x7f) {
+		EFI_PRINT("Data is too short\n");
+		return NULL;
+	}
+
+	ebuf = malloc(ebuflen);
+	if (!ebuf) {
+		EFI_PRINT("Out of memory\n");
+		return NULL;
+	}
+
+	memcpy(ebuf, pkcs7_hdr, sizeof(pkcs7_hdr));
+	memcpy(ebuf + sizeof(pkcs7_hdr), buf, buflen);
+	len = ebuflen - 4;
+	ebuf[2] = (len >> 8) & 0xff;
+	ebuf[3] = len & 0xff;
+	len = ebuflen - 0x13;
+	ebuf[0x11] = (len >> 8) & 0xff;
+	ebuf[0x12] = len & 0xff;
+
+	msg = pkcs7_parse_message(ebuf, ebuflen);
+
+	if (IS_ERR(msg)) {
+		free(ebuf);
+		return NULL;
+	}
+
+	*tmpbuf = ebuf;
+	return msg;
+}
 
 /**
  * efi_hash_regions - calculate a hash value
diff --git a/lib/efi_loader/efi_variable.c b/lib/efi_loader/efi_variable.c
index 0c689cfb47..ba0874e9e7 100644
--- a/lib/efi_loader/efi_variable.c
+++ b/lib/efi_loader/efi_variable.c
@@ -24,91 +24,6 @@
 #include <asm/sections.h>
 
 #ifdef CONFIG_EFI_SECURE_BOOT
-static u8 pkcs7_hdr[] = {
-	/* SEQUENCE */
-	0x30, 0x82, 0x05, 0xc7,
-	/* OID: pkcs7-signedData */
-	0x06, 0x09, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d, 0x01, 0x07, 0x02,
-	/* Context Structured? */
-	0xa0, 0x82, 0x05, 0xb8,
-};
-
-/**
- * efi_variable_parse_signature - parse a signature in variable
- * @buf:	Pointer to variable's value
- * @buflen:	Length of @buf
- * @tmpbuf:	Pointer to temporary buffer
- *
- * Parse a signature embedded in variable's value and instantiate
- * a pkcs7_message structure. Since pkcs7_parse_message() accepts only
- * pkcs7's signedData, some header needed be prepended for correctly
- * parsing authentication data, particularly for variable's.
- * A temporary buffer will be allocated if needed, and it should be
- * kept valid during the authentication because some data in the buffer
- * will be referenced by efi_signature_verify().
- *
- * Return:	Pointer to pkcs7_message structure on success, NULL on error
- */
-static struct pkcs7_message *efi_variable_parse_signature(const void *buf,
-							  size_t buflen,
-							  u8 **tmpbuf)
-{
-	u8 *ebuf;
-	size_t ebuflen, len;
-	struct pkcs7_message *msg;
-
-	/*
-	 * This is the best assumption to check if the binary is
-	 * already in a form of pkcs7's signedData.
-	 */
-	if (buflen > sizeof(pkcs7_hdr) &&
-	    !memcmp(&((u8 *)buf)[4], &pkcs7_hdr[4], 11)) {
-		msg = pkcs7_parse_message(buf, buflen);
-		if (IS_ERR(msg))
-			return NULL;
-		return msg;
-	}
-
-	/*
-	 * Otherwise, we should add a dummy prefix sequence for pkcs7
-	 * message parser to be able to process.
-	 * NOTE: EDK2 also uses similar hack in WrapPkcs7Data()
-	 * in CryptoPkg/Library/BaseCryptLib/Pk/CryptPkcs7VerifyCommon.c
-	 * TODO:
-	 * The header should be composed in a more refined manner.
-	 */
-	EFI_PRINT("Makeshift prefix added to authentication data\n");
-	ebuflen = sizeof(pkcs7_hdr) + buflen;
-	if (ebuflen <= 0x7f) {
-		EFI_PRINT("Data is too short\n");
-		return NULL;
-	}
-
-	ebuf = malloc(ebuflen);
-	if (!ebuf) {
-		EFI_PRINT("Out of memory\n");
-		return NULL;
-	}
-
-	memcpy(ebuf, pkcs7_hdr, sizeof(pkcs7_hdr));
-	memcpy(ebuf + sizeof(pkcs7_hdr), buf, buflen);
-	len = ebuflen - 4;
-	ebuf[2] = (len >> 8) & 0xff;
-	ebuf[3] = len & 0xff;
-	len = ebuflen - 0x13;
-	ebuf[0x11] = (len >> 8) & 0xff;
-	ebuf[0x12] = len & 0xff;
-
-	msg = pkcs7_parse_message(ebuf, ebuflen);
-
-	if (IS_ERR(msg)) {
-		free(ebuf);
-		return NULL;
-	}
-
-	*tmpbuf = ebuf;
-	return msg;
-}
 
 /**
  * efi_variable_authenticate - authenticate a variable
@@ -215,10 +130,10 @@ static efi_status_t efi_variable_authenticate(u16 *variable,
 		goto err;
 
 	/* ebuf should be kept valid during the authentication */
-	var_sig = efi_variable_parse_signature(auth->auth_info.cert_data,
-					       auth->auth_info.hdr.dwLength
-						   - sizeof(auth->auth_info),
-					       &ebuf);
+	var_sig = efi_parse_pkcs7_header(auth->auth_info.cert_data,
+					 auth->auth_info.hdr.dwLength
+					 - sizeof(auth->auth_info),
+					 &ebuf);
 	if (!var_sig) {
 		EFI_PRINT("Parsing variable's signature failed\n");
 		goto err;
-- 
2.17.1