Go API for GmSSL

go/cipher.go

@@ -0,0 +1,121 @@
+/* +build cgo */
+package gmssl
+
+/*
+#include <openssl/evp.h>
+*/
+import "C"
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"unsafe"
+)
+
+func GetCiphers(aliases bool) []string {
+	return []string{"sms4-cbc", "aes-128-cbc", "aes-256-cbc"}
+}
+
+func GetCipherKeyLength(name string) (int, error) {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	cipher := C.EVP_get_cipherbyname(cname)
+	if cipher == nil {
+		return 0, errors.New("Invalid cipher name")
+	}
+	return int(C.EVP_CIPHER_key_length(cipher)), nil
+}
+
+func GetCipherBlockSize(name string) (int, error) {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	cipher := C.EVP_get_cipherbyname(cname)
+	if cipher == nil {
+		return 0, errors.New("Invalid cipher")
+	}
+	return int(C.EVP_CIPHER_block_size(cipher)), nil
+}
+
+func GetCipherIVLength(name string) (int, error) {
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+	cipher := C.EVP_get_cipherbyname(cname)
+	if cipher == nil {
+		return 0, errors.New("Invalid cipher")
+	}
+	return int(C.EVP_CIPHER_iv_length(cipher)), nil
+}
+
+type CipherContext struct {
+	ctx *C.EVP_CIPHER_CTX
+}
+
+func NewCipherContext(name string, args map[string]string, key, iv []byte, encrypt bool) (
+	*CipherContext, error) {
+
+	cname := C.CString(name)
+	defer C.free(unsafe.Pointer(cname))
+
+	cipher := C.EVP_get_cipherbyname(cname)
+	if cipher == nil {
+		return nil, fmt.Errorf("shit")
+	}
+
+	if key == nil {
+		return nil, errors.New("No key")
+	}
+	if len(key) != int(C.EVP_CIPHER_key_length(cipher)) {
+		return nil, errors.New("Invalid key length")
+	}
+
+	if 0 != int(C.EVP_CIPHER_iv_length(cipher)) {
+		if iv == nil {
+			return nil, errors.New("No IV")
+		}
+		if len(iv) != int(C.EVP_CIPHER_iv_length(cipher)) {
+			return nil, errors.New("Invalid IV")
+		}
+	}
+
+	ctx := C.EVP_CIPHER_CTX_new()
+	if ctx == nil {
+		return nil, fmt.Errorf("shit")
+	}
+
+	ret := &CipherContext{ctx}
+	runtime.SetFinalizer(ret, func(ret *CipherContext) {
+		C.EVP_CIPHER_CTX_free(ret.ctx)
+	})
+
+	enc := 1
+	if encrypt == false {
+		enc = 0
+	}
+
+	if 1 != C.EVP_CipherInit(ctx, cipher, (*C.uchar)(&key[0]),
+		(*C.uchar)(&iv[0]), C.int(enc)) {
+		return nil, fmt.Errorf("shit")
+	}
+
+	return ret, nil
+}
+
+func (ctx *CipherContext) Update(in []byte) ([]byte, error) {
+	outbuf := make([]byte, len(in)+int(C.EVP_CIPHER_CTX_block_size(ctx.ctx)))
+	outlen := C.int(len(outbuf))
+	if 1 != C.EVP_CipherUpdate(ctx.ctx, (*C.uchar)(&outbuf[0]), &outlen,
+		(*C.uchar)(&in[0]), C.int(len(in))) {
+		return nil, fmt.Errorf("failed to decrypt")
+	}
+	return outbuf[:outlen], nil
+}
+
+func (ctx *CipherContext) Final() ([]byte, error) {
+	outbuf := make([]byte, int(C.EVP_CIPHER_CTX_block_size(ctx.ctx)))
+	outlen := C.int(len(outbuf))
+	if 1 != C.EVP_CipherFinal(ctx.ctx, (*C.uchar)(&outbuf[0]), &outlen) {
+		return nil, fmt.Errorf("failed to decrypt")
+	}
+	return outbuf[:outlen], nil
+}