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@ -5,6 +5,7 @@
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package stupidgcm
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// #include <openssl/evp.h>
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// #include "chacha.h"
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// #cgo pkg-config: libcrypto
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import "C"
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@ -76,63 +77,17 @@ func (g *StupidGCM) Seal(dst, iv, in, authData []byte) []byte {
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buf = make([]byte, outLen)
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}
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// https://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decryption#Authenticated_Encryption_using_GCM_mode
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// Create scratch space "context"
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ctx := C.EVP_CIPHER_CTX_new()
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if ctx == nil {
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log.Panic("EVP_CIPHER_CTX_new failed")
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}
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// Set cipher to AES-256
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if C.EVP_EncryptInit_ex(ctx, C.EVP_aes_256_gcm(), nil, nil, nil) != 1 {
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log.Panic("EVP_EncryptInit_ex I failed")
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}
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// Use 16-byte IV
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if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_SET_IVLEN, ivLen, nil) != 1 {
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log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_GCM_SET_IVLEN failed")
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}
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// Set key and IV
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if C.EVP_EncryptInit_ex(ctx, nil, nil, (*C.uchar)(&g.key[0]), (*C.uchar)(&iv[0])) != 1 {
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log.Panic("EVP_EncryptInit_ex II failed")
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}
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// Provide authentication data
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var resultLen C.int
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if C.EVP_EncryptUpdate(ctx, nil, &resultLen, (*C.uchar)(&authData[0]), C.int(len(authData))) != 1 {
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log.Panic("EVP_EncryptUpdate authData failed")
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}
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if int(resultLen) != len(authData) {
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log.Panicf("Unexpected length %d", resultLen)
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}
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// Encrypt "in" into "buf"
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if C.EVP_EncryptUpdate(ctx, (*C.uchar)(&buf[0]), &resultLen, (*C.uchar)(&in[0]), C.int(len(in))) != 1 {
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log.Panic("EVP_EncryptUpdate failed")
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}
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if int(resultLen) != len(in) {
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log.Panicf("Unexpected length %d", resultLen)
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}
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// Finalise encryption
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// Because GCM is a stream encryption, this will not write out any data.
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dummy := make([]byte, 16)
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if C.EVP_EncryptFinal_ex(ctx, (*C.uchar)(&dummy[0]), &resultLen) != 1 {
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log.Panic("EVP_EncryptFinal_ex failed")
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}
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if resultLen != 0 {
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log.Panicf("Unexpected length %d", resultLen)
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}
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// Get GMAC tag and append it to the ciphertext in "buf"
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if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_GET_TAG, tagLen, (unsafe.Pointer)(&buf[len(in)])) != 1 {
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log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_GCM_GET_TAG failed")
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}
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// Free scratch space
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C.EVP_CIPHER_CTX_free(ctx)
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C.aead_seal(C.aeadTypeGcm,
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(*C.uchar)(&in[0]),
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C.int(len(in)),
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(*C.uchar)(&authData[0]),
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C.int(len(authData)),
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(*C.uchar)(&g.key[0]),
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C.int(len(g.key)),
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(*C.uchar)(&iv[0]),
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C.int(len(iv)),
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(*C.uchar)(&buf[0]),
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C.int(len(buf)))
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if inplace {
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return dst[:len(dst)+outLen]
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