stupidgcm: add chacha20poly1305 via openssl
"stupidChacha20poly1305". XChaCha will build upon this.
This commit is contained in:
Jakob Unterwurzacher
parent
cbf282861b
commit
c9b090770a
222
internal/stupidgcm/stupidchacha.go
Normal file
222
internal/stupidgcm/stupidchacha.go
Normal file
@ -0,0 +1,222 @@
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// +build !without_openssl
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package stupidgcm
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// #include <openssl/evp.h>
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// #cgo pkg-config: libcrypto
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import "C"
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import (
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"crypto/cipher"
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"fmt"
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"log"
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"unsafe"
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"golang.org/x/crypto/chacha20poly1305"
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)
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type stupidChacha20poly1305 struct {
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key []byte
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}
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// Verify that we satisfy the cipher.AEAD interface
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var _ cipher.AEAD = &stupidChacha20poly1305{}
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func newChacha20poly1305(keyIn []byte) cipher.AEAD {
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if len(keyIn) != chacha20poly1305.KeySize {
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log.Panicf("Only %d-byte keys are supported, you passed %d bytes", chacha20poly1305.KeySize, len(keyIn))
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}
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// Create a private copy of the key
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key := append([]byte{}, keyIn...)
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return &stupidChacha20poly1305{key: key}
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}
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// NonceSize returns the required size of the nonce / IV.
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func (g *stupidChacha20poly1305) NonceSize() int {
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return chacha20poly1305.NonceSize
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}
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// Overhead returns the number of bytes that are added for authentication.
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func (g *stupidChacha20poly1305) Overhead() int {
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return tagLen
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}
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// Seal encrypts "in" using "iv" and "authData" and append the result to "dst"
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func (g *stupidChacha20poly1305) Seal(dst, iv, in, authData []byte) []byte {
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if len(iv) != g.NonceSize() {
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log.Panicf("Only %d-byte IVs are supported, you passed %d bytes", g.NonceSize(), len(iv))
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}
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if len(in) == 0 {
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log.Panic("Zero-length input data is not supported")
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}
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if len(g.key) != chacha20poly1305.KeySize {
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log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
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}
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// If the "dst" slice is large enough we can use it as our output buffer
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outLen := len(in) + tagLen
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var buf []byte
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inplace := false
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if cap(dst)-len(dst) >= outLen {
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inplace = true
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buf = dst[len(dst) : len(dst)+outLen]
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} else {
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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
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if C.EVP_EncryptInit_ex(ctx, C.EVP_chacha20_poly1305(), nil, nil, nil) != 1 {
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log.Panic("EVP_EncryptInit_ex I 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 MAC tag and append it to the ciphertext in "buf"
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if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_AEAD_GET_TAG, tagLen, (unsafe.Pointer)(&buf[len(in)])) != 1 {
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log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_AEAD_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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if inplace {
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return dst[:len(dst)+outLen]
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}
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return append(dst, buf...)
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}
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// Open decrypts "in" using "iv" and "authData" and append the result to "dst"
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func (g *stupidChacha20poly1305) Open(dst, iv, in, authData []byte) ([]byte, error) {
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if len(iv) != g.NonceSize() {
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log.Panicf("Only %d-byte IVs are supported", g.NonceSize())
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}
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if len(g.key) != chacha20poly1305.KeySize {
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log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
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}
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if len(in) <= tagLen {
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return nil, fmt.Errorf("stupidChacha20poly1305: input data too short (%d bytes)", len(in))
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}
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// If the "dst" slice is large enough we can use it as our output buffer
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outLen := len(in) - tagLen
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var buf []byte
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inplace := false
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if cap(dst)-len(dst) >= outLen {
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inplace = true
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buf = dst[len(dst) : len(dst)+outLen]
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} else {
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buf = make([]byte, len(in)-tagLen)
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}
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ciphertext := in[:len(in)-tagLen]
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tag := in[len(in)-tagLen:]
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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_DecryptInit_ex(ctx, C.EVP_chacha20_poly1305(), nil, nil, nil) != 1 {
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log.Panic("EVP_DecryptInit_ex I failed")
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}
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// Set key and IV
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if C.EVP_DecryptInit_ex(ctx, nil, nil, (*C.uchar)(&g.key[0]), (*C.uchar)(&iv[0])) != 1 {
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log.Panic("EVP_DecryptInit_ex II failed")
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}
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// Set expected MAC tag
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if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_AEAD_SET_TAG, tagLen, (unsafe.Pointer)(&tag[0])) != 1 {
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log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_AEAD_SET_TAG 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_DecryptUpdate(ctx, nil, &resultLen, (*C.uchar)(&authData[0]), C.int(len(authData))) != 1 {
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log.Panic("EVP_DecryptUpdate 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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// Decrypt "ciphertext" into "buf"
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if C.EVP_DecryptUpdate(ctx, (*C.uchar)(&buf[0]), &resultLen, (*C.uchar)(&ciphertext[0]), C.int(len(ciphertext))) != 1 {
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log.Panic("EVP_DecryptUpdate failed")
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}
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if int(resultLen) != len(ciphertext) {
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log.Panicf("Unexpected length %d", resultLen)
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}
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// Check MAC
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dummy := make([]byte, 16)
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res := C.EVP_DecryptFinal_ex(ctx, (*C.uchar)(&dummy[0]), &resultLen)
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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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// Free scratch space
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C.EVP_CIPHER_CTX_free(ctx)
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if res != 1 {
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return nil, ErrAuth
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}
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if inplace {
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return dst[:len(dst)+outLen], nil
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}
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return append(dst, buf...), nil
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}
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// Wipe tries to wipe the AES key from memory by overwriting it with zeros
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// and setting the reference to nil.
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//
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// This is not bulletproof due to possible GC copies, but
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// still raises to bar for extracting the key.
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func (g *stupidChacha20poly1305) Wipe() {
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for i := range g.key {
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g.key[i] = 0
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}
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g.key = nil
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}
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171
internal/stupidgcm/stupidchacha_test.go
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171
internal/stupidgcm/stupidchacha_test.go
Normal file
@ -0,0 +1,171 @@
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// +build !without_openssl
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// We compare against Go's built-in GCM implementation. Since stupidgcm only
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// supports 128-bit IVs and Go only supports that from 1.5 onward, we cannot
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// run these tests on older Go versions.
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package stupidgcm
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import (
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"bytes"
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"encoding/hex"
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"testing"
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"golang.org/x/crypto/chacha20poly1305"
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)
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// TestEncryptDecrypt encrypts and decrypts using both stupidgcm and Go's built-in
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// GCM implementation and verifies that the results are identical.
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func TestEncryptDecryptChacha(t *testing.T) {
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key := randBytes(32)
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sGCM := newChacha20poly1305(key)
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authData := randBytes(24)
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iv := randBytes(sGCM.NonceSize())
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dst := make([]byte, 71) // 71 = random length
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gGCM, err := chacha20poly1305.New(key)
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if err != nil {
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t.Fatal(err)
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}
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// Check all block sizes from 1 to 5000
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for i := 1; i < 5000; i++ {
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in := make([]byte, i)
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sOut := sGCM.Seal(dst, iv, in, authData)
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gOut := gGCM.Seal(dst, iv, in, authData)
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// Ciphertext must be identical to Go GCM
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if !bytes.Equal(sOut, gOut) {
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t.Fatalf("Compare failed for encryption, size %d", i)
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t.Log("sOut:")
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t.Log("\n" + hex.Dump(sOut))
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t.Log("gOut:")
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t.Log("\n" + hex.Dump(gOut))
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}
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sOut2, sErr := sGCM.Open(dst, iv, sOut[len(dst):], authData)
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if sErr != nil {
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t.Fatal(sErr)
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}
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gOut2, gErr := gGCM.Open(dst, iv, gOut[len(dst):], authData)
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if gErr != nil {
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t.Fatal(gErr)
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}
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// Plaintext must be identical to Go GCM
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if !bytes.Equal(sOut2, gOut2) {
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t.Fatalf("Compare failed for decryption, size %d", i)
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}
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}
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}
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// Seal re-uses the "dst" buffer it is large enough.
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// Check that this works correctly by testing different "dst" capacities from
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// 5000 to 16 and "in" lengths from 1 to 5000.
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func TestInplaceSealChacha(t *testing.T) {
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key := randBytes(32)
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sGCM := newChacha20poly1305(key)
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authData := randBytes(24)
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iv := randBytes(sGCM.NonceSize())
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gGCM, err := chacha20poly1305.New(key)
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if err != nil {
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t.Fatal(err)
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}
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max := 5016
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// Check all block sizes from 1 to 5000
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for i := 1; i < max-len(iv); i++ {
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in := make([]byte, i)
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dst := make([]byte, max-i)
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dst = dst[:len(iv)]
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sOut := sGCM.Seal(dst, iv, in, authData)
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dst2 := make([]byte, len(iv))
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gOut := gGCM.Seal(dst2, iv, in, authData)
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// Ciphertext must be identical to Go GCM
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if !bytes.Equal(sOut, gOut) {
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t.Fatalf("Compare failed for encryption, size %d", i)
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t.Log("sOut:")
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t.Log("\n" + hex.Dump(sOut))
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t.Log("gOut:")
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t.Log("\n" + hex.Dump(gOut))
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}
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}
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}
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// Open re-uses the "dst" buffer it is large enough.
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// Check that this works correctly by testing different "dst" capacities from
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// 5000 to 16 and "in" lengths from 1 to 5000.
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func TestInplaceOpenChacha(t *testing.T) {
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key := randBytes(32)
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sGCM := newChacha20poly1305(key)
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authData := randBytes(24)
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iv := randBytes(sGCM.NonceSize())
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gGCM, err := chacha20poly1305.New(key)
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if err != nil {
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t.Fatal(err)
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}
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max := 5016
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// Check all block sizes from 1 to 5000
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for i := 1; i < max-len(iv); i++ {
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in := make([]byte, i)
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gCiphertext := gGCM.Seal(iv, iv, in, authData)
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dst := make([]byte, max-i)
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// sPlaintext ... stupidgcm plaintext
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sPlaintext, err := sGCM.Open(dst[:0], iv, gCiphertext[len(iv):], authData)
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if err != nil {
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t.Fatal(err)
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}
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// Plaintext must be identical to Go GCM
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if !bytes.Equal(in, sPlaintext) {
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t.Fatalf("Compare failed, i=%d", i)
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}
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}
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}
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// TestCorruption verifies that changes in the ciphertext result in a decryption
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// error
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func TestCorruptionChacha(t *testing.T) {
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key := randBytes(32)
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sGCM := newChacha20poly1305(key)
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authData := randBytes(24)
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iv := randBytes(sGCM.NonceSize())
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in := make([]byte, 354)
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sOut := sGCM.Seal(nil, iv, in, authData)
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sOut2, sErr := sGCM.Open(nil, iv, sOut, authData)
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if sErr != nil {
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t.Fatal(sErr)
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}
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if !bytes.Equal(in, sOut2) {
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t.Fatalf("Compare failed")
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}
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// Corrupt first byte
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sOut[0]++
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sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
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if sErr == nil || sOut2 != nil {
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t.Fatalf("Should have gotten error")
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}
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sOut[0]--
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// Corrupt last byte
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sOut[len(sOut)-1]++
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sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
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if sErr == nil || sOut2 != nil {
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t.Fatalf("Should have gotten error")
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}
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sOut[len(sOut)-1]--
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// Append one byte
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sOut = append(sOut, 0)
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sOut2, sErr = sGCM.Open(nil, iv, sOut, authData)
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if sErr == nil || sOut2 != nil {
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t.Fatalf("Should have gotten error")
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}
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}
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