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Diffstat (limited to 'internal/stupidgcm/stupidgcm.go')
-rw-r--r--internal/stupidgcm/stupidgcm.go204
1 files changed, 0 insertions, 204 deletions
diff --git a/internal/stupidgcm/stupidgcm.go b/internal/stupidgcm/stupidgcm.go
deleted file mode 100644
index 46b6b86..0000000
--- a/internal/stupidgcm/stupidgcm.go
+++ /dev/null
@@ -1,204 +0,0 @@
-// +build !without_openssl
-
-// Package stupidgcm is a thin wrapper for OpenSSL's GCM encryption and
-// decryption functions. It only support 32-byte keys and 16-bit IVs.
-package stupidgcm
-
-// #include <openssl/evp.h>
-// #include "chacha.h"
-// #cgo pkg-config: libcrypto
-import "C"
-
-import (
- "crypto/cipher"
- "fmt"
- "log"
- "unsafe"
-)
-
-const (
- // BuiltWithoutOpenssl indicates if openssl been disabled at compile-time
- BuiltWithoutOpenssl = false
-
- keyLen = 32
- ivLen = 16
- tagLen = 16
-)
-
-// StupidGCM implements the cipher.AEAD interface
-type StupidGCM struct {
- key []byte
- forceDecode bool
-}
-
-// Verify that we satisfy the cipher.AEAD interface
-var _ cipher.AEAD = &StupidGCM{}
-
-// New returns a new cipher.AEAD implementation..
-func New(keyIn []byte, forceDecode bool) cipher.AEAD {
- if len(keyIn) != keyLen {
- log.Panicf("Only %d-byte keys are supported", keyLen)
- }
- // Create a private copy of the key
- key := append([]byte{}, keyIn...)
- return &StupidGCM{key: key, forceDecode: forceDecode}
-}
-
-// NonceSize returns the required size of the nonce / IV.
-func (g *StupidGCM) NonceSize() int {
- return ivLen
-}
-
-// Overhead returns the number of bytes that are added for authentication.
-func (g *StupidGCM) Overhead() int {
- return tagLen
-}
-
-// Seal encrypts "in" using "iv" and "authData" and append the result to "dst"
-func (g *StupidGCM) Seal(dst, iv, in, authData []byte) []byte {
- if len(iv) != ivLen {
- log.Panicf("Only %d-byte IVs are supported", ivLen)
- }
- if len(in) == 0 {
- log.Panic("Zero-length input data is not supported")
- }
- if len(g.key) != keyLen {
- log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
- }
-
- // If the "dst" slice is large enough we can use it as our output buffer
- outLen := len(in) + tagLen
- var buf []byte
- inplace := false
- if cap(dst)-len(dst) >= outLen {
- inplace = true
- buf = dst[len(dst) : len(dst)+outLen]
- } else {
- buf = make([]byte, outLen)
- }
-
- C.aead_seal(C.aeadTypeGcm,
- (*C.uchar)(&in[0]),
- C.int(len(in)),
- (*C.uchar)(&authData[0]),
- C.int(len(authData)),
- (*C.uchar)(&g.key[0]),
- C.int(len(g.key)),
- (*C.uchar)(&iv[0]),
- C.int(len(iv)),
- (*C.uchar)(&buf[0]),
- C.int(len(buf)))
-
- if inplace {
- return dst[:len(dst)+outLen]
- }
- return append(dst, buf...)
-}
-
-// Open decrypts "in" using "iv" and "authData" and append the result to "dst"
-func (g *StupidGCM) Open(dst, iv, in, authData []byte) ([]byte, error) {
- if len(iv) != ivLen {
- log.Panicf("Only %d-byte IVs are supported", ivLen)
- }
- if len(g.key) != keyLen {
- log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key))
- }
- if len(in) <= tagLen {
- return nil, fmt.Errorf("stupidgcm: input data too short (%d bytes)", len(in))
- }
-
- // If the "dst" slice is large enough we can use it as our output buffer
- outLen := len(in) - tagLen
- var buf []byte
- inplace := false
- if cap(dst)-len(dst) >= outLen {
- inplace = true
- buf = dst[len(dst) : len(dst)+outLen]
- } else {
- buf = make([]byte, len(in)-tagLen)
- }
-
- ciphertext := in[:len(in)-tagLen]
- tag := in[len(in)-tagLen:]
-
- // https://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decryption#Authenticated_Encryption_using_GCM_mode
-
- // Create scratch space "context"
- ctx := C.EVP_CIPHER_CTX_new()
- if ctx == nil {
- log.Panic("EVP_CIPHER_CTX_new failed")
- }
-
- // Set cipher to AES-256
- if C.EVP_DecryptInit_ex(ctx, C.EVP_aes_256_gcm(), nil, nil, nil) != 1 {
- log.Panic("EVP_DecryptInit_ex I failed")
- }
-
- // Use 16-byte IV
- if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_SET_IVLEN, ivLen, nil) != 1 {
- log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_GCM_SET_IVLEN failed")
- }
-
- // Set key and IV
- if C.EVP_DecryptInit_ex(ctx, nil, nil, (*C.uchar)(&g.key[0]), (*C.uchar)(&iv[0])) != 1 {
- log.Panic("EVP_DecryptInit_ex II failed")
- }
-
- // Set expected GMAC tag
- if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_SET_TAG, tagLen, (unsafe.Pointer)(&tag[0])) != 1 {
- log.Panic("EVP_CIPHER_CTX_ctrl failed")
- }
-
- // Provide authentication data
- var resultLen C.int
- if C.EVP_DecryptUpdate(ctx, nil, &resultLen, (*C.uchar)(&authData[0]), C.int(len(authData))) != 1 {
- log.Panic("EVP_DecryptUpdate authData failed")
- }
- if int(resultLen) != len(authData) {
- log.Panicf("Unexpected length %d", resultLen)
- }
-
- // Decrypt "ciphertext" into "buf"
- if C.EVP_DecryptUpdate(ctx, (*C.uchar)(&buf[0]), &resultLen, (*C.uchar)(&ciphertext[0]), C.int(len(ciphertext))) != 1 {
- log.Panic("EVP_DecryptUpdate failed")
- }
- if int(resultLen) != len(ciphertext) {
- log.Panicf("Unexpected length %d", resultLen)
- }
-
- // Check GMAC
- dummy := make([]byte, 16)
- res := C.EVP_DecryptFinal_ex(ctx, (*C.uchar)(&dummy[0]), &resultLen)
- if resultLen != 0 {
- log.Panicf("Unexpected length %d", resultLen)
- }
-
- // Free scratch space
- C.EVP_CIPHER_CTX_free(ctx)
-
- if res != 1 {
- // The error code must always be checked by the calling function, because the decrypted buffer
- // may contain corrupted data that we are returning in case the user forced reads
- if g.forceDecode {
- return append(dst, buf...), ErrAuth
- }
- return nil, ErrAuth
- }
-
- if inplace {
- return dst[:len(dst)+outLen], nil
- }
- return append(dst, buf...), nil
-}
-
-// Wipe tries to wipe the AES key from memory by overwriting it with zeros
-// and setting the reference to nil.
-//
-// This is not bulletproof due to possible GC copies, but
-// still raises the bar for extracting the key.
-func (g *StupidGCM) Wipe() {
- for i := range g.key {
- g.key[i] = 0
- }
- g.key = nil
-}