// +build !without_openssl package stupidgcm import ( "crypto/cipher" "fmt" "log" "golang.org/x/crypto/chacha20poly1305" ) /* #include #include "chacha.h" #cgo pkg-config: libcrypto */ import "C" type stupidChacha20poly1305 struct { key [chacha20poly1305.KeySize]byte wiped bool } // Verify that we satisfy the cipher.AEAD interface var _ cipher.AEAD = &stupidChacha20poly1305{} func newChacha20poly1305(key []byte) cipher.AEAD { if len(key) != chacha20poly1305.KeySize { log.Panicf("Only %d-byte keys are supported, you passed %d bytes", chacha20poly1305.KeySize, len(key)) } ret := new(stupidChacha20poly1305) copy(ret.key[:], key) return ret } // NonceSize returns the required size of the nonce / IV. func (g *stupidChacha20poly1305) NonceSize() int { return chacha20poly1305.NonceSize } // Overhead returns the number of bytes that are added for authentication. func (g *stupidChacha20poly1305) Overhead() int { return tagLen } // Seal encrypts "in" using "iv" and "authData" and append the result to "dst" func (g *stupidChacha20poly1305) Seal(dst, iv, in, authData []byte) []byte { if g.wiped { panic("BUG: tried to use wiped key") } if len(iv) != g.NonceSize() { log.Panicf("Only %d-byte IVs are supported, you passed %d bytes", g.NonceSize(), len(iv)) } if len(in) == 0 { log.Panic("Zero-length input data is not supported") } if len(g.key) != chacha20poly1305.KeySize { 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.aeadTypeChacha, (*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 *stupidChacha20poly1305) Open(dst, iv, in, authData []byte) ([]byte, error) { if g.wiped { panic("BUG: tried to use wiped key") } if len(iv) != g.NonceSize() { log.Panicf("Only %d-byte IVs are supported", g.NonceSize()) } if len(g.key) != chacha20poly1305.KeySize { log.Panicf("Wrong key length: %d. Key has been wiped?", len(g.key)) } if len(in) <= tagLen { return nil, fmt.Errorf("stupidChacha20poly1305: 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:] res := int(C.aead_open(C.aeadTypeChacha, (*C.uchar)(&ciphertext[0]), C.int(len(ciphertext)), (*C.uchar)(&authData[0]), C.int(len(authData)), (*C.uchar)(&tag[0]), C.int(len(tag)), (*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 res < 0 { return nil, ErrAuth } if res != outLen { log.Panicf("unexpected length %d", res) } if inplace { return dst[:len(dst)+outLen], nil } return append(dst, buf...), nil } // Wipe tries to wipe the key from memory by overwriting it with zeros. // // This is not bulletproof due to possible GC copies, but // still raises the bar for extracting the key. func (g *stupidChacha20poly1305) Wipe() { g.wiped = true for i := range g.key { g.key[i] = 0 } }