Re-design of the original gocryptfs code to work as a library.
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// +build !without_openssl
package stupidgcm
import (
"fmt"
"log"
)
/*
#include "openssl_aead.h"
#cgo pkg-config: libcrypto
*/
import "C"
func openSSLSeal(a *stupidAEADCommon, dst, iv, in, authData []byte) []byte {
if a.Wiped() {
log.Panic("BUG: tried to use wiped key")
}
if len(iv) != a.NonceSize() {
log.Panicf("Only %d-byte IVs are supported, you passed %d bytes", a.NonceSize(), len(iv))
}
// 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)
}
res := int(C.openssl_aead_seal(a.openSSLEVPCipher,
slicePointerOrNull(in),
C.int(len(in)),
(*C.uchar)(&authData[0]),
C.int(len(authData)),
(*C.uchar)(&a.key[0]),
C.int(len(a.key)),
(*C.uchar)(&iv[0]),
C.int(len(iv)),
(*C.uchar)(&buf[0]),
C.int(len(buf))))
if res != outLen {
log.Panicf("expected length %d, got %d", outLen, res)
}
if inplace {
return dst[:len(dst)+outLen]
}
return append(dst, buf...)
}
func openSSLOpen(a *stupidAEADCommon, dst, iv, in, authData []byte) ([]byte, error) {
if a.Wiped() {
log.Panic("BUG: tried to use wiped key")
}
if len(iv) != a.NonceSize() {
log.Panicf("Only %d-byte IVs are supported, you passed %d bytes", a.NonceSize(), len(iv))
}
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.openssl_aead_open(a.openSSLEVPCipher,
slicePointerOrNull(ciphertext),
C.int(len(ciphertext)),
(*C.uchar)(&authData[0]),
C.int(len(authData)),
(*C.uchar)(&tag[0]),
C.int(len(tag)),
(*C.uchar)(&a.key[0]),
C.int(len(a.key)),
(*C.uchar)(&iv[0]),
C.int(len(iv)),
slicePointerOrNull(buf),
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
}
// slicePointerOrNull returns a C pointer to the beginning of the byte slice,
// or NULL if the byte slice is empty. This is useful for slices that can be
// empty, otherwise you can directly use "(*C.uchar)(&s[0])".
func slicePointerOrNull(s []byte) (ptr *C.uchar) {
if len(s) == 0 {
return
}
return (*C.uchar)(&s[0])
}
// This functions exists to benchmark the C call overhead from Go.
// See BenchmarkCCall for resuts.
func noopCFunction() {
C.noop_c_function()
}