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hkdf.go
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hkdf.go
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//go:build !cmd_go_bootstrap
package openssl
// #include "goopenssl.h"
import "C"
import (
"errors"
"hash"
"io"
"runtime"
"unsafe"
)
func SupportsHKDF() bool {
return versionAtOrAbove(1, 1, 1)
}
func newHKDF(h func() hash.Hash, mode C.int) (*hkdf, error) {
if !SupportsHKDF() {
return nil, errUnsupportedVersion()
}
ch := h()
md := hashToMD(ch)
if md == nil {
return nil, errors.New("unsupported hash function")
}
ctx := C.go_openssl_EVP_PKEY_CTX_new_id(C.GO_EVP_PKEY_HKDF, nil)
if ctx == nil {
return nil, newOpenSSLError("EVP_PKEY_CTX_new_id")
}
defer func() {
C.go_openssl_EVP_PKEY_CTX_free(ctx)
}()
if C.go_openssl_EVP_PKEY_derive_init(ctx) != 1 {
return nil, newOpenSSLError("EVP_PKEY_derive_init")
}
switch vMajor {
case 3:
if C.go_openssl_EVP_PKEY_CTX_set_hkdf_mode(ctx, mode) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set_hkdf_mode")
}
if C.go_openssl_EVP_PKEY_CTX_set_hkdf_md(ctx, md) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set_hkdf_md")
}
case 1:
if C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_MODE,
C.int(mode), nil) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set_hkdf_mode")
}
if C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_MD,
0, unsafe.Pointer(md)) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set_hkdf_md")
}
}
c := &hkdf{ctx: ctx, hashLen: ch.Size()}
ctx = nil
runtime.SetFinalizer(c, (*hkdf).finalize)
return c, nil
}
type hkdf struct {
ctx C.GO_EVP_PKEY_CTX_PTR
hashLen int
buf []byte
}
func (c *hkdf) finalize() {
if c.ctx != nil {
C.go_openssl_EVP_PKEY_CTX_free(c.ctx)
}
}
func (c *hkdf) Read(p []byte) (int, error) {
defer runtime.KeepAlive(c)
// EVP_PKEY_derive doesn't support incremental output, each call
// derives the key from scratch and returns the requested bytes.
// To implement io.Reader, we need to ask for len(c.buf) + len(p)
// bytes and copy the last derived len(p) bytes to p.
// We use c.buf to know how many bytes we've already derived and
// to avoid allocating the whole output buffer on each call.
prevLen := len(c.buf)
needLen := len(p)
remains := 255*c.hashLen - prevLen
// Check whether enough data can be generated.
if remains < needLen {
return 0, errors.New("hkdf: entropy limit reached")
}
c.buf = append(c.buf, make([]byte, needLen)...)
outLen := C.size_t(prevLen + needLen)
if C.go_openssl_EVP_PKEY_derive_wrapper(c.ctx, base(c.buf), outLen).result != 1 {
return 0, newOpenSSLError("EVP_PKEY_derive")
}
n := copy(p, c.buf[prevLen:outLen])
return n, nil
}
func ExtractHKDF(h func() hash.Hash, secret, salt []byte) ([]byte, error) {
c, err := newHKDF(h, C.GO_EVP_KDF_HKDF_MODE_EXTRACT_ONLY)
if err != nil {
return nil, err
}
switch vMajor {
case 3:
if C.go_openssl_EVP_PKEY_CTX_set1_hkdf_key(c.ctx,
base(secret), C.int(len(secret))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_key")
}
if C.go_openssl_EVP_PKEY_CTX_set1_hkdf_salt(c.ctx,
base(salt), C.int(len(salt))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_salt")
}
case 1:
if C.go_openssl_EVP_PKEY_CTX_ctrl(c.ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_KEY,
C.int(len(secret)), unsafe.Pointer(base(secret))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_key")
}
if C.go_openssl_EVP_PKEY_CTX_ctrl(c.ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_SALT,
C.int(len(salt)), unsafe.Pointer(base(salt))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_salt")
}
}
r := C.go_openssl_EVP_PKEY_derive_wrapper(c.ctx, nil, 0)
if r.result != 1 {
return nil, newOpenSSLError("EVP_PKEY_derive_init")
}
out := make([]byte, r.keylen)
if C.go_openssl_EVP_PKEY_derive_wrapper(c.ctx, base(out), r.keylen).result != 1 {
return nil, newOpenSSLError("EVP_PKEY_derive")
}
return out[:r.keylen], nil
}
func ExpandHKDF(h func() hash.Hash, pseudorandomKey, info []byte) (io.Reader, error) {
c, err := newHKDF(h, C.GO_EVP_KDF_HKDF_MODE_EXPAND_ONLY)
if err != nil {
return nil, err
}
switch vMajor {
case 3:
if C.go_openssl_EVP_PKEY_CTX_set1_hkdf_key(c.ctx,
base(pseudorandomKey), C.int(len(pseudorandomKey))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_key")
}
if C.go_openssl_EVP_PKEY_CTX_add1_hkdf_info(c.ctx,
base(info), C.int(len(info))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_add1_hkdf_info")
}
case 1:
if C.go_openssl_EVP_PKEY_CTX_ctrl(c.ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_KEY,
C.int(len(pseudorandomKey)), unsafe.Pointer(base(pseudorandomKey))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_set1_hkdf_key")
}
if C.go_openssl_EVP_PKEY_CTX_ctrl(c.ctx, -1, C.GO1_EVP_PKEY_OP_DERIVE,
C.GO_EVP_PKEY_CTRL_HKDF_INFO,
C.int(len(info)), unsafe.Pointer(base(info))) != 1 {
return nil, newOpenSSLError("EVP_PKEY_CTX_add1_hkdf_info")
}
}
return c, nil
}