51 lines
1.6 KiB
Go
51 lines
1.6 KiB
Go
package crypto
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import (
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"crypto/sha256"
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"fmt"
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"io"
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wrapping "github.com/hashicorp/go-kms-wrapping"
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"github.com/hashicorp/go-kms-wrapping/wrappers/aead"
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"github.com/hashicorp/go-kms-wrapping/wrappers/multiwrapper"
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"golang.org/x/crypto/hkdf"
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)
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// DerivedReader returns a reader from which keys can be read, using the
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// given wrapper, reader length limit, salt and context info. Salt and info can
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// be nil.
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//
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// Example:
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// reader, _ := NewDerivedReader(wrapper, userId, jobId)
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// key := ed25519.GenerateKey(reader)
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func NewDerivedReader(wrapper wrapping.Wrapper, lenLimit int64, salt, info []byte) (*io.LimitedReader, error) {
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const op = "crypto.NewDerivedReader"
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if wrapper == nil {
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return nil, fmt.Errorf("%s: missing wrapper: %w", op, ErrInvalidParameter)
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}
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if lenLimit < 20 {
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return nil, fmt.Errorf("%s: lenLimit must be >= 20: %w", op, ErrInvalidParameter)
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}
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var aeadWrapper *aead.Wrapper
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switch w := wrapper.(type) {
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case *multiwrapper.MultiWrapper:
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raw := w.WrapperForKeyID("__base__")
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var ok bool
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if aeadWrapper, ok = raw.(*aead.Wrapper); !ok {
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return nil, fmt.Errorf("%s: unexpected wrapper type from multiwrapper base: %w", op, ErrInvalidParameter)
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}
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case *aead.Wrapper:
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if w.GetKeyBytes() == nil {
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return nil, fmt.Errorf("%s: aead wrapper missing bytes: %w", op, ErrInvalidParameter)
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}
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aeadWrapper = w
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default:
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return nil, fmt.Errorf("%s: unknown wrapper type: %w", op, ErrInvalidParameter)
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}
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reader := hkdf.New(sha256.New, aeadWrapper.GetKeyBytes(), salt, info)
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return &io.LimitedReader{
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R: reader,
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N: lenLimit,
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}, nil
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}
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