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Use recommended crypto library to create ECC seed #480

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Use recommended crypto library to create ECC seed #480

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1993889
Remove P224 support and upgrade deprecated methods
yawangwang Aug 23, 2024
809e4a7
Merge branch 'main' into remove_p224_support
yawangwang Aug 23, 2024
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6 changes: 3 additions & 3 deletions cmd/token.go
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Original file line number Diff line number Diff line change
Expand Up @@ -107,7 +107,7 @@ The OIDC token includes claims regarding the GCE VM, which is verified by Attest
}

cloudLogger = cloudLogClient.Logger(toolName)
fmt.Fprintf(debugOutput(), "cloudLogger created for project: "+projectID+"\n")
fmt.Fprint(debugOutput(), "cloudLogger created for project: "+projectID+"\n")
}

key = "gceAK"
Expand Down Expand Up @@ -175,7 +175,7 @@ The OIDC token includes claims regarding the GCE VM, which is verified by Attest
}

if output == "" {
fmt.Fprintf(messageOutput(), string(token)+"\n")
fmt.Fprint(messageOutput(), string(token)+"\n")
} else {
out := []byte(token)
if _, err := dataOutput().Write(out); err != nil {
Expand All @@ -194,7 +194,7 @@ The OIDC token includes claims regarding the GCE VM, which is verified by Attest
}
}

fmt.Fprintf(debugOutput(), string(claimsString)+"\n"+"Note: these Claims are for debugging purpose and not verified"+"\n")
fmt.Fprint(debugOutput(), string(claimsString)+"\n"+"Note: these Claims are for debugging purpose and not verified"+"\n")

return nil
},
Expand Down
37 changes: 29 additions & 8 deletions server/import.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,13 +5,14 @@ import (
"crypto"
"crypto/aes"
"crypto/cipher"
"crypto/elliptic"
"crypto/ecdsa"
"crypto/hmac"
"crypto/rand"
"crypto/rsa"
"fmt"
"hash"
"io"
"math/big"

"github.com/google/go-tpm/legacy/tpm2"
"github.com/google/go-tpm/tpmutil"
Expand Down Expand Up @@ -131,25 +132,45 @@ func createECCSeed(ek tpm2.Public) (seed, encryptedSeed []byte, err error) {
if err != nil {
return nil, nil, err
}
priv, x, y, err := elliptic.GenerateKey(curve, rand.Reader)

ecdsaPriv, err := ecdsa.GenerateKey(curve, rand.Reader)
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We're doing ecdh here so you should use the utilities in crypto/ecdh instead

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We need EC points {x, y} to compute ECC seed in the following operations. Using crypto/ecdh utilities is an ideal way, however they don't provide a method to expose the EC points {x, y} in public key.

crypto/ecdsa provides a method to do that, also there are methods which convert each key type to their counterparts in the the ecdh package. See line 141 that converts an ecdsa private key to its corresponding ecdh private key.

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Makes sense. LGTM

if err != nil {
return nil, nil, err
}

ecdhPriv, err := ecdsaPriv.ECDH()
if err != nil {
return nil, nil, err
}

pub, err := ek.Key()
if err != nil {
return nil, nil, err
}
ekPoint := ek.ECCParameters.Point
z, _ := curve.ScalarMult(ekPoint.X(), ekPoint.Y(), priv)
xBytes := eccIntToBytes(curve, x)

ekPub, err := pub.(*ecdsa.PublicKey).ECDH()
if err != nil {
return nil, nil, err
}

zBytes, err := ecdhPriv.ECDH(ekPub)
if err != nil {
return nil, nil, err
}

xBytes := eccIntToBytes(curve, ecdsaPriv.X)

seed, err = tpm2.KDFe(
ek.NameAlg,
eccIntToBytes(curve, z),
eccIntToBytes(curve, new(big.Int).SetBytes(zBytes)),
"DUPLICATE",
xBytes,
eccIntToBytes(curve, ekPoint.X()),
eccIntToBytes(curve, ek.ECCParameters.Point.X()),
getHash(ek.NameAlg).Size()*8)
if err != nil {
return nil, nil, err
}
encryptedSeed, err = tpmutil.Pack(tpmutil.U16Bytes(xBytes), tpmutil.U16Bytes(eccIntToBytes(curve, y)))
encryptedSeed, err = tpmutil.Pack(tpmutil.U16Bytes(xBytes), tpmutil.U16Bytes(eccIntToBytes(curve, ecdsaPriv.Y)))
return seed, encryptedSeed, err
}

Expand Down
1 change: 0 additions & 1 deletion server/import_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,6 @@ func TestImport(t *testing.T) {
{"ECC", client.DefaultEKTemplateECC()},
{"SRK-RSA", client.SRKTemplateRSA()},
{"SRK-ECC", client.SRKTemplateECC()},
{"ECC-P224", getECCTemplate(tpm2.CurveNISTP224)},
{"ECC-P256", getECCTemplate(tpm2.CurveNISTP256)},
{"ECC-P384", getECCTemplate(tpm2.CurveNISTP384)},
{"ECC-P521", getECCTemplate(tpm2.CurveNISTP521)},
Expand Down
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