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[macOS] Specify kSecUseDataProtectionKeychain when generating RSA/ECC keys #52759

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Jun 3, 2021
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[macOS] Specify kSecUseDataProtectionKeychain when generating RSA/ECC keys #52759

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4 changes: 4 additions & 0 deletions src/libraries/Native/Unix/System.Security.Cryptography.Native.Apple/pal_ecc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,10 @@ int32_t AppleCryptoNative_EccGenerateKey(int32_t keySizeBits,
{
CFDictionaryAddValue(attributes, kSecAttrKeyType, kSecAttrKeyTypeEC);
CFDictionaryAddValue(attributes, kSecAttrKeySizeInBits, cfKeySizeValue);
if (__builtin_available(macOS 10.15, iOS 13, tvOS 13, *))
{
CFDictionaryAddValue(attributes, kSecUseDataProtectionKeychain, kCFBooleanTrue);
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The Apple docs for this are... lacking. What's the effect? Does this let us get rid of the temporary keychains, and therefore make ephemeral load work?

If someone does PersistKeySet (where we load it into the default keychain for them) does this do anything weird?

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@filipnavara filipnavara May 14, 2021 •
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The temporary keychains were already removed here in previous PR (#51620) that unified the key generation between iOS and macOS. However, by default macOS still generates ephemeral legacy CSSM keys that could be imported into (legacy) keychains. This attribute causes the code to create the iOS-style data keys instead. They don't interoperate with the legacy keychain SecItem* APIs well but that's never directly used in .NET (X509Certificate2.CopyWithPrivateKey will go through export and re-import using old APIs).

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@filipnavara filipnavara May 14, 2021 •
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Note that the attribute existed in earlier macOS versions under the name kSecAttrNoLegacy which was more fitting (but private API).

}

*pPrivateKey = SecKeyCreateRandomKey(attributes, pErrorOut);
if (*pPrivateKey != NULL)
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4 changes: 4 additions & 0 deletions src/libraries/Native/Unix/System.Security.Cryptography.Native.Apple/pal_rsa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,10 @@ int32_t AppleCryptoNative_RsaGenerateKey(int32_t keySizeBits,
{
CFDictionaryAddValue(attributes, kSecAttrKeyType, kSecAttrKeyTypeRSA);
CFDictionaryAddValue(attributes, kSecAttrKeySizeInBits, cfKeySizeValue);
if (__builtin_available(macOS 10.15, iOS 13, tvOS 13, *))
{
CFDictionaryAddValue(attributes, kSecUseDataProtectionKeychain, kCFBooleanTrue);
}

*pPrivateKey = SecKeyCreateRandomKey(attributes, pErrorOut);
if (*pPrivateKey != NULL)
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