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Clarify guarantees made by rsa_complete and rsa_check_privkey

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This commit is contained in:
Hanno Becker 2017-10-10 16:44:47 +01:00
parent 68b4d58bd8
commit 1e801f5706
1 changed files with 39 additions and 26 deletions
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59
include/mbedtls/rsa.h
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@ -405,19 +405,16 @@ int mbedtls_rsa_import_raw( mbedtls_rsa_context *ctx,
*
* \return
* - 0 if successful. In this case, it is guaranteed
* the functions \c mbedtls_rsa_check_pubkey resp.
* \c mbedtls_rsa_check_privkey pass in case of a
* public resp. private key.
* that the RSA context can be used for RSA operations
* without the risk of failure or crash.
* - \c MBEDTLS_ERR_RSA_BAD_INPUT_DATA if the attempted
* derivations failed.
*
* \warning Implementations are *not* obliged to perform exhaustive
* validation of the imported parameters!
* In particular, parameters that are not needed by the
* implementation may be silently discarded and left unchecked.
* If the user mistrusts the given key material, he should
* employ other means for verification like the helper functions
* \c mbedtls_rsa_validate_params, \c mbedtls_rsa_validate_crt.
* \warning This function need not perform consistency checks
* for the imported parameters! In particular, parameters that
* are not needed by the implementation may be silently discarded
* and left unchecked. For the purpose of checking the consistency
* of the key material, see \c mbedtls_rsa_check_privkey.
*
*/
int mbedtls_rsa_complete( mbedtls_rsa_context *ctx,
@ -582,24 +579,40 @@ int mbedtls_rsa_check_pubkey( const mbedtls_rsa_context *ctx );
/**
* \brief Check if a context contains an RSA private key
* and perform basic sanity checks.
* and perform basic consistency checks.
*
* \param ctx RSA context to be checked
*
* \return 0 if successful, or an \c MBEDTLS_ERR_RSA_XXX error code.
* On success, it is guaranteed that enough information is
* present to perform RSA private and public key operations.
*
* \warning This function is *not* obliged to perform an exhaustive
* sanity check what would guarantee the internal parameters
* to match and \c mbedtls_rsa_private and \c mbedtls_rsa_public
* to be mutually inverse to each other.
* The reason is that for minimal non-CRT implementations
* using only N, D, E, for example, checking the validity
* would be computationally expensive.
* Users mistrusting their key material should use other
* means for verification; see the documentation of
* \c mbedtls_rsa_complete.
* \note This function performs checks substantiating
* the consistency of the key material used to setup
* the RSA context. In case of implementations saving
* all core RSA parameters, this might mean a consistency
* check in the sense of \c mbedtls_rsa_validate_params,
* while other implementations might perform an empirical
* check consisting of an encryption-decryption pair.
*
* \warning This function should catch accidental misconfigurations
* like swapping of parameters, but it cannot establish full
* trust in neither the quality nor the consistency of the key
* material that was used to setup the given RSA context:
* - Regarding consistency, note (see \c mbedtls_rsa_complete)
* that imported parameters irrelevant for the implementation
* might be silently dropped, in which case the present
* function doesn't have access to and hence cannot check them.
* If the user desires to check the consistency of the entire
* content of, say, an PKCS1-encoded RSA private key, he
* should use \c mbedtls_rsa_validate_params before setting
* up the RSA context.
* Further, if the implementation performs empirical checks,
* these checks will substantiate but not guarantee consistency.
* - Regarding quality, this function is not expected to perform
* extended quality assessments like checking that the prime
* factors are safe. Further, it is the user's responsibility to
* ensure trustworthiness of the source of his RSA parameters,
* a question going beyond what's effectively checkable
* by the library.
*
*/
int mbedtls_rsa_check_privkey( const mbedtls_rsa_context *ctx );