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SSL asynchronous private key operation callbacks: interface

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New compile-time option MBEDTLS_SSL_ASYNC_PRIVATE_C, enabling
callbacks to replace private key operations. These callbacks allow the
SSL stack to make an asynchronous call to an external cryptographic
module instead of calling the cryptography layer inside the library.
The call is asynchronous in that it may return the new status code
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS, in which case the SSL stack returns
and can be later called where it left off.

This commit introduces the configuration option. Later commits will
implement the feature proper.
This commit is contained in:
Gilles Peskine 2018-01-05 21:11:53 +01:00
parent 59e83d96db
commit 8bf79f6dc6
7 changed files with 246 additions and 1 deletions
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11
include/mbedtls/config.h
View file

@ -2333,6 +2333,17 @@
*/ */
#define MBEDTLS_SHA512_C #define MBEDTLS_SHA512_C
/**
* \def MBEDTLS_SSL_ASYNC_PRIVATE_C
*
* Enable asynchronous external private key operations in SSL. This allows
* you to configure an SSL connection to call an external cryptographic
* module to perform private key operations instead of performing the
* operation inside the library.
*
*/
#define MBEDTLS_SSL_ASYNC_PRIVATE_C
/** /**
* \def MBEDTLS_SSL_CACHE_C * \def MBEDTLS_SSL_CACHE_C
* *

2
include/mbedtls/error.h
View file

@ -79,7 +79,7 @@
* ECP 4 8 (Started from top) * ECP 4 8 (Started from top)
* MD 5 4 * MD 5 4
* CIPHER 6 6 * CIPHER 6 6
* SSL 6 17 (Started from top) * SSL 6 21 (Started from top)
* SSL 7 31 * SSL 7 31
* *
* Module dependent error code (5 bits 0x.00.-0x.F8.) * Module dependent error code (5 bits 0x.00.-0x.F8.)

199
include/mbedtls/ssl.h
View file

@ -109,6 +109,7 @@
#define MBEDTLS_ERR_SSL_UNEXPECTED_RECORD -0x6700 /**< Record header looks valid but is not expected. */ #define MBEDTLS_ERR_SSL_UNEXPECTED_RECORD -0x6700 /**< Record header looks valid but is not expected. */
#define MBEDTLS_ERR_SSL_NON_FATAL -0x6680 /**< The alert message received indicates a non-fatal error. */ #define MBEDTLS_ERR_SSL_NON_FATAL -0x6680 /**< The alert message received indicates a non-fatal error. */
#define MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH -0x6600 /**< Couldn't set the hash for verifying CertificateVerify */ #define MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH -0x6600 /**< Couldn't set the hash for verifying CertificateVerify */
#define MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS -0x6580 /**< Asynchronous operation is not completed yet */
/* /*
* Various constants * Various constants
@ -525,6 +526,160 @@ typedef void mbedtls_ssl_set_timer_t( void * ctx,
*/ */
typedef int mbedtls_ssl_get_timer_t( void * ctx ); typedef int mbedtls_ssl_get_timer_t( void * ctx );
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
#if defined(MBEDTLS_X509_CRT_PARSE_C)
/**
* \brief Callback type: start external signature operation
*
* Callback to start a signature operation using an
* external processor. The parameter \c cert contains
* the public key; it is up to the callback function to
* look up the associated private key or a handle to the
* private key.
*
* This function must start the signature operation.
* It is expected to be non-blocking, i.e. typically
* this function sends or enqueues a request and does
* not wait for the operation to complete.
*
* The parameters \c connection_ctx and \c cert are
* guaranteed to remain valid as long as the SSL
* configuration remains valid. On the other hand, this
* function must save the contents of \c hash, as the
* \c hash buffer is no longer valid when this function
* returns.
*
* \param connection_ctx Pointer to the connection context set in the
* SSL configuration
* \param p_operation_ctx On output, pointer to the operation context.
* This pointer will be passed later to the resume
* or detach function. The value is only used if
* an operation is started, i.e. if this callback
* returns 0 or \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* \param cert Certificate containing the public key
* \param md_alg Hash algorithm
* \param hash Buffer containing the hash. This buffer is
* no longer valid when the function returns.
* \param hash_len Size of the \c hash buffer in bytes
*
* \return - 0 if the SSL stack should call the resume callback
* immediately. The resume function may provide the
* or may itself return
* \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* - \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS if the SSL stack
* should return immediately without calling the resume
* callback.
* - \c MBEDTLS_ERR_SSL_HW_ACCEL_FALLTHROUGH if the external
* processor does not support this key. The SSL stack will
* use the associated private key object instead.
* - Any other error is propagated up the call chain.
*/
typedef int mbedtls_ssl_async_sign_t( void *connection_ctx,
void **p_operation_ctx,
mbedtls_x509_crt *cert,
mbedtls_md_type_t md_alg,
const unsigned char *hash,
size_t hash_len );
/**
* \brief Callback type: start external decryption operation
*
* Callback to start a decryption operation using an
* external processor. The parameter \c cert contains
* the public key; it is up to the callback function to
* look up the associated private key or a handle to the
* private key.
*
* This function must start the decryption operation.
* It is expected to be non-blocking, i.e. typically
* this function sends or enqueues a request and does
* not wait for the operation to complete.
*
* The parameters \c connection_ctx and \c cert are
* guaranteed to remain valid as long as the SSL
* configuration remains valid. On the other hand, this
* function must save the contents of \c hash, as the
* \c hash buffer is no longer valid when this function
* returns.
*
* \param connection_ctx Pointer to the connection context set in the
* SSL configuration
* \param p_operation_ctx On output, pointer to the operation context.
* This pointer will be passed later to the resume
* or detach function. The value is only used if
* an operation is started, i.e. if this callback
* returns 0 or \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* \param cert Certificate containing the public key
* \param input Buffer containing the input ciphertext. This buffer
* is no longer valid when the function returns.
* \param input_len Size of the \c input buffer in bytes
*
* \return - 0 if the SSL stack should call the resume callback
* immediately. The resume function may provide the
* or may itself return
* \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* - \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS if the SSL stack
* should return immediately without calling the resume
* callback.
* - \c MBEDTLS_ERR_SSL_HW_ACCEL_FALLTHROUGH if the external
* processor does not support this key. The SSL stack will
* use the associated private key object instead.
* - Any other error is propagated up the call chain.
*/
typedef int mbedtls_ssl_async_decrypt_t( void *connection_ctx,
void **p_operation_ctx,
mbedtls_x509_crt *cert,
const unsigned char *input,
size_t input_len );
#endif /* MBEDTLS_X509_CRT_PARSE_C */
/**
* \brief Callback type: resume external operation
*
* Callback to resume an external operation
* started by the \c mbedtls_ssl_async_sign_t callback.
*
* \param connection_ctx Pointer to the connection context set in the
* SSL configuration
* \param operation_ctx Pointer to the operation context created by
* the start function. If this callback returns
* any value other than
* \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS, it should
* free all resources associated with this context.
* \param output Buffer containing the output on success
* \param output_len On success, number of bytes written to \c output
* \param output_size Size of the \c output buffer in bytes
*
* \return - 0 if output of the operation is available in the
* \c output buffer.
* - \c MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS if the operation
* is still in progress. Subsequent requests for progress
* on the SSL connection will call the resume callback
* again.
* - Any other error means that the operation is aborted.
* The SSL handshake is aborted.
*/
typedef int mbedtls_ssl_async_resume_t( void *connection_ctx,
void *operation_ctx,
unsigned char *output,
size_t *output_len,
size_t output_size );
/**
* \brief Callback type: cancel external operation
*
* Callback to cancel an external operation
* started by the \c mbedtls_ssl_async_sign_t callback.
*
* \param connection_ctx Pointer to the connection context set in the
* SSL configuration
* \param operation_ctx Pointer to the operation context created by
* the start function. The callback should free
* all resources associated with this context.
*/
typedef void mbedtls_ssl_async_cancel_t( void *connection_ctx,
void *operation_ctx );
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
/* Defined below */ /* Defined below */
typedef struct mbedtls_ssl_session mbedtls_ssl_session; typedef struct mbedtls_ssl_session mbedtls_ssl_session;
@ -658,6 +813,16 @@ struct mbedtls_ssl_config
mbedtls_x509_crl *ca_crl; /*!< trusted CAs CRLs */ mbedtls_x509_crl *ca_crl; /*!< trusted CAs CRLs */
#endif /* MBEDTLS_X509_CRT_PARSE_C */ #endif /* MBEDTLS_X509_CRT_PARSE_C */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
#if defined(MBEDTLS_X509_CRT_PARSE_C)
mbedtls_ssl_async_sign_t *f_async_sign_start; /*!< start asynchronous signature operation */
mbedtls_ssl_async_decrypt_t *f_async_decrypt_start; /*!< start asynchronous decryption operation */
#endif /* MBEDTLS_X509_CRT_PARSE_C */
mbedtls_ssl_async_resume_t *f_async_resume; /*!< resume asynchronous operation */
mbedtls_ssl_async_cancel_t *f_async_cancel; /*!< cancel asynchronous operation */
void *p_async_connection_ctx; /*!< connection context for asynchronous operation callbacks */
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
#if defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED) #if defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
const int *sig_hashes; /*!< allowed signature hashes */ const int *sig_hashes; /*!< allowed signature hashes */
#endif #endif
@ -1291,6 +1456,40 @@ void mbedtls_ssl_conf_export_keys_cb( mbedtls_ssl_config *conf,
void *p_export_keys ); void *p_export_keys );
#endif /* MBEDTLS_SSL_EXPORT_KEYS */ #endif /* MBEDTLS_SSL_EXPORT_KEYS */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
/**
* \brief Configure asynchronous private key operation callbacks.
*
* \param conf SSL configuration context
* \param f_async_sign Callback to start a signature operation. See
* the description of \c mbedtls_ssl_async_sign_t
* for more information. This may be NULL if the
* external processor does no support any signature
* operation; in this case the private key object
* associated with the certificate will be used.
* \param f_async_decrypt Callback to start a decryption operation. See
* the description of \c mbedtls_ssl_async_decrypt_t
* for more information. This may be NULL if the
* external processor does no support any decryption
* operation; in this case the private key object
* associated with the certificate will be used.
* \param f_async_resume Callback to resume an asynchronous operation. See
* the description of \c mbedtls_ssl_async_resume_t
* for more information.
* \param f_async_cancel Callback to cancel an asynchronous operation. See
* the description of \c mbedtls_ssl_async_cancel_t
* for more information.
* \param connection_ctx Pointer to the connection context which will be
* passed to the callbacks
*/
void mbedtls_ssl_conf_async_private_cb( mbedtls_ssl_config *conf,
mbedtls_ssl_async_sign_t *f_async_sign,
mbedtls_ssl_async_decrypt_t *f_async_decrypt,
mbedtls_ssl_async_resume_t *f_async_resume,
mbedtls_ssl_async_cancel_t *f_async_cancel,
void *connection_ctx );
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
/** /**
* \brief Callback type: generate a cookie * \brief Callback type: generate a cookie
* *

4
include/mbedtls/ssl_internal.h
View file

@ -218,6 +218,10 @@ struct mbedtls_ssl_handshake_params
mbedtls_x509_crl *sni_ca_crl; /*!< trusted CAs CRLs from SNI */ mbedtls_x509_crl *sni_ca_crl; /*!< trusted CAs CRLs from SNI */
#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */ #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
#endif /* MBEDTLS_X509_CRT_PARSE_C */ #endif /* MBEDTLS_X509_CRT_PARSE_C */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
void *p_async_operation_ctx; /*!< asynchronous operation context */
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
#if defined(MBEDTLS_SSL_PROTO_DTLS) #if defined(MBEDTLS_SSL_PROTO_DTLS)
unsigned int out_msg_seq; /*!< Outgoing handshake sequence number */ unsigned int out_msg_seq; /*!< Outgoing handshake sequence number */
unsigned int in_msg_seq; /*!< Incoming handshake sequence number */ unsigned int in_msg_seq; /*!< Incoming handshake sequence number */

2
library/error.c
View file

@ -441,6 +441,8 @@ void mbedtls_strerror( int ret, char *buf, size_t buflen )
mbedtls_snprintf( buf, buflen, "SSL - The alert message received indicates a non-fatal error" ); mbedtls_snprintf( buf, buflen, "SSL - The alert message received indicates a non-fatal error" );
if( use_ret == -(MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH) ) if( use_ret == -(MBEDTLS_ERR_SSL_INVALID_VERIFY_HASH) )
mbedtls_snprintf( buf, buflen, "SSL - Couldn't set the hash for verifying CertificateVerify" ); mbedtls_snprintf( buf, buflen, "SSL - Couldn't set the hash for verifying CertificateVerify" );
if( use_ret == -(MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS) )
mbedtls_snprintf( buf, buflen, "SSL - Asynchronous operation is not completed yet" );
#endif /* MBEDTLS_SSL_TLS_C */ #endif /* MBEDTLS_SSL_TLS_C */
#if defined(MBEDTLS_X509_USE_C) || defined(MBEDTLS_X509_CREATE_C) #if defined(MBEDTLS_X509_USE_C) || defined(MBEDTLS_X509_CREATE_C)

26
library/ssl_tls.c
View file

@ -6399,6 +6399,23 @@ void mbedtls_ssl_conf_export_keys_cb( mbedtls_ssl_config *conf,
} }
#endif #endif
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
void mbedtls_ssl_conf_async_private_cb(
mbedtls_ssl_config *conf,
mbedtls_ssl_async_sign_t *f_async_sign,
mbedtls_ssl_async_decrypt_t *f_async_decrypt,
mbedtls_ssl_async_resume_t *f_async_resume,
mbedtls_ssl_async_cancel_t *f_async_cancel,
void *connection_ctx )
{
conf->f_async_sign_start = f_async_sign;
conf->f_async_decrypt_start = f_async_decrypt;
conf->f_async_resume = f_async_resume;
conf->f_async_cancel = f_async_cancel;
conf->p_async_connection_ctx = connection_ctx;
}
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
/* /*
* SSL get accessors * SSL get accessors
*/ */
@ -7332,6 +7349,15 @@ void mbedtls_ssl_handshake_free( const mbedtls_ssl_config *conf,
} }
#endif /* MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_SSL_SERVER_NAME_INDICATION */ #endif /* MBEDTLS_X509_CRT_PARSE_C && MBEDTLS_SSL_SERVER_NAME_INDICATION */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
if( conf->f_async_cancel != NULL &&
handshake->p_async_operation_ctx != NULL )
{
conf->f_async_cancel( conf->p_async_connection_ctx,
handshake->p_async_operation_ctx );
}
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
#if defined(MBEDTLS_SSL_PROTO_DTLS) #if defined(MBEDTLS_SSL_PROTO_DTLS)
mbedtls_free( handshake->verify_cookie ); mbedtls_free( handshake->verify_cookie );
mbedtls_free( handshake->hs_msg ); mbedtls_free( handshake->hs_msg );

3
library/version_features.c
View file

@ -615,6 +615,9 @@ static const char *features[] = {
#if defined(MBEDTLS_SHA512_C) #if defined(MBEDTLS_SHA512_C)
"MBEDTLS_SHA512_C", "MBEDTLS_SHA512_C",
#endif /* MBEDTLS_SHA512_C */ #endif /* MBEDTLS_SHA512_C */
#if defined(MBEDTLS_SSL_ASYNC_PRIVATE_C)
"MBEDTLS_SSL_ASYNC_PRIVATE_C",
#endif /* MBEDTLS_SSL_ASYNC_PRIVATE_C */
#if defined(MBEDTLS_SSL_CACHE_C) #if defined(MBEDTLS_SSL_CACHE_C)
"MBEDTLS_SSL_CACHE_C", "MBEDTLS_SSL_CACHE_C",
#endif /* MBEDTLS_SSL_CACHE_C */ #endif /* MBEDTLS_SSL_CACHE_C */