Document parameter preconditions in ECDSA module
diff --git a/include/mbedtls/ecdsa.h b/include/mbedtls/ecdsa.h
index 4057828..86f4944 100644
--- a/include/mbedtls/ecdsa.h
+++ b/include/mbedtls/ecdsa.h
@@ -118,7 +118,8 @@
* \brief This function computes the ECDSA signature of a
* previously-hashed message.
*
- * \note The deterministic version is usually preferred.
+ * \note The deterministic version implemented in
+ * mbedtls_ecdsa_sign_det() is usually preferred.
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated
@@ -128,14 +129,22 @@
*
* \see ecp.h
*
- * \param grp The ECP group.
- * \param r The first output integer.
- * \param s The second output integer.
- * \param d The private signing key.
- * \param buf The message hash.
- * \param blen The length of \p buf.
- * \param f_rng The RNG function.
- * \param p_rng The RNG context.
+ * \param grp The context for the elliptic curve to use.
+ * This must be initialized and have group parameters
+ * set, for example through mbedtls_ecp_group_load().
+ * \param r The MPI context in which to store the first part
+ * the signature. This must be initialized.
+ * \param s The MPI context in which to store the second part
+ * the signature. This must be initialized.
+ * \param d The private signing key. This must be initialized.
+ * \param buf The content to be signed. This is usually the hash of
+ * the original data to be signed. This must be a readable
+ * buffer of length \p blen Bytes. It may be \c NULL if
+ * \p blen is zero.
+ * \param blen The length of \p buf in Bytes.
+ * \param f_rng The RNG function. This must not be \c NULL.
+ * \param p_rng The RNG context to be passed to \p f_rng. This may be
+ * \c NULL if \p f_rng doesn't need a context parameter.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX
@@ -162,21 +171,29 @@
*
* \see ecp.h
*
- * \param grp The ECP group.
- * \param r The first output integer.
- * \param s The second output integer.
- * \param d The private signing key.
- * \param buf The message hash.
- * \param blen The length of \p buf.
- * \param md_alg The MD algorithm used to hash the message.
+ * \param grp The context for the elliptic curve to use.
+ * This must be initialized and have group parameters
+ * set, for example through mbedtls_ecp_group_load().
+ * \param r The MPI context in which to store the first part
+ * the signature. This must be initialized.
+ * \param s The MPI context in which to store the second part
+ * the signature. This must be initialized.
+ * \param d The private signing key. This must be initialized
+ * and setup, for example through mbedtls_ecp_gen_privkey().
+ * \param buf The hashed content to be signed. This must be a readable
+ * buffer of length \p blen Bytes. It may be \c NULL if
+ * \p blen is zero.
+ * \param blen The length of \p buf in Bytes.
+ * \param md_alg The hash algorithm used to hash the original data.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX or \c MBEDTLS_MPI_XXX
* error code on failure.
*/
-int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
- const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
- mbedtls_md_type_t md_alg );
+int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r,
+ mbedtls_mpi *s, const mbedtls_mpi *d,
+ const unsigned char *buf, size_t blen,
+ mbedtls_md_type_t md_alg );
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */
/**
@@ -191,12 +208,19 @@
*
* \see ecp.h
*
- * \param grp The ECP group.
- * \param buf The message hash.
- * \param blen The length of \p buf.
- * \param Q The public key to use for verification.
+ * \param grp The ECP group to use.
+ * This must be initialized and have group parameters
+ * set, for example through mbedtls_ecp_group_load().
+ * \param buf The hashed content that was signed. This must be a readable
+ * buffer of length \p blen Bytes. It may be \c NULL if
+ * \p blen is zero.
+ * \param blen The length of \p buf in Bytes.
+ * \param Q The public key to use for verification. This must be
+ * initialized and setup.
* \param r The first integer of the signature.
+ * This must be initialized.
* \param s The second integer of the signature.
+ * This must be initialized.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if the signature
@@ -205,8 +229,9 @@
* error code on failure for any other reason.
*/
int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
- const unsigned char *buf, size_t blen,
- const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s);
+ const unsigned char *buf, size_t blen,
+ const mbedtls_ecp_point *Q, const mbedtls_mpi *r,
+ const mbedtls_mpi *s);
/**
* \brief This function computes the ECDSA signature and writes it
@@ -223,11 +248,6 @@
* of the Digital Signature Algorithm (DSA) and Elliptic
* Curve Digital Signature Algorithm (ECDSA)</em>.
*
- * \note The \p sig buffer must be at least twice as large as the
- * size of the curve used, plus 9. For example, 73 Bytes if
- * a 256-bit curve is used. A buffer length of
- * #MBEDTLS_ECDSA_MAX_LEN is always safe.
- *
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* defined in <em>Standards for Efficient Cryptography Group
@@ -236,20 +256,32 @@
*
* \see ecp.h
*
- * \param ctx The ECDSA context.
+ * \param ctx The ECDSA context to use. This must be initialized
+ * and have a group and private key bound to it, for example
+ * via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
* \param md_alg The message digest that was used to hash the message.
- * \param hash The message hash.
- * \param hlen The length of the hash.
- * \param sig The buffer that holds the signature.
- * \param slen The length of the signature written.
- * \param f_rng The RNG function.
- * \param p_rng The RNG context.
+ * \param hash The message hash to be signed. This must be a readable
+ * buffer of length \p blen Bytes.
+ * \param hlen The length of the hash \p hash in Bytes.
+ * \param sig The buffer to which to write the signature. This must be a
+ * writable buffer of length at least twice as large as the
+ * size of the curve used, plus 9. For example, 73 Bytes if
+ * a 256-bit curve is used. A buffer length of
+ * #MBEDTLS_ECDSA_MAX_LEN is always safe.
+ * \param slen The address at which to store the actual length of
+ * the signature written. Must not be \c NULL.
+ * \param f_rng The RNG function. This must not be \c NULL if
+ * #MBEDTLS_ECDSA_DETERMINISTIC is unset. Otherwise,
+ * it is unused and may be set to \c NULL.
+ * \param p_rng The RNG context to be passed to \p f_rng. This may be
+ * \c NULL if \p f_rng is \c NULL or doesn't use a context.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX, \c MBEDTLS_ERR_MPI_XXX or
* \c MBEDTLS_ERR_ASN1_XXX error code on failure.
*/
-int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
+int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx,
+ mbedtls_md_type_t md_alg,
const unsigned char *hash, size_t hlen,
unsigned char *sig, size_t *slen,
int (*f_rng)(void *, unsigned char *, size_t),
@@ -265,15 +297,28 @@
* but it can return early and restart according to the limit
* set with \c mbedtls_ecp_set_max_ops() to reduce blocking.
*
- * \param ctx The ECDSA context.
+ * \param ctx The ECDSA context to use. This must be initialized
+ * and have a group and private key bound to it, for example
+ * via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
* \param md_alg The message digest that was used to hash the message.
- * \param hash The message hash.
- * \param hlen The length of the hash.
- * \param sig The buffer that holds the signature.
- * \param slen The length of the signature written.
- * \param f_rng The RNG function.
- * \param p_rng The RNG context.
- * \param rs_ctx The restart context (NULL disables restart).
+ * \param hash The message hash to be signed. This must be a readable
+ * buffer of length \p blen Bytes.
+ * \param hlen The length of the hash \p hash in Bytes.
+ * \param sig The buffer to which to write the signature. This must be a
+ * writable buffer of length at least twice as large as the
+ * size of the curve used, plus 9. For example, 73 Bytes if
+ * a 256-bit curve is used. A buffer length of
+ * #MBEDTLS_ECDSA_MAX_LEN is always safe.
+ * \param slen The address at which to store the actual length of
+ * the signature written. Must not be \c NULL.
+ * \param f_rng The RNG function. This must not be \c NULL if
+ * #MBEDTLS_ECDSA_DETERMINISTIC is unset. Otherwise,
+ * it is unused and may be set to \c NULL.
+ * \param p_rng The RNG context to be passed to \p f_rng. This may be
+ * \c NULL if \p f_rng is \c NULL or doesn't use a context.
+ * \param rs_ctx The restart context to use. This may be \c NULL to disable
+ * restarting. If it is not \c NULL, it must point to an
+ * initialized restart context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_IN_PROGRESS if maximum number of
@@ -309,11 +354,6 @@
* \warning It is not thread-safe to use the same context in
* multiple threads.
*
- * \note The \p sig buffer must be at least twice as large as the
- * size of the curve used, plus 9. For example, 73 Bytes if a
- * 256-bit curve is used. A buffer length of
- * #MBEDTLS_ECDSA_MAX_LEN is always safe.
- *
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* defined in <em>Standards for Efficient Cryptography Group
@@ -325,12 +365,20 @@
* \deprecated Superseded by mbedtls_ecdsa_write_signature() in
* Mbed TLS version 2.0 and later.
*
- * \param ctx The ECDSA context.
- * \param hash The message hash.
- * \param hlen The length of the hash.
- * \param sig The buffer that holds the signature.
- * \param slen The length of the signature written.
- * \param md_alg The MD algorithm used to hash the message.
+ * \param ctx The ECDSA context to use. This must be initialized
+ * and have a group and private key bound to it, for example
+ * via mbedtls_ecdsa_genkey() or mbedtls_ecdsa_from_keypair().
+ * \param hash The message hash to be signed. This must be a readable
+ * buffer of length \p blen Bytes.
+ * \param hlen The length of the hash \p hash in Bytes.
+ * \param sig The buffer to which to write the signature. This must be a
+ * writable buffer of length at least twice as large as the
+ * size of the curve used, plus 9. For example, 73 Bytes if
+ * a 256-bit curve is used. A buffer length of
+ * #MBEDTLS_ECDSA_MAX_LEN is always safe.
+ * \param slen The address at which to store the actual length of
+ * the signature written. Must not be \c NULL.
+ * \param md_alg The message digest that was used to hash the message.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX, \c MBEDTLS_ERR_MPI_XXX or
@@ -355,11 +403,14 @@
*
* \see ecp.h
*
- * \param ctx The ECDSA context.
- * \param hash The message hash.
- * \param hlen The size of the hash.
- * \param sig The signature to read and verify.
- * \param slen The size of \p sig.
+ * \param ctx The ECDSA context to use. This must be initialized
+ * and have a group and public key bound to it.
+ * \param hash The message hash that was signed. This must be a readable
+ * buffer of length \p size Bytes.
+ * \param hlen The size of the hash \p hash.
+ * \param sig The signature to read and verify. This must be a readable
+ * buffer of length \p slen Bytes.
+ * \param slen The size of \p sig in Bytes.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid.
@@ -382,12 +433,17 @@
* but it can return early and restart according to the limit
* set with \c mbedtls_ecp_set_max_ops() to reduce blocking.
*
- * \param ctx The ECDSA context.
- * \param hash The message hash.
- * \param hlen The size of the hash.
- * \param sig The signature to read and verify.
- * \param slen The size of \p sig.
- * \param rs_ctx The restart context (NULL disables restart).
+ * \param ctx The ECDSA context to use. This must be initialized
+ * and have a group and public key bound to it.
+ * \param hash The message hash that was signed. This must be a readable
+ * buffer of length \p size Bytes.
+ * \param hlen The size of the hash \p hash.
+ * \param sig The signature to read and verify. This must be a readable
+ * buffer of length \p slen Bytes.
+ * \param slen The size of \p sig in Bytes.
+ * \param rs_ctx The restart context to use. This may be \c NULL to disable
+ * restarting. If it is not \c NULL, it must point to an
+ * initialized restart context.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid.
@@ -409,10 +465,12 @@
* \see ecp.h
*
* \param ctx The ECDSA context to store the keypair in.
+ * This must be initialized.
* \param gid The elliptic curve to use. One of the various
* \c MBEDTLS_ECP_DP_XXX macros depending on configuration.
- * \param f_rng The RNG function.
- * \param p_rng The RNG context.
+ * \param f_rng The RNG function to use. This must not be \c NULL.
+ * \param p_rng The RNG context to be passed to \p f_rng. This may be
+ * \c NULL if \p f_rng doesn't need a context argument.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX code on failure.
@@ -425,36 +483,51 @@
*
* \see ecp.h
*
- * \param ctx The ECDSA context to set.
- * \param key The EC key to use.
+ * \param ctx The ECDSA context to set. This must be initialized.
+ * \param key The EC key to use. This must be initialized and hold
+ * a private-public key pair or a public key. In the former
+ * case, the ECDSA context may be used for signature creation
+ * after this call. In the latter case, it may be used for
+ * signature verification.
*
* \return \c 0 on success.
* \return An \c MBEDTLS_ERR_ECP_XXX code on failure.
*/
-int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key );
+int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx,
+ const mbedtls_ecp_keypair *key );
/**
* \brief This function initializes an ECDSA context.
*
* \param ctx The ECDSA context to initialize.
+ * This must not be \c NULL.
*/
void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx );
/**
* \brief This function frees an ECDSA context.
*
- * \param ctx The ECDSA context to free.
+ * \param ctx The ECDSA context to free. This may be \c NULL,
+ * in which case this function does nothing. If it
+ * is not \c NULL, it must be initialized.
*/
void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx );
#if defined(MBEDTLS_ECP_RESTARTABLE)
/**
- * \brief Initialize a restart context
+ * \brief Initialize a restart context.
+ *
+ * \param ctx The restart context to initialize.
+ * This must not be \c NULL.
*/
void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx );
/**
- * \brief Free the components of a restart context
+ * \brief Free the components of a restart context.
+ *
+ * \param ctx The restart context to free. This may be \c NULL,
+ * in which case this function does nothing. If it
+ * is not \c NULL, it must be initialized.
*/
void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx );
#endif /* MBEDTLS_ECP_RESTARTABLE */