From eee98e9d82e92b47e267222571293dc556a30489 Mon Sep 17 00:00:00 2001
From: k-stachowiak <krzysiek.stachowiak@gmail.com>
Date: Fri, 31 May 2019 20:16:50 +0200
Subject: [PATCH] Add documentation notes about the required size of the
 signature buffers

---
 include/mbedtls/pk.h  | 4 ++++
 include/mbedtls/rsa.h | 3 +++
 2 files changed, 7 insertions(+)

diff --git a/include/mbedtls/pk.h b/include/mbedtls/pk.h
index ee06b2fd2..8beb2af41 100644
--- a/include/mbedtls/pk.h
+++ b/include/mbedtls/pk.h
@@ -343,6 +343,10 @@ int mbedtls_pk_verify_ext( mbedtls_pk_type_t type, const void *options,
  *
  * \note            For RSA, md_alg may be MBEDTLS_MD_NONE if hash_len != 0.
  *                  For ECDSA, md_alg may never be MBEDTLS_MD_NONE.
+ *
+ * \note            In order to ensure enough space for the signature, the
+ *                  \p sig buffer size must be of at least
+ *                  `max(MBEDTLS_ECDSA_MAX_LEN, MBEDTLS_MPI_MAX_SIZE)` bytes.
  */
 int mbedtls_pk_sign( mbedtls_pk_context *ctx, mbedtls_md_type_t md_alg,
              const unsigned char *hash, size_t hash_len,
diff --git a/include/mbedtls/rsa.h b/include/mbedtls/rsa.h
index 5548f3c12..92efa474a 100644
--- a/include/mbedtls/rsa.h
+++ b/include/mbedtls/rsa.h
@@ -819,6 +819,7 @@ int mbedtls_rsa_rsaes_oaep_decrypt( mbedtls_rsa_context *ctx,
  *
  * \note           The \p sig buffer must be as large as the size
  *                 of \p ctx->N. For example, 128 Bytes if RSA-1024 is used.
+ *                 A buffer length of #MBEDTLS_MPI_MAX_SIZE is always safe.
  *
  * \note           For PKCS#1 v2.1 encoding, see comments on
  *                 mbedtls_rsa_rsassa_pss_sign() for details on
@@ -862,6 +863,7 @@ int mbedtls_rsa_pkcs1_sign( mbedtls_rsa_context *ctx,
  *
  * \note           The \p sig buffer must be as large as the size
  *                 of \p ctx->N. For example, 128 Bytes if RSA-1024 is used.
+ *                 A buffer length of #MBEDTLS_MPI_MAX_SIZE is always safe.
  */
 int mbedtls_rsa_rsassa_pkcs1_v15_sign( mbedtls_rsa_context *ctx,
                                int (*f_rng)(void *, unsigned char *, size_t),
@@ -902,6 +904,7 @@ int mbedtls_rsa_rsassa_pkcs1_v15_sign( mbedtls_rsa_context *ctx,
  *
  * \note           The \p sig buffer must be as large as the size
  *                 of \p ctx->N. For example, 128 Bytes if RSA-1024 is used.
+ *                 A buffer length of #MBEDTLS_MPI_MAX_SIZE is always safe.
  *
  * \note           The \p hash_id in the RSA context is the one used for the
  *                 encoding. \p md_alg in the function call is the type of hash