mbedtls: Update to upstream version 2.16.4

Fixes CVE-2019-18222.

`include/mbedtls/version.h` was modified to include the forgotten
version bump to 2.16.4, fixed upstream by ARMmbed/mbedtls#2992.

6 files changed, 413 insertions, 164 deletions

diff --git a/thirdparty/mbedtls/include/mbedtls/bignum.h b/thirdparty/mbedtls/include/mbedtls/bignum.h
index 1c8607264f..22b373113e 100644
--- a/thirdparty/mbedtls/include/mbedtls/bignum.h
+++ b/thirdparty/mbedtls/include/mbedtls/bignum.h
@@ -184,7 +184,7 @@ extern "C" {
  */
 typedef struct mbedtls_mpi
 {
-    int s;              /*!<  integer sign      */
+    int s;              /*!<  Sign: -1 if the mpi is negative, 1 otherwise */
     size_t n;           /*!<  total # of limbs  */
     mbedtls_mpi_uint *p;          /*!<  pointer to limbs  */
 }
@@ -560,6 +560,24 @@ int mbedtls_mpi_cmp_abs( const mbedtls_mpi *X, const mbedtls_mpi *Y );
 int mbedtls_mpi_cmp_mpi( const mbedtls_mpi *X, const mbedtls_mpi *Y );
 
 /**
+ * \brief          Check if an MPI is less than the other in constant time.
+ *
+ * \param X        The left-hand MPI. This must point to an initialized MPI
+ *                 with the same allocated length as Y.
+ * \param Y        The right-hand MPI. This must point to an initialized MPI
+ *                 with the same allocated length as X.
+ * \param ret      The result of the comparison:
+ *                 \c 1 if \p X is less than \p Y.
+ *                 \c 0 if \p X is greater than or equal to \p Y.
+ *
+ * \return         0 on success.
+ * \return         MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the allocated length of
+ *                 the two input MPIs is not the same.
+ */
+int mbedtls_mpi_lt_mpi_ct( const mbedtls_mpi *X, const mbedtls_mpi *Y,
+        unsigned *ret );
+
+/**
  * \brief          Compare an MPI with an integer.
  *
  * \param X        The left-hand MPI. This must point to an initialized MPI.
diff --git a/thirdparty/mbedtls/include/mbedtls/check_config.h b/thirdparty/mbedtls/include/mbedtls/check_config.h
index 6eabcc8748..d076c2352f 100644
--- a/thirdparty/mbedtls/include/mbedtls/check_config.h
+++ b/thirdparty/mbedtls/include/mbedtls/check_config.h
@@ -281,6 +281,14 @@
 #error "MBEDTLS_MEMORY_BUFFER_ALLOC_C defined, but not all prerequisites"
 #endif
 
+#if defined(MBEDTLS_MEMORY_BACKTRACE) && !defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
+#error "MBEDTLS_MEMORY_BACKTRACE defined, but not all prerequesites"
+#endif
+
+#if defined(MBEDTLS_MEMORY_DEBUG) && !defined(MBEDTLS_MEMORY_BUFFER_ALLOC_C)
+#error "MBEDTLS_MEMORY_DEBUG defined, but not all prerequesites"
+#endif
+
 #if defined(MBEDTLS_PADLOCK_C) && !defined(MBEDTLS_HAVE_ASM)
 #error "MBEDTLS_PADLOCK_C defined, but not all prerequisites"
 #endif
diff --git a/thirdparty/mbedtls/include/mbedtls/config.h b/thirdparty/mbedtls/include/mbedtls/config.h
index 0cc502cd79..8d9c31a504 100644
--- a/thirdparty/mbedtls/include/mbedtls/config.h
+++ b/thirdparty/mbedtls/include/mbedtls/config.h
@@ -689,6 +689,13 @@
 #define MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN
 #define MBEDTLS_CIPHER_PADDING_ZEROS
 
+/** \def MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+ *
+ * Uncomment this macro to use a 128-bit key in the CTR_DRBG module.
+ * By default, CTR_DRBG uses a 256-bit key.
+ */
+//#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY
+
 /**
  * \def MBEDTLS_ENABLE_WEAK_CIPHERSUITES
  *
@@ -2149,7 +2156,11 @@
  *
  * Enable the CTR_DRBG AES-based random generator.
  * The CTR_DRBG generator uses AES-256 by default.
- * To use AES-128 instead, enable MBEDTLS_CTR_DRBG_USE_128_BIT_KEY below.
+ * To use AES-128 instead, enable \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY above.
+ *
+ * \note To achieve a 256-bit security strength with CTR_DRBG,
+ *       you must use AES-256 *and* use sufficient entropy.
+ *       See ctr_drbg.h for more details.
  *
  * Module:  library/ctr_drbg.c
  * Caller:
@@ -3043,7 +3054,6 @@
 //#define MBEDTLS_CTR_DRBG_MAX_INPUT                256 /**< Maximum number of additional input bytes */
 //#define MBEDTLS_CTR_DRBG_MAX_REQUEST             1024 /**< Maximum number of requested bytes per call */
 //#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT           384 /**< Maximum size of (re)seed buffer */
-//#define MBEDTLS_CTR_DRBG_USE_128_BIT_KEY              /**< Use 128-bit key for CTR_DRBG - may reduce security (see ctr_drbg.h) */
 
 /* HMAC_DRBG options */
 //#define MBEDTLS_HMAC_DRBG_RESEED_INTERVAL   10000 /**< Interval before reseed is performed by default */
diff --git a/thirdparty/mbedtls/include/mbedtls/ctr_drbg.h b/thirdparty/mbedtls/include/mbedtls/ctr_drbg.h
index cc3df7b113..e0b5ed9c93 100644
--- a/thirdparty/mbedtls/include/mbedtls/ctr_drbg.h
+++ b/thirdparty/mbedtls/include/mbedtls/ctr_drbg.h
@@ -1,7 +1,8 @@
 /**
  * \file ctr_drbg.h
  *
- * \brief    This file contains CTR_DRBG definitions and functions.
+ * \brief    This file contains definitions and functions for the
+ *           CTR_DRBG pseudorandom generator.
  *
  * CTR_DRBG is a standardized way of building a PRNG from a block-cipher
  * in counter mode operation, as defined in <em>NIST SP 800-90A:
@@ -9,13 +10,35 @@
  * Bit Generators</em>.
  *
  * The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128
- * as the underlying block cipher.
- *
- *  \warning Using 128-bit keys for CTR_DRBG limits the security of generated
- *  keys and operations that use random values generated to 128-bit security.
+ * (if \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled at compile time)
+ * as the underlying block cipher, with a derivation function.
+ * The initial seeding grabs #MBEDTLS_CTR_DRBG_ENTROPY_LEN bytes of entropy.
+ * See the documentation of mbedtls_ctr_drbg_seed() for more details.
+ *
+ * Based on NIST SP 800-90A §10.2.1 table 3 and NIST SP 800-57 part 1 table 2,
+ * here are the security strengths achieved in typical configuration:
+ * - 256 bits under the default configuration of the library, with AES-256
+ *   and with #MBEDTLS_CTR_DRBG_ENTROPY_LEN set to 48 or more.
+ * - 256 bits if AES-256 is used, #MBEDTLS_CTR_DRBG_ENTROPY_LEN is set
+ *   to 32 or more, and the DRBG is initialized with an explicit
+ *   nonce in the \c custom parameter to mbedtls_ctr_drbg_seed().
+ * - 128 bits if AES-256 is used but #MBEDTLS_CTR_DRBG_ENTROPY_LEN is
+ *   between 24 and 47 and the DRBG is not initialized with an explicit
+ *   nonce (see mbedtls_ctr_drbg_seed()).
+ * - 128 bits if AES-128 is used (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY enabled)
+ *   and #MBEDTLS_CTR_DRBG_ENTROPY_LEN is set to 24 or more (which is
+ *   always the case unless it is explicitly set to a different value
+ *   in config.h).
+ *
+ * Note that the value of #MBEDTLS_CTR_DRBG_ENTROPY_LEN defaults to:
+ * - \c 48 if the module \c MBEDTLS_SHA512_C is enabled and the symbol
+ *   \c MBEDTLS_ENTROPY_FORCE_SHA256 is disabled at compile time.
+ *   This is the default configuration of the library.
+ * - \c 32 if the module \c MBEDTLS_SHA512_C is disabled at compile time.
+ * - \c 32 if \c MBEDTLS_ENTROPY_FORCE_SHA256 is enabled at compile time.
  */
 /*
- *  Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved
+ *  Copyright (C) 2006-2019, Arm Limited (or its affiliates), All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -56,9 +79,19 @@
 #define MBEDTLS_CTR_DRBG_BLOCKSIZE          16 /**< The block size used by the cipher. */
 
 #if defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY)
-#define MBEDTLS_CTR_DRBG_KEYSIZE            16 /**< The key size used by the cipher (compile-time choice: 128 bits). */
+#define MBEDTLS_CTR_DRBG_KEYSIZE            16
+/**< The key size in bytes used by the cipher.
+ *
+ * Compile-time choice: 16 bytes (128 bits)
+ * because #MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled.
+ */
 #else
-#define MBEDTLS_CTR_DRBG_KEYSIZE            32 /**< The key size used by the cipher (compile-time choice: 256 bits). */
+#define MBEDTLS_CTR_DRBG_KEYSIZE            32
+/**< The key size in bytes used by the cipher.
+ *
+ * Compile-time choice: 32 bytes (256 bits)
+ * because \c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled.
+ */
 #endif
 
 #define MBEDTLS_CTR_DRBG_KEYBITS            ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 ) /**< The key size for the DRBG operation, in bits. */
@@ -73,21 +106,31 @@
  * \{
  */
 
+/** \def MBEDTLS_CTR_DRBG_ENTROPY_LEN
+ *
+ * \brief The amount of entropy used per seed by default, in bytes.
+ */
 #if !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN)
 #if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
+/** This is 48 bytes because the entropy module uses SHA-512
+ * (\c MBEDTLS_ENTROPY_FORCE_SHA256 is disabled).
+ */
 #define MBEDTLS_CTR_DRBG_ENTROPY_LEN        48
-/**< The amount of entropy used per seed by default:
- * <ul><li>48 with SHA-512.</li>
- * <li>32 with SHA-256.</li></ul>
+
+#else /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */
+
+/** This is 32 bytes because the entropy module uses SHA-256
+ * (the SHA512 module is disabled or
+ * \c MBEDTLS_ENTROPY_FORCE_SHA256 is enabled).
  */
-#else
-#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        32
-/**< Amount of entropy used per seed by default:
- * <ul><li>48 with SHA-512.</li>
- * <li>32 with SHA-256.</li></ul>
+#if !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY)
+/** \warning To achieve a 256-bit security strength, you must pass a nonce
+ *           to mbedtls_ctr_drbg_seed().
  */
-#endif
-#endif
+#endif /* !defined(MBEDTLS_CTR_DRBG_USE_128_BIT_KEY) */
+#define MBEDTLS_CTR_DRBG_ENTROPY_LEN        32
+#endif /* defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256) */
+#endif /* !defined(MBEDTLS_CTR_DRBG_ENTROPY_LEN) */
 
 #if !defined(MBEDTLS_CTR_DRBG_RESEED_INTERVAL)
 #define MBEDTLS_CTR_DRBG_RESEED_INTERVAL    10000
@@ -106,7 +149,7 @@
 
 #if !defined(MBEDTLS_CTR_DRBG_MAX_SEED_INPUT)
 #define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT     384
-/**< The maximum size of seed or reseed buffer. */
+/**< The maximum size of seed or reseed buffer in bytes. */
 #endif
 
 /* \} name SECTION: Module settings */
@@ -164,17 +207,68 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
  * \brief               This function seeds and sets up the CTR_DRBG
  *                      entropy source for future reseeds.
  *
- * \note Personalization data can be provided in addition to the more generic
- *       entropy source, to make this instantiation as unique as possible.
- *
+ * A typical choice for the \p f_entropy and \p p_entropy parameters is
+ * to use the entropy module:
+ * - \p f_entropy is mbedtls_entropy_func();
+ * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized
+ *   with mbedtls_entropy_init() (which registers the platform's default
+ *   entropy sources).
+ *
+ * The entropy length is #MBEDTLS_CTR_DRBG_ENTROPY_LEN by default.
+ * You can override it by calling mbedtls_ctr_drbg_set_entropy_len().
+ *
+ * You can provide a personalization string in addition to the
+ * entropy source, to make this instantiation as unique as possible.
+ *
+ * \note                The _seed_material_ value passed to the derivation
+ *                      function in the CTR_DRBG Instantiate Process
+ *                      described in NIST SP 800-90A §10.2.1.3.2
+ *                      is the concatenation of the string obtained from
+ *                      calling \p f_entropy and the \p custom string.
+ *                      The origin of the nonce depends on the value of
+ *                      the entropy length relative to the security strength.
+ *                      - If the entropy length is at least 1.5 times the
+ *                        security strength then the nonce is taken from the
+ *                        string obtained with \p f_entropy.
+ *                      - If the entropy length is less than the security
+ *                        strength, then the nonce is taken from \p custom.
+ *                        In this case, for compliance with SP 800-90A,
+ *                        you must pass a unique value of \p custom at
+ *                        each invocation. See SP 800-90A §8.6.7 for more
+ *                        details.
+ */
+#if MBEDTLS_CTR_DRBG_ENTROPY_LEN < MBEDTLS_CTR_DRBG_KEYSIZE * 3 / 2
+/** \warning            When #MBEDTLS_CTR_DRBG_ENTROPY_LEN is less than
+ *                      #MBEDTLS_CTR_DRBG_KEYSIZE * 3 / 2, to achieve the
+ *                      maximum security strength permitted by CTR_DRBG,
+ *                      you must pass a value of \p custom that is a nonce:
+ *                      this value must never be repeated in subsequent
+ *                      runs of the same application or on a different
+ *                      device.
+ */
+#endif
+/**
  * \param ctx           The CTR_DRBG context to seed.
+ *                      It must have been initialized with
+ *                      mbedtls_ctr_drbg_init().
+ *                      After a successful call to mbedtls_ctr_drbg_seed(),
+ *                      you may not call mbedtls_ctr_drbg_seed() again on
+ *                      the same context unless you call
+ *                      mbedtls_ctr_drbg_free() and mbedtls_ctr_drbg_init()
+ *                      again first.
  * \param f_entropy     The entropy callback, taking as arguments the
  *                      \p p_entropy context, the buffer to fill, and the
-                        length of the buffer.
- * \param p_entropy     The entropy context.
- * \param custom        Personalization data, that is device-specific
-                        identifiers. Can be NULL.
- * \param len           The length of the personalization data.
+ *                      length of the buffer.
+ *                      \p f_entropy is always called with a buffer size
+ *                      equal to the entropy length.
+ * \param p_entropy     The entropy context to pass to \p f_entropy.
+ * \param custom        The personalization string.
+ *                      This can be \c NULL, in which case the personalization
+ *                      string is empty regardless of the value of \p len.
+ * \param len           The length of the personalization string.
+ *                      This must be at most
+ *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT
+ *                      - #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
@@ -197,7 +291,8 @@ void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx );
  *                      The default value is off.
  *
  * \note                If enabled, entropy is gathered at the beginning of
- *                      every call to mbedtls_ctr_drbg_random_with_add().
+ *                      every call to mbedtls_ctr_drbg_random_with_add()
+ *                      or mbedtls_ctr_drbg_random().
  *                      Only use this if your entropy source has sufficient
  *                      throughput.
  *
@@ -209,18 +304,37 @@ void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
 
 /**
  * \brief               This function sets the amount of entropy grabbed on each
- *                      seed or reseed. The default value is
- *                      #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
+ *                      seed or reseed.
+ *
+ * The default value is #MBEDTLS_CTR_DRBG_ENTROPY_LEN.
+ *
+ * \note                The security strength of CTR_DRBG is bounded by the
+ *                      entropy length. Thus:
+ *                      - When using AES-256
+ *                        (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled,
+ *                        which is the default),
+ *                        \p len must be at least 32 (in bytes)
+ *                        to achieve a 256-bit strength.
+ *                      - When using AES-128
+ *                        (\c MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled)
+ *                        \p len must be at least 16 (in bytes)
+ *                        to achieve a 128-bit strength.
  *
  * \param ctx           The CTR_DRBG context.
- * \param len           The amount of entropy to grab.
+ * \param len           The amount of entropy to grab, in bytes.
+ *                      This must be at most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  */
 void mbedtls_ctr_drbg_set_entropy_len( mbedtls_ctr_drbg_context *ctx,
                                size_t len );
 
 /**
  * \brief               This function sets the reseed interval.
- *                      The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
+ *
+ * The reseed interval is the number of calls to mbedtls_ctr_drbg_random()
+ * or mbedtls_ctr_drbg_random_with_add() after which the entropy function
+ * is called again.
+ *
+ * The default value is #MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
  *
  * \param ctx           The CTR_DRBG context.
  * \param interval      The reseed interval.
@@ -233,8 +347,12 @@ void mbedtls_ctr_drbg_set_reseed_interval( mbedtls_ctr_drbg_context *ctx,
  *                      extracts data from the entropy source.
  *
  * \param ctx           The CTR_DRBG context.
- * \param additional    Additional data to add to the state. Can be NULL.
+ * \param additional    Additional data to add to the state. Can be \c NULL.
  * \param len           The length of the additional data.
+ *                      This must be less than
+ *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len
+ *                      where \c entropy_len is the entropy length
+ *                      configured for the context.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.
@@ -246,7 +364,8 @@ int mbedtls_ctr_drbg_reseed( mbedtls_ctr_drbg_context *ctx,
  * \brief              This function updates the state of the CTR_DRBG context.
  *
  * \param ctx          The CTR_DRBG context.
- * \param additional   The data to update the state with.
+ * \param additional   The data to update the state with. This must not be
+ *                     \c NULL unless \p add_len is \c 0.
  * \param add_len      Length of \p additional in bytes. This must be at
  *                     most #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT.
  *
@@ -264,14 +383,23 @@ int mbedtls_ctr_drbg_update_ret( mbedtls_ctr_drbg_context *ctx,
  * \brief   This function updates a CTR_DRBG instance with additional
  *          data and uses it to generate random data.
  *
- * \note    The function automatically reseeds if the reseed counter is exceeded.
+ * This function automatically reseeds if the reseed counter is exceeded
+ * or prediction resistance is enabled.
  *
  * \param p_rng         The CTR_DRBG context. This must be a pointer to a
  *                      #mbedtls_ctr_drbg_context structure.
  * \param output        The buffer to fill.
- * \param output_len    The length of the buffer.
- * \param additional    Additional data to update. Can be NULL.
- * \param add_len       The length of the additional data.
+ * \param output_len    The length of the buffer in bytes.
+ * \param additional    Additional data to update. Can be \c NULL, in which
+ *                      case the additional data is empty regardless of
+ *                      the value of \p add_len.
+ * \param add_len       The length of the additional data
+ *                      if \p additional is not \c NULL.
+ *                      This must be less than #MBEDTLS_CTR_DRBG_MAX_INPUT
+ *                      and less than
+ *                      #MBEDTLS_CTR_DRBG_MAX_SEED_INPUT - \c entropy_len
+ *                      where \c entropy_len is the entropy length
+ *                      configured for the context.
  *
  * \return    \c 0 on success.
  * \return    #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
@@ -284,12 +412,14 @@ int mbedtls_ctr_drbg_random_with_add( void *p_rng,
 /**
  * \brief   This function uses CTR_DRBG to generate random data.
  *
- * \note    The function automatically reseeds if the reseed counter is exceeded.
+ * This function automatically reseeds if the reseed counter is exceeded
+ * or prediction resistance is enabled.
+ *
  *
  * \param p_rng         The CTR_DRBG context. This must be a pointer to a
  *                      #mbedtls_ctr_drbg_context structure.
  * \param output        The buffer to fill.
- * \param output_len    The length of the buffer.
+ * \param output_len    The length of the buffer in bytes.
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
@@ -336,7 +466,7 @@ MBEDTLS_DEPRECATED void mbedtls_ctr_drbg_update(
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
- * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on reseed
  *                      failure.
  */
 int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
@@ -350,8 +480,10 @@ int mbedtls_ctr_drbg_write_seed_file( mbedtls_ctr_drbg_context *ctx, const char
  *
  * \return              \c 0 on success.
  * \return              #MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error.
- * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
- *                      #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on
+ *                      reseed failure.
+ * \return              #MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG if the existing
+ *                      seed file is too large.
  */
 int mbedtls_ctr_drbg_update_seed_file( mbedtls_ctr_drbg_context *ctx, const char *path );
 #endif /* MBEDTLS_FS_IO */
diff --git a/thirdparty/mbedtls/include/mbedtls/hmac_drbg.h b/thirdparty/mbedtls/include/mbedtls/hmac_drbg.h
index f1289cb306..7931c2281c 100644
--- a/thirdparty/mbedtls/include/mbedtls/hmac_drbg.h
+++ b/thirdparty/mbedtls/include/mbedtls/hmac_drbg.h
@@ -1,10 +1,14 @@
 /**
  * \file hmac_drbg.h
  *
- * \brief HMAC_DRBG (NIST SP 800-90A)
+ * \brief The HMAC_DRBG pseudorandom generator.
+ *
+ * This module implements the HMAC_DRBG pseudorandom generator described
+ * in <em>NIST SP 800-90A: Recommendation for Random Number Generation Using
+ * Deterministic Random Bit Generators</em>.
  */
 /*
- *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  Copyright (C) 2006-2019, ARM Limited, All Rights Reserved
  *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -104,38 +108,72 @@ typedef struct mbedtls_hmac_drbg_context
 } mbedtls_hmac_drbg_context;
 
 /**
- * \brief               HMAC_DRBG context initialization
- *                      Makes the context ready for mbedtls_hmac_drbg_seed(),
- *                      mbedtls_hmac_drbg_seed_buf() or
- *                      mbedtls_hmac_drbg_free().
+ * \brief               HMAC_DRBG context initialization.
+ *
+ * This function makes the context ready for mbedtls_hmac_drbg_seed(),
+ * mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free().
  *
- * \param ctx           HMAC_DRBG context to be initialized
+ * \param ctx           HMAC_DRBG context to be initialized.
  */
 void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
 
 /**
- * \brief               HMAC_DRBG initial seeding
- *                      Seed and setup entropy source for future reseeds.
- *
- * \param ctx           HMAC_DRBG context to be seeded
- * \param md_info       MD algorithm to use for HMAC_DRBG
- * \param f_entropy     Entropy callback (p_entropy, buffer to fill, buffer
- *                      length)
- * \param p_entropy     Entropy context
- * \param custom        Personalization data (Device specific identifiers)
- *                      (Can be NULL)
- * \param len           Length of personalization data
- *
- * \note                The "security strength" as defined by NIST is set to:
- *                      128 bits if md_alg is SHA-1,
- *                      192 bits if md_alg is SHA-224,
- *                      256 bits if md_alg is SHA-256 or higher.
- *                      Note that SHA-256 is just as efficient as SHA-224.
+ * \brief               HMAC_DRBG initial seeding.
+ *
+ * Set the initial seed and set up the entropy source for future reseeds.
+ *
+ * A typical choice for the \p f_entropy and \p p_entropy parameters is
+ * to use the entropy module:
+ * - \p f_entropy is mbedtls_entropy_func();
+ * - \p p_entropy is an instance of ::mbedtls_entropy_context initialized
+ *   with mbedtls_entropy_init() (which registers the platform's default
+ *   entropy sources).
+ *
+ * You can provide a personalization string in addition to the
+ * entropy source, to make this instantiation as unique as possible.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_MD_BAD_INPUT_DATA, or
- *                      MBEDTLS_ERR_MD_ALLOC_FAILED, or
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED.
+ * \note                By default, the security strength as defined by NIST is:
+ *                      - 128 bits if \p md_info is SHA-1;
+ *                      - 192 bits if \p md_info is SHA-224;
+ *                      - 256 bits if \p md_info is SHA-256, SHA-384 or SHA-512.
+ *                      Note that SHA-256 is just as efficient as SHA-224.
+ *                      The security strength can be reduced if a smaller
+ *                      entropy length is set with
+ *                      mbedtls_hmac_drbg_set_entropy_len().
+ *
+ * \note                The default entropy length is the security strength
+ *                      (converted from bits to bytes). You can override
+ *                      it by calling mbedtls_hmac_drbg_set_entropy_len().
+ *
+ * \note                During the initial seeding, this function calls
+ *                      the entropy source to obtain a nonce
+ *                      whose length is half the entropy length.
+ *
+ * \param ctx           HMAC_DRBG context to be seeded.
+ * \param md_info       MD algorithm to use for HMAC_DRBG.
+ * \param f_entropy     The entropy callback, taking as arguments the
+ *                      \p p_entropy context, the buffer to fill, and the
+ *                      length of the buffer.
+ *                      \p f_entropy is always called with a length that is
+ *                      less than or equal to the entropy length.
+ * \param p_entropy     The entropy context to pass to \p f_entropy.
+ * \param custom        The personalization string.
+ *                      This can be \c NULL, in which case the personalization
+ *                      string is empty regardless of the value of \p len.
+ * \param len           The length of the personalization string.
+ *                      This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
+ *                      and also at most
+ *                      #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len * 3 / 2
+ *                      where \p entropy_len is the entropy length
+ *                      described above.
+ *
+ * \return              \c 0 if successful.
+ * \return              #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
+ *                      invalid.
+ * \return              #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
+ *                      memory to allocate context data.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ *                      if the call to \p f_entropy failed.
  */
 int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
                     const mbedtls_md_info_t * md_info,
@@ -146,98 +184,131 @@ int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx,
 
 /**
  * \brief               Initilisation of simpified HMAC_DRBG (never reseeds).
- *                      (For use with deterministic ECDSA.)
  *
- * \param ctx           HMAC_DRBG context to be initialised
- * \param md_info       MD algorithm to use for HMAC_DRBG
- * \param data          Concatenation of entropy string and additional data
- * \param data_len      Length of data in bytes
+ * This function is meant for use in algorithms that need a pseudorandom
+ * input such as deterministic ECDSA.
+ *
+ * \param ctx           HMAC_DRBG context to be initialised.
+ * \param md_info       MD algorithm to use for HMAC_DRBG.
+ * \param data          Concatenation of the initial entropy string and
+ *                      the additional data.
+ * \param data_len      Length of \p data in bytes.
  *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_MD_BAD_INPUT_DATA, or
- *                      MBEDTLS_ERR_MD_ALLOC_FAILED.
+ * \return              \c 0 if successful. or
+ * \return              #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info is
+ *                      invalid.
+ * \return              #MBEDTLS_ERR_MD_ALLOC_FAILED if there was not enough
+ *                      memory to allocate context data.
  */
 int mbedtls_hmac_drbg_seed_buf( mbedtls_hmac_drbg_context *ctx,
                         const mbedtls_md_info_t * md_info,
                         const unsigned char *data, size_t data_len );
 
 /**
- * \brief               Enable / disable prediction resistance (Default: Off)
+ * \brief               This function turns prediction resistance on or off.
+ *                      The default value is off.
  *
- * Note: If enabled, entropy is used for ctx->entropy_len before each call!
- *       Only use this if you have ample supply of good entropy!
+ * \note                If enabled, entropy is gathered at the beginning of
+ *                      every call to mbedtls_hmac_drbg_random_with_add()
+ *                      or mbedtls_hmac_drbg_random().
+ *                      Only use this if your entropy source has sufficient
+ *                      throughput.
  *
- * \param ctx           HMAC_DRBG context
- * \param resistance    MBEDTLS_HMAC_DRBG_PR_ON or MBEDTLS_HMAC_DRBG_PR_OFF
+ * \param ctx           The HMAC_DRBG context.
+ * \param resistance    #MBEDTLS_HMAC_DRBG_PR_ON or #MBEDTLS_HMAC_DRBG_PR_OFF.
  */
 void mbedtls_hmac_drbg_set_prediction_resistance( mbedtls_hmac_drbg_context *ctx,
                                           int resistance );
 
 /**
- * \brief               Set the amount of entropy grabbed on each reseed
- *                      (Default: given by the security strength, which
- *                      depends on the hash used, see \c mbedtls_hmac_drbg_init() )
+ * \brief               This function sets the amount of entropy grabbed on each
+ *                      seed or reseed.
+ *
+ * See the documentation of mbedtls_hmac_drbg_seed() for the default value.
  *
- * \param ctx           HMAC_DRBG context
- * \param len           Amount of entropy to grab, in bytes
+ * \param ctx           The HMAC_DRBG context.
+ * \param len           The amount of entropy to grab, in bytes.
  */
 void mbedtls_hmac_drbg_set_entropy_len( mbedtls_hmac_drbg_context *ctx,
                                 size_t len );
 
 /**
- * \brief               Set the reseed interval
- *                      (Default: MBEDTLS_HMAC_DRBG_RESEED_INTERVAL)
+ * \brief               Set the reseed interval.
  *
- * \param ctx           HMAC_DRBG context
- * \param interval      Reseed interval
+ * The reseed interval is the number of calls to mbedtls_hmac_drbg_random()
+ * or mbedtls_hmac_drbg_random_with_add() after which the entropy function
+ * is called again.
+ *
+ * The default value is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL.
+ *
+ * \param ctx           The HMAC_DRBG context.
+ * \param interval      The reseed interval.
  */
 void mbedtls_hmac_drbg_set_reseed_interval( mbedtls_hmac_drbg_context *ctx,
                                     int interval );
 
 /**
- * \brief               HMAC_DRBG update state
+ * \brief               This function updates the state of the HMAC_DRBG context.
  *
- * \param ctx           HMAC_DRBG context
- * \param additional    Additional data to update state with, or NULL
- * \param add_len       Length of additional data, or 0
+ * \param ctx           The HMAC_DRBG context.
+ * \param additional    The data to update the state with.
+ *                      If this is \c NULL, there is no additional data.
+ * \param add_len       Length of \p additional in bytes.
+ *                      Unused if \p additional is \c NULL.
  *
  * \return              \c 0 on success, or an error from the underlying
  *                      hash calculation.
- *
- * \note                Additional data is optional, pass NULL and 0 as second
- *                      third argument if no additional data is being used.
  */
 int mbedtls_hmac_drbg_update_ret( mbedtls_hmac_drbg_context *ctx,
                        const unsigned char *additional, size_t add_len );
 
 /**
- * \brief               HMAC_DRBG reseeding (extracts data from entropy source)
- *
- * \param ctx           HMAC_DRBG context
- * \param additional    Additional data to add to state (Can be NULL)
- * \param len           Length of additional data
- *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ * \brief               This function reseeds the HMAC_DRBG context, that is
+ *                      extracts data from the entropy source.
+ *
+ * \param ctx           The HMAC_DRBG context.
+ * \param additional    Additional data to add to the state.
+ *                      If this is \c NULL, there is no additional data
+ *                      and \p len should be \c 0.
+ * \param len           The length of the additional data.
+ *                      This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT
+ *                      and also at most
+ *                      #MBEDTLS_HMAC_DRBG_MAX_SEED_INPUT - \p entropy_len
+ *                      where \p entropy_len is the entropy length
+ *                      (see mbedtls_hmac_drbg_set_entropy_len()).
+ *
+ * \return              \c 0 if successful.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ *                      if a call to the entropy function failed.
  */
 int mbedtls_hmac_drbg_reseed( mbedtls_hmac_drbg_context *ctx,
                       const unsigned char *additional, size_t len );
 
 /**
- * \brief               HMAC_DRBG generate random with additional update input
- *
- * Note: Automatically reseeds if reseed_counter is reached or PR is enabled.
- *
- * \param p_rng         HMAC_DRBG context
- * \param output        Buffer to fill
- * \param output_len    Length of the buffer
- * \param additional    Additional data to update with (can be NULL)
- * \param add_len       Length of additional data (can be 0)
- *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or
- *                      MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG, or
- *                      MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG.
+ * \brief   This function updates an HMAC_DRBG instance with additional
+ *          data and uses it to generate random data.
+ *
+ * This function automatically reseeds if the reseed counter is exceeded
+ * or prediction resistance is enabled.
+ *
+ * \param p_rng         The HMAC_DRBG context. This must be a pointer to a
+ *                      #mbedtls_hmac_drbg_context structure.
+ * \param output        The buffer to fill.
+ * \param output_len    The length of the buffer in bytes.
+ *                      This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
+ * \param additional    Additional data to update with.
+ *                      If this is \c NULL, there is no additional data
+ *                      and \p add_len should be \c 0.
+ * \param add_len       The length of the additional data.
+ *                      This must be at most #MBEDTLS_HMAC_DRBG_MAX_INPUT.
+ *
+ * \return              \c 0 if successful.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ *                      if a call to the entropy source failed.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
+ *                      \p output_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if
+ *                      \p add_len > #MBEDTLS_HMAC_DRBG_MAX_INPUT.
  */
 int mbedtls_hmac_drbg_random_with_add( void *p_rng,
                                unsigned char *output, size_t output_len,
@@ -245,24 +316,29 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng,
                                size_t add_len );
 
 /**
- * \brief               HMAC_DRBG generate random
- *
- * Note: Automatically reseeds if reseed_counter is reached or PR is enabled.
- *
- * \param p_rng         HMAC_DRBG context
- * \param output        Buffer to fill
- * \param out_len       Length of the buffer
- *
- * \return              0 if successful, or
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED, or
- *                      MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG
+ * \brief   This function uses HMAC_DRBG to generate random data.
+ *
+ * This function automatically reseeds if the reseed counter is exceeded
+ * or prediction resistance is enabled.
+ *
+ * \param p_rng         The HMAC_DRBG context. This must be a pointer to a
+ *                      #mbedtls_hmac_drbg_context structure.
+ * \param output        The buffer to fill.
+ * \param out_len       The length of the buffer in bytes.
+ *                      This must be at most #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
+ *
+ * \return              \c 0 if successful.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ *                      if a call to the entropy source failed.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_REQUEST_TOO_BIG if
+ *                      \p out_len > #MBEDTLS_HMAC_DRBG_MAX_REQUEST.
  */
 int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
 
 /**
  * \brief               Free an HMAC_DRBG context
  *
- * \param ctx           HMAC_DRBG context to free.
+ * \param ctx           The HMAC_DRBG context to free.
  */
 void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
 
@@ -273,17 +349,16 @@ void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx );
 #define MBEDTLS_DEPRECATED
 #endif
 /**
- * \brief               HMAC_DRBG update state
+ * \brief               This function updates the state of the HMAC_DRBG context.
  *
  * \deprecated          Superseded by mbedtls_hmac_drbg_update_ret()
  *                      in 2.16.0.
  *
- * \param ctx           HMAC_DRBG context
- * \param additional    Additional data to update state with, or NULL
- * \param add_len       Length of additional data, or 0
- *
- * \note                Additional data is optional, pass NULL and 0 as second
- *                      third argument if no additional data is being used.
+ * \param ctx           The HMAC_DRBG context.
+ * \param additional    The data to update the state with.
+ *                      If this is \c NULL, there is no additional data.
+ * \param add_len       Length of \p additional in bytes.
+ *                      Unused if \p additional is \c NULL.
  */
 MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update(
     mbedtls_hmac_drbg_context *ctx,
@@ -293,26 +368,31 @@ MBEDTLS_DEPRECATED void mbedtls_hmac_drbg_update(
 
 #if defined(MBEDTLS_FS_IO)
 /**
- * \brief               Write a seed file
+ * \brief               This function writes a seed file.
  *
- * \param ctx           HMAC_DRBG context
- * \param path          Name of the file
+ * \param ctx           The HMAC_DRBG context.
+ * \param path          The name of the file.
  *
- * \return              0 if successful, 1 on file error, or
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on reseed
+ *                      failure.
  */
 int mbedtls_hmac_drbg_write_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
 
 /**
- * \brief               Read and update a seed file. Seed is added to this
- *                      instance
- *
- * \param ctx           HMAC_DRBG context
- * \param path          Name of the file
- *
- * \return              0 if successful, 1 on file error,
- *                      MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED or
- *                      MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG
+ * \brief               This function reads and updates a seed file. The seed
+ *                      is added to this instance.
+ *
+ * \param ctx           The HMAC_DRBG context.
+ * \param path          The name of the file.
+ *
+ * \return              \c 0 on success.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR on file error.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_ENTROPY_SOURCE_FAILED on
+ *                      reseed failure.
+ * \return              #MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG if the existing
+ *                      seed file is too large.
  */
 int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path );
 #endif /* MBEDTLS_FS_IO */
@@ -320,9 +400,10 @@ int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const ch
 
 #if defined(MBEDTLS_SELF_TEST)
 /**
- * \brief               Checkup routine
+ * \brief               The HMAC_DRBG Checkup routine.
  *
- * \return              0 if successful, or 1 if the test failed
+ * \return              \c 0 if successful.
+ * \return              \c 1 if the test failed.
  */
 int mbedtls_hmac_drbg_self_test( int verbose );
 #endif
diff --git a/thirdparty/mbedtls/include/mbedtls/version.h b/thirdparty/mbedtls/include/mbedtls/version.h
index b4eef71e50..aeffb16699 100644
--- a/thirdparty/mbedtls/include/mbedtls/version.h
+++ b/thirdparty/mbedtls/include/mbedtls/version.h
@@ -40,16 +40,16 @@
  */
 #define MBEDTLS_VERSION_MAJOR  2
 #define MBEDTLS_VERSION_MINOR  16
-#define MBEDTLS_VERSION_PATCH  3
+#define MBEDTLS_VERSION_PATCH  4
 
 /**
  * The single version number has the following structure:
  *    MMNNPP00
  *    Major version | Minor version | Patch version
  */
-#define MBEDTLS_VERSION_NUMBER         0x02100300
-#define MBEDTLS_VERSION_STRING         "2.16.3"
-#define MBEDTLS_VERSION_STRING_FULL    "mbed TLS 2.16.3"
+#define MBEDTLS_VERSION_NUMBER         0x02100400
+#define MBEDTLS_VERSION_STRING         "2.16.4"
+#define MBEDTLS_VERSION_STRING_FULL    "mbed TLS 2.16.4"
 
 #if defined(MBEDTLS_VERSION_C)