extmod/modussl: Improve exception error messages.

This commit adds human readable error messages when mbedtls or axtls raise
an exception.  Currently often just an EIO error is raised so the user is
lost and can't tell whether it's a cert error, buffer overrun, connecting
to a non-ssl port, etc.  The axtls and mbedtls error raising in the ussl
module is modified to raise:

    OSError(-err_num, "error string")

For axtls a small error table of strings is added and used for the second
argument of the OSErrer.  For mbedtls the code uses mbedtls' built-in
strerror function, and if there is an out of memory condition it just
produces OSError(-err_num).  Producing the error string for mbedtls is
conditional on them being included in the mbedtls build, via
MBEDTLS_ERROR_C.
This commit is contained in:
Thorsten von Eicken 2020-03-26 23:17:35 -07:00 committed by Damien George
parent c7f7c0214c
commit 9aa214077e
7 changed files with 173 additions and 9 deletions

View File

@ -29,6 +29,7 @@
#include "py/runtime.h"
#include "py/stream.h"
#include "py/objstr.h"
#if MICROPY_PY_USSL && MICROPY_SSL_AXTLS
@ -54,6 +55,56 @@ struct ssl_args {
STATIC const mp_obj_type_t ussl_socket_type;
// Table of errors
struct ssl_errs {
int16_t errnum;
const char *errstr;
};
STATIC const struct ssl_errs ssl_error_tab[] = {
{ SSL_NOT_OK, "NOT_OK" },
{ SSL_ERROR_DEAD, "DEAD" },
{ SSL_CLOSE_NOTIFY, "CLOSE_NOTIFY" },
{ SSL_EAGAIN, "EAGAIN" },
{ SSL_ERROR_CONN_LOST, "CONN_LOST" },
{ SSL_ERROR_RECORD_OVERFLOW, "RECORD_OVERFLOW" },
{ SSL_ERROR_SOCK_SETUP_FAILURE, "SOCK_SETUP_FAILURE" },
{ SSL_ERROR_INVALID_HANDSHAKE, "INVALID_HANDSHAKE" },
{ SSL_ERROR_INVALID_PROT_MSG, "INVALID_PROT_MSG" },
{ SSL_ERROR_INVALID_HMAC, "INVALID_HMAC" },
{ SSL_ERROR_INVALID_VERSION, "INVALID_VERSION" },
{ SSL_ERROR_UNSUPPORTED_EXTENSION, "UNSUPPORTED_EXTENSION" },
{ SSL_ERROR_INVALID_SESSION, "INVALID_SESSION" },
{ SSL_ERROR_NO_CIPHER, "NO_CIPHER" },
{ SSL_ERROR_INVALID_CERT_HASH_ALG, "INVALID_CERT_HASH_ALG" },
{ SSL_ERROR_BAD_CERTIFICATE, "BAD_CERTIFICATE" },
{ SSL_ERROR_INVALID_KEY, "INVALID_KEY" },
{ SSL_ERROR_FINISHED_INVALID, "FINISHED_INVALID" },
{ SSL_ERROR_NO_CERT_DEFINED, "NO_CERT_DEFINED" },
{ SSL_ERROR_NO_CLIENT_RENOG, "NO_CLIENT_RENOG" },
{ SSL_ERROR_NOT_SUPPORTED, "NOT_SUPPORTED" },
};
STATIC NORETURN void ussl_raise_error(int err) {
for (size_t i = 0; i < MP_ARRAY_SIZE(ssl_error_tab); i++) {
if (ssl_error_tab[i].errnum == err) {
// construct string object
mp_obj_str_t *o_str = m_new_obj_maybe(mp_obj_str_t);
if (o_str == NULL) {
break;
}
o_str->base.type = &mp_type_str;
o_str->data = (const byte *)ssl_error_tab[i].errstr;
o_str->len = strlen((char *)o_str->data);
o_str->hash = qstr_compute_hash(o_str->data, o_str->len);
// raise
mp_obj_t args[2] = { MP_OBJ_NEW_SMALL_INT(err), MP_OBJ_FROM_PTR(o_str)};
nlr_raise(mp_obj_exception_make_new(&mp_type_OSError, 2, 0, args));
}
}
mp_raise_OSError(err);
}
STATIC mp_obj_ssl_socket_t *ussl_socket_new(mp_obj_t sock, struct ssl_args *args) {
#if MICROPY_PY_USSL_FINALISER
mp_obj_ssl_socket_t *o = m_new_obj_with_finaliser(mp_obj_ssl_socket_t);
@ -107,9 +158,7 @@ STATIC mp_obj_ssl_socket_t *ussl_socket_new(mp_obj_t sock, struct ssl_args *args
int res = ssl_handshake_status(o->ssl_sock);
if (res != SSL_OK) {
printf("ssl_handshake_status: %d\n", res);
ssl_display_error(res);
mp_raise_OSError(MP_EIO);
ussl_raise_error(res);
}
}

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@ -34,6 +34,7 @@
#include "py/runtime.h"
#include "py/stream.h"
#include "py/objstr.h"
// mbedtls_time_t
#include "mbedtls/platform.h"
@ -43,6 +44,7 @@
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/debug.h"
#include "mbedtls/error.h"
typedef struct _mp_obj_ssl_socket_t {
mp_obj_base_t base;
@ -74,6 +76,42 @@ STATIC void mbedtls_debug(void *ctx, int level, const char *file, int line, cons
}
#endif
STATIC NORETURN void mbedtls_raise_error(int err) {
#if defined(MBEDTLS_ERROR_C)
// Including mbedtls_strerror takes about 16KB on the esp32 due to all the strings.
// MBEDTLS_ERROR_C is the define used by mbedtls to conditionally include mbedtls_strerror.
// It is set/unset in the MBEDTLS_CONFIG_FILE which is defined in the Makefile.
// "small" negative integer error codes come from underlying stream/sockets, not mbedtls
if (err < 0 && err > -256) {
mp_raise_OSError(-err);
}
// Try to allocate memory for the message
#define ERR_STR_MAX 100 // mbedtls_strerror truncates if it doesn't fit
mp_obj_str_t *o_str = m_new_obj_maybe(mp_obj_str_t);
byte *o_str_buf = m_new_maybe(byte, ERR_STR_MAX);
if (o_str == NULL || o_str_buf == NULL) {
mp_raise_OSError(err);
}
// print the error message into the allocated buffer
mbedtls_strerror(err, (char *)o_str_buf, ERR_STR_MAX);
size_t len = strnlen((char *)o_str_buf, ERR_STR_MAX);
// Put the exception object together
o_str->base.type = &mp_type_str;
o_str->data = o_str_buf;
o_str->len = len;
o_str->hash = qstr_compute_hash(o_str->data, o_str->len);
// raise
mp_obj_t args[2] = { MP_OBJ_NEW_SMALL_INT(err), MP_OBJ_FROM_PTR(o_str)};
nlr_raise(mp_obj_exception_make_new(&mp_type_OSError, 2, 0, args));
#else
// mbedtls is compiled without error strings so we simply return the err number
mp_raise_OSError(err); // typ. err is negative
#endif
}
STATIC int _mbedtls_ssl_send(void *ctx, const byte *buf, size_t len) {
mp_obj_t sock = *(mp_obj_t *)ctx;
@ -85,7 +123,7 @@ STATIC int _mbedtls_ssl_send(void *ctx, const byte *buf, size_t len) {
if (mp_is_nonblocking_error(err)) {
return MBEDTLS_ERR_SSL_WANT_WRITE;
}
return -err;
return -err; // convert an MP_ERRNO to something mbedtls passes through as error
} else {
return out_sz;
}
@ -197,7 +235,6 @@ STATIC mp_obj_ssl_socket_t *socket_new(mp_obj_t sock, struct ssl_args *args) {
if (args->do_handshake.u_bool) {
while ((ret = mbedtls_ssl_handshake(&o->ssl)) != 0) {
if (ret != MBEDTLS_ERR_SSL_WANT_READ && ret != MBEDTLS_ERR_SSL_WANT_WRITE) {
printf("mbedtls_ssl_handshake error: -%x\n", -ret);
goto cleanup;
}
}
@ -221,7 +258,7 @@ cleanup:
} else if (ret == MBEDTLS_ERR_X509_BAD_INPUT_DATA) {
mp_raise_ValueError(MP_ERROR_TEXT("invalid cert"));
} else {
mp_raise_OSError(MP_EIO);
mbedtls_raise_error(ret);
}
}

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@ -9,7 +9,7 @@ except ImportError:
# create in client mode
try:
ss = ssl.wrap_socket(io.BytesIO())
ss = ssl.wrap_socket(io.BytesIO(), server_hostname="test.example.com")
except OSError as er:
print("wrap_socket:", repr(er))

View File

@ -1,5 +1,4 @@
ssl_handshake_status: -256
wrap_socket: OSError(5,)
wrap_socket: OSError(-256, 'CONN_LOST')
<_SSLSocket
4
b''

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@ -0,0 +1,44 @@
# test that modtls produces a numerical error message when out of heap
try:
import usocket as socket, ussl as ssl, sys
except:
import socket, ssl, sys
try:
from micropython import alloc_emergency_exception_buf, heap_lock, heap_unlock
except:
print("SKIP")
raise SystemExit
# test with heap locked to see it switch to number-only error message
def test(addr):
alloc_emergency_exception_buf(256)
s = socket.socket()
s.connect(addr)
try:
s.setblocking(False)
s = ssl.wrap_socket(s, do_handshake=False)
heap_lock()
print("heap is locked")
while True:
ret = s.write("foo")
if ret:
break
heap_unlock()
print("wrap: no exception")
except OSError as e:
heap_unlock()
# mbedtls produces "-29184"
# axtls produces "RECORD_OVERFLOW"
ok = "-29184" in str(e) or "RECORD_OVERFLOW" in str(e)
print("wrap:", ok)
if not ok:
print("got exception:", e)
s.close()
if __name__ == "__main__":
# connect to plain HTTP port, oops!
addr = socket.getaddrinfo("micropython.org", 80)[0][-1]
test(addr)

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@ -0,0 +1,2 @@
heap is locked
wrap: True

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@ -0,0 +1,33 @@
# test that modtls produces a text error message
try:
import usocket as socket, ussl as ssl, sys
except:
import socket, ssl, sys
def test(addr):
s = socket.socket()
s.connect(addr)
try:
s = ssl.wrap_socket(s)
print("wrap: no exception")
except OSError as e:
# mbedtls produces "mbedtls -0x7200: SSL - An invalid SSL record was received"
# axtls produces "RECORD_OVERFLOW"
# CPython produces "[SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1108)"
ok = (
"invalid SSL record" in str(e)
or "RECORD_OVERFLOW" in str(e)
or "wrong version" in str(e)
)
print("wrap:", ok)
if not ok:
print("got exception:", e)
s.close()
if __name__ == "__main__":
# connect to plain HTTP port, oops!
addr = socket.getaddrinfo("micropython.org", 80)[0][-1]
test(addr)