This setting belongs to the individual connection, not to a configuration
shared by many connections. (If a default value is desired, that can be handled
by the application code that calls mbedtls_ssl_set_mtu().)
There are at least two ways in which this matters:
- per-connection settings can be adjusted if MTU estimates become available
during the lifetime of the connection
- it is at least conceivable that a server might recognize restricted clients
based on range of IPs and immediately set a lower MTU for them. This is much
easier to do with a per-connection setting than by maintaining multiple
near-duplicated ssl_config objects that differ only by the MTU setting.
For now, just check that it causes us to fragment. More tests are coming in
follow-up commits to ensure we respect the exact value set, including when
renegotiating.
When MBEDTLS_MEMORY_BUFFER_ALLOC_C was defined, the sample ssl_server2.c was
using its own memory buffer for memory allocated by the library. The memory
used wasn't obvious, so this adds a macro for the memory buffer allocated to
make the allocated memory size more obvious and hence easier to configure.
Newer features in the library have increased the overall RAM usage of the
library, when all features are enabled. ssl_server2.c, with all features enabled
was running out of memory for the ssl-opt.sh test 'Authentication: client
max_int chain, server required'.
This commit increases the memory buffer allocation for ssl_server2.c to allow
the test to work with all features enabled.
In ssl_server2, the private key objects are normally local variables
of the main function. However this does not hold for private keys in
the SNI configuration. When async callbacks are used, the test code
transfers the ownership of the private keys to the async callbacks.
Therefore the test code must free the SNI private keys through the
async callbacks (but it must not free the straight private keys this
way since they are not even heap-allocated).
When testing async callbacks with SNI, make all the keys async, not
just the first one. Otherwise the test is fragile with respect to
whether a key is used directly or through the async callbacks.
In the current test code, the object that is used as a public key in
the certificate also contains a private key. However this is because
of the way the stest code is built and does not demonstrate the API in
a useful way. Use mbedtls_pk_check_pair, which is not what real-world
code would do (since the private key would typically be in an external
cryptoprocessor) but is a more representative placeholder.
Rename to mbedtls_ssl_get_async_operation_data and
mbedtls_ssl_set_async_operation_data so that they're about
"async operation data" and not about some not-obvious "data".
The certificate passed to async callbacks may not be the one set by
mbedtls_ssl_conf_own_cert. For example, when using an SNI callback,
it's whatever the callback is using. Document this, and add a test
case (and code sample) with SNI.
In ssl_server2, the private key objects are normally local variables
of the main function. However this does not hold for private keys in
the SNI configuration. When async callbacks are used, the test code
transfers the ownership of the private keys to the async callbacks.
Therefore the test code must free the SNI private keys through the
async callbacks (but it must not free the straight private keys this
way since they are not even heap-allocated).
When testing async callbacks with SNI, make all the keys async, not
just the first one. Otherwise the test is fragile with respect to
whether a key is used directly or through the async callbacks.
In the current test code, the object that is used as a public key in
the certificate also contains a private key. However this is because
of the way the stest code is built and does not demonstrate the API in
a useful way. Use mbedtls_pk_check_pair, which is not what real-world
code would do (since the private key would typically be in an external
cryptoprocessor) but is a more representative placeholder.
Rename to mbedtls_ssl_get_async_operation_data and
mbedtls_ssl_set_async_operation_data so that they're about
"async operation data" and not about some not-obvious "data".
The certificate passed to async callbacks may not be the one set by
mbedtls_ssl_conf_own_cert. For example, when using an SNI callback,
it's whatever the callback is using. Document this, and add a test
case (and code sample) with SNI.
Testing the case where the resume callback returns an error at the
beginning and the case where it returns an error at the end is
redundant. Keep the test after the output has been produced, to
validate that the product does not use even a valid output if the
return value is an error code.
Document how the SSL async sign callback must treat its md_alg and
hash parameters when doing an RSA signature: sign-the-hash if md_alg
is nonzero (TLS 1.2), and sign-the-digestinfo if md_alg is zero
(TLS <= 1.1).
In ssl_server2, don't use md_alg=MBEDTLS_MD_NONE to indicate that
ssl_async_resume must perform an encryption, because md_alg is also
MBEDTLS_MD_NONE in TLS <= 1.1. Add a test case to exercise this
case (signature with MBEDTLS_MD_NONE).
When a handshake step starts an asynchronous operation, the
application needs to know which SSL connection the operation is for,
so that when the operation completes, the application can wake that
connection up. Therefore the async start callbacks need to take the
SSL context as an argument. It isn't enough to let them set a cookie
in the SSL connection, the application needs to be able to find the
right SSL connection later.
Also pass the SSL context to the other callbacks for consistency. Add
a new field to the handshake that the application can use to store a
per-connection context. This new field replaces the former
context (operation_ctx) that was created by the start function and
passed to the resume function.
Add a boolean flag to the handshake structure to track whether an
asynchronous operation is in progress. This is more robust than
relying on the application to set a non-null application context.
Conflict resolution:
* ChangeLog: put the new entry from my branch in the proper place.
* include/mbedtls/error.h: counted high-level module error codes again.
* include/mbedtls/ssl.h: picked different numeric codes for the
concurrently added errors; made the new error a full sentence per
current standards.
* library/error.c: ran scripts/generate_errors.pl.
* library/ssl_srv.c:
* ssl_prepare_server_key_exchange "DHE key exchanges": the conflict
was due to style corrections in development
(4cb1f4d49c) which I merged with
my refactoring.
* ssl_prepare_server_key_exchange "For key exchanges involving the
server signing", first case, variable declarations: merged line
by line:
* dig_signed_len: added in async
* signature_len: removed in async
* hashlen: type changed to size_t in development
* hash: size changed to MBEDTLS_MD_MAX_SIZE in async
* ret: added in async
* ssl_prepare_server_key_exchange "For key exchanges involving the
server signing", first cae comment: the conflict was due to style
corrections in development (4cb1f4d49c)
which I merged with my comment changes made as part of refactoring
the function.
* ssl_prepare_server_key_exchange "Compute the hash to be signed" if
`md_alg != MBEDTLS_MD_NONE`: conflict between
ebd652fe2d
"ssl_write_server_key_exchange: calculate hashlen explicitly" and
46f5a3e9b4 "Check return codes from
MD in ssl code". I took the code from commit
ca1d742904 made on top of development
which makes mbedtls_ssl_get_key_exchange_md_ssl_tls return the
hash length.
* programs/ssl/ssl_server2.c: multiple conflicts between the introduction
of MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS and new auxiliary functions and
definitions for async support, and the introduction of idle().
* definitions before main: concurrent additions, kept both.
* main, just after `handshake:`: in the loop around
mbedtls_ssl_handshake(), merge the addition of support for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS and SSL_ASYNC_INJECT_ERROR_CANCEL
with the addition of the idle() call.
* main, if `opt.transport == MBEDTLS_SSL_TRANSPORT_STREAM`: take the
code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS.
* main, loop around mbedtls_ssl_read() in the datagram case:
take the code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS; revert to a do...while loop.
* main, loop around mbedtls_ssl_write() in the datagram case:
take the code from development and add a check for
MBEDTLS_ERR_SSL_ASYNC_IN_PROGRESS; revert to a do...while loop.
