The stack buffer used to hold the decrypted key in pk_parse_pkcs8_encrypted_der
was statically sized to 2048 bytes, which is not enough for DER encoded 4096bit
RSA keys.
This commit resolves the problem by performing the key-decryption in-place,
circumventing the introduction of another stack or heap copy of the key.
There are two situations where pk_parse_pkcs8_encrypted_der is invoked:
1. When processing a PEM-encoded encrypted key in mbedtls_pk_parse_key.
This does not need adaption since the PEM context used to hold the decoded
key is already constructed and owned by mbedtls_pk_parse_key.
2. When processing a DER-encoded encrypted key in mbedtls_pk_parse_key.
In this case, mbedtls_pk_parse_key calls pk_parse_pkcs8_encrypted_der with
the buffer provided by the user, which is declared const. The commit
therefore adds a small code paths making a copy of the keybuffer before
calling pk_parse_pkcs8_encrypted_der.
This commit adds the function mbedtls_rsa_validate_crt for validating a set of CRT parameters. The function
mbedtls_rsa_check_crt is simplified accordingly.
Primality testing is guarded by the configuration flag MBEDTLS_GENPRIME and used in the new RSA helper functions. This
commit adds a corresponding preprocessor directive.
Alternative RSA implementations can be provided by defining MBEDTLS_RSA_ALT in
config.h, defining an mbedtls_rsa_context struct in a new file rsa_alt.h and
re-implementing the RSA interface specified in rsa.h.
Through the previous reworkings, the adherence to the interface is the only
implementation obligation - in particular, implementors are free to use a
different layout for the RSA context structure.
This commit adds test for the new library function mbedtls_rsa_check_params for
checking a set of RSA core parameters. There are some toy example tests with
small numbers that can be verified by hand, as well as tests with real world
numbers. Complete, partial and corrupted data are tested, as well the check for
primality exactly if a PRNG is provided.
This commit adds tests for the new library function mbedtls_rsa_export_raw.
Each test case performs the following steps:
- Parse and convert a set of hex-string decoded core RSA parameters into big
endian byte arrays.
- Use these to initialize an RSA context
- Export core RSA parameters as byte arrays again afterwards
- Compare byte strings.
Each test split is performed twice, once with successive and once with
simultaneous exporting.
This commit adds tests for the new library function mbedtls_rsa_export. Each
test case performs the following steps:
- Parse and convert a set of hex-string decoded core RSA parameters into MPI's.
- Use these to initialize an RSA context
- Export core RSA parameters as MPI's again afterwards
- Compare initial MPI's to exported ones.
In the private key case, all core parameters are exported and sanity-checked,
regardless of whether they were also used during setup.
Each test split is performed twice, once with successive and once with
simultaneous exporting.
This commit adds numerous tests for the new library functions mbedtls_rsa_import
and mbedtls_rsa_import_raw in conjunction with mbedtls_rsa_complete for
importing and completing core sets of core RSA parameters (N,P,Q,D,E) into an
RSA context, with the importing accepting either MPI's or raw big endian
buffers.
Each test is determined by the following parameters:
1) Set of parameters provided
We're testing full sets (N,P,Q,D,E), partial sets (N,-,-,D,E) and (N,P,Q,-,E)
that are sufficient to generate missing parameters, and the partial and
insufficient set (N, -, Q, -, E).
2) Simultaenous or successive importing
The functions rsa_import and rsa_import_raw accept importing parameters at
once or one after another. We test both.
3) Sanity of parameters
This commit adds test for the new library function mbedtls_rsa_deduce_moduli for
deducing the prime factors (P,Q) of an RSA modulus N from knowledge of a
pair (D,E) of public and private exponent:
- Two toy examples that can be checked by hand, one fine and with bad parameters.
- Two real world examples, one fine and one with bad parameters.
This commit adds tests for the new library function mbedtls_rsa_deduce_private
for deducing the private RSA exponent D from the public exponent E and the
factorization (P,Q) of the RSA modulus:
- Two toy examples with small numbers that can be checked by hand, one
working fine and another failing due to bad parameters.
- Two real world examples, one fine and one with bad parameters.
This commit extends the RSA interface by import/export calls that can be used to
setup an RSA context from a subset of the core RSA parameters (N,P,Q,D,E).
The intended workflow is the following:
1. Call mbedtls_rsa_import one or multiple times to import the core parameters.
2. Call mbedtls_rsa_complete to deduce remaining core parameters as well as any
implementation-defined internal helper variables.
The RSA context is ready for use after this call.
The import function comes in two variants mbedtls_rsa_import and
mbedtls_rsa_import_raw, the former taking pointers to MPI's as input, the latter
pointers buffers holding to big-endian encoded MPI's.
The reason for this splitting is the following: When only providing an import
function accepting const MPI's, a user trying to import raw binary data into an
RSA context has to convert these to MPI's first which before passing them to the
import function, introducing an unnecessary copy of the data in memory. The
alternative would be to have another MPI-based import-function with
move-semantics, but this would be in contrast to the rest of the library's
interfaces.
Similarly, there are functions mbedtls_rsa_export and mbedtls_rsa_export_raw for
exporting the core RSA parameters, either as MPI's or in big-endian binary
format.
The main import/export functions deliberately do not include the additional
helper values DP, DQ and QP present in ASN.1-encoded RSA private keys. To
nonetheless be able to check whether given parameters DP, DQ and QP are in
accordance with a given RSA private key, the interface is extended by a function
mbedtls_rsa_check_opt (in line with mbedtls_rsa_check_privkey,
mbedtls_rsa_check_pubkey and mbedtls_rsa_check_pub_priv). Exporting the optional
parameters is taken care of by mbedtls_export_opt (currently MPI format only).
This commit adds convenience functions to the RSA module for computing a
complete RSA private key (with fields N, P, Q, D, E, DP, DQ, QP) from a subset
of core parameters, e.g. (N, D, E).
