File rsa.h

This file provides an API for the RSA public-key cryptosystem.

The RSA public-key cryptosystem is defined in Public-Key Cryptography Standards (PKCS) #1 v1.5: RSA Encryption and Public-Key Cryptography Standards (PKCS) #1 v2.1: RSA Cryptography Specifications.

Defines

MBEDTLS_ERR_RSA_BAD_INPUT_DATA: Bad input parameters to function.

MBEDTLS_ERR_RSA_INVALID_PADDING: Input data contains invalid padding and is rejected.

MBEDTLS_ERR_RSA_KEY_GEN_FAILED: Something failed during generation of a key.

MBEDTLS_ERR_RSA_KEY_CHECK_FAILED: Key failed to pass the validity check of the library.

MBEDTLS_ERR_RSA_PUBLIC_FAILED: The public key operation failed.

MBEDTLS_ERR_RSA_PRIVATE_FAILED: The private key operation failed.

MBEDTLS_ERR_RSA_VERIFY_FAILED: The PKCS#1 verification failed.

MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE: The output buffer for decryption is not large enough.

MBEDTLS_ERR_RSA_RNG_FAILED: The random generator failed to generate non-zeros.

MBEDTLS_RSA_PKCS_V15: Use PKCS#1 v1.5 encoding.

MBEDTLS_RSA_PKCS_V21: Use PKCS#1 v2.1 encoding.

MBEDTLS_RSA_SIGN: Identifier for RSA signature operations.

MBEDTLS_RSA_CRYPT: Identifier for RSA encryption and decryption operations.

MBEDTLS_RSA_SALT_LEN_ANY

Typedefs

typedef struct mbedtls_rsa_context mbedtls_rsa_context: The RSA context structure.

Functions

void mbedtls_rsa_init(mbedtls_rsa_context *ctx)

This function initializes an RSA context.

Note

This function initializes the padding and the hash identifier to respectively MBEDTLS_RSA_PKCS_V15 and MBEDTLS_MD_NONE. See mbedtls_rsa_set_padding() for more information about those parameters.

Parameters:: ctx – The RSA context to initialize. This must not be NULL.

int mbedtls_rsa_set_padding(mbedtls_rsa_context *ctx, int padding, mbedtls_md_type_t hash_id)

This function sets padding for an already initialized RSA context.

Note

Set padding to MBEDTLS_RSA_PKCS_V21 for the RSAES-OAEP encryption scheme and the RSASSA-PSS signature scheme.

Note

The hash_id parameter is ignored when using MBEDTLS_RSA_PKCS_V15 padding.

Note

The choice of padding mode is strictly enforced for private key operations, since there might be security concerns in mixing padding modes. For public key operations it is a default value, which can be overridden by calling specific mbedtls_rsa_rsaes_xxx or mbedtls_rsa_rsassa_xxx functions.

Note

The hash selected in hash_id is always used for OEAP encryption. For PSS signatures, it is always used for making signatures, but can be overridden for verifying them. If set to MBEDTLS_MD_NONE, it is always overridden.

Parameters:

ctx – The initialized RSA context to be configured.
padding – The padding mode to use. This must be either MBEDTLS_RSA_PKCS_V15 or MBEDTLS_RSA_PKCS_V21.
hash_id – The hash identifier for PSS or OAEP, if padding is MBEDTLS_RSA_PKCS_V21. MBEDTLS_MD_NONE is accepted by this function but may be not suitable for some operations. Ignored if padding is MBEDTLS_RSA_PKCS_V15.

Returns:

0 on success.

Returns:

MBEDTLS_ERR_RSA_INVALID_PADDING failure: padding or hash_id is invalid.

int mbedtls_rsa_get_padding_mode(const mbedtls_rsa_context *ctx)

This function retrieves padding mode of initialized RSA context.

Parameters:: ctx – The initialized RSA context.
Returns:: RSA padding mode.

int mbedtls_rsa_get_md_alg(const mbedtls_rsa_context *ctx)

This function retrieves hash identifier of mbedtls_md_type_t type.

Parameters:: ctx – The initialized RSA context.
Returns:: Hash identifier of mbedtls_md_type_t type.

int mbedtls_rsa_import(mbedtls_rsa_context *ctx, const mbedtls_mpi *N, const mbedtls_mpi *P, const mbedtls_mpi *Q, const mbedtls_mpi *D, const mbedtls_mpi *E)

This function imports a set of core parameters into an RSA context.

Any sequence of calls to this function should be followed by a call to mbedtls_rsa_complete(), which checks and completes the provided information to a ready-for-use public or private RSA key.

Note

This function can be called multiple times for successive imports, if the parameters are not simultaneously present.

Note

See mbedtls_rsa_complete() for more information on which parameters are necessary to set up a private or public RSA key.

Note

The imported parameters are copied and need not be preserved for the lifetime of the RSA context being set up.

Parameters:

ctx – The initialized RSA context to store the parameters in.
N – The RSA modulus. This may be NULL.
P – The first prime factor of N. This may be NULL.
Q – The second prime factor of N. This may be NULL.
D – The private exponent. This may be NULL.
E – The public exponent. This may be NULL.

Returns:

0 on success.

Returns:

A non-zero error code on failure.

int mbedtls_rsa_import_raw(mbedtls_rsa_context *ctx, unsigned char const *N, size_t N_len, unsigned char const *P, size_t P_len, unsigned char const *Q, size_t Q_len, unsigned char const *D, size_t D_len, unsigned char const *E, size_t E_len)

This function imports core RSA parameters, in raw big-endian binary format, into an RSA context.

Any sequence of calls to this function should be followed by a call to mbedtls_rsa_complete(), which checks and completes the provided information to a ready-for-use public or private RSA key.

Note

This function can be called multiple times for successive imports, if the parameters are not simultaneously present.

Note

See mbedtls_rsa_complete() for more information on which parameters are necessary to set up a private or public RSA key.

Note

The imported parameters are copied and need not be preserved for the lifetime of the RSA context being set up.

Parameters:

ctx – The initialized RSA context to store the parameters in.
N – The RSA modulus. This may be NULL.
N_len – The Byte length of N; it is ignored if N == NULL.
P – The first prime factor of N. This may be NULL.
P_len – The Byte length of P; it is ignored if P == NULL.
Q – The second prime factor of N. This may be NULL.
Q_len – The Byte length of Q; it is ignored if Q == NULL.
D – The private exponent. This may be NULL.
D_len – The Byte length of D; it is ignored if D == NULL.
E – The public exponent. This may be NULL.
E_len – The Byte length of E; it is ignored if E == NULL.

Returns:

0 on success.

Returns:

A non-zero error code on failure.

int mbedtls_rsa_complete(mbedtls_rsa_context *ctx)

This function completes an RSA context from a set of imported core parameters.

To setup an RSA public key, precisely N and E must have been imported.

To setup an RSA private key, sufficient information must be present for the other parameters to be derivable.

The default implementation supports the following:

Derive P, Q from N, D, E.
Derive N, D from P, Q, E.

Alternative implementations need not support these.

If this function runs successfully, it guarantees that the RSA context can be used for RSA operations without the risk of failure or crash.

Warning

This function need not perform consistency checks for the imported parameters. In particular, parameters that are not needed by the implementation might be silently discarded and left unchecked. To check the consistency of the key material, see mbedtls_rsa_check_privkey().

Parameters:: ctx – The initialized RSA context holding imported parameters.
Returns:: 0 on success.
Returns:: MBEDTLS_ERR_RSA_BAD_INPUT_DATA if the attempted derivations failed.

int mbedtls_rsa_export(const mbedtls_rsa_context *ctx, mbedtls_mpi *N, mbedtls_mpi *P, mbedtls_mpi *Q, mbedtls_mpi *D, mbedtls_mpi *E)

This function exports the core parameters of an RSA key.

            If this function runs successfully, the non-NULL buffers
            pointed to by \p N, \p P, \p Q, \p D, and \p E are fully
            written, with additional unused space filled leading by
            zero Bytes.

            Possible reasons for returning
            #MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED:<ul>
            <li>An alternative RSA implementation is in use, which
            stores the key externally, and either cannot or should
            not export it into RAM.</li>
            <li>A SW or HW implementation might not support a certain
            deduction. For example, \p P, \p Q from \p N, \p D,
            and \p E if the former are not part of the
            implementation.</li></ul>

            If the function fails due to an unsupported operation,
            the RSA context stays intact and remains usable.

Parameters:

ctx – The initialized RSA context.
N – The MPI to hold the RSA modulus. This may be NULL if this field need not be exported.
P – The MPI to hold the first prime factor of N. This may be NULL if this field need not be exported.
Q – The MPI to hold the second prime factor of N. This may be NULL if this field need not be exported.
D – The MPI to hold the private exponent. This may be NULL if this field need not be exported.
E – The MPI to hold the public exponent. This may be NULL if this field need not be exported.

Returns:

0 on success.

Returns:

MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED if exporting the requested parameters cannot be done due to missing functionality or because of security policies.

Returns:

A non-zero return code on any other failure.

int mbedtls_rsa_export_raw(const mbedtls_rsa_context *ctx, unsigned char *N, size_t N_len, unsigned char *P, size_t P_len, unsigned char *Q, size_t Q_len, unsigned char *D, size_t D_len, unsigned char *E, size_t E_len)

This function exports core parameters of an RSA key in raw big-endian binary format.

If this function runs successfully, the non-NULL buffers pointed to by N, P, Q, D, and E are fully written, with additional unused space filled leading by zero Bytes.

Possible reasons for returning MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED:

An alternative RSA implementation is in use, which stores the key externally, and either cannot or should not export it into RAM.
A SW or HW implementation might not support a certain deduction. For example, P, Q from N, D, and E if the former are not part of the implementation.

If the function fails due to an unsupported operation, the RSA context stays intact and remains usable.

Note

The length parameters are ignored if the corresponding buffer pointers are NULL.

Parameters:

ctx – The initialized RSA context.
N – The Byte array to store the RSA modulus, or NULL if this field need not be exported.
N_len – The size of the buffer for the modulus.
P – The Byte array to hold the first prime factor of N, or NULL if this field need not be exported.
P_len – The size of the buffer for the first prime factor.
Q – The Byte array to hold the second prime factor of N, or NULL if this field need not be exported.
Q_len – The size of the buffer for the second prime factor.
D – The Byte array to hold the private exponent, or NULL if this field need not be exported.
D_len – The size of the buffer for the private exponent.
E – The Byte array to hold the public exponent, or NULL if this field need not be exported.
E_len – The size of the buffer for the public exponent.

Returns:

0 on success.

Returns:

MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED if exporting the requested parameters cannot be done due to missing functionality or because of security policies.

Returns:

A non-zero return code on any other failure.

int mbedtls_rsa_export_crt(const mbedtls_rsa_context *ctx, mbedtls_mpi *DP, mbedtls_mpi *DQ, mbedtls_mpi *QP)

This function exports CRT parameters of a private RSA key.

Note

Alternative RSA implementations not using CRT-parameters internally can implement this function based on mbedtls_rsa_deduce_opt().

Parameters:

ctx – The initialized RSA context.
DP – The MPI to hold D modulo P-1, or NULL if it need not be exported.
DQ – The MPI to hold D modulo Q-1, or NULL if it need not be exported.
QP – The MPI to hold modular inverse of Q modulo P, or NULL if it need not be exported.

Returns:

0 on success.

Returns:

A non-zero error code on failure.

size_t mbedtls_rsa_get_bitlen(const mbedtls_rsa_context *ctx)

This function retrieves the length of the RSA modulus in bits.

Parameters:: ctx – The initialized RSA context.
Returns:: The length of the RSA modulus in bits.

size_t mbedtls_rsa_get_len(const mbedtls_rsa_context *ctx)

This function retrieves the length of RSA modulus in Bytes.

Parameters:: ctx – The initialized RSA context.
Returns:: The length of the RSA modulus in Bytes.

int mbedtls_rsa_gen_key(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, unsigned int nbits, int exponent)

This function generates an RSA keypair.

Note

mbedtls_rsa_init() must be called before this function, to set up the RSA context.

Parameters:

ctx – The initialized RSA context used to hold the key.
f_rng – The RNG function to be used for key generation. This is mandatory and must not be NULL.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context.
nbits – The size of the public key in bits.
exponent – The public exponent to use. For example, 65537. This must be odd and greater than 1.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_check_pubkey(const mbedtls_rsa_context *ctx)

This function checks if a context contains at least an RSA public key.

If the function runs successfully, it is guaranteed that enough information is present to perform an RSA public key operation using mbedtls_rsa_public().

Parameters:: ctx – The initialized RSA context to check.
Returns:: 0 on success.
Returns:: An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_check_privkey(const mbedtls_rsa_context *ctx)

This function checks if a context contains an RSA private key and perform basic consistency checks.

Note

The consistency checks performed by this function not only ensure that mbedtls_rsa_private() can be called successfully on the given context, but that the various parameters are mutually consistent with high probability, in the sense that mbedtls_rsa_public() and mbedtls_rsa_private() are inverses.

Warning

This function should catch accidental misconfigurations like swapping of parameters, but it cannot establish full trust in neither the quality nor the consistency of the key material that was used to setup the given RSA context:

Consistency: Imported parameters that are irrelevant for the implementation might be silently dropped. If dropped, the current function does not have access to them, and therefore cannot check them. See mbedtls_rsa_complete(). If you want to check the consistency of the entire content of a PKCS1-encoded RSA private key, for example, you should use mbedtls_rsa_validate_params() before setting up the RSA context. Additionally, if the implementation performs empirical checks, these checks substantiate but do not guarantee consistency.
Quality: This function is not expected to perform extended quality assessments like checking that the prime factors are safe. Additionally, it is the responsibility of the user to ensure the trustworthiness of the source of his RSA parameters, which goes beyond what is effectively checkable by the library.

Parameters:: ctx – The initialized RSA context to check.
Returns:: 0 on success.
Returns:: An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_check_pub_priv(const mbedtls_rsa_context *pub, const mbedtls_rsa_context *prv)

This function checks a public-private RSA key pair.

            It checks each of the contexts, and makes sure they match.

Parameters:

pub – The initialized RSA context holding the public key.
prv – The initialized RSA context holding the private key.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_public(mbedtls_rsa_context *ctx, const unsigned char *input, unsigned char *output)

This function performs an RSA public key operation.

Note

This function does not handle message padding.

Note

Make sure to set input[0] = 0 or ensure that input is smaller than N.

Parameters:

ctx – The initialized RSA context to use.
input – The input buffer. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.
output – The output buffer. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_private(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, const unsigned char *input, unsigned char *output)

This function performs an RSA private key operation.

Note

Blinding is used if and only if a PRNG is provided.

Note

If blinding is used, both the base of exponentiation and the exponent are blinded, providing protection against some side-channel attacks.

Warning

It is deprecated and a security risk to not provide a PRNG here and thereby prevent the use of blinding. Future versions of the library may enforce the presence of a PRNG.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function, used for blinding. It is mandatory.
p_rng – The RNG context to pass to f_rng. This may be NULL if f_rng doesn’t need a context.
input – The input buffer. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.
output – The output buffer. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_pkcs1_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, size_t ilen, const unsigned char *input, unsigned char *output)

This function adds the message padding, then performs an RSA operation.

It is the generic wrapper for performing a PKCS#1 encryption operation.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG to use. It is used for padding generation and it is mandatory.
p_rng – The RNG context to be passed to f_rng. May be NULL if f_rng doesn’t need a context argument.
ilen – The length of the plaintext in Bytes.
input – The input data to encrypt. This must be a readable buffer of size ilen Bytes. It may be NULL if ilen == 0.
output – The output buffer. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsaes_pkcs1_v15_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, size_t ilen, const unsigned char *input, unsigned char *output)

This function performs a PKCS#1 v1.5 encryption operation (RSAES-PKCS1-v1_5-ENCRYPT).

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function to use. It is mandatory and used for padding generation.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
ilen – The length of the plaintext in Bytes.
input – The input data to encrypt. This must be a readable buffer of size ilen Bytes. It may be NULL if ilen == 0.
output – The output buffer. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsaes_oaep_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, const unsigned char *label, size_t label_len, size_t ilen, const unsigned char *input, unsigned char *output)

This function performs a PKCS#1 v2.1 OAEP encryption operation (RSAES-OAEP-ENCRYPT).

Note

The output buffer must be as large as the size of ctx->N. For example, 128 Bytes if RSA-1024 is used.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function to use. This is needed for padding generation and is mandatory.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
label – The buffer holding the custom label to use. This must be a readable buffer of length label_len Bytes. It may be NULL if label_len is 0.
label_len – The length of the label in Bytes.
ilen – The length of the plaintext buffer input in Bytes.
input – The input data to encrypt. This must be a readable buffer of size ilen Bytes. It may be NULL if ilen == 0.
output – The output buffer. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_pkcs1_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len)

This function performs an RSA operation, then removes the message padding.

It is the generic wrapper for performing a PKCS#1 decryption operation.

Note

The output buffer length output_max_len should be as large as the size ctx->len of ctx->N (for example, 128 Bytes if RSA-1024 is used) to be able to hold an arbitrary decrypted message. If it is not large enough to hold the decryption of the particular ciphertext provided, the function returns MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE.

Warning

When ctx->padding is set to MBEDTLS_RSA_PKCS_V15, mbedtls_rsa_rsaes_pkcs1_v15_decrypt() is called, which is an inherently dangerous function (CWE-242).

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. This is used for blinding and is mandatory; see mbedtls_rsa_private() for more.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context.
olen – The address at which to store the length of the plaintext. This must not be NULL.
input – The ciphertext buffer. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.
output – The buffer used to hold the plaintext. This must be a writable buffer of length output_max_len Bytes.
output_max_len – The length in Bytes of the output buffer output.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsaes_pkcs1_v15_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len)

This function performs a PKCS#1 v1.5 decryption operation (RSAES-PKCS1-v1_5-DECRYPT).

Note

The output buffer length output_max_len should be as large as the size ctx->len of ctx->N, for example, 128 Bytes if RSA-1024 is used, to be able to hold an arbitrary decrypted message. If it is not large enough to hold the decryption of the particular ciphertext provided, the function returns MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE.

Warning

This is an inherently dangerous function (CWE-242). Unless it is used in a side channel free and safe way (eg. implementing the TLS protocol as per 7.4.7.1 of RFC 5246), the calling code is vulnerable.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. This is used for blinding and is mandatory; see mbedtls_rsa_private() for more.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context.
olen – The address at which to store the length of the plaintext. This must not be NULL.
input – The ciphertext buffer. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.
output – The buffer used to hold the plaintext. This must be a writable buffer of length output_max_len Bytes.
output_max_len – The length in Bytes of the output buffer output.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsaes_oaep_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, const unsigned char *label, size_t label_len, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len)

This function performs a PKCS#1 v2.1 OAEP decryption operation (RSAES-OAEP-DECRYPT).

Note

The output buffer length output_max_len should be as large as the size ctx->len of ctx->N, for example, 128 Bytes if RSA-1024 is used, to be able to hold an arbitrary decrypted message. If it is not large enough to hold the decryption of the particular ciphertext provided, the function returns MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. This is used for blinding and is mandatory.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context.
label – The buffer holding the custom label to use. This must be a readable buffer of length label_len Bytes. It may be NULL if label_len is 0.
label_len – The length of the label in Bytes.
olen – The address at which to store the length of the plaintext. This must not be NULL.
input – The ciphertext buffer. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.
output – The buffer used to hold the plaintext. This must be a writable buffer of length output_max_len Bytes.
output_max_len – The length in Bytes of the output buffer output.

Returns:

0 on success.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_pkcs1_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig)

This function performs a private RSA operation to sign a message digest using PKCS#1.

It is the generic wrapper for performing a PKCS#1 signature.

Note

The sig buffer must be as large as the size of ctx->N. For example, 128 Bytes if RSA-1024 is used.

Note

For PKCS#1 v2.1 encoding, see comments on mbedtls_rsa_rsassa_pss_sign() for details on md_alg and hash_id.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function to use. This is mandatory and must not be NULL.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer to hold the signature. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus. A buffer length of MBEDTLS_MPI_MAX_SIZE is always safe.

Returns:

0 if the signing operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pkcs1_v15_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig)

This function performs a PKCS#1 v1.5 signature operation (RSASSA-PKCS1-v1_5-SIGN).

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. This is used for blinding and is mandatory; see mbedtls_rsa_private() for more.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer to hold the signature. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus. A buffer length of MBEDTLS_MPI_MAX_SIZE is always safe.

Returns:

0 if the signing operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pss_sign_ext(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, int saltlen, unsigned char *sig)

This function performs a PKCS#1 v2.1 PSS signature operation (RSASSA-PSS-SIGN).

Note

The hash_id set in ctx by calling mbedtls_rsa_set_padding() selects the hash used for the encoding operation and for the mask generation function (MGF1). For more details on the encoding operation and the mask generation function, consult RFC-3447: Public-Key Cryptography Standards (PKCS) #1 v2.1: RSA Cryptography Specifications.

Note

This function enforces that the provided salt length complies with FIPS 186-4 §5.5 (e) and RFC 8017 (PKCS#1 v2.2) §9.1.1 step 3. The constraint is that the hash length plus the salt length plus 2 bytes must be at most the key length. If this constraint is not met, this function returns MBEDTLS_ERR_RSA_BAD_INPUT_DATA.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. It is mandatory and must not be NULL.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
saltlen – The length of the salt that should be used. If passed MBEDTLS_RSA_SALT_LEN_ANY, the function will use the largest possible salt length up to the hash length, which is the largest permitted by some standards including FIPS 186-4 §5.5.
sig – The buffer to hold the signature. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus. A buffer length of MBEDTLS_MPI_MAX_SIZE is always safe.

Returns:

0 if the signing operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pss_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void*, unsigned char*, size_t), void *p_rng, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig)

This function performs a PKCS#1 v2.1 PSS signature operation (RSASSA-PSS-SIGN).

Note

The hash_id set in ctx by calling mbedtls_rsa_set_padding() selects the hash used for the encoding operation and for the mask generation function (MGF1). For more details on the encoding operation and the mask generation function, consult RFC-3447: Public-Key Cryptography Standards (PKCS) #1 v2.1: RSA Cryptography Specifications.

Note

This function always uses the maximum possible salt size, up to the length of the payload hash. This choice of salt size complies with FIPS 186-4 §5.5 (e) and RFC 8017 (PKCS#1 v2.2) §9.1.1 step 3. Furthermore this function enforces a minimum salt size which is the hash size minus 2 bytes. If this minimum size is too large given the key size (the salt size, plus the hash size, plus 2 bytes must be no more than the key size in bytes), this function returns MBEDTLS_ERR_RSA_BAD_INPUT_DATA.

Parameters:

ctx – The initialized RSA context to use.
f_rng – The RNG function. It is mandatory and must not be NULL.
p_rng – The RNG context to be passed to f_rng. This may be NULL if f_rng doesn’t need a context argument.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer to hold the signature. This must be a writable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus. A buffer length of MBEDTLS_MPI_MAX_SIZE is always safe.

Returns:

0 if the signing operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_pkcs1_verify(mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig)

This function performs a public RSA operation and checks the message digest.

This is the generic wrapper for performing a PKCS#1 verification.

Note

For PKCS#1 v2.1 encoding, see comments on mbedtls_rsa_rsassa_pss_verify() about md_alg and hash_id.

Parameters:

ctx – The initialized RSA public key context to use.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer holding the signature. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 if the verify operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pkcs1_v15_verify(mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig)

This function performs a PKCS#1 v1.5 verification operation (RSASSA-PKCS1-v1_5-VERIFY).

Parameters:

ctx – The initialized RSA public key context to use.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer holding the signature. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 if the verify operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pss_verify(mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig)

This function performs a PKCS#1 v2.1 PSS verification operation (RSASSA-PSS-VERIFY).

Note

The hash_id set in ctx by calling mbedtls_rsa_set_padding() selects the hash used for the encoding operation and for the mask generation function (MGF1). For more details on the encoding operation and the mask generation function, consult RFC-3447: Public-Key Cryptography Standards (PKCS) #1 v2.1: RSA Cryptography Specifications. If the hash_id set in ctx by mbedtls_rsa_set_padding() is MBEDTLS_MD_NONE, the md_alg parameter is used.

Parameters:

ctx – The initialized RSA public key context to use.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
sig – The buffer holding the signature. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 if the verify operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_rsassa_pss_verify_ext(mbedtls_rsa_context *ctx, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, mbedtls_md_type_t mgf1_hash_id, int expected_salt_len, const unsigned char *sig)

This function performs a PKCS#1 v2.1 PSS verification operation (RSASSA-PSS-VERIFY).

Note

The sig buffer must be as large as the size of ctx->N. For example, 128 Bytes if RSA-1024 is used.

Note

The hash_id set in ctx by mbedtls_rsa_set_padding() is ignored.

Parameters:

ctx – The initialized RSA public key context to use.
md_alg – The message-digest algorithm used to hash the original data. Use MBEDTLS_MD_NONE for signing raw data.
hashlen – The length of the message digest or raw data in Bytes. If md_alg is not MBEDTLS_MD_NONE, this must match the output length of the corresponding hash algorithm.
hash – The buffer holding the message digest or raw data. This must be a readable buffer of at least hashlen Bytes.
mgf1_hash_id – The message digest algorithm used for the verification operation and the mask generation function (MGF1). For more details on the encoding operation and the mask generation function, consult RFC-3447: Public-Key Cryptography Standards (PKCS) #1 v2.1: RSA Cryptography Specifications.
expected_salt_len – The length of the salt used in padding. Use MBEDTLS_RSA_SALT_LEN_ANY to accept any salt length.
sig – The buffer holding the signature. This must be a readable buffer of length ctx->len Bytes. For example, 256 Bytes for an 2048-bit RSA modulus.

Returns:

0 if the verify operation was successful.

Returns:

An MBEDTLS_ERR_RSA_XXX error code on failure.

int mbedtls_rsa_copy(mbedtls_rsa_context *dst, const mbedtls_rsa_context *src)

This function copies the components of an RSA context.

Parameters:

dst – The destination context. This must be initialized.
src – The source context. This must be initialized.

Returns:

0 on success.

Returns:

MBEDTLS_ERR_MPI_ALLOC_FAILED on memory allocation failure.

void mbedtls_rsa_free(mbedtls_rsa_context *ctx)

This function frees the components of an RSA key.

Parameters:: ctx – The RSA context to free. May be NULL, in which case this function is a no-op. If it is not NULL, it must point to an initialized RSA context.

int mbedtls_rsa_self_test(int verbose)

The RSA checkup routine.

Returns:: 0 on success.
Returns:: 1 on failure.

struct mbedtls_rsa_context

#include <rsa.h>

The RSA context structure.

Public Members

int private_ver: Reserved for internal purposes. Do not set this field in application code. Its meaning might change without notice.

size_t private_len: The size of N in Bytes.

mbedtls_mpi private_N: The public modulus.

mbedtls_mpi private_E: The public exponent.

mbedtls_mpi private_D: The private exponent.

mbedtls_mpi private_P: The first prime factor.

mbedtls_mpi private_Q: The second prime factor.

mbedtls_mpi private_DP: D % (P - 1).

mbedtls_mpi private_DQ: D % (Q - 1).

mbedtls_mpi private_QP: 1 / (Q % P).

mbedtls_mpi private_RN: cached R^2 mod N.

mbedtls_mpi private_RP: cached R^2 mod P.

mbedtls_mpi private_RQ: cached R^2 mod Q.

mbedtls_mpi private_Vi: The cached blinding value.

mbedtls_mpi private_Vf: The cached un-blinding value.

int private_padding: Selects padding mode: MBEDTLS_RSA_PKCS_V15 for 1.5 padding and MBEDTLS_RSA_PKCS_V21 for OAEP or PSS.

int private_hash_id: Hash identifier of mbedtls_md_type_t type, as specified in md.h for use in the MGF mask generating function used in the EME-OAEP and EMSA-PSS encodings.

mbedtls_threading_mutex_t private_mutex: Thread-safety mutex.