rsa.c

Purpose

OpenSSL-backed RSA utilities. Present only when _XUTILS_USE_SSL is enabled.

API Reference

int XRSA_HaveSSL(void)

• Does:
  • reports whether RSA/SSL support is built in.
• Returns:
  • non-zero when SSL-backed RSA is available.
  • 0 otherwise.

Context Lifecycle

void XRSA_Init(xrsa_ctx_t *pCtx)

• Arguments:
  • pCtx: destination RSA context.
• Does:
  • zeroes the context and sets default padding to RSA_PKCS1_PADDING.
• Returns:
  • no return value.

void XRSA_Destroy(xrsa_ctx_t *pCtx)

• Arguments:
  • pCtx: context to clean.
• Does:
  • frees loaded/generated keys, stored PEM strings and last error string.
• Returns:
  • no return value.

char *XSSL_LastErrors(size_t *pOutLen)

• Arguments:
  • pOutLen: optional output length pointer.
• Does:
  • collects OpenSSL error text into a newly allocated string.
• Returns:
  • allocated string or NULL.

Key Loading / Generation

XSTATUS XRSA_GenerateKeys(xrsa_ctx_t *pCtx, size_t nKeyLength, size_t nPubKeyExp)

• Arguments:
  • pCtx: destination context.
  • nKeyLength: RSA modulus size in bits.
  • nPubKeyExp: public exponent.
• Does:
  • generates a keypair and stores PEM private/public strings and parsed keys in the context.
• Returns:
  • XSTDOK on success, XSTDERR on failure.

XSTATUS XRSA_LoadKeyFiles(xrsa_ctx_t *pCtx, const char *pPrivPath, const char *pPubPath)

XSTATUS XRSA_LoadPrivKeyFile(xrsa_ctx_t *pCtx, const char *pPath)

XSTATUS XRSA_LoadPubKeyFile(xrsa_ctx_t *pCtx, const char *pPath)

• Arguments:
  • context plus PEM file path(s).
• Does:
  • reads PEM text via XPath_Load() and loads parsed key objects.
• Returns:
  • XSTDOK or XSTDERR.

XSTATUS XRSA_LoadPrivKey(xrsa_ctx_t *pCtx)

XSTATUS XRSA_LoadPubKey(xrsa_ctx_t *pCtx)

• Arguments:
  • context whose PEM text fields are already filled.
• Does:
  • parses PEM text already stored in the context.
• Returns:
  • XSTDOK or XSTDERR.

XSTATUS XRSA_SetPubKey(xrsa_ctx_t *pCtx, const char *pPubKey, size_t nLength)

XSTATUS XRSA_SetPrivKey(xrsa_ctx_t *pCtx, const char *pPrivKey, size_t nLength)

• Arguments:
  • context, PEM text pointer and PEM length.
• Does:
  • copies PEM text into context-owned memory and immediately loads it.
• Returns:
  • XSTDOK or XSTDERR.

RSA Operations

uint8_t *XRSA_Crypt(xrsa_ctx_t *pCtx, const uint8_t *pData, size_t nLength, size_t *pOutLength)

• Does:
  • encrypts with public key.
• Returns:
  • allocated ciphertext or NULL.

uint8_t *XRSA_Decrypt(xrsa_ctx_t *pCtx, const uint8_t *pData, size_t nLength, size_t *pOutLength)

• Does:
  • decrypts with private key.
• Returns:
  • allocated plaintext or NULL.

uint8_t *XRSA_PrivCrypt(xrsa_ctx_t *pCtx, const uint8_t *pData, size_t nLength, size_t *pOutLength)

• Does:
  • private-key RSA operation used for signature-style flows.
• Returns:
  • allocated output or NULL.

uint8_t *XRSA_PubDecrypt(xrsa_ctx_t *pCtx, const uint8_t *pData, size_t nLength, size_t *pOutLength)

• Does:
  • inverse public-key decrypt for private-key-encrypted data.
• Returns:
  • allocated output or NULL.

One-Shot Wrappers

uint8_t *XCrypt_RSA(...)

uint8_t *XCrypt_PrivRSA(...)

uint8_t *XDecrypt_RSA(...)

uint8_t *XDecrypt_PubRSA(...)

• Arguments:
  • input bytes, input length, PEM text pointer, PEM length, output length pointer.
• Does:
  • creates a temporary RSA context and performs one encrypt/decrypt operation.
• Returns:
  • allocated output or NULL.

RS256 Helpers

uint8_t *XCrypt_RS256(const uint8_t *pInput, size_t nLength, const char *pPrivKey, size_t nKeyLen, size_t *pOutLen)

• Does:
  • computes SHA-256 of input.
  • prepends ASN.1 DigestInfo padding.
  • applies private-key RSA operation.
• Returns:
  • allocated signature bytes or NULL.

XSTATUS XCrypt_VerifyRS256(const uint8_t *pSignature, size_t nSignatureLen, const uint8_t *pData, size_t nLength, const char *pPubKey, size_t nKeyLen)

• Does:
  • decrypts signature with public key.
  • rebuilds local padded SHA-256 digest.
  • byte-compares the two.
• Returns:
  • XSTDOK on match.
  • XSTDNON/XSTDERR on mismatch or failure.