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[crypto] Construct asymmetric ciphered data using ASN.1 builders

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Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-12-02 13:12:25 +00:00
parent d4258272c6
commit 1ccc320ee9
7 changed files with 156 additions and 129 deletions
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src/crypto/rsa.c
+38 -27
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@@ -338,12 +338,12 @@ static void rsa_cipher ( struct rsa_context *context,
*
* @v key Key
* @v plaintext Plaintext
* @v plaintext_len Length of plaintext
* @v ciphertext Ciphertext
* @ret ciphertext_len Length of ciphertext, or negative error
*/
static int rsa_encrypt ( const struct asn1_cursor *key, const void *plaintext,
size_t plaintext_len, void *ciphertext ) {
static int rsa_encrypt ( const struct asn1_cursor *key,
const struct asn1_cursor *plaintext,
struct asn1_builder *ciphertext ) {
struct rsa_context context;
void *temp;
uint8_t *encoded;
@@ -352,7 +352,7 @@ static int rsa_encrypt ( const struct asn1_cursor *key, const void *plaintext,
int rc;
DBGC ( &context, "RSA %p encrypting:\n", &context );
DBGC_HDA ( &context, 0, plaintext, plaintext_len );
DBGC_HDA ( &context, 0, plaintext->data, plaintext->len );
/* Initialise context */
if ( ( rc = rsa_init ( &context, key ) ) != 0 )
@@ -360,12 +360,12 @@ static int rsa_encrypt ( const struct asn1_cursor *key, const void *plaintext,
/* Calculate lengths */
max_len = ( context.max_len - 11 );
random_nz_len = ( max_len - plaintext_len + 8 );
random_nz_len = ( max_len - plaintext->len + 8 );
/* Sanity check */
if ( plaintext_len > max_len ) {
if ( plaintext->len > max_len ) {
DBGC ( &context, "RSA %p plaintext too long (%zd bytes, max "
"%zd)\n", &context, plaintext_len, max_len );
"%zd)\n", &context, plaintext->len, max_len );
rc = -ERANGE;
goto err_sanity;
}
@@ -383,19 +383,24 @@ static int rsa_encrypt ( const struct asn1_cursor *key, const void *plaintext,
goto err_random;
}
encoded[ 2 + random_nz_len ] = 0x00;
memcpy ( &encoded[ context.max_len - plaintext_len ],
plaintext, plaintext_len );
memcpy ( &encoded[ context.max_len - plaintext->len ],
plaintext->data, plaintext->len );
/* Create space for ciphertext */
if ( ( rc = asn1_grow ( ciphertext, context.max_len ) ) != 0 )
goto err_grow;
/* Encipher the encoded message */
rsa_cipher ( &context, encoded, ciphertext );
rsa_cipher ( &context, encoded, ciphertext->data );
DBGC ( &context, "RSA %p encrypted:\n", &context );
DBGC_HDA ( &context, 0, ciphertext, context.max_len );
DBGC_HDA ( &context, 0, ciphertext->data, context.max_len );
/* Free context */
rsa_free ( &context );
return context.max_len;
return 0;
err_grow:
err_random:
err_sanity:
rsa_free ( &context );
@@ -408,33 +413,33 @@ static int rsa_encrypt ( const struct asn1_cursor *key, const void *plaintext,
*
* @v key Key
* @v ciphertext Ciphertext
* @v ciphertext_len Ciphertext length
* @v plaintext Plaintext
* @ret plaintext_len Plaintext length, or negative error
* @ret rc Return status code
*/
static int rsa_decrypt ( const struct asn1_cursor *key, const void *ciphertext,
size_t ciphertext_len, void *plaintext ) {
static int rsa_decrypt ( const struct asn1_cursor *key,
const struct asn1_cursor *ciphertext,
struct asn1_builder *plaintext ) {
struct rsa_context context;
void *temp;
uint8_t *encoded;
uint8_t *end;
uint8_t *zero;
uint8_t *start;
size_t plaintext_len;
size_t len;
int rc;
DBGC ( &context, "RSA %p decrypting:\n", &context );
DBGC_HDA ( &context, 0, ciphertext, ciphertext_len );
DBGC_HDA ( &context, 0, ciphertext->data, ciphertext->len );
/* Initialise context */
if ( ( rc = rsa_init ( &context, key ) ) != 0 )
goto err_init;
/* Sanity check */
if ( ciphertext_len != context.max_len ) {
if ( ciphertext->len != context.max_len ) {
DBGC ( &context, "RSA %p ciphertext incorrect length (%zd "
"bytes, should be %zd)\n",
&context, ciphertext_len, context.max_len );
&context, ciphertext->len, context.max_len );
rc = -ERANGE;
goto err_sanity;
}
@@ -444,7 +449,7 @@ static int rsa_decrypt ( const struct asn1_cursor *key, const void *ciphertext,
*/
temp = context.input0;
encoded = temp;
rsa_cipher ( &context, ciphertext, encoded );
rsa_cipher ( &context, ciphertext->data, encoded );
/* Parse the message */
end = ( encoded + context.max_len );
@@ -454,25 +459,31 @@ static int rsa_decrypt ( const struct asn1_cursor *key, const void *ciphertext,
}
zero = memchr ( &encoded[2], 0, ( end - &encoded[2] ) );
if ( ! zero ) {
DBGC ( &context, "RSA %p invalid decrypted message:\n",
&context );
DBGC_HDA ( &context, 0, encoded, context.max_len );
rc = -EINVAL;
goto err_invalid;
}
start = ( zero + 1 );
plaintext_len = ( end - start );
len = ( end - start );
/* Create space for plaintext */
if ( ( rc = asn1_grow ( plaintext, len ) ) != 0 )
goto err_grow;
/* Copy out message */
memcpy ( plaintext, start, plaintext_len );
memcpy ( plaintext->data, start, len );
DBGC ( &context, "RSA %p decrypted:\n", &context );
DBGC_HDA ( &context, 0, plaintext, plaintext_len );
DBGC_HDA ( &context, 0, plaintext->data, len );
/* Free context */
rsa_free ( &context );
return plaintext_len;
return 0;
err_grow:
err_invalid:
DBGC ( &context, "RSA %p invalid decrypted message:\n", &context );
DBGC_HDA ( &context, 0, encoded, context.max_len );
err_sanity:
rsa_free ( &context );
err_init: