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@@ -677,6 +677,32 @@ int mbedtls_pk_parse_subpubkey( unsigned char **p, const unsigned char *end,
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}
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}
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#if defined(MBEDTLS_RSA_C)
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#if defined(MBEDTLS_RSA_C)
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+/*
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+ * Wrapper around mbedtls_asn1_get_mpi() that rejects zero.
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+ *
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+ * The value zero is:
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+ * - never a valid value for an RSA parameter
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+ * - interpreted as "omitted, please reconstruct" by mbedtls_rsa_complete().
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+ *
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+ * Since values can't be omitted in PKCS#1, passing a zero value to
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+ * rsa_complete() would be incorrect, so reject zero values early.
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+ */
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+static int asn1_get_nonzero_mpi( unsigned char **p,
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+ const unsigned char *end,
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+ mbedtls_mpi *X )
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+{
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+ int ret;
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+
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+ ret = mbedtls_asn1_get_mpi( p, end, X );
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+ if( ret != 0 )
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+ return( ret );
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+
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+ if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
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+ return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
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+
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+ return( 0 );
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+}
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+
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/*
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/*
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* Parse a PKCS#1 encoded private RSA key
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* Parse a PKCS#1 encoded private RSA key
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*/
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*/
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@@ -729,54 +755,84 @@ static int pk_parse_key_pkcs1_der( mbedtls_rsa_context *rsa,
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}
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}
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/* Import N */
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/* Import N */
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- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
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- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
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- ( ret = mbedtls_rsa_import_raw( rsa, p, len, NULL, 0, NULL, 0,
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- NULL, 0, NULL, 0 ) ) != 0 )
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_rsa_import( rsa, &T, NULL, NULL,
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+ NULL, NULL ) ) != 0 )
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goto cleanup;
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goto cleanup;
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- p += len;
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/* Import E */
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/* Import E */
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- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
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- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
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- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
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- NULL, 0, p, len ) ) != 0 )
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
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+ NULL, &T ) ) != 0 )
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goto cleanup;
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goto cleanup;
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- p += len;
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/* Import D */
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/* Import D */
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- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
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- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
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- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
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- p, len, NULL, 0 ) ) != 0 )
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
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+ &T, NULL ) ) != 0 )
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goto cleanup;
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goto cleanup;
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- p += len;
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/* Import P */
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/* Import P */
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- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
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- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
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- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, p, len, NULL, 0,
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- NULL, 0, NULL, 0 ) ) != 0 )
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_rsa_import( rsa, NULL, &T, NULL,
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+ NULL, NULL ) ) != 0 )
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goto cleanup;
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goto cleanup;
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- p += len;
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/* Import Q */
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/* Import Q */
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- if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
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- MBEDTLS_ASN1_INTEGER ) ) != 0 ||
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- ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, p, len,
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- NULL, 0, NULL, 0 ) ) != 0 )
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_rsa_import( rsa, NULL, NULL, &T,
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+ NULL, NULL ) ) != 0 )
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goto cleanup;
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goto cleanup;
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- p += len;
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- /* Complete the RSA private key */
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- if( ( ret = mbedtls_rsa_complete( rsa ) ) != 0 )
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- goto cleanup;
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+#if !defined(MBEDTLS_RSA_NO_CRT) && !defined(MBEDTLS_RSA_ALT)
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+ /*
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+ * The RSA CRT parameters DP, DQ and QP are nominally redundant, in
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+ * that they can be easily recomputed from D, P and Q. However by
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+ * parsing them from the PKCS1 structure it is possible to avoid
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+ * recalculating them which both reduces the overhead of loading
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+ * RSA private keys into memory and also avoids side channels which
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+ * can arise when computing those values, since all of D, P, and Q
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+ * are secret. See https://eprint.iacr.org/2020/055 for a
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+ * description of one such attack.
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+ */
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+
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+ /* Import DP */
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_mpi_copy( &rsa->DP, &T ) ) != 0 )
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+ goto cleanup;
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+
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+ /* Import DQ */
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_mpi_copy( &rsa->DQ, &T ) ) != 0 )
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+ goto cleanup;
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+
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+ /* Import QP */
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = mbedtls_mpi_copy( &rsa->QP, &T ) ) != 0 )
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+ goto cleanup;
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+
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+#else
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+ /* Verify existance of the CRT params */
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+ if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
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+ ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 )
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+ goto cleanup;
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+#endif
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- /* Check optional parameters */
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- if( ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
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- ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
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- ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 )
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+ /* rsa_complete() doesn't complete anything with the default
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+ * implementation but is still called:
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+ * - for the benefit of alternative implementation that may want to
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+ * pre-compute stuff beyond what's provided (eg Montgomery factors)
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+ * - as is also sanity-checks the key
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+ *
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+ * Furthermore, we also check the public part for consistency with
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+ * mbedtls_pk_parse_pubkey(), as it includes size minima for example.
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+ */
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+ if( ( ret = mbedtls_rsa_complete( rsa ) ) != 0 ||
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+ ( ret = mbedtls_rsa_check_pubkey( rsa ) ) != 0 )
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+ {
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goto cleanup;
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goto cleanup;
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+ }
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if( p != end )
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if( p != end )
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{
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{
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