Adding TLS 1.2 Support to Your TLS Library - Implementing SSL/TLS Using Cryptography and PKI - page 488

1.2 to include a list of supported signature and hash algorithms. The enumera-
tions from Listing 9-9 are reused here. To properly parse the certifi cate request,
modify the parse_certificate_request routine from Listing 8-29 as shown
in Listing 9-11:
Listing 9-11: “tls.c” parse_certifi cate_request with TLS 1.2 support
#define MAX_CERTIFICATE_TYPES 4
typedef enum
{
rsa_signed = 1,
dss_signed = 2,
rsa_fixed_dh = 3,
dss_fixed_dh = 4
}
certificate_type;
#define MAX_SIGNATURE_ALGORITHMS 28
typedef struct
{
HashAlgorithm hash;
SignatureAlgorithm signature;
}
SignatureAndHashAlgorithm;
typedef struct
{
unsigned char certificate_types_count;
certificate_type supported_certificate_types[ MAX_CERTIFICATE_TYPES ];
unsigned char signature_algorithms_length;
SignatureAndHashAlgorithm
supported_signature_algorithms[ MAX_SIGNATURE_ALGORITHMS ];
}
CertificateRequest;
static unsigned char *parse_certificate_request( unsigned char *read_pos,
TLSParameters *parameters )
{
…
read_pos = read_buffer(
( void * ) &request.supported_certificate_types[ i ], read_pos, 1 );
}
read_pos = read_buffer( &request.signature_algorithms_length, read_pos, 2 );
for ( i = 0; i < request.signature_algorithms_length; i++ )
{
read_pos = read_buffer( ( void * )
&request.supported_signature_algorithms[ i ].hash, read_pos, 1 );