asn1.c File Reference

ASN.1 encoding. More...

#include <stdint.h>
#include <stddef.h>
#include <errno.h>
#include <gpxe/asn1.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER)
static int	asn1_start (struct asn1_cursor *cursor, unsigned int type)
	Start parsing ASN.1 object.
int	asn1_enter (struct asn1_cursor *cursor, unsigned int type)
	Enter ASN.1 object.
int	asn1_skip (struct asn1_cursor *cursor, unsigned int type)
	Skip ASN.1 object.

---

Detailed Description

ASN.1 encoding.

Definition in file asn1.c.

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

static int asn1_start	(	struct asn1_cursor *	cursor,
		unsigned int	type
	)			[static]

Start parsing ASN.1 object.

Parameters:

	cursor	ASN.1 object cursor
	type	Expected type

Return values:

len

Length of object body, or negative error

The object cursor will be updated to point to the start of the object body (i.e. the first byte following the length byte(s)), and the length of the object body (i.e. the number of bytes until the following object tag, if any) is returned.

If any error occurs (i.e. if the object is not of the expected type, or if we overflow beyond the end of the ASN.1 object), then the cursor will be invalidated and a negative value will be returned.

Definition at line 49 of file asn1.c.

References asn1_cursor::data, DBGC, EINVAL, ENXIO, asn1_cursor::len, and NULL.

Referenced by asn1_enter(), and asn1_skip().

                                                   {
        unsigned int len_len;
        unsigned int len;
        int rc;

        /* Sanity check */
        if ( cursor->len < 2 /* Tag byte and first length byte */ ) {
                if ( cursor->len )
                        DBGC ( cursor, "ASN1 %p too short\n", cursor );
                rc = -EINVAL;
                goto notfound;
        }

        /* Check the tag byte */
        if ( *( ( uint8_t * ) cursor->data ) != type ) {
                DBGC ( cursor, "ASN1 %p type mismatch (expected %d, got %d)\n",
                       cursor, type, *( ( uint8_t * ) cursor->data ) );
                rc = -ENXIO;
                goto notfound;
        }
        cursor->data++;
        cursor->len--;

        /* Extract length of the length field and sanity check */
        len_len = *( ( uint8_t * ) cursor->data );
        if ( len_len & 0x80 ) {
                len_len = ( len_len & 0x7f );
                cursor->data++;
                cursor->len--;
        } else {
                len_len = 1;
        }
        if ( cursor->len < len_len ) {
                DBGC ( cursor, "ASN1 %p bad length field length %d (max "
                       "%zd)\n", cursor, len_len, cursor->len );
                rc = -EINVAL;
                goto notfound;
        }

        /* Extract the length and sanity check */
        for ( len = 0 ; len_len ; len_len-- ) {
                len <<= 8;
                len |= *( ( uint8_t * ) cursor->data );
                cursor->data++;
                cursor->len--;
        }
        if ( cursor->len < len ) {
                DBGC ( cursor, "ASN1 %p bad length %d (max %zd)\n",
                       cursor, len, cursor->len );
                rc = -EINVAL;
                goto notfound;
        }

        return len;

 notfound:
        cursor->data = NULL;
        cursor->len = 0;
        return rc;
}

int asn1_enter	(	struct asn1_cursor *	cursor,
		unsigned int	type
	)

Enter ASN.1 object.

Parameters:

	cursor	ASN.1 object cursor
	type	Expected type

Return values:

rc

Return status code

The object cursor will be updated to point to the body of the current ASN.1 object. If any error occurs, the object cursor will be invalidated.

Definition at line 122 of file asn1.c.

References asn1_start(), DBGC, and asn1_cursor::len.

Referenced by x509_public_key(), and x509_rsa_public_key().

                                                                 {
        int len;

        len = asn1_start ( cursor, type );
        if ( len < 0 )
                return len;

        cursor->len = len;
        DBGC ( cursor, "ASN1 %p entered object type %02x (len %x)\n",
               cursor, type, len );

        return 0;
}

int asn1_skip	(	struct asn1_cursor *	cursor,
		unsigned int	type
	)

Skip ASN.1 object.

Parameters:

	cursor	ASN.1 object cursor
	type	Expected type

Return values:

rc

Return status code

The object cursor will be updated to point to the next ASN.1 object. If any error occurs, the object cursor will be invalidated.

Definition at line 147 of file asn1.c.

References asn1_start(), asn1_cursor::data, DBGC, ENOENT, asn1_cursor::len, and NULL.

Referenced by x509_public_key(), and x509_rsa_public_key().

                                                                {
        int len;

        len = asn1_start ( cursor, type );
        if ( len < 0 )
                return len;

        cursor->data += len;
        cursor->len -= len;
        DBGC ( cursor, "ASN1 %p skipped object type %02x (len %x)\n",
               cursor, type, len );

        if ( ! cursor->len ) {
                DBGC ( cursor, "ASN1 %p reached end of object\n", cursor );
                cursor->data = NULL;
                return -ENOENT;
        }

        return 0;
}