• David Howells's avatar
    X.509: Add an ASN.1 decoder · 42d5ec27
    David Howells authored
    Add an ASN.1 BER/DER/CER decoder.  This uses the bytecode from the ASN.1
    compiler in the previous patch to inform it as to what to expect to find in the
    encoded byte stream.  The output from the compiler also tells it what functions
    to call on what tags, thus allowing the caller to retrieve information.
    
    The decoder is called as follows:
    
    	int asn1_decoder(const struct asn1_decoder *decoder,
    			 void *context,
    			 const unsigned char *data,
    			 size_t datalen);
    
    The decoder argument points to the bytecode from the ASN.1 compiler.  context
    is the caller's context and is passed to the action functions.  data and
    datalen define the byte stream to be decoded.
    
    Note that the decoder is currently limited to datalen being less than 64K.
    This reduces the amount of stack space used by the decoder because ASN.1 is a
    nested construct.  Similarly, the decoder is limited to a maximum of 10 levels
    of constructed data outside of a leaf node also in an effort to keep stack
    usage down.
    
    These restrictions can be raised if necessary.
    Signed-off-by: 's avatarDavid Howells <dhowells@redhat.com>
    Signed-off-by: 's avatarRusty Russell <rusty@rustcorp.com.au>
    42d5ec27
asn1_decoder.c 12.1 KB