diff options
Diffstat (limited to 'src/der_encoder.c')
| -rw-r--r-- | src/der_encoder.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/src/der_encoder.c b/src/der_encoder.c new file mode 100644 index 0000000..6c859e1 --- /dev/null +++ b/src/der_encoder.c @@ -0,0 +1,199 @@ +/*- + * Copyright (c) 2003, 2004 Lev Walkin <vlm@lionet.info>. All rights reserved. + * Redistribution and modifications are permitted subject to BSD license. + */ +#include <asn_internal.h> +#include <errno.h> + +static ssize_t der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len, + asn_app_consume_bytes_f *cb, void *app_key, int constructed); + +/* + * The DER encoder of any type. + */ +asn_enc_rval_t +der_encode(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr, + asn_app_consume_bytes_f *consume_bytes, void *app_key) { + + ASN_DEBUG("DER encoder invoked for %s", + type_descriptor->name); + + /* + * Invoke type-specific encoder. + */ + return type_descriptor->der_encoder(type_descriptor, + struct_ptr, /* Pointer to the destination structure */ + 0, 0, + consume_bytes, app_key); +} + +/* + * Argument type and callback necessary for der_encode_to_buffer(). + */ +typedef struct enc_to_buf_arg { + void *buffer; + size_t left; +} enc_to_buf_arg; +static int encode_to_buffer_cb(const void *buffer, size_t size, void *key) { + enc_to_buf_arg *arg = (enc_to_buf_arg *)key; + + if(arg->left < size) + return -1; /* Data exceeds the available buffer size */ + + memcpy(arg->buffer, buffer, size); + arg->buffer = ((char *)arg->buffer) + size; + arg->left -= size; + + return 0; +} + +/* + * A variant of the der_encode() which encodes the data into the provided buffer + */ +asn_enc_rval_t +der_encode_to_buffer(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr, + void *buffer, size_t buffer_size) { + enc_to_buf_arg arg; + asn_enc_rval_t ec; + + arg.buffer = buffer; + arg.left = buffer_size; + + ec = type_descriptor->der_encoder(type_descriptor, + struct_ptr, /* Pointer to the destination structure */ + 0, 0, encode_to_buffer_cb, &arg); + if(ec.encoded != -1) { + assert(ec.encoded == (ssize_t)(buffer_size - arg.left)); + /* Return the encoded contents size */ + } + return ec; +} + + +/* + * Write out leading TL[v] sequence according to the type definition. + */ +ssize_t +der_write_tags(asn_TYPE_descriptor_t *sd, + size_t struct_length, + int tag_mode, int last_tag_form, + ber_tlv_tag_t tag, /* EXPLICIT or IMPLICIT tag */ + asn_app_consume_bytes_f *cb, + void *app_key) { + ber_tlv_tag_t *tags; /* Copy of tags stream */ + int tags_count; /* Number of tags */ + size_t overall_length; + ssize_t *lens; + int i; + + ASN_DEBUG("Writing tags (%s, tm=%d, tc=%d, tag=%s, mtc=%d)", + sd->name, tag_mode, sd->tags_count, + ber_tlv_tag_string(tag), + tag_mode + ?(sd->tags_count+1 + -((tag_mode == -1) && sd->tags_count)) + :sd->tags_count + ); + + if(tag_mode) { + /* + * Instead of doing shaman dance like we do in ber_check_tags(), + * allocate a small array on the stack + * and initialize it appropriately. + */ + int stag_offset; + tags = (ber_tlv_tag_t *)alloca((sd->tags_count + 1) * sizeof(ber_tlv_tag_t)); + if(!tags) { /* Can fail on !x86 */ + errno = ENOMEM; + return -1; + } + tags_count = sd->tags_count + + 1 /* EXPLICIT or IMPLICIT tag is given */ + - ((tag_mode == -1) && sd->tags_count); + /* Copy tags over */ + tags[0] = tag; + stag_offset = -1 + ((tag_mode == -1) && sd->tags_count); + for(i = 1; i < tags_count; i++) + tags[i] = sd->tags[i + stag_offset]; + } else { + tags = sd->tags; + tags_count = sd->tags_count; + } + + /* No tags to write */ + if(tags_count == 0) + return 0; + + lens = (ssize_t *)alloca(tags_count * sizeof(lens[0])); + if(!lens) { + errno = ENOMEM; + return -1; + } + + /* + * Array of tags is initialized. + * Now, compute the size of the TLV pairs, from right to left. + */ + overall_length = struct_length; + for(i = tags_count - 1; i >= 0; --i) { + lens[i] = der_write_TL(tags[i], overall_length, 0, 0, 0); + if(lens[i] == -1) return -1; + overall_length += lens[i]; + lens[i] = overall_length - lens[i]; + } + + if(!cb) return overall_length - struct_length; + + ASN_DEBUG("%s %s TL sequence (%d elements)", + cb?"Encoding":"Estimating", sd->name, tags_count); + + /* + * Encode the TL sequence for real. + */ + for(i = 0; i < tags_count; i++) { + ssize_t len; + int _constr; + + /* Check if this tag happens to be constructed */ + _constr = (last_tag_form || i < (tags_count - 1)); + + len = der_write_TL(tags[i], lens[i], cb, app_key, _constr); + if(len == -1) return -1; + } + + return overall_length - struct_length; +} + +static ssize_t +der_write_TL(ber_tlv_tag_t tag, ber_tlv_len_t len, + asn_app_consume_bytes_f *cb, void *app_key, + int constructed) { + uint8_t buf[32]; + size_t size = 0; + int buf_size = cb?sizeof(buf):0; + ssize_t tmp; + + /* Serialize tag (T from TLV) into possibly zero-length buffer */ + tmp = ber_tlv_tag_serialize(tag, buf, buf_size); + if(tmp == -1 || tmp > (ssize_t)sizeof(buf)) return -1; + size += tmp; + + /* Serialize length (L from TLV) into possibly zero-length buffer */ + tmp = der_tlv_length_serialize(len, buf+size, buf_size?buf_size-size:0); + if(tmp == -1) return -1; + size += tmp; + + if(size > sizeof(buf)) + return -1; + + /* + * If callback is specified, invoke it, and check its return value. + */ + if(cb) { + if(constructed) *buf |= 0x20; + if(cb(buf, size, app_key) < 0) + return -1; + } + + return size; +} |