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Rust ASN.1 Toolkit
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Fragmentation procedure missing #20

Open gabhijit opened 2 years ago

gabhijit commented 2 years ago

From @huixue

The more I look into decoder, I think there's something missing on handling the X.691 section 10.9.3.8.4, the "fragmentation procedure". 10.9.3.8.1-10.9.3.8.4 is describing the array of fragments which should be added, when the length is too big, over 16K. The content is being fragmented, and lengths are added to each of them (some are just number 1-4 indicating numbers of 16K chunks)

If you take a look at the attached INTEGER_aper.c, generated by asn1c compiler, line 292-301 is encoding a roll of fragment, using a loop. Line 126-142 is doing the decoding, accordingly.

I don't see this part in the decoder. Am I missing `something?```

huixue commented 2 years ago 
/*
 * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
 * All rights reserved.
 * Redistribution and modifications are permitted subject to BSD license.
 */
#include <asn_internal.h>
#include <INTEGER.h>

asn_dec_rval_t
INTEGER_decode_aper(const asn_codec_ctx_t *opt_codec_ctx,
                    const asn_TYPE_descriptor_t *td,
                    const asn_per_constraints_t *constraints, void **sptr, asn_per_data_t *pd) {
    const asn_INTEGER_specifics_t *specs = (const asn_INTEGER_specifics_t *)td->specifics;
    asn_dec_rval_t rval = { RC_OK, 0 };
    INTEGER_t *st = (INTEGER_t *)*sptr;
    const asn_per_constraint_t *ct;
    int repeat;

    (void)opt_codec_ctx;

    if(!st) {
        st = (INTEGER_t *)(*sptr = CALLOC(1, sizeof(*st)));
        if(!st) ASN__DECODE_FAILED;
    }

    if(!constraints) constraints = td->encoding_constraints.per_constraints;
    ct = constraints ? &constraints->value : 0;

    if(ct && ct->flags & APC_EXTENSIBLE) {
        int inext = per_get_few_bits(pd, 1);
        if(inext < 0) ASN__DECODE_STARVED;
        if(inext) ct = 0;
    }

    FREEMEM(st->buf);
    st->buf = 0;
    st->size = 0;
    if(ct) {
        if(ct->flags & APC_SEMI_CONSTRAINED) {
            st->buf = (uint8_t *)CALLOC(1, 2);
            if(!st->buf) ASN__DECODE_FAILED;
            st->size = 1;
        } else if(ct->flags & APC_CONSTRAINED && ct->range_bits >= 0) {
            size_t size = (ct->range_bits + 7) >> 3;
            st->buf = (uint8_t *)MALLOC(1 + size + 1);
            if(!st->buf) ASN__DECODE_FAILED;
            st->size = size;
        }
    }

    /* X.691, #12.2.2 */
    if(ct && ct->flags != APC_UNCONSTRAINED) {
        /* #10.5.6 */
        ASN_DEBUG("Integer with range %d bits", ct->range_bits);
        if(ct->range_bits >= 0) {
            if (ct->range_bits > 16) {
                int max_range_bytes = (ct->range_bits >> 3) +
                                      (((ct->range_bits % 8) > 0) ? 1 : 0);
                int length = 0, i;
                long value = 0;

                for (i = 1; ; i++) {
                    int upper = 1 << i;
                    if (upper >= max_range_bytes)
                        break;
                }
                ASN_DEBUG("Can encode %d (%d bytes) in %d bits", ct->range_bits,
                          max_range_bytes, i);

                if ((length = per_get_few_bits(pd, i)) < 0)
                    ASN__DECODE_FAILED;

                /* X.691 #12.2.6 length determinant + lb (1) */
                length += 1;
                ASN_DEBUG("Got length %d", length);
                if (aper_get_align(pd) != 0)
                    ASN__DECODE_FAILED;
                while (length--) {
                    int buf = per_get_few_bits(pd, 8);
                    if (buf < 0)
                        ASN__DECODE_FAILED;
                    value += (((long)buf) << (8 * length));
                }

                value += ct->lower_bound;
                if((specs && specs->field_unsigned)
                        ? asn_uint642INTEGER(st, (unsigned long)value)
                        : asn_int642INTEGER(st, value))
                    ASN__DECODE_FAILED;
                ASN_DEBUG("Got value %ld + low %ld",
                          value, ct->lower_bound);
            } else {
                long value = 0;
                if (ct->range_bits < 8) {
                    value = per_get_few_bits(pd, ct->range_bits);
                    if(value < 0) ASN__DECODE_STARVED;
                } else if (ct->range_bits == 8) {
                    if (aper_get_align(pd) < 0)
                        ASN__DECODE_FAILED;
                    value = per_get_few_bits(pd, ct->range_bits);
                    if(value < 0) ASN__DECODE_STARVED;
                } else {
                    /* Align */
                    if (aper_get_align(pd) < 0)
                        ASN__DECODE_FAILED;
                    value = per_get_few_bits(pd, 16);
                    if(value < 0) ASN__DECODE_STARVED;
                }
                value += ct->lower_bound;
                if((specs && specs->field_unsigned)
                        ? asn_ulong2INTEGER(st, value)
                        : asn_long2INTEGER(st, value))
                    ASN__DECODE_FAILED;
                ASN_DEBUG("Got value %ld + low %ld",
                          value, ct->lower_bound);
            }
            return rval;
        } else {
            ASN__DECODE_FAILED;
        }
    } else {
        ASN_DEBUG("Decoding unconstrained integer %s", td->name);
    }

    /* X.691, #12.2.3, #12.2.4 */
    do {
        ssize_t len;
        void *p;
        int ret;

        /* Get the PER length */
        len = aper_get_length(pd, -1, -1, &repeat);
        if(len < 0) ASN__DECODE_STARVED;

        p = REALLOC(st->buf, st->size + len + 1);
        if(!p) ASN__DECODE_FAILED;
        st->buf = (uint8_t *)p;

        ret = per_get_many_bits(pd, &st->buf[st->size], 0, 8 * len);
        if(ret < 0) ASN__DECODE_STARVED;
        st->size += len;
    } while(repeat);
    st->buf[st->size] = 0;  /* JIC */

    /* #12.2.3 */
    if(ct && ct->lower_bound) {
        /*
         * TODO: replace by in-place arithmetics.
         */
        long value;
        if(asn_INTEGER2long(st, &value))
            ASN__DECODE_FAILED;
        if(asn_long2INTEGER(st, value + ct->lower_bound))
            ASN__DECODE_FAILED;
    }

    return rval;
}

asn_enc_rval_t
INTEGER_encode_aper(const asn_TYPE_descriptor_t *td,
                    const asn_per_constraints_t *constraints,
                    const void *sptr, asn_per_outp_t *po) {
    const asn_INTEGER_specifics_t *specs = (const asn_INTEGER_specifics_t *)td->specifics;
    asn_enc_rval_t er = {0,0,0};
    const INTEGER_t *st = (const INTEGER_t *)sptr;
    const uint8_t *buf;
    const uint8_t *end;
    const asn_per_constraint_t *ct;
    long value = 0;

    if(!st || st->size == 0) ASN__ENCODE_FAILED;

    if(!constraints) constraints = td->encoding_constraints.per_constraints;
    ct = constraints ? &constraints->value : 0;

    er.encoded = 0;

    if(ct) {
        int inext = 0;
        if(specs && specs->field_unsigned) {
            unsigned long uval;
            if(asn_INTEGER2ulong(st, &uval))
                ASN__ENCODE_FAILED;
            /* Check proper range */
            if(ct->flags & APC_SEMI_CONSTRAINED) {
                if(uval < (unsigned long)ct->lower_bound)
                    inext = 1;
            } else if(ct->range_bits >= 0) {
                if(uval < (unsigned long)ct->lower_bound
                        || uval > (unsigned long)ct->upper_bound)
                    inext = 1;
            }
            ASN_DEBUG("Value %lu (%02x/%lu) lb %ld ub %ld %s",
                      uval, st->buf[0], st->size,
                      ct->lower_bound, ct->upper_bound,
                      inext ? "ext" : "fix");
            value = uval;
        } else {
            if(asn_INTEGER2long(st, &value)) ASN__ENCODE_FAILED;
            /* Check proper range */
            if(ct->flags & APC_SEMI_CONSTRAINED) {
                if(value < ct->lower_bound)
                    inext = 1;
            } else if(ct->range_bits >= 0) {
                if(value < ct->lower_bound
                        || value > ct->upper_bound)
                    inext = 1;
            }
            ASN_DEBUG("Value %lu (%02x/%lu) lb %ld ub %ld %s",
                      value, st->buf[0], st->size,
                      ct->lower_bound, ct->upper_bound,
                      inext ? "ext" : "fix");
        }
        if(ct->flags & APC_EXTENSIBLE) {
            if(per_put_few_bits(po, inext, 1))
                ASN__ENCODE_FAILED;
            if(inext) ct = 0;
        } else if(inext) {
            ASN__ENCODE_FAILED;
        }
    }

    /* X.691, #12.2.2 */
    if(ct && ct->range_bits >= 0) {
        unsigned long v;

        /* #10.5.6 */
        ASN_DEBUG("Encoding integer %ld (%lu) with range %d bits",
                  value, value - ct->lower_bound, ct->range_bits);

        v = value - ct->lower_bound;

        /* #12 <= 8 -> alignment ? */
        int range = ct->upper_bound - ct->lower_bound + 1;
        if (ct->range_bits < 8 || (ct->range_bits == 8 && range < 256)) {
            if(per_put_few_bits(po, 0x00 | v, ct->range_bits))
                ASN__ENCODE_FAILED;
        } else if (ct->range_bits == 8) {
            if(aper_put_align(po) < 0)
                ASN__ENCODE_FAILED;
            if(per_put_few_bits(po, 0x00 | v, ct->range_bits))
                ASN__ENCODE_FAILED;
        } else if (ct->range_bits <= 16) {
            /* Consume the bytes to align on octet */
            if(aper_put_align(po) < 0)
                ASN__ENCODE_FAILED;
            if(per_put_few_bits(po, 0x0000 | v, 16))
                ASN__ENCODE_FAILED;
        } else {
            /* TODO: extend to >64 bits */
            int64_t v64 = v;
            int i, j;
            int max_range_bytes = (ct->range_bits >> 3) +
                                  (((ct->range_bits % 8) > 0) ? 1 : 0);

            for (i = 1; ; i++) {
                int upper = 1 << i;
                if (upper >= max_range_bytes)
                    break;
            }

            for (j = sizeof(int64_t) -1; j != 0; j--) {
                int64_t val;
                val = v64 >> (j * 8);
                if (val != 0)
                    break;
            }

            /* Putting length in the minimum number of bits ex: 5 = 3bits */
            if (per_put_few_bits(po, j, i))
                ASN__ENCODE_FAILED;

            /* Consume the bits to align on octet */
            if (aper_put_align(po) < 0)
                ASN__ENCODE_FAILED;
            /* Put the value */
            for (i = 0; i <= j; i++) {
                if(per_put_few_bits(po, (v64 >> (8 * (j - i))) & 0xff, 8))
                    ASN__ENCODE_FAILED;
            }
        }
        ASN__ENCODED_OK(er);
    }

    if(ct && ct->lower_bound) {
        ASN_DEBUG("Adjust lower bound to %ld", ct->lower_bound);
        /* TODO: adjust lower bound */
        ASN__ENCODE_FAILED;
    }

    for(buf = st->buf, end = st->buf + st->size; buf < end;) {
        int need_eom = 0;
        ssize_t mayEncode = aper_put_length(po, -1, end - buf, &need_eom);
        if(mayEncode < 0)
            ASN__ENCODE_FAILED;
        if(per_put_many_bits(po, buf, 8 * mayEncode))
            ASN__ENCODE_FAILED;
        buf += mayEncode;
        if(need_eom && aper_put_length(po, -1, 0, 0)) ASN__ENCODE_FAILED;
    }

    ASN__ENCODED_OK(er);
}
huixue commented 2 years ago

292-301 lines are as below:

    for(buf = st->buf, end = st->buf + st->size; buf < end;) {
        int need_eom = 0;
        ssize_t mayEncode = aper_put_length(po, -1, end - buf, &need_eom);
        if(mayEncode < 0)
            ASN__ENCODE_FAILED;
        if(per_put_many_bits(po, buf, 8 * mayEncode))
            ASN__ENCODE_FAILED;
        buf += mayEncode;
        if(need_eom && aper_put_length(po, -1, 0, 0)) ASN__ENCODE_FAILED;
    }