C concatenate string buffer overflow

Question

my C prog return buffer overflow , i want concatenate one string and one input string this my code

#include "ring.h"
#include "string.h"
#include "stdlib.h"

RING_FUNC(ring_bingetaccount)
{
       char Address[100] = {0};
    // Check Parameters Count
        if (RING_API_PARACOUNT != 1) {
            RING_API_ERROR(RING_API_MISS1PARA);
            return;
        }
    // Check Parameters Type
        if ( ! RING_API_ISSTRING(1) ) {
            RING_API_ERROR(RING_API_BADPARATYPE);
            return;
        }
        char destination[] = "curl -X GET  https://dex.binance.org/api/v1/account/";
        strcpy(Address,RING_API_GETSTRING(1));
        strcat(destination,Address);
        int status = system(destination);
}

if i remove strcat(destination,Address); not return buffer overflow but ofcourse not do what i want , thanks at all

destination has enough space for exactly just "curl -X GET https://dex.binance.org/api/v1/account/" yet you try to strcat() more characters in there. Try char destination[4200] = "whatever"; for a larger space in the array (that is still unused (but filled with '\0's) as of the initialization). — pmg
– pmg, Commented Oct 24, 2021 at 15:58

chux · Accepted Answer · 2021-10-24 16:15:01Z

2

strcat(destination,Address); fails as destination[] has no more room to append any characters.

    char destination[] = "curl -X GET  https://dex.binance.org/api/v1/account/";
    strcpy(Address,RING_API_GETSTRING(1));
    strcat(destination,Address);  // Fails, unless Address is ""

Instead, form a large enough array with a VLA or malloc()

    const char *curl = "curl -X GET  https://dex.binance.org/api/v1/account/";
    const char *ring = RING_API_GETSTRING(1)
    size_t sz = strlen(curl) + strlen(ring) + 1;
    char destination[sz];
    strcpy(destination, curl);
    strcat(destination, ring);
    int status = system(destination);

with malloc()

    size_t sz = strlen(curl) + strlen(ring) + 1;
    char *destination = malloc(sz);
    if (destination) {
      strcpy(destination, curl);
      strcat(destination, ring);
      int status = system(destination);
      free(destination);
      destination = NULL:
    } else {
      TBD_Handle_OutOfMemory();
    }

answered Oct 24, 2021 at 16:15

chux

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1 Comment

armanvanlendel Over a year ago

thanks at all so much

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