/*------------------------------------------------------------------ * strncat_s.c * * October 2008, Bo Berry * * Copyright (c) 2008-2011 by Cisco Systems, Inc * All rights reserved. * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, * copy, modify, merge, publish, distribute, sublicense, and/or * sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following * conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. *------------------------------------------------------------------ */ #include "safeclib_private.h" #include "safe_str_constraint.h" #include "safe_str_lib.h" /** * NAME * strncat_s * * SYNOPSIS * #include "safe_str_lib.h" * errno_t * strncat_s(char *dest, rsize_t dmax, const char *src, rsize_t slen) * * DESCRIPTION * The strncat_s function appends a copy of the string pointed * to by src (including the terminating null character) to the * end of the string pointed to by dest. The initial character * from src overwrites the null character at the end of dest. * * All elements following the terminating null character (if * any) written by strncat_s in the array of dmax characters * pointed to by dest take unspecified values when strncat_s returns. * * SPECIFIED IN * ISO/IEC TR 24731, Programming languages, environments * and system software interfaces, Extensions to the C Library, * Part I: Bounds-checking interfaces * * INPUT PARAMETERS * dest pointer to string that will be extended by src * if dmax allows. The string is null terminated. * If the resulting concatenated string is less * than dmax, the remaining slack space is nulled. * * dmax restricted maximum length of the resulting dest, * including the null * * src pointer to the string that will be concatenaed * to string dest * * slen maximum characters to append * * OUTPUT PARAMETERS * dest updated string * * RUNTIME CONSTRAINTS * Neither dest nor src shall be a null pointer * dmax shall not equal zero * dmax shall not be greater than RSIZE_STR_MAX * dmax shall be greater than strnlen_s(src,m). * Copying shall not takeplace between objects that overlap * If there is a runtime-constraint violation, then if dest is * not a null pointer and dmax is greater than zero and not * greater thanRSIZE_MAX, then strncat_s sets dest[0] to the * null character. * * RETURN VALUE * EOK successful operation, all the characters from src * were appended to dest and the result in dest is * null terminated. * ESNULLP NULL pointer * ESZEROL zero length * ESLEMAX length exceeds max limit * ESUNTERM dest not terminated * * */ errno_t strncat_s (char *dest, rsize_t dmax, const char *src, rsize_t slen) { rsize_t orig_dmax; char *orig_dest; const char *overlap_bumper; if (dest == NULL) { invoke_safe_str_constraint_handler("strncat_s: dest is null", NULL, ESNULLP); return RCNEGATE(ESNULLP); } if (src == NULL) { invoke_safe_str_constraint_handler("strncat_s: src is null", NULL, ESNULLP); return RCNEGATE(ESNULLP); } if (slen > RSIZE_MAX_STR) { invoke_safe_str_constraint_handler("strncat_s: slen exceeds max", NULL, ESLEMAX); return RCNEGATE(ESLEMAX); } if (dmax == 0) { invoke_safe_str_constraint_handler("strncat_s: dmax is 0", NULL, ESZEROL); return RCNEGATE(ESZEROL); } if (dmax > RSIZE_MAX_STR) { invoke_safe_str_constraint_handler("strncat_s: dmax exceeds max", NULL, ESLEMAX); return RCNEGATE(ESLEMAX); } /* hold base of dest in case src was not copied */ orig_dmax = dmax; orig_dest = dest; if (dest < src) { overlap_bumper = src; /* Find the end of dest */ while (*dest != '\0') { if (dest == overlap_bumper) { handle_error(orig_dest, orig_dmax, "strncat_s: " "overlapping objects", ESOVRLP); return RCNEGATE(ESOVRLP); } dest++; dmax--; if (dmax == 0) { handle_error(orig_dest, orig_dmax, "strncat_s: " "dest unterminated", ESUNTERM); return RCNEGATE(ESUNTERM); } } while (dmax > 0) { if (dest == overlap_bumper) { handle_error(orig_dest, orig_dmax, "strncat_s: " "overlapping objects", ESOVRLP); return RCNEGATE(ESOVRLP); } /* * Copying truncated before the source null is encountered */ if (slen == 0) { #ifdef SAFECLIB_STR_NULL_SLACK /* null remaining string */ while (dmax) { *dest = '\0'; dmax--; dest++; } #else *dest = '\0'; #endif return RCNEGATE(EOK); } *dest = *src; if (*dest == '\0') { #ifdef SAFECLIB_STR_NULL_SLACK /* null slack to clear data */ while (dmax) { *dest = '\0'; dmax--; dest++; } #endif return RCNEGATE(EOK); } dmax--; slen--; dest++; src++; } } else { overlap_bumper = dest; /* Find the end of dest */ while (*dest != '\0') { /* * NOTE: no need to check for overlap here since src comes first * in memory and we're not incrementing src here. */ dest++; dmax--; if (dmax == 0) { handle_error(orig_dest, orig_dmax, "strncat_s: " "dest unterminated", ESUNTERM); return RCNEGATE(ESUNTERM); } } while (dmax > 0) { if (src == overlap_bumper) { handle_error(orig_dest, orig_dmax, "strncat_s: " "overlapping objects", ESOVRLP); return RCNEGATE(ESOVRLP); } /* * Copying truncated */ if (slen == 0) { #ifdef SAFECLIB_STR_NULL_SLACK /* null remaining string */ while (dmax) { *dest = '\0'; dmax--; dest++; } #else *dest = '\0'; #endif return RCNEGATE(EOK); } *dest = *src; if (*dest == '\0') { #ifdef SAFECLIB_STR_NULL_SLACK /* null slack to clear any data */ while (dmax) { *dest = '\0'; dmax--; dest++; } #endif return RCNEGATE(EOK); } dmax--; slen--; dest++; src++; } } /* * the entire src was not copied, so the string will be nulled. */ handle_error(orig_dest, orig_dmax, "strncat_s: not enough " "space for src", ESNOSPC); return RCNEGATE(ESNOSPC); } EXPORT_SYMBOL(strncat_s)