Problem - Kevin Tafuro

86 | Chapter 3: Input Validation
Casting a safe string to a normal C-style string and modifying it using
C-style string-manipulation functions or other means defeats the protections
and accounting afforded by the SafeStr library.
The SafeStr library provides a rich set of API functions to manipulate the strings it
manages. The large number of functions prohibits us from enumerating them all
here, but note that the library comes with complete documentation in the form of
Unix man pages, HTML, and PDF. Table 3-1 lists the functions that have C equivalents,
along with those equivalents.
Table 3-1. SafeStr API functions and equivalents for normal C strings
SafeStr function C function
safestr_append( ) strcat( )
safestr_nappend( ) strncat( )
safestr_find( ) strstr( )
safestr_copy( ) strcpy( )
safestr_ncopy( ) strncpy( )
safestr_compare( ) strcmp( )
safestr_ncompare( ) strncmp( )
safestr_length( ) strlen( )
safestr_sprintf( ) sprintf( )
safestr_vsprintf( ) vsprintf( )
You can typically create safe strings in any of the following three ways:
SAFESTR_ALLOC( )
Allocates a resizable string with an initial allocation size in bytes as specified by
its only argument. The string returned will be an empty string (actual size zero).
Normally the size allocated for a string will be larger than the actual size of the
string. The library rounds memory allocations up, so if you know that you will
need a large string, it is worth allocating it with a large initial allocation size up
front to avoid reallocations as the actual string length grows.
SAFESTR_CREATE( )
Creates a resizable string from the normal C-style string passed as its only argument.
This is normally the appropriate way to convert a C-style string to a safe
string.
SAFESTR_TEMP( )
Creates a temporary resizable string from the normal C-style string passed as its
only argument. SAFESTR_CREATE( ) and SAFESTR_TEMP( ) behave similarly, except
that a string created by SAFESTR_TEMP( ) will be automatically destroyed by the
next SafeStr function that uses it. The only exception is safestr_reference( ),
which increments the reference count on the string, allowing it to survive until
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