Vulnerable code analysis

Vulnerable code analysis

Below is the psuedocode created from the disassembly of the binary. I have
renamed the function to “bxc_backdoor” to visually identify it more easily.

struct passwd *__fastcall bxc_backdoor(const char *a1, const char *a2)
{
const char *v2; // r5@1
const char *v3; // r4@1
struct passwd *result; // r0@4
FILE *v5; // r6@5
struct passwd *v6; // r5@7
const char *v7; // r0@9
size_t v8; // r0@10
int v9; // [sp+0h] [bp-1090h]@1
char s; // [sp+1000h] [bp-90h]@1
char dest; // [sp+1040h] [bp-50h]@1

v2 = a2;
v3 = a1;
memset(&s, 0, 0x40u);
memset(&dest, 0, 0x40u);
memset(&v9, 0, 0x1000u);
if ( *v2 )
{
v8 = strlen(v2);
_b64_pton(v2, (u_char *)&v9, v8);
if ( dword_2C2E4 )
{
sub_1194C((const char *)&unk_1B1A4, v2);
sub_1194C(“pwd decode[%s]\n”, &v9);
}
}
if (!strcmp(v3, “mydlink”)
&& !strcmp((const char *)&v9, “abc12345cba”) )
{
result = (struct passwd *)1;
}
else
{
v5 = (FILE *)fopen64(“/etc/shadow”, “r”);
while ( 1 )
{
result = fgetpwent(v5);
v6 = result;
if ( !result )
break;
if ( !strcmp(result->pw_name, v3) )
{
strcpy(&s, v6->pw_passwd);
fclose(v5);
strcpy(&dest, (const char *)&v9);
v7 = (const char *)sub_1603C(&dest, &s);
return (struct passwd *)(strcmp(v7, &s) == 0);
}
}
}
return result;
}