 |
|
| Navigation:First_Community->Software->Linux development | Goto:New Topic•Setting•Search | |
CopyRight owned by the original author.--(www.MegaEntry.com)
char *crypt(const char *key, const char *salt); key是使用者的密码。salt是两个字，每个字可从[a-zA-Z0-9./]中选出来，因此同一密码增加了4096种可能性。透过使用key中每个字的低七位元，取得56-bit关键字，这56-bit关键字被用来加密成一组字，这组字有13个可显示的ASCII字，包含开头两个salt。 crypt在您有自行管理使用者的场合时使用，例如会员网站、BBS等等。MegaEntry - Social networking and discussion site!
-------------------------------------------------------------------------------- 例一 : crypt_word.c #includeMegaEntry - Social networking and discussion site!
#includeMegaEntry - Social networking and discussion site!
} 编译 gcc -o crypt_word crypt.c -lcrypt 检验 请先看您的/etc/passwd，找一个您自己的帐号，看前面两个字，那是您自己的salt。接下来输入:CopyRight owned by the original author.--(www.MegaEntry.com)
./crypt_word your_password salt 看看它们是否相同(应该要相同，除非您加了crypt plugin或使用不同的crypt function，例如shadow、pam，这种状况下，加密字是不同的)，另外检验看看他们是否为13个字。 您也可以利用Apache上所附的htpasswd来产生加密字做为验。MegaEntry - Social networking and discussion site!
例二: verify_passwd.c 注意，这个例读取/etc/passwd的资料，不适用於使用shadow或已经使用pam的系统(例如slackware，RedHat及Debian在不外加crypt plugin的状况下，应当相同)。此例仅供参考，做为解crypt函数运作的情形，真正撰写程式时，应该避免类似的写法。 #includeCopyRight owned by the original author.--(www.MegaEntry.com)
typedef struct { char username[64]; char passwd[16]; int uid; int gid; char name[256];MegaEntry - Social networking and discussion site!
char root[256]; char shell[256]; } account; /* 注意! 以下的写法，真实世界的软体开发状况下，千万不要用! */ int acc_info(char *info,account *user)MegaEntry - Social networking and discussion site!
{ char * start = info; char * now = info; /* username */ while (*now&&*now!= ': ') now++; /* 这是超级大安全漏洞 */CopyRight owned by the original author.--(www.MegaEntry.com)
if (!*now) return 0; *now = 0; now++; strcpy(user->username,start); /* 这会导致buffer overflow */ start = now; /* passwd */ while (*now&&*now!= ': ') now++; /* 这是超级大安全漏洞 */CopyRight owned by the original author.--(www.MegaEntry.com)
if (!*now) return 0; *now = 0; now++; strcpy(user->passwd,start); /* 这会导致buffer overflow */ start = now; /* uid */ while (*now&&*now!= ': ') now++;CopyRight owned by the original author.--(www.MegaEntry.com)
if (!*now) return 0; *now = 0; now++; user->uid = atoi(start); start = now; /* gid */ while (*now&&*now!= ': ') now++;MegaEntry - Social networking and discussion site!
if (!*now) return 0; *now = 0; now++; user->gid = atoi(start); start = now; /* name */ while (*now&&*now!= ': ') now++; /* 这是超级大安全漏洞 */CopyRight owned by the original author.--(www.MegaEntry.com)
if (!*now) return 0; *now = 0; now++; strcpy(user->name,start); /* 这会导致buffer overflow */ start = now; /* root */ while (*now&&*now!= ': ') now++; /* 这是超级大安全漏洞 */MegaEntry - Social networking and discussion site!
if (!*now) return 0; *now = 0; now++; strcpy(user->root,start); /* 这会导致buffer overflow */ start = now; /* shell */ while (*now&&*now!= ': ') now++; /* 这是超级大安全漏洞 */MegaEntry - Social networking and discussion site!
*now = 0; now++; strcpy(user->shell,start); /* 这会导致buffer overflow */ start = now; return 1; }MegaEntry - Social networking and discussion site!
int read_password(char *filename,account *users) { FILE *fp; char buf[1024]; int n;CopyRight owned by the original author.--(www.MegaEntry.com)
n = 0; fp = fopen(filename, "rt "); while (fgets(buf,1024,fp)!=NULL) { if (acc_info(buf,&users[n])) n++; } fclose(fp);CopyRight owned by the original author.--(www.MegaEntry.com)
return n; } void main(int argc,char **argv) { int n,i,done;MegaEntry - Social networking and discussion site!
account ACC[128]; char username[256]; char password[256]; char * passwd; char salt[4];MegaEntry - Social networking and discussion site!
if (argc<2) { printf( "username: "); scanf( "%s ",username); /* 这是超级大安全漏洞 */ } else strcpy(username,argv[1]); /* 这是超级大安全漏洞 */ if (argc<3) { printf( "password: ");MegaEntry - Social networking and discussion site!
scanf( "%s ",password); /* 这是超级大安全漏洞 */ } else strcpy(password,argv[2]); /* 这是超级大安全漏洞 */ n = read_password( "/etc/passwd ",ACC); for (i=0,done=0;iMegaEntry - Social networking and discussion site!
if (strcmp(passwd,ACC[i].passwd)==0) { printf( "login successfully! "); } else { printf( "incorrect password! "); } done = 1;CopyRight owned by the original author.--(www.MegaEntry.com)
} if (!done) printf( "invalid username! "); } 编译 gcc -o verify_passwd verify_passwd.c -lcryptCopyRight owned by the original author.--(www.MegaEntry.com)
检验 ./verify_passwd your_username your_password 避免安全漏洞 buffer overflow是个很严重的安全漏洞，通常您不可使用像char buf[xxxx]的宣告。在这一类与安全有相关的任何程式写作中(不是只有密码，例如像www/ftp/telnet的这一类对外窗口都要算在内)，您应该要先检查字串长度。例如以下例子: len = strlen(incoming_username); if (len>xxx) invalid;MegaEntry - Social networking and discussion site!
new_string = (char*)malloc(len+1); strcpy(new_string,incoming_username); your_own_operations... 如此才能避免buffer overflow，万万不可滥做假设，切记切记，连许多数十年经验丰富的老手都会犯这个错误。MegaEntry - Social networking and discussion site!
-------------------------------------------------------------------------------- 与crypt函数相关者尚有以下三个: void setkey (const char *key);MegaEntry - Social networking and discussion site!
void encrypt (char *block, int edflag); void swab (const char *from, char *to, ssize_t n); 一般来说，除非您有特殊需求，你不会用到这三个。Copyright 2005-2006 megaentry,All Rights Reserved
|
IE 6.0 or above is perfect |
ICP No.06021001