本文共 8272 字，大约阅读时间需要 27 分钟。

在Linux上,

1) receiver 要 setsockopt SO_PASSCRED 2) sender 要显式的调用 sendmsg [cmsg_type SCM_CRENDENTIALS, cmsg_data 为 ucred 并由 sender 填充 (kernel会作检验，如果pid/uid/gid不正确, 则会报错 "Operation not permitted" )] 3) receiver 用 recvmsg 接收。 在 FreeBSD 上, 1) receiver 无需设定 socket选项，直接用 recvmsg 接收。 2) sender 用 sendmsg 发送一个 cmsg_type 为 SCM_CREDS 的 msg (相关结构为 struct cmsgcred, 这个无需 sender 显式填充, kernel会填入cmsgcred的相关成员值) /* Based on the UNP's code, tested on kernel 2.4.20-8 *//* server.c  --  credentials receiver */#include <sys/types.h>#include <sys/socket.h>#include <sys/un.h>#include <sys/uio.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include <linux/socket.h>#define PATH "./myserv.unix"typedef struct sockaddr SA;static ssize_t read_cred(int, void *, size_t, struct ucred *);int main(void){         struct sockaddr_un      serv, cli;        int                     listenfd, connfd;        socklen_t               clilen;        struct ucred            cred;        char                    buf[10];        const int               on = 1;        if ((listenfd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0) {                 perror("socket error");                exit(1);        }        memset(&serv, 0, sizeof(serv));        serv.sun_family = AF_LOCAL;        unlink(PATH);        strncpy(serv.sun_path, PATH, sizeof(serv.sun_path) - 1);        if (bind(listenfd, (SA *) &serv, sizeof(serv)) < 0) {                 perror("bind error");                exit(1);        }        if (listen(listenfd, 1024) < 0) {                 perror("listen error");                exit(1);        }        for ( ; ; ) {                 clilen = sizeof(cli);                if ((connfd = accept(listenfd, (SA *) &cli, &clilen)) < 0){                         if (errno == EINTR)                                continue;                        else {                                 perror("accept error");                                exit(1);                        }                }                if (setsockopt(connfd, SOL_SOCKET, SO_PASSCRED, &on,                        sizeof(on)) < 0) {                         perror("setsockopt error");                        exit(1);                }                if (read_cred(connfd, buf, 5, &cred) < 0) {                         perror("read_cred error");                        exit(1);                }                buf[5] = '/0';                printf("read data: %s/n", buf);                printf("pid = %d, uid = %d, gid = %d/n", cred.pid,                            cred.uid, cred.gid);        }        return 0;}static ssize_tread_cred(int fd, void *ptr, size_t nbytes, struct ucred *credptr){         struct msghdr   msg;        struct iovec    iov[1];        ssize_t         n;        union {                 struct cmsghdr  cm; char control[CMSG_SPACE(sizeof(struct ucred))];         } control_un;        struct cmsghdr  *cmptr;        msg.msg_control = control_un.control;        msg.msg_controllen = sizeof(control_un.control);        msg.msg_name = NULL;        msg.msg_namelen = 0;        iov[0].iov_base = ptr;        iov[0].iov_len = nbytes;        msg.msg_iov = iov;        msg.msg_iovlen = 1;        if ((n = recvmsg(fd, &msg, 0)) < 0)                return n;        if (credptr) {                 if (msg.msg_controllen > sizeof(struct cmsghdr)) {                         cmptr = CMSG_FIRSTHDR(&msg);                        if (cmptr->cmsg_len != CMSG_LEN(                  sizeof(struct ucred))) {                                 fprintf(stderr, "cmsg_len error/n");                                exit(1);                        }                        if (cmptr->cmsg_level != SOL_SOCKET) {                                 fprintf(stderr, "cmsg_level != SOL_SOCKET/n");                                exit(1);                        }                        if (cmptr->cmsg_type != SCM_CREDENTIALS) {                                 fprintf(stderr, "cmsg_type != SCM_CREDENTIALS/n");                                exit(1);                        }                        memcpy(credptr, CMSG_DATA(cmptr),                            sizeof(struct ucred));                } else                        memset(credptr, 0, sizeof(struct ucred));        }        return n;}/* client.c  --  credentials sender */#include <sys/types.h>#include <sys/socket.h>#include <sys/un.h>#include <sys/uio.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include <linux/socket.h>#define PATH "./myserv.unix"typedef struct sockaddr SA;static ssize_t write_cred(int, void *, size_t);int main(void){         struct sockaddr_un      serv;        int                     sockfd;        char                    *buf = "hello";        if ((sockfd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0) {                 perror("socket error");                exit(1);        }        memset(&serv, 0, sizeof(serv));        serv.sun_family = AF_LOCAL;        strncpy(serv.sun_path, PATH, sizeof(serv.sun_path) - 1);        if (connect(sockfd, (SA *)&serv, sizeof(serv)) < 0) {                 perror("connect error");                exit(1);        }        if (write_cred(sockfd, buf, 5) < 0) {                 perror("write_cred error");                exit(1);        }        return 0;}static ssize_t write_cred(int fd, void *ptr, size_t nbytes){         struct msghdr   msg;        struct iovec    iov[1];        union {                 struct cmsghdr  cm;                char            control[CMSG_SPACE(sizeof(struct ucred))];        } control_un;        struct cmsghdr  *cmptr;        struct ucred    *ucptr;        msg.msg_control = control_un.control;        msg.msg_controllen = sizeof(control_un.control);        cmptr = CMSG_FIRSTHDR(&msg);        cmptr->cmsg_len = CMSG_LEN(sizeof(struct ucred));        cmptr->cmsg_level = SOL_SOCKET;        cmptr->cmsg_type = SCM_CREDENTIALS;        ucptr = (struct ucred *) CMSG_DATA(cmptr);        ucptr->pid = getpid();        ucptr->uid = getuid();        ucptr->gid = getgid();        msg.msg_name = NULL;        msg.msg_namelen = 0;        iov[0].iov_base = ptr;        iov[0].iov_len = nbytes;        msg.msg_iov = iov;        msg.msg_iovlen = 1;        return (sendmsg(fd, &msg, 0));} /* Based on the UNP's code, tested on FreeBSD 4.7-Release *//* server.c -- creds receiver */#include <sys/types.h>#include <sys/socket.h>#include <sys/un.h>#include <sys/uio.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#define PATH "./myserv.unix"typedef struct sockaddr SA;static ssize_t read_cred(int, void *, size_t, struct cmsgcred *);int main(void){ struct sockaddr_un serv, cli; int listenfd, connfd; socklen_t clilen; struct cmsgcred cred; char buf[10]; if ((listenfd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0) { perror("socket error"); exit(1); } memset(&serv, 0, sizeof(serv)); serv.sun_family = AF_LOCAL; unlink(PATH); strncpy(serv.sun_path, PATH, sizeof(serv.sun_path) - 1); if (bind(listenfd, (SA *) &serv, sizeof(serv)) < 0) { perror("bind error"); exit(1); } if (listen(listenfd, 1024) < 0) { perror("listen error"); exit(1); } for ( ; ; ) { clilen = sizeof(cli); if ((connfd = accept(listenfd, (SA *) &cli, &clilen)) < 0) { if (errno == EINTR) continue; else { perror("accept error"); exit(1); } } if (read_cred(connfd, buf, 5, &cred) < 0) { perror("read_cred error"); exit(1); } buf[5] = '/0'; printf("read data: %s/n", buf); if (cred.cmcred_ngroups == 0) printf("no credentials returned/n"); else printf("pid = %d, uid = %d, euid = %d, "     "gid = %d/n", cred.cmcred_pid,     cred.cmcred_uid, cred.cmcred_euid,     cred.cmcred_gid); } return 0;}static ssize_tread_cred(int fd, void *ptr, size_t nbytes, struct cmsgcred *credptr){ struct msghdr msg; struct iovec iov[1]; ssize_t n; union { struct cmsghdr cm; char control[CMSG_SPACE(sizeof(struct cmsgcred))]; } control_un; struct cmsghdr *cmptr; msg.msg_control = control_un.control; msg.msg_controllen = sizeof(control_un.control); msg.msg_name = NULL; msg.msg_namelen = 0; iov[0].iov_base = ptr; iov[0].iov_len = nbytes; msg.msg_iov = iov; msg.msg_iovlen = 1; if ((n = recvmsg(fd, &msg, 0)) < 0) return n; if (credptr) { if (msg.msg_controllen > sizeof(struct cmsghdr)) { cmptr = CMSG_FIRSTHDR(&msg); if (cmptr->cmsg_len != CMSG_LEN(     sizeof(struct cmsgcred))) { fprintf(stderr, "cmsg_len error/n"); exit(1); } if (cmptr->cmsg_level != SOL_SOCKET) { fprintf(stderr, "cmsg_level != SOL_SOCKET/n"); exit(1); } if (cmptr->cmsg_type != SCM_CREDS) { fprintf(stderr, "cmsg_type != SCM_CREDS/n"); exit(1); } memcpy(credptr, CMSG_DATA(cmptr),     sizeof(struct cmsgcred)); } else memset(credptr, 0, sizeof(struct cmsgcred)); } return n;}/* client.c -- creds sender */#include <sys/types.h>#include <sys/socket.h>#include <sys/un.h>#include <sys/uio.h>#include <unistd.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#define PATH "./myserv.unix"typedef struct sockaddr SA;static ssize_t write_cred(int, void *, size_t);int main(void){ struct sockaddr_un serv; int sockfd; char *buf = "hello"; if ((sockfd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0) { perror("socket error"); exit(1); } memset(&serv, 0, sizeof(serv)); serv.sun_family = AF_LOCAL; strncpy(serv.sun_path, PATH, sizeof(serv.sun_path) - 1); if (connect(sockfd, (SA *)&serv, sizeof(serv)) < 0) { perror("connect error"); exit(1); } if (write_cred(sockfd, buf, 5) < 0) { perror("write_cred error"); exit(1); } return 0;}static ssize_t write_cred(int fd, void *ptr, size_t nbytes){ struct msghdr msg; struct iovec iov[1]; union { struct cmsghdr cm; char control[CMSG_SPACE(sizeof(struct cmsgcred))]; } control_un; struct cmsghdr *cmptr; msg.msg_control = control_un.control; msg.msg_controllen = sizeof(control_un.control); cmptr = CMSG_FIRSTHDR(&msg); cmptr->cmsg_len = CMSG_LEN(sizeof(struct cmsgcred)); cmptr->cmsg_level = SOL_SOCKET; cmptr->cmsg_type = SCM_CREDS; msg.msg_name = NULL; msg.msg_namelen = 0; iov[0].iov_base = ptr; iov[0].iov_len = nbytes; msg.msg_iov = iov; msg.msg_iovlen = 1; return (sendmsg(fd, &msg, 0));}

转载地址：http://ntpbi.baihongyu.com/