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/*
fp2alias, a basic authentication and authorization helper
This is free and unencumbered software released into the public
domain.
*/
#include <config.h>
#include <syslog.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
/* This value is used in format strings as well */
#define MAX_ALIAS_LEN 32
#define DEFAULT_ALIAS_FILE "/etc/tls/aliases"
/* Get an alias from a file, or from a user */
int get_alias (const char *filename,
const char *fingerprint,
char *alias,
int add_new)
{
FILE * fd;
char hash[65];
char login[MAX_ALIAS_LEN + 1];
int l;
/* Try to find the fingerprint */
fd = fopen(filename, "r");
if (!fd) {
syslog(LOG_ERR, "Can't open %s for reading: %s (errno=%d)",
filename, strerror(errno), errno);
return -1;
}
do {
l = fscanf(fd, "%64[a-f0-9] %32[a-z0-9]\n", hash, login);
if (! strncmp(hash, fingerprint, 64)) {
fclose(fd);
strncpy(alias, login, MAX_ALIAS_LEN + 1);
return 0;
}
} while (l != EOF);
/* In read-only mode, that's all */
if (! add_new) {
fclose(fd);
puts("I don't recognize you.");
return -1;
}
/* Ask for an alias to add */
puts("Enter your alias, please.");
fflush(stdout);
l = scanf("%32[a-z0-9]", alias);
if (l == EOF || strlen(alias) < 2) {
fclose(fd);
return -1;
}
/* Check that the alias is not taken */
fd = freopen(filename, "a+", fd);
if (!fd) {
syslog(LOG_ERR, "Can't reopen %s for writing: %s (errno=%d)",
filename, strerror(errno), errno);
return -1;
}
do {
l = fscanf(fd, "%64[a-f0-9] %32[a-z0-9]\n", hash, login);
if (! strncmp(alias, login, MAX_ALIAS_LEN)) {
fclose(fd);
printf("The '%s' alias is taken already.", alias);
return -1;
}
} while (l != EOF);
/* Everything appears to be fine; add it */
fprintf(fd, "%s %s\n", fingerprint, alias);
fclose(fd);
return 0;
}
void print_help (const char *name)
{
printf("Usage: %s [option ...] [--] [<command> [argument ...]]\n", name);
puts("Options:");
puts(" -f <file> a file with \"<fingerprint> <alias>\" entries");
puts(" -a add new aliases");
puts(" -i <ident> syslog ident to use");
puts(" -e print messages into stderr, in addition to syslog");
puts(" -h print this help message and exit");
}
int main (int argc,
char **argv)
{
int c;
int syslog_options = 0;
char *ident = "fp2alias";
char *alias_file = DEFAULT_ALIAS_FILE;
char *sha256;
char alias[MAX_ALIAS_LEN + 1];
int add_new = 0;
ident = argv[0];
while ((c = getopt (argc, argv, "f:ai:eh")) != -1)
switch (c)
{
case 'f': alias_file = optarg; break;
case 'a': add_new = 1; break;
case 'i': ident = optarg; break;
case 'e': syslog_options |= LOG_PERROR; break;
case 'h': print_help(argv[0]); return 0;
default: print_help(argv[0]); return 1;
}
openlog(ident, syslog_options, LOG_USER);
sha256 = getenv("SHA256");
if (! sha256) {
syslog(LOG_ERR, "The SHA256 environment variable is not defined");
closelog();
return 1;
}
if (get_alias(alias_file, sha256, alias, add_new) < 0) {
closelog();
return 1;
}
syslog(LOG_INFO, "Identified %s as %s", sha256, alias);
closelog();
/* Run a program if one is specified */
if (argc > optind) {
setenv("ALIAS", alias, 1);
return execvp(argv[optind], &argv[optind]);
}
return 0;
}
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