| 1 | #include <stdlib.h> |
| 2 | #include <stdio.h> |
| 3 | #include <unistd.h> |
| 4 | #include <string.h> |
| 5 | #include <stdarg.h> |
| 6 | #include <malloc.h> |
| 7 | #include <krb5.h> |
| 8 | #include <pwd.h> |
| 9 | #include <errno.h> |
| 10 | |
| 11 | #define PAM_SM_AUTH |
| 12 | |
| 13 | #include <security/pam_modules.h> |
| 14 | |
| 15 | #define DEF_INSTANCE "autologin" |
| 16 | |
| 17 | struct options |
| 18 | { |
| 19 | char *realm; |
| 20 | char *instance; |
| 21 | char *keytab; |
| 22 | int debug; |
| 23 | int forwardable; |
| 24 | int renewable; |
| 25 | }; |
| 26 | |
| 27 | struct data |
| 28 | { |
| 29 | krb5_context ctx; |
| 30 | krb5_ccache cc; |
| 31 | krb5_principal me; |
| 32 | krb5_creds initcreds; |
| 33 | int hascreds; |
| 34 | uid_t uid; |
| 35 | gid_t gid; |
| 36 | }; |
| 37 | |
| 38 | static void log(int prio, char *format, ...) |
| 39 | { |
| 40 | va_list args; |
| 41 | char buf[1024]; |
| 42 | |
| 43 | va_start(args, format); |
| 44 | snprintf(buf, sizeof(buf), "pam_krb5auto[%i]: %s", getpid(), format); |
| 45 | vsyslog(prio, buf, args); |
| 46 | va_end(args); |
| 47 | } |
| 48 | |
| 49 | static struct options *parseopts(int argc, const char **argv) |
| 50 | { |
| 51 | int i; |
| 52 | struct options *opts; |
| 53 | |
| 54 | opts = malloc(sizeof(*opts)); |
| 55 | memset(opts, 0, sizeof(*opts)); |
| 56 | for(i = 0; i < argc; i++) { |
| 57 | if(!strncmp(argv[i], "realm=", 6)) |
| 58 | opts->realm = strdup(argv[i] + 6); |
| 59 | if(!strncmp(argv[i], "instance=", 9)) |
| 60 | opts->instance = strdup(argv[i] + 9); |
| 61 | if(!strncmp(argv[i], "keytab=", 7)) |
| 62 | opts->keytab = strdup(argv[i] + 7); |
| 63 | if(!strncmp(argv[i], "renew=", 6)) |
| 64 | opts->renewable = atoi(argv[i] + 6); |
| 65 | if(!strcmp(argv[i], "forwardable")) |
| 66 | opts->forwardable = 1; |
| 67 | if(!strcmp(argv[i], "debug")) |
| 68 | opts->debug = 1; |
| 69 | } |
| 70 | return(opts); |
| 71 | } |
| 72 | |
| 73 | static void freeopts(struct options *opts) |
| 74 | { |
| 75 | if(opts->realm != NULL) |
| 76 | free(opts->realm); |
| 77 | if(opts->instance != NULL) |
| 78 | free(opts->instance); |
| 79 | if(opts->keytab != NULL) |
| 80 | free(opts->keytab); |
| 81 | free(opts); |
| 82 | } |
| 83 | |
| 84 | static void freedata(struct data *data) |
| 85 | { |
| 86 | if(data->hascreds) |
| 87 | krb5_free_cred_contents(data->ctx, &data->initcreds); |
| 88 | if(data->cc != NULL) |
| 89 | krb5_cc_close(data->ctx, data->cc); |
| 90 | if(data->me != NULL) |
| 91 | krb5_free_principal(data->ctx, data->me); |
| 92 | if(data->ctx != NULL) |
| 93 | krb5_free_context(data->ctx); |
| 94 | free(data); |
| 95 | } |
| 96 | |
| 97 | static void cleanupdata(pam_handle_t *pamh, struct data *data, int error_status) |
| 98 | { |
| 99 | freedata(data); |
| 100 | } |
| 101 | |
| 102 | static struct data *getdata(pam_handle_t *pamh, struct options *opts) |
| 103 | { |
| 104 | int ret; |
| 105 | struct data *data; |
| 106 | char buf[1024]; |
| 107 | const char *user, *instance; |
| 108 | struct passwd *pwent; |
| 109 | |
| 110 | data = NULL; |
| 111 | pam_get_data(pamh, "krb5auto-data", (const void **)&data); |
| 112 | if(data == NULL) { |
| 113 | if(opts->debug) |
| 114 | log(LOG_DEBUG, "creating new instance"); |
| 115 | data = malloc(sizeof(*data)); |
| 116 | memset(data, 0, sizeof(*data)); |
| 117 | pam_get_user(pamh, &user, NULL); |
| 118 | if(user == NULL) { |
| 119 | log(LOG_ERR, "could not get user name"); |
| 120 | freedata(data); |
| 121 | return(NULL); |
| 122 | } |
| 123 | errno = 0; |
| 124 | if((pwent = getpwnam(user)) == NULL) { |
| 125 | log(LOG_ERR, "could not user information for `%s': %s", user, (errno == 0)?"user not found":strerror(errno)); |
| 126 | freedata(data); |
| 127 | return(NULL); |
| 128 | } |
| 129 | data->uid = pwent->pw_uid; |
| 130 | data->gid = pwent->pw_gid; |
| 131 | if((ret = krb5_init_context(&data->ctx)) != 0) { |
| 132 | log(LOG_CRIT, "could not create krb5 context: %s", error_message(ret)); |
| 133 | freedata(data); |
| 134 | return(NULL); |
| 135 | } |
| 136 | if(opts->instance) |
| 137 | instance = opts->instance; |
| 138 | else |
| 139 | instance = DEF_INSTANCE; |
| 140 | if(opts->realm) |
| 141 | snprintf(buf, sizeof(buf), "%s/%s@%s", user, instance, opts->realm); |
| 142 | else |
| 143 | snprintf(buf, sizeof(buf), "%s/%s", user, instance); |
| 144 | if((ret = krb5_parse_name(data->ctx, buf, &data->me)) != 0) { |
| 145 | log(LOG_ERR, "could not parse principal name `%s': %s", buf, error_message(ret)); |
| 146 | freedata(data); |
| 147 | return(NULL); |
| 148 | } |
| 149 | pam_set_data(pamh, "krb5auto-data", data, (void (*)(pam_handle_t *, void *, int))cleanupdata); |
| 150 | } |
| 151 | return(data); |
| 152 | } |
| 153 | |
| 154 | static int savecreds(pam_handle_t *pamh, struct options *opts, struct data *data) |
| 155 | { |
| 156 | int ret, fd; |
| 157 | krb5_keytab kt; |
| 158 | krb5_get_init_creds_opt icopts; |
| 159 | char buf[1024], *ccname, *filename; |
| 160 | |
| 161 | krb5_get_init_creds_opt_init(&icopts); |
| 162 | kt = NULL; |
| 163 | |
| 164 | if(opts->keytab) { |
| 165 | if((ret = krb5_kt_resolve(data->ctx, opts->keytab, &kt)) != 0) { |
| 166 | log(LOG_ERR, "could not resolve keytab `%s': %s", opts->keytab, error_message(ret)); |
| 167 | ret = PAM_SERVICE_ERR; |
| 168 | goto out; |
| 169 | } |
| 170 | if(opts->debug) |
| 171 | log(LOG_DEBUG, "using keytab `%s'", opts->keytab); |
| 172 | } |
| 173 | krb5_get_init_creds_opt_set_forwardable(&icopts, opts->forwardable); |
| 174 | krb5_get_init_creds_opt_set_renew_life(&icopts, opts->renewable); |
| 175 | if(data->hascreds) { |
| 176 | krb5_free_cred_contents(data->ctx, &data->initcreds); |
| 177 | data->hascreds = 0; |
| 178 | } |
| 179 | if((ret = krb5_get_init_creds_keytab(data->ctx, &data->initcreds, data->me, kt, 0, NULL, &icopts)) != 0) { |
| 180 | log(LOG_ERR, "could not get credentials: %s", error_message(ret)); |
| 181 | ret = PAM_SERVICE_ERR; |
| 182 | goto out; |
| 183 | } |
| 184 | data->hascreds = 1; |
| 185 | if(opts->debug) |
| 186 | log(LOG_DEBUG, "got creds successfully"); |
| 187 | snprintf(buf, sizeof(buf), "KRB5CCNAME=FILE:/tmp/krb5cc_%i_XXXXXX", data->uid); |
| 188 | ccname = buf + sizeof("KRB5CCNAME=") - 1; |
| 189 | filename = ccname + sizeof("FILE:") - 1; |
| 190 | if((fd = mkstemp(filename)) < 0) { |
| 191 | log(LOG_ERR, "could not create tempfile for credentials cache: %s", strerror(errno)); |
| 192 | ret = PAM_SERVICE_ERR; |
| 193 | goto out; |
| 194 | } |
| 195 | close(fd); |
| 196 | if(opts->debug) |
| 197 | log(LOG_DEBUG, "created ccache `%s'", filename); |
| 198 | if((ret = krb5_cc_resolve(data->ctx, ccname, &data->cc)) != 0) { |
| 199 | log(LOG_ERR, "could not resolve ccache `%s': %s", ccname, error_message(ret)); |
| 200 | unlink(filename); |
| 201 | ret = PAM_SERVICE_ERR; |
| 202 | goto out; |
| 203 | } |
| 204 | if((ret = krb5_cc_initialize(data->ctx, data->cc, data->me)) != 0) { |
| 205 | log(LOG_ERR, "could not initialize credentials cache `%s': %s", ccname, error_message(ret)); |
| 206 | unlink(filename); |
| 207 | ret = PAM_SERVICE_ERR; |
| 208 | goto out; |
| 209 | } |
| 210 | if((ret = krb5_cc_store_cred(data->ctx, data->cc, &data->initcreds)) != 0) { |
| 211 | log(LOG_ERR, "could not store credentials: %s", error_message(ret)); |
| 212 | unlink(filename); |
| 213 | ret = PAM_SERVICE_ERR; |
| 214 | goto out; |
| 215 | } |
| 216 | chown(filename, data->uid, data->gid); |
| 217 | pam_putenv(pamh, strdup(buf)); |
| 218 | if(opts->debug) |
| 219 | log(LOG_DEBUG, "successfully initialized ccache"); |
| 220 | ret = PAM_SUCCESS; |
| 221 | |
| 222 | out: |
| 223 | if(kt != NULL) |
| 224 | krb5_kt_close(data->ctx, kt); |
| 225 | return(ret); |
| 226 | } |
| 227 | |
| 228 | static int delcreds(pam_handle_t *pamh, struct options *opts, struct data *data) |
| 229 | { |
| 230 | if(opts->debug) |
| 231 | log(LOG_DEBUG, "deleting credentials"); |
| 232 | if(data->hascreds) { |
| 233 | krb5_free_cred_contents(data->ctx, &data->initcreds); |
| 234 | data->hascreds = 0; |
| 235 | if(opts->debug) |
| 236 | log(LOG_DEBUG, "freed internal creds"); |
| 237 | } |
| 238 | if(data->cc != NULL) { |
| 239 | krb5_cc_destroy(data->ctx, data->cc); |
| 240 | data->cc = NULL; |
| 241 | if(opts->debug) |
| 242 | log(LOG_DEBUG, "destroyed ccache"); |
| 243 | } |
| 244 | return(PAM_SUCCESS); |
| 245 | } |
| 246 | |
| 247 | PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags, int argc, const char **argv) |
| 248 | { |
| 249 | struct options *opts; |
| 250 | |
| 251 | opts = parseopts(argc, argv); |
| 252 | if(opts->debug) |
| 253 | log(LOG_DEBUG, "pam_sm_authenticate called"); |
| 254 | freeopts(opts); |
| 255 | return(PAM_IGNORE); |
| 256 | } |
| 257 | |
| 258 | PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv) |
| 259 | { |
| 260 | struct options *opts; |
| 261 | struct data *data; |
| 262 | int ret; |
| 263 | |
| 264 | opts = parseopts(argc, argv); |
| 265 | if(opts->debug) |
| 266 | log(LOG_DEBUG, "pam_sm_setcred called"); |
| 267 | data = getdata(pamh, opts); |
| 268 | if(data == NULL) { |
| 269 | log(LOG_ERR, "could not get data, erroring out"); |
| 270 | return(PAM_SERVICE_ERR); |
| 271 | } |
| 272 | ret = PAM_SERVICE_ERR; |
| 273 | if(flags & PAM_ESTABLISH_CRED) { |
| 274 | ret = savecreds(pamh, opts, data); |
| 275 | } else if(flags & PAM_DELETE_CRED) { |
| 276 | ret = delcreds(pamh, opts, data); |
| 277 | } |
| 278 | freeopts(opts); |
| 279 | return(ret); |
| 280 | } |
| 281 | |
| 282 | /* |
| 283 | * Local Variables: |
| 284 | * compile-command: "gcc -Wall -g --shared -fPIC -o pam_krb5auto.so pam_krb5auto.c -lkrb5" |
| 285 | * End: |
| 286 | */ |