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authorAndrew G. Morgan <morgan@kernel.org>2000-06-20 22:10:38 +0000
committerAndrew G. Morgan <morgan@kernel.org>2000-06-20 22:10:38 +0000
commitea488580c42e8918445a945484de3c8a5addc761 (patch)
treec992f3ba699caafedfadc16af38e6359c3c24698 /libpamc/pamc_load.c
Initial revision
Diffstat (limited to 'libpamc/pamc_load.c')
-rw-r--r--libpamc/pamc_load.c477
1 files changed, 477 insertions, 0 deletions
diff --git a/libpamc/pamc_load.c b/libpamc/pamc_load.c
new file mode 100644
index 00000000..b3c0b5d5
--- /dev/null
+++ b/libpamc/pamc_load.c
@@ -0,0 +1,477 @@
+/*
+ * $Id$
+ *
+ * Copyright (c) 1999 Andrew G. Morgan <morgan@ftp.kernel.org>
+ *
+ * pamc_load
+ */
+
+#include "libpamc.h"
+
+static int __pamc_exec_agent(pamc_handle_t pch, pamc_agent_t *agent)
+{
+ char *full_path;
+ int found_agent, length, reset_length, to_agent[2], from_agent[2];
+ int return_code = PAM_BPC_FAIL;
+
+ if (agent->id[agent->id_length] != '\0') {
+ PAM_BP_ASSERT("libpamc: internal error agent_id not terminated");
+ }
+
+ for (length=0; (length < agent->id_length); ++length) {
+ switch (agent->id[length]) {
+ case '/':
+ D(("ill formed agent id"));
+ return PAM_BPC_FAIL;
+ }
+ }
+
+ /* enough memory for any path + this agent */
+ reset_length = 3 + pch->max_path + agent->id_length;
+ D(("reset_length = %d (3+%d+%d)",
+ reset_length, pch->max_path, agent->id_length));
+ full_path = malloc(reset_length);
+ if (full_path == NULL) {
+ D(("no memory for agent path"));
+ return PAM_BPC_FAIL;
+ }
+
+ found_agent = 0;
+ for (length=0; pch->agent_paths[length]; ++length) {
+ struct stat buf;
+
+ D(("path: [%s]", pch->agent_paths[length]));
+ D(("agent id: [%s]", agent->id));
+
+ sprintf(full_path, "%s/%s", pch->agent_paths[length], agent->id);
+
+ D(("looking for agent here: [%s]\n", full_path));
+ if (stat(full_path, &buf) == 0) {
+ D(("file existis"));
+ found_agent = 1;
+ break;
+ }
+ }
+
+ if (! found_agent) {
+ D(("no agent was found"));
+ goto free_and_return;
+ }
+
+ if (pipe(to_agent)) {
+ D(("failed to open pipe to agent"));
+ goto free_and_return;
+ }
+
+ if (pipe(from_agent)) {
+ D(("failed to open pipe from agent"));
+ goto close_the_agent;
+ }
+
+ agent->pid = fork();
+ if (agent->pid == -1) {
+
+ D(("failed to fork for agent"));
+ goto close_both_pipes;
+
+ } else if (agent->pid == 0) {
+
+ int i;
+
+ dup2(from_agent[1], STDOUT_FILENO);
+ dup2(to_agent[0], STDIN_FILENO);
+
+ /* we close all of the files that have filedescriptors lower
+ and equal to twice the highest we have seen, The idea is
+ that we don't want to leak filedescriptors to agents from a
+ privileged client application.
+
+ XXX - this is a heuristic at this point. There is a growing
+ need for an extra 'set param' libpamc function, that could
+ be used to supply info like the highest fd to close etc..
+ */
+
+ if (from_agent[1] > pch->highest_fd_to_close) {
+ pch->highest_fd_to_close = 2*from_agent[1];
+ }
+
+ for (i=0; i <= pch->highest_fd_to_close; ++i) {
+ switch (i) {
+ case STDOUT_FILENO:
+ case STDERR_FILENO:
+ case STDIN_FILENO:
+ /* only these three remain open */
+ break;
+ default:
+ (void) close(i); /* don't care if its not open */
+ }
+ }
+
+ /* we make no attempt to drop other privileges - this library
+ has no idea how that would be done in the general case. It
+ is up to the client application (when calling
+ pamc_converse) to make sure no privilege will leak into an
+ (untrusted) agent. */
+
+ /* we propogate no environment - future versions of this
+ library may have the ability to audit all agent
+ transactions. */
+
+ D(("exec'ing agent %s", full_path));
+ execle(full_path, "pam-agent", NULL, NULL);
+
+ D(("exec failed"));
+ exit(1);
+
+ }
+
+ close(to_agent[0]);
+ close(from_agent[1]);
+
+ agent->writer = to_agent[1];
+ agent->reader = from_agent[0];
+
+ return_code = PAM_BPC_TRUE;
+ goto free_and_return;
+
+close_both_pipes:
+ close(from_agent[0]);
+ close(from_agent[1]);
+
+close_the_agent:
+ close(to_agent[0]);
+ close(to_agent[1]);
+
+free_and_return:
+ memset(full_path, 0, reset_length);
+ free(full_path);
+
+ D(("returning %d", return_code));
+
+ return return_code;
+}
+
+/*
+ * has the named agent been loaded?
+ */
+
+static int __pamc_agent_is_enabled(pamc_handle_t pch, const char *agent_id)
+{
+ pamc_agent_t *agent;
+
+ for (agent = pch->chain; agent; agent = agent->next) {
+ if (!strcmp(agent->id, agent_id)) {
+ D(("agent already loaded"));
+ return PAM_BPC_TRUE;
+ }
+ }
+
+ D(("agent is not loaded"));
+ return PAM_BPC_FALSE;
+}
+
+/*
+ * has the named agent been disabled?
+ */
+
+static int __pamc_agent_is_disabled(pamc_handle_t pch, const char *agent_id)
+{
+ pamc_blocked_t *blocked;
+
+ for (blocked=pch->blocked_agents; blocked; blocked = blocked->next) {
+ if (!strcmp(agent_id, blocked->id)) {
+ D(("agent is disabled"));
+ return PAM_BPC_TRUE;
+ }
+ }
+
+ D(("agent is not disabled"));
+ return PAM_BPC_FALSE;
+}
+
+/*
+ * disable an agent
+ */
+
+int pamc_disable(pamc_handle_t pch, const char *agent_id)
+{
+ pamc_blocked_t *block;
+
+ if (pch == NULL) {
+ D(("pch is NULL"));
+ return PAM_BPC_FALSE;
+ }
+
+ if (agent_id == NULL) {
+ D(("agent_id is NULL"));
+ return PAM_BPC_FALSE;
+ }
+
+ if (__pamc_agent_is_enabled(pch, agent_id) != PAM_BPC_FALSE) {
+ D(("agent is already loaded"));
+ return PAM_BPC_FALSE;
+ }
+
+ if (__pamc_agent_is_disabled(pch, agent_id) != PAM_BPC_FALSE) {
+ D(("agent is already disabled"));
+ return PAM_BPC_TRUE;
+ }
+
+ block = calloc(1, sizeof(pamc_blocked_t));
+ if (block == NULL) {
+ D(("no memory for new blocking structure"));
+ return PAM_BPC_FALSE;
+ }
+
+ block->id = malloc(1 + strlen(agent_id));
+ if (block->id == NULL) {
+ D(("no memory for agent id"));
+ free(block);
+ return PAM_BPC_FALSE;
+ }
+
+ strcpy(block->id, agent_id);
+ block->next = pch->blocked_agents;
+ pch->blocked_agents = block;
+
+ return PAM_BPC_TRUE;
+}
+
+/*
+ * force the loading of a particular agent
+ */
+
+int pamc_load(pamc_handle_t pch, const char *agent_id)
+{
+ pamc_agent_t *agent;
+ int length;
+
+ /* santity checking */
+
+ if (pch == NULL) {
+ D(("pch is NULL"));
+ return PAM_BPC_FALSE;
+ }
+
+ if (agent_id == NULL) {
+ D(("agent_id is NULL"));
+ return PAM_BPC_FALSE;
+ }
+
+ if (__pamc_agent_is_disabled(pch, agent_id) != PAM_BPC_FALSE) {
+ D(("sorry agent is disabled"));
+ return PAM_BPC_FALSE;
+ }
+
+ length = strlen(agent_id);
+
+ /* scan list to see if agent is loaded */
+
+ if (__pamc_agent_is_enabled(pch, agent_id) == PAM_BPC_TRUE) {
+ D(("no need to load an already loaded agent (%s)", agent_id));
+ return PAM_BPC_TRUE;
+ }
+
+ /* not in the list, so we need to load it and add it to the head
+ of the chain */
+
+ agent = calloc(1, sizeof(pamc_agent_t));
+ if (agent == NULL) {
+ D(("no memory for new agent"));
+ return PAM_BPC_FALSE;
+ }
+ agent->id = calloc(1, 1+length);
+ if (agent->id == NULL) {
+ D(("no memory for new agent's id"));
+ goto fail_free_agent;
+ }
+ memcpy(agent->id, agent_id, length);
+ agent->id[length] = '\0';
+ agent->id_length = length;
+
+ if (__pamc_exec_agent(pch, agent) != PAM_BPC_TRUE) {
+ D(("unable to exec agent"));
+ goto fail_free_agent_id;
+ }
+
+ agent->next = pch->chain;
+ pch->chain = agent;
+
+ return PAM_BPC_TRUE;
+
+fail_free_agent_id:
+
+ memset(agent->id, 0, agent->id_length);
+ free(agent->id);
+
+ memset(agent, 0, sizeof(*agent));
+
+fail_free_agent:
+
+ free(agent);
+ return PAM_BPC_FALSE;
+}
+
+/*
+ * what's a valid agent name?
+ */
+
+int __pamc_valid_agent_id(int id_length, const char *id)
+{
+ int post, i;
+
+ for (i=post=0 ; i < id_length; ++i) {
+ int ch = id[i++];
+
+ if (isalpha(ch) || isdigit(ch) || (ch == '_')) {
+ continue;
+ } else if (post && (ch == '.')) {
+ continue;
+ } else if ((i > 1) && (!post) && (ch == '@')) {
+ post = 1;
+ } else {
+ D(("id=%s contains '%c' which is illegal", id, ch));
+ return 0;
+ }
+ }
+
+ if (!i) {
+ D(("length of id is 0"));
+ return 0;
+ } else {
+ return 1; /* id is valid */
+ }
+}
+
+/*
+ * building a tree of available agent names
+ */
+
+static pamc_id_node_t *__pamc_add_node(pamc_id_node_t *root, const char *id,
+ int *counter)
+{
+ if (root) {
+
+ int cmp;
+
+ if ((cmp = strcmp(id, root->agent_id))) {
+ if (cmp > 0) {
+ root->right = __pamc_add_node(root->right, id,
+ &(root->child_count));
+ } else {
+ root->left = __pamc_add_node(root->left, id,
+ &(root->child_count));
+ }
+ }
+
+ return root;
+
+ } else {
+
+ pamc_id_node_t *node = calloc(1, sizeof(pamc_id_node_t));
+
+ if (node) {
+ node->agent_id = malloc(1+strlen(id));
+ if (node->agent_id) {
+ strcpy(node->agent_id, id);
+ } else {
+ free(node);
+ node = NULL;
+ }
+ }
+
+ (*counter)++;
+ return node;
+ }
+}
+
+/*
+ * drop all of the tree and any remaining ids
+ */
+
+static pamc_id_node_t *__pamc_liberate_nodes(pamc_id_node_t *tree)
+{
+ if (tree) {
+ if (tree->agent_id) {
+ free(tree->agent_id);
+ tree->agent_id = NULL;
+ }
+
+ tree->left = __pamc_liberate_nodes(tree->left);
+ tree->right = __pamc_liberate_nodes(tree->right);
+
+ tree->child_count = 0;
+ free(tree);
+ }
+
+ return NULL;
+}
+
+/*
+ * fill a list with the contents of the tree (in ascii order)
+ */
+
+static void __pamc_fill_list_from_tree(pamc_id_node_t *tree, char **agent_list,
+ int *counter)
+{
+ if (tree) {
+ __pamc_fill_list_from_tree(tree->left, agent_list, counter);
+ agent_list[(*counter)++] = tree->agent_id;
+ tree->agent_id = NULL;
+ __pamc_fill_list_from_tree(tree->right, agent_list, counter);
+ }
+}
+
+/*
+ * get a list of the available agents
+ */
+
+char **pamc_list_agents(pamc_handle_t pch)
+{
+ int i, total_agent_count=0;
+ pamc_id_node_t *tree = NULL;
+ char **agent_list;
+
+ /* loop over agent paths */
+
+ for (i=0; pch->agent_paths[i]; ++i) {
+ DIR *dir;
+
+ dir = opendir(pch->agent_paths[i]);
+ if (dir) {
+ struct dirent *item;
+
+ while ((item = readdir(dir))) {
+
+ /* this is a cheat on recognizing agent_ids */
+ if (!__pamc_valid_agent_id(strlen(item->d_name),
+ item->d_name)) {
+ continue;
+ }
+
+ tree = __pamc_add_node(tree, item->d_name, &total_agent_count);
+ }
+
+ closedir(dir);
+ }
+ }
+
+ /* now, we build a list of ids */
+ D(("total of %d available agents\n", total_agent_count));
+
+ agent_list = calloc(total_agent_count+1, sizeof(char *));
+ if (agent_list) {
+ int counter=0;
+
+ __pamc_fill_list_from_tree(tree, agent_list, &counter);
+ if (counter != total_agent_count) {
+ PAM_BP_ASSERT("libpamc: internal error transcribing tree");
+ }
+ } else {
+ D(("no memory for agent list"));
+ }
+
+ __pamc_liberate_nodes(tree);
+
+ return agent_list;
+}