1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * AppArmor security module 4 * 5 * This file contains AppArmor task related definitions and mediation 6 * 7 * Copyright 2017 Canonical Ltd. 8 * 9 * TODO 10 * If a task uses change_hat it currently does not return to the old 11 * cred or task context but instead creates a new one. Ideally the task 12 * should return to the previous cred if it has not been modified. 13 */ 14 15 #include "include/cred.h" 16 #include "include/task.h" 17 18 /** 19 * aa_get_task_label - Get another task's label 20 * @task: task to query (NOT NULL) 21 * 22 * Returns: counted reference to @task's label 23 */ 24 struct aa_label *aa_get_task_label(struct task_struct *task) 25 { 26 struct aa_label *p; 27 28 rcu_read_lock(); 29 p = aa_get_newest_label(__aa_task_raw_label(task)); 30 rcu_read_unlock(); 31 32 return p; 33 } 34 35 /** 36 * aa_replace_current_label - replace the current tasks label 37 * @label: new label (NOT NULL) 38 * 39 * Returns: 0 or error on failure 40 */ 41 int aa_replace_current_label(struct aa_label *label) 42 { 43 struct aa_label *old = aa_current_raw_label(); 44 struct aa_task_ctx *ctx = task_ctx(current); 45 struct cred *new; 46 47 AA_BUG(!label); 48 49 if (old == label) 50 return 0; 51 52 if (current_cred() != current_real_cred()) 53 return -EBUSY; 54 55 new = prepare_creds(); 56 if (!new) 57 return -ENOMEM; 58 59 if (ctx->nnp && label_is_stale(ctx->nnp)) { 60 struct aa_label *tmp = ctx->nnp; 61 62 ctx->nnp = aa_get_newest_label(tmp); 63 aa_put_label(tmp); 64 } 65 if (unconfined(label) || (labels_ns(old) != labels_ns(label))) 66 /* 67 * if switching to unconfined or a different label namespace 68 * clear out context state 69 */ 70 aa_clear_task_ctx_trans(task_ctx(current)); 71 72 /* 73 * be careful switching cred label, when racing replacement it 74 * is possible that the cred labels's->proxy->label is the reference 75 * keeping @label valid, so make sure to get its reference before 76 * dropping the reference on the cred's label 77 */ 78 aa_get_label(label); 79 aa_put_label(cred_label(new)); 80 set_cred_label(new, label); 81 82 commit_creds(new); 83 return 0; 84 } 85 86 87 /** 88 * aa_set_current_onexec - set the tasks change_profile to happen onexec 89 * @label: system label to set at exec (MAYBE NULL to clear value) 90 * @stack: whether stacking should be done 91 * Returns: 0 or error on failure 92 */ 93 int aa_set_current_onexec(struct aa_label *label, bool stack) 94 { 95 struct aa_task_ctx *ctx = task_ctx(current); 96 97 aa_get_label(label); 98 aa_put_label(ctx->onexec); 99 ctx->onexec = label; 100 ctx->token = stack; 101 102 return 0; 103 } 104 105 /** 106 * aa_set_current_hat - set the current tasks hat 107 * @label: label to set as the current hat (NOT NULL) 108 * @token: token value that must be specified to change from the hat 109 * 110 * Do switch of tasks hat. If the task is currently in a hat 111 * validate the token to match. 112 * 113 * Returns: 0 or error on failure 114 */ 115 int aa_set_current_hat(struct aa_label *label, u64 token) 116 { 117 struct aa_task_ctx *ctx = task_ctx(current); 118 struct cred *new; 119 120 new = prepare_creds(); 121 if (!new) 122 return -ENOMEM; 123 AA_BUG(!label); 124 125 if (!ctx->previous) { 126 /* transfer refcount */ 127 ctx->previous = cred_label(new); 128 ctx->token = token; 129 } else if (ctx->token == token) { 130 aa_put_label(cred_label(new)); 131 } else { 132 /* previous_profile && ctx->token != token */ 133 abort_creds(new); 134 return -EACCES; 135 } 136 137 set_cred_label(new, aa_get_newest_label(label)); 138 /* clear exec on switching context */ 139 aa_put_label(ctx->onexec); 140 ctx->onexec = NULL; 141 142 commit_creds(new); 143 return 0; 144 } 145 146 /** 147 * aa_restore_previous_label - exit from hat context restoring previous label 148 * @token: the token that must be matched to exit hat context 149 * 150 * Attempt to return out of a hat to the previous label. The token 151 * must match the stored token value. 152 * 153 * Returns: 0 or error of failure 154 */ 155 int aa_restore_previous_label(u64 token) 156 { 157 struct aa_task_ctx *ctx = task_ctx(current); 158 struct cred *new; 159 160 if (ctx->token != token) 161 return -EACCES; 162 /* ignore restores when there is no saved label */ 163 if (!ctx->previous) 164 return 0; 165 166 new = prepare_creds(); 167 if (!new) 168 return -ENOMEM; 169 170 aa_put_label(cred_label(new)); 171 set_cred_label(new, aa_get_newest_label(ctx->previous)); 172 AA_BUG(!cred_label(new)); 173 /* clear exec && prev information when restoring to previous context */ 174 aa_clear_task_ctx_trans(ctx); 175 176 commit_creds(new); 177 178 return 0; 179 } 180