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293 lines
7.2 KiB
293 lines
7.2 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* AppArmor security module |
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* |
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* This file contains AppArmor task related definitions and mediation |
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* |
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* Copyright 2017 Canonical Ltd. |
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* |
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* TODO |
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* If a task uses change_hat it currently does not return to the old |
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* cred or task context but instead creates a new one. Ideally the task |
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* should return to the previous cred if it has not been modified. |
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*/ |
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#include <linux/gfp.h> |
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#include <linux/ptrace.h> |
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#include "include/audit.h" |
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#include "include/cred.h" |
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#include "include/policy.h" |
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#include "include/task.h" |
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/** |
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* aa_get_task_label - Get another task's label |
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* @task: task to query (NOT NULL) |
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* |
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* Returns: counted reference to @task's label |
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*/ |
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struct aa_label *aa_get_task_label(struct task_struct *task) |
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{ |
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struct aa_label *p; |
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rcu_read_lock(); |
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p = aa_get_newest_label(__aa_task_raw_label(task)); |
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rcu_read_unlock(); |
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return p; |
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} |
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/** |
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* aa_replace_current_label - replace the current tasks label |
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* @label: new label (NOT NULL) |
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* |
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* Returns: 0 or error on failure |
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*/ |
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int aa_replace_current_label(struct aa_label *label) |
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{ |
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struct aa_label *old = aa_current_raw_label(); |
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struct aa_task_ctx *ctx = task_ctx(current); |
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struct cred *new; |
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AA_BUG(!label); |
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if (old == label) |
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return 0; |
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if (current_cred() != current_real_cred()) |
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return -EBUSY; |
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new = prepare_creds(); |
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if (!new) |
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return -ENOMEM; |
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if (ctx->nnp && label_is_stale(ctx->nnp)) { |
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struct aa_label *tmp = ctx->nnp; |
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ctx->nnp = aa_get_newest_label(tmp); |
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aa_put_label(tmp); |
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} |
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if (unconfined(label) || (labels_ns(old) != labels_ns(label))) |
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/* |
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* if switching to unconfined or a different label namespace |
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* clear out context state |
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*/ |
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aa_clear_task_ctx_trans(task_ctx(current)); |
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/* |
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* be careful switching cred label, when racing replacement it |
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* is possible that the cred labels's->proxy->label is the reference |
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* keeping @label valid, so make sure to get its reference before |
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* dropping the reference on the cred's label |
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*/ |
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aa_get_label(label); |
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aa_put_label(cred_label(new)); |
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set_cred_label(new, label); |
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commit_creds(new); |
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return 0; |
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} |
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/** |
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* aa_set_current_onexec - set the tasks change_profile to happen onexec |
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* @label: system label to set at exec (MAYBE NULL to clear value) |
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* @stack: whether stacking should be done |
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* Returns: 0 or error on failure |
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*/ |
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int aa_set_current_onexec(struct aa_label *label, bool stack) |
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{ |
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struct aa_task_ctx *ctx = task_ctx(current); |
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aa_get_label(label); |
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aa_put_label(ctx->onexec); |
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ctx->onexec = label; |
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ctx->token = stack; |
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return 0; |
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} |
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/** |
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* aa_set_current_hat - set the current tasks hat |
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* @label: label to set as the current hat (NOT NULL) |
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* @token: token value that must be specified to change from the hat |
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* |
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* Do switch of tasks hat. If the task is currently in a hat |
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* validate the token to match. |
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* |
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* Returns: 0 or error on failure |
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*/ |
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int aa_set_current_hat(struct aa_label *label, u64 token) |
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{ |
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struct aa_task_ctx *ctx = task_ctx(current); |
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struct cred *new; |
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new = prepare_creds(); |
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if (!new) |
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return -ENOMEM; |
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AA_BUG(!label); |
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if (!ctx->previous) { |
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/* transfer refcount */ |
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ctx->previous = cred_label(new); |
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ctx->token = token; |
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} else if (ctx->token == token) { |
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aa_put_label(cred_label(new)); |
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} else { |
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/* previous_profile && ctx->token != token */ |
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abort_creds(new); |
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return -EACCES; |
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} |
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set_cred_label(new, aa_get_newest_label(label)); |
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/* clear exec on switching context */ |
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aa_put_label(ctx->onexec); |
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ctx->onexec = NULL; |
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commit_creds(new); |
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return 0; |
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} |
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/** |
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* aa_restore_previous_label - exit from hat context restoring previous label |
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* @token: the token that must be matched to exit hat context |
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* |
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* Attempt to return out of a hat to the previous label. The token |
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* must match the stored token value. |
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* |
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* Returns: 0 or error of failure |
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*/ |
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int aa_restore_previous_label(u64 token) |
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{ |
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struct aa_task_ctx *ctx = task_ctx(current); |
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struct cred *new; |
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if (ctx->token != token) |
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return -EACCES; |
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/* ignore restores when there is no saved label */ |
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if (!ctx->previous) |
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return 0; |
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new = prepare_creds(); |
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if (!new) |
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return -ENOMEM; |
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aa_put_label(cred_label(new)); |
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set_cred_label(new, aa_get_newest_label(ctx->previous)); |
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AA_BUG(!cred_label(new)); |
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/* clear exec && prev information when restoring to previous context */ |
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aa_clear_task_ctx_trans(ctx); |
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commit_creds(new); |
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return 0; |
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} |
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/** |
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* audit_ptrace_mask - convert mask to permission string |
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* @mask: permission mask to convert |
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* |
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* Returns: pointer to static string |
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*/ |
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static const char *audit_ptrace_mask(u32 mask) |
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{ |
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switch (mask) { |
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case MAY_READ: |
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return "read"; |
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case MAY_WRITE: |
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return "trace"; |
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case AA_MAY_BE_READ: |
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return "readby"; |
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case AA_MAY_BE_TRACED: |
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return "tracedby"; |
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} |
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return ""; |
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} |
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/* call back to audit ptrace fields */ |
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static void audit_ptrace_cb(struct audit_buffer *ab, void *va) |
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{ |
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struct common_audit_data *sa = va; |
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if (aad(sa)->request & AA_PTRACE_PERM_MASK) { |
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audit_log_format(ab, " requested_mask=\"%s\"", |
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audit_ptrace_mask(aad(sa)->request)); |
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if (aad(sa)->denied & AA_PTRACE_PERM_MASK) { |
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audit_log_format(ab, " denied_mask=\"%s\"", |
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audit_ptrace_mask(aad(sa)->denied)); |
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} |
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} |
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audit_log_format(ab, " peer="); |
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aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer, |
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FLAGS_NONE, GFP_ATOMIC); |
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} |
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/* assumes check for PROFILE_MEDIATES is already done */ |
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/* TODO: conditionals */ |
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static int profile_ptrace_perm(struct aa_profile *profile, |
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struct aa_label *peer, u32 request, |
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struct common_audit_data *sa) |
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{ |
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struct aa_perms perms = { }; |
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aad(sa)->peer = peer; |
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aa_profile_match_label(profile, peer, AA_CLASS_PTRACE, request, |
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&perms); |
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aa_apply_modes_to_perms(profile, &perms); |
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return aa_check_perms(profile, &perms, request, sa, audit_ptrace_cb); |
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} |
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static int profile_tracee_perm(struct aa_profile *tracee, |
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struct aa_label *tracer, u32 request, |
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struct common_audit_data *sa) |
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{ |
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if (profile_unconfined(tracee) || unconfined(tracer) || |
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!PROFILE_MEDIATES(tracee, AA_CLASS_PTRACE)) |
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return 0; |
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return profile_ptrace_perm(tracee, tracer, request, sa); |
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} |
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static int profile_tracer_perm(struct aa_profile *tracer, |
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struct aa_label *tracee, u32 request, |
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struct common_audit_data *sa) |
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{ |
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if (profile_unconfined(tracer)) |
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return 0; |
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if (PROFILE_MEDIATES(tracer, AA_CLASS_PTRACE)) |
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return profile_ptrace_perm(tracer, tracee, request, sa); |
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/* profile uses the old style capability check for ptrace */ |
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if (&tracer->label == tracee) |
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return 0; |
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aad(sa)->label = &tracer->label; |
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aad(sa)->peer = tracee; |
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aad(sa)->request = 0; |
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aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE, |
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CAP_OPT_NONE); |
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return aa_audit(AUDIT_APPARMOR_AUTO, tracer, sa, audit_ptrace_cb); |
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} |
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/** |
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* aa_may_ptrace - test if tracer task can trace the tracee |
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* @tracer: label of the task doing the tracing (NOT NULL) |
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* @tracee: task label to be traced |
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* @request: permission request |
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* |
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* Returns: %0 else error code if permission denied or error |
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*/ |
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int aa_may_ptrace(struct aa_label *tracer, struct aa_label *tracee, |
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u32 request) |
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{ |
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struct aa_profile *profile; |
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u32 xrequest = request << PTRACE_PERM_SHIFT; |
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DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, OP_PTRACE); |
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return xcheck_labels(tracer, tracee, profile, |
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profile_tracer_perm(profile, tracee, request, &sa), |
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profile_tracee_perm(profile, tracer, xrequest, &sa)); |
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}
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