diff options
Diffstat (limited to 'Documentation/security')
| -rw-r--r-- | Documentation/security/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/security/keys/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/security/keys/request-key.rst (renamed from Documentation/security/keys-request-key.txt) | 69 |
3 files changed, 34 insertions, 38 deletions
diff --git a/Documentation/security/00-INDEX b/Documentation/security/00-INDEX index 08a6e7a195ef..c8dbbc227326 100644 --- a/Documentation/security/00-INDEX +++ b/Documentation/security/00-INDEX @@ -1,6 +1,4 @@ 00-INDEX - this file. -keys-request-key.txt - - description of the kernel key request service. keys-trusted-encrypted.txt - info on the Trusted and Encrypted keys in the kernel key ring service. diff --git a/Documentation/security/keys/index.rst b/Documentation/security/keys/index.rst index d34f663354bb..d7ddbc1c2502 100644 --- a/Documentation/security/keys/index.rst +++ b/Documentation/security/keys/index.rst @@ -7,3 +7,4 @@ Kernel Keys core ecryptfs + request-key diff --git a/Documentation/security/keys-request-key.txt b/Documentation/security/keys/request-key.rst index 51987bfecfed..5cdcee28479e 100644 --- a/Documentation/security/keys-request-key.txt +++ b/Documentation/security/keys/request-key.rst @@ -1,19 +1,19 @@ - =================== - KEY REQUEST SERVICE - =================== +=================== +Key Request Service +=================== The key request service is part of the key retention service (refer to Documentation/security/keys.txt). This document explains more fully how the requesting algorithm works. The process starts by either the kernel requesting a service by calling -request_key*(): +``request_key*()``:: struct key *request_key(const struct key_type *type, const char *description, const char *callout_info); -or: +or:: struct key *request_key_with_auxdata(const struct key_type *type, const char *description, @@ -21,14 +21,14 @@ or: size_t callout_len, void *aux); -or: +or:: struct key *request_key_async(const struct key_type *type, const char *description, const char *callout_info, size_t callout_len); -or: +or:: struct key *request_key_async_with_auxdata(const struct key_type *type, const char *description, @@ -36,7 +36,7 @@ or: size_t callout_len, void *aux); -Or by userspace invoking the request_key system call: +Or by userspace invoking the request_key system call:: key_serial_t request_key(const char *type, const char *description, @@ -67,38 +67,37 @@ own upcall mechanisms. If they do, then those should be substituted for the forking and execution of /sbin/request-key. -=========== -THE PROCESS +The Process =========== A request proceeds in the following manner: - (1) Process A calls request_key() [the userspace syscall calls the kernel + 1) Process A calls request_key() [the userspace syscall calls the kernel interface]. - (2) request_key() searches the process's subscribed keyrings to see if there's + 2) request_key() searches the process's subscribed keyrings to see if there's a suitable key there. If there is, it returns the key. If there isn't, and callout_info is not set, an error is returned. Otherwise the process proceeds to the next step. - (3) request_key() sees that A doesn't have the desired key yet, so it creates + 3) request_key() sees that A doesn't have the desired key yet, so it creates two things: - (a) An uninstantiated key U of requested type and description. + a) An uninstantiated key U of requested type and description. - (b) An authorisation key V that refers to key U and notes that process A + b) An authorisation key V that refers to key U and notes that process A is the context in which key U should be instantiated and secured, and from which associated key requests may be satisfied. - (4) request_key() then forks and executes /sbin/request-key with a new session + 4) request_key() then forks and executes /sbin/request-key with a new session keyring that contains a link to auth key V. - (5) /sbin/request-key assumes the authority associated with key U. + 5) /sbin/request-key assumes the authority associated with key U. - (6) /sbin/request-key execs an appropriate program to perform the actual + 6) /sbin/request-key execs an appropriate program to perform the actual instantiation. - (7) The program may want to access another key from A's context (say a + 7) The program may want to access another key from A's context (say a Kerberos TGT key). It just requests the appropriate key, and the keyring search notes that the session keyring has auth key V in its bottom level. @@ -110,10 +109,10 @@ A request proceeds in the following manner: instantiate key U, using key W as a reference (perhaps it contacts a Kerberos server using the TGT) and then instantiates key U. - (9) Upon instantiating key U, auth key V is automatically revoked so that it + 9) Upon instantiating key U, auth key V is automatically revoked so that it may not be used again. -(10) The program then exits 0 and request_key() deletes key V and returns key + 10) The program then exits 0 and request_key() deletes key V and returns key U to the caller. This also extends further. If key W (step 7 above) didn't exist, key W would @@ -127,8 +126,7 @@ This is because process A's keyrings can't simply be attached to of them, and (b) it requires the same UID/GID/Groups all the way through. -==================================== -NEGATIVE INSTANTIATION AND REJECTION +Negative Instantiation And Rejection ==================================== Rather than instantiating a key, it is possible for the possessor of an @@ -145,23 +143,22 @@ signal, the key under construction will be automatically negatively instantiated for a short amount of time. -==================== -THE SEARCH ALGORITHM +The Search Algorithm ==================== A search of any particular keyring proceeds in the following fashion: - (1) When the key management code searches for a key (keyring_search_aux) it + 1) When the key management code searches for a key (keyring_search_aux) it firstly calls key_permission(SEARCH) on the keyring it's starting with, if this denies permission, it doesn't search further. - (2) It considers all the non-keyring keys within that keyring and, if any key + 2) It considers all the non-keyring keys within that keyring and, if any key matches the criteria specified, calls key_permission(SEARCH) on it to see if the key is allowed to be found. If it is, that key is returned; if not, the search continues, and the error code is retained if of higher priority than the one currently set. - (3) It then considers all the keyring-type keys in the keyring it's currently + 3) It then considers all the keyring-type keys in the keyring it's currently searching. It calls key_permission(SEARCH) on each keyring, and if this grants permission, it recurses, executing steps (2) and (3) on that keyring. @@ -173,20 +170,20 @@ returned. When search_process_keyrings() is invoked, it performs the following searches until one succeeds: - (1) If extant, the process's thread keyring is searched. + 1) If extant, the process's thread keyring is searched. - (2) If extant, the process's process keyring is searched. + 2) If extant, the process's process keyring is searched. - (3) The process's session keyring is searched. + 3) The process's session keyring is searched. - (4) If the process has assumed the authority associated with a request_key() + 4) If the process has assumed the authority associated with a request_key() authorisation key then: - (a) If extant, the calling process's thread keyring is searched. + a) If extant, the calling process's thread keyring is searched. - (b) If extant, the calling process's process keyring is searched. + b) If extant, the calling process's process keyring is searched. - (c) The calling process's session keyring is searched. + c) The calling process's session keyring is searched. The moment one succeeds, all pending errors are discarded and the found key is returned. @@ -194,7 +191,7 @@ returned. Only if all these fail does the whole thing fail with the highest priority error. Note that several errors may have come from LSM. -The error priority is: +The error priority is:: EKEYREVOKED > EKEYEXPIRED > ENOKEY |