diff options
Diffstat (limited to 'Documentation/security')
| -rw-r--r-- | Documentation/security/00-INDEX | 6 | ||||
| -rw-r--r-- | Documentation/security/IMA-templates.txt | 89 | ||||
| -rw-r--r-- | Documentation/security/Smack.txt | 231 | ||||
| -rw-r--r-- | Documentation/security/Yama.txt | 73 | ||||
| -rw-r--r-- | Documentation/security/keys-trusted-encrypted.txt | 2 | ||||
| -rw-r--r-- | Documentation/security/keys.txt | 124 |
6 files changed, 470 insertions, 55 deletions
diff --git a/Documentation/security/00-INDEX b/Documentation/security/00-INDEX index 99b85d39751..45c82fd3e9d 100644 --- a/Documentation/security/00-INDEX +++ b/Documentation/security/00-INDEX @@ -6,10 +6,14 @@ SELinux.txt - how to get started with the SELinux security enhancement. Smack.txt - documentation on the Smack Linux Security Module. +Yama.txt + - documentation on the Yama Linux Security Module. apparmor.txt - documentation on the AppArmor security extension. credentials.txt - documentation about credentials in Linux. +keys-ecryptfs.txt + - description of the encryption keys for the ecryptfs filesystem. keys-request-key.txt - description of the kernel key request service. keys-trusted-encrypted.txt @@ -18,3 +22,5 @@ keys.txt - description of the kernel key retention service. tomoyo.txt - documentation on the TOMOYO Linux Security Module. +IMA-templates.txt + - documentation on the template management mechanism for IMA. diff --git a/Documentation/security/IMA-templates.txt b/Documentation/security/IMA-templates.txt new file mode 100644 index 00000000000..a4e102dddfe --- /dev/null +++ b/Documentation/security/IMA-templates.txt @@ -0,0 +1,89 @@ + IMA Template Management Mechanism + + +==== INTRODUCTION ==== + +The original 'ima' template is fixed length, containing the filedata hash +and pathname. The filedata hash is limited to 20 bytes (md5/sha1). +The pathname is a null terminated string, limited to 255 characters. +To overcome these limitations and to add additional file metadata, it is +necessary to extend the current version of IMA by defining additional +templates. For example, information that could be possibly reported are +the inode UID/GID or the LSM labels either of the inode and of the process +that is accessing it. + +However, the main problem to introduce this feature is that, each time +a new template is defined, the functions that generate and display +the measurements list would include the code for handling a new format +and, thus, would significantly grow over the time. + +The proposed solution solves this problem by separating the template +management from the remaining IMA code. The core of this solution is the +definition of two new data structures: a template descriptor, to determine +which information should be included in the measurement list; a template +field, to generate and display data of a given type. + +Managing templates with these structures is very simple. To support +a new data type, developers define the field identifier and implement +two functions, init() and show(), respectively to generate and display +measurement entries. Defining a new template descriptor requires +specifying the template format, a string of field identifiers separated +by the '|' character. While in the current implementation it is possible +to define new template descriptors only by adding their definition in the +template specific code (ima_template.c), in a future version it will be +possible to register a new template on a running kernel by supplying to IMA +the desired format string. In this version, IMA initializes at boot time +all defined template descriptors by translating the format into an array +of template fields structures taken from the set of the supported ones. + +After the initialization step, IMA will call ima_alloc_init_template() +(new function defined within the patches for the new template management +mechanism) to generate a new measurement entry by using the template +descriptor chosen through the kernel configuration or through the newly +introduced 'ima_template=' kernel command line parameter. It is during this +phase that the advantages of the new architecture are clearly shown: +the latter function will not contain specific code to handle a given template +but, instead, it simply calls the init() method of the template fields +associated to the chosen template descriptor and store the result (pointer +to allocated data and data length) in the measurement entry structure. + +The same mechanism is employed to display measurements entries. +The functions ima[_ascii]_measurements_show() retrieve, for each entry, +the template descriptor used to produce that entry and call the show() +method for each item of the array of template fields structures. + + + +==== SUPPORTED TEMPLATE FIELDS AND DESCRIPTORS ==== + +In the following, there is the list of supported template fields +('<identifier>': description), that can be used to define new template +descriptors by adding their identifier to the format string +(support for more data types will be added later): + + - 'd': the digest of the event (i.e. the digest of a measured file), + calculated with the SHA1 or MD5 hash algorithm; + - 'n': the name of the event (i.e. the file name), with size up to 255 bytes; + - 'd-ng': the digest of the event, calculated with an arbitrary hash + algorithm (field format: [<hash algo>:]digest, where the digest + prefix is shown only if the hash algorithm is not SHA1 or MD5); + - 'n-ng': the name of the event, without size limitations; + - 'sig': the file signature. + + +Below, there is the list of defined template descriptors: + - "ima": its format is 'd|n'; + - "ima-ng" (default): its format is 'd-ng|n-ng'; + - "ima-sig": its format is 'd-ng|n-ng|sig'. + + + +==== USE ==== + +To specify the template descriptor to be used to generate measurement entries, +currently the following methods are supported: + + - select a template descriptor among those supported in the kernel + configuration ('ima-ng' is the default choice); + - specify a template descriptor name from the kernel command line through + the 'ima_template=' parameter. diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt index e9dab41c0fe..b6ef7e9dba3 100644 --- a/Documentation/security/Smack.txt +++ b/Documentation/security/Smack.txt @@ -3,7 +3,7 @@ "Good for you, you've decided to clean the elevator!" - The Elevator, from Dark Star -Smack is the the Simplified Mandatory Access Control Kernel. +Smack is the Simplified Mandatory Access Control Kernel. Smack is a kernel based implementation of mandatory access control that includes simplicity in its primary design goals. @@ -15,7 +15,7 @@ at hand. Smack consists of three major components: - The kernel - - A start-up script and a few modified applications + - Basic utilities, which are helpful but not required - Configuration data The kernel component of Smack is implemented as a Linux @@ -23,37 +23,27 @@ Security Modules (LSM) module. It requires netlabel and works best with file systems that support extended attributes, although xattr support is not strictly required. It is safe to run a Smack kernel under a "vanilla" distribution. + Smack kernels use the CIPSO IP option. Some network configurations are intolerant of IP options and can impede access to systems that use them as Smack does. -The startup script etc-init.d-smack should be installed -in /etc/init.d/smack and should be invoked early in the -start-up process. On Fedora rc5.d/S02smack is recommended. -This script ensures that certain devices have the correct -Smack attributes and loads the Smack configuration if -any is defined. This script invokes two programs that -ensure configuration data is properly formatted. These -programs are /usr/sbin/smackload and /usr/sin/smackcipso. -The system will run just fine without these programs, -but it will be difficult to set access rules properly. - -A version of "ls" that provides a "-M" option to display -Smack labels on long listing is available. +The current git repository for Smack user space is: -A hacked version of sshd that allows network logins by users -with specific Smack labels is available. This version does -not work for scp. You must set the /etc/ssh/sshd_config -line: - UsePrivilegeSeparation no + git://github.com/smack-team/smack.git -The format of /etc/smack/usr is: +This should make and install on most modern distributions. +There are three commands included in smackutil: - username smack +smackload - properly formats data for writing to /smack/load +smackcipso - properly formats data for writing to /smack/cipso +chsmack - display or set Smack extended attribute values In keeping with the intent of Smack, configuration data is minimal and not strictly required. The most important configuration step is mounting the smackfs pseudo filesystem. +If smackutil is installed the startup script will take care +of this, but it can be manually as well. Add this line to /etc/fstab: @@ -61,19 +51,172 @@ Add this line to /etc/fstab: and create the /smack directory for mounting. -Smack uses extended attributes (xattrs) to store file labels. -The command to set a Smack label on a file is: +Smack uses extended attributes (xattrs) to store labels on filesystem +objects. The attributes are stored in the extended attribute security +name space. A process must have CAP_MAC_ADMIN to change any of these +attributes. + +The extended attributes that Smack uses are: + +SMACK64 + Used to make access control decisions. In almost all cases + the label given to a new filesystem object will be the label + of the process that created it. +SMACK64EXEC + The Smack label of a process that execs a program file with + this attribute set will run with this attribute's value. +SMACK64MMAP + Don't allow the file to be mmapped by a process whose Smack + label does not allow all of the access permitted to a process + with the label contained in this attribute. This is a very + specific use case for shared libraries. +SMACK64TRANSMUTE + Can only have the value "TRUE". If this attribute is present + on a directory when an object is created in the directory and + the Smack rule (more below) that permitted the write access + to the directory includes the transmute ("t") mode the object + gets the label of the directory instead of the label of the + creating process. If the object being created is a directory + the SMACK64TRANSMUTE attribute is set as well. +SMACK64IPIN + This attribute is only available on file descriptors for sockets. + Use the Smack label in this attribute for access control + decisions on packets being delivered to this socket. +SMACK64IPOUT + This attribute is only available on file descriptors for sockets. + Use the Smack label in this attribute for access control + decisions on packets coming from this socket. + +There are multiple ways to set a Smack label on a file: # attr -S -s SMACK64 -V "value" path + # chsmack -a value path -NOTE: Smack labels are limited to 23 characters. The attr command - does not enforce this restriction and can be used to set - invalid Smack labels on files. - -If you don't do anything special all users will get the floor ("_") -label when they log in. If you do want to log in via the hacked ssh -at other labels use the attr command to set the smack value on the -home directory and its contents. +A process can see the smack label it is running with by +reading /proc/self/attr/current. A process with CAP_MAC_ADMIN +can set the process smack by writing there. + +Most Smack configuration is accomplished by writing to files +in the smackfs filesystem. This pseudo-filesystem is usually +mounted on /smack. + +access + This interface reports whether a subject with the specified + Smack label has a particular access to an object with a + specified Smack label. Write a fixed format access rule to + this file. The next read will indicate whether the access + would be permitted. The text will be either "1" indicating + access, or "0" indicating denial. +access2 + This interface reports whether a subject with the specified + Smack label has a particular access to an object with a + specified Smack label. Write a long format access rule to + this file. The next read will indicate whether the access + would be permitted. The text will be either "1" indicating + access, or "0" indicating denial. +ambient + This contains the Smack label applied to unlabeled network + packets. +change-rule + This interface allows modification of existing access control rules. + The format accepted on write is: + "%s %s %s %s" + where the first string is the subject label, the second the + object label, the third the access to allow and the fourth the + access to deny. The access strings may contain only the characters + "rwxat-". If a rule for a given subject and object exists it will be + modified by enabling the permissions in the third string and disabling + those in the fourth string. If there is no such rule it will be + created using the access specified in the third and the fourth strings. +cipso + This interface allows a specific CIPSO header to be assigned + to a Smack label. The format accepted on write is: + "%24s%4d%4d"["%4d"]... + The first string is a fixed Smack label. The first number is + the level to use. The second number is the number of categories. + The following numbers are the categories. + "level-3-cats-5-19 3 2 5 19" +cipso2 + This interface allows a specific CIPSO header to be assigned + to a Smack label. The format accepted on write is: + "%s%4d%4d"["%4d"]... + The first string is a long Smack label. The first number is + the level to use. The second number is the number of categories. + The following numbers are the categories. + "level-3-cats-5-19 3 2 5 19" +direct + This contains the CIPSO level used for Smack direct label + representation in network packets. +doi + This contains the CIPSO domain of interpretation used in + network packets. +load + This interface allows access control rules in addition to + the system defined rules to be specified. The format accepted + on write is: + "%24s%24s%5s" + where the first string is the subject label, the second the + object label, and the third the requested access. The access + string may contain only the characters "rwxat-", and specifies + which sort of access is allowed. The "-" is a placeholder for + permissions that are not allowed. The string "r-x--" would + specify read and execute access. Labels are limited to 23 + characters in length. +load2 + This interface allows access control rules in addition to + the system defined rules to be specified. The format accepted + on write is: + "%s %s %s" + where the first string is the subject label, the second the + object label, and the third the requested access. The access + string may contain only the characters "rwxat-", and specifies + which sort of access is allowed. The "-" is a placeholder for + permissions that are not allowed. The string "r-x--" would + specify read and execute access. +load-self + This interface allows process specific access rules to be + defined. These rules are only consulted if access would + otherwise be permitted, and are intended to provide additional + restrictions on the process. The format is the same as for + the load interface. +load-self2 + This interface allows process specific access rules to be + defined. These rules are only consulted if access would + otherwise be permitted, and are intended to provide additional + restrictions on the process. The format is the same as for + the load2 interface. +logging + This contains the Smack logging state. +mapped + This contains the CIPSO level used for Smack mapped label + representation in network packets. +netlabel + This interface allows specific internet addresses to be + treated as single label hosts. Packets are sent to single + label hosts without CIPSO headers, but only from processes + that have Smack write access to the host label. All packets + received from single label hosts are given the specified + label. The format accepted on write is: + "%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label". +onlycap + This contains the label processes must have for CAP_MAC_ADMIN + and CAP_MAC_OVERRIDE to be effective. If this file is empty + these capabilities are effective at for processes with any + label. The value is set by writing the desired label to the + file or cleared by writing "-" to the file. +ptrace + This is used to define the current ptrace policy + 0 - default: this is the policy that relies on smack access rules. + For the PTRACE_READ a subject needs to have a read access on + object. For the PTRACE_ATTACH a read-write access is required. + 1 - exact: this is the policy that limits PTRACE_ATTACH. Attach is + only allowed when subject's and object's labels are equal. + PTRACE_READ is not affected. Can be overriden with CAP_SYS_PTRACE. + 2 - draconian: this policy behaves like the 'exact' above with an + exception that it can't be overriden with CAP_SYS_PTRACE. +revoke-subject + Writing a Smack label here sets the access to '-' for all access + rules with that subject label. You can add access rules in /etc/smack/accesses. They take the form: @@ -83,10 +226,6 @@ access is a combination of the letters rwxa which specify the kind of access permitted a subject with subjectlabel on an object with objectlabel. If there is no rule no access is allowed. -A process can see the smack label it is running with by -reading /proc/self/attr/current. A privileged process can -set the process smack by writing there. - Look for additional programs on http://schaufler-ca.com From the Smack Whitepaper: @@ -186,7 +325,7 @@ team. Smack labels are unstructured, case sensitive, and the only operation ever performed on them is comparison for equality. Smack labels cannot contain unprintable characters, the "/" (slash), the "\" (backslash), the "'" (quote) and '"' (double-quote) characters. -Smack labels cannot begin with a '-', which is reserved for special options. +Smack labels cannot begin with a '-'. This is reserved for special options. There are some predefined labels: @@ -194,7 +333,7 @@ There are some predefined labels: ^ Pronounced "hat", a single circumflex character. * Pronounced "star", a single asterisk character. ? Pronounced "huh", a single question mark character. - @ Pronounced "Internet", a single at sign character. + @ Pronounced "web", a single at sign character. Every task on a Smack system is assigned a label. System tasks, such as init(8) and systems daemons, are run with the floor ("_") label. User tasks @@ -246,13 +385,14 @@ The format of an access rule is: Where subject-label is the Smack label of the task, object-label is the Smack label of the thing being accessed, and access is a string specifying the sort -of access allowed. The Smack labels are limited to 23 characters. The access -specification is searched for letters that describe access modes: +of access allowed. The access specification is searched for letters that +describe access modes: a: indicates that append access should be granted. r: indicates that read access should be granted. w: indicates that write access should be granted. x: indicates that execute access should be granted. + t: indicates that the rule requests transmutation. Uppercase values for the specification letters are allowed as well. Access mode specifications can be in any order. Examples of acceptable rules @@ -273,7 +413,7 @@ Examples of unacceptable rules are: Spaces are not allowed in labels. Since a subject always has access to files with the same label specifying a rule for that case is pointless. Only -valid letters (rwxaRWXA) and the dash ('-') character are allowed in +valid letters (rwxatRWXAT) and the dash ('-') character are allowed in access specifications. The dash is a placeholder, so "a-r" is the same as "ar". A lone dash is used to specify that no access should be allowed. @@ -297,6 +437,13 @@ but not any of its attributes by the circumstance of having read access to the containing directory but not to the differently labeled file. This is an artifact of the file name being data in the directory, not a part of the file. +If a directory is marked as transmuting (SMACK64TRANSMUTE=TRUE) and the +access rule that allows a process to create an object in that directory +includes 't' access the label assigned to the new object will be that +of the directory, not the creating process. This makes it much easier +for two processes with different labels to share data without granting +access to all of their files. + IPC objects, message queues, semaphore sets, and memory segments exist in flat namespaces and access requests are only required to match the object in question. @@ -536,6 +683,6 @@ writing a single character to the /smack/logging file : 3 : log denied & accepted Events are logged as 'key=value' pairs, for each event you at least will get -the subjet, the object, the rights requested, the action, the kernel function +the subject, the object, the rights requested, the action, the kernel function that triggered the event, plus other pairs depending on the type of event audited. diff --git a/Documentation/security/Yama.txt b/Documentation/security/Yama.txt new file mode 100644 index 00000000000..227a63f018a --- /dev/null +++ b/Documentation/security/Yama.txt @@ -0,0 +1,73 @@ +Yama is a Linux Security Module that collects a number of system-wide DAC +security protections that are not handled by the core kernel itself. To +select it at boot time, specify "security=yama" (though this will disable +any other LSM). + +Yama is controlled through sysctl in /proc/sys/kernel/yama: + +- ptrace_scope + +============================================================== + +ptrace_scope: + +As Linux grows in popularity, it will become a larger target for +malware. One particularly troubling weakness of the Linux process +interfaces is that a single user is able to examine the memory and +running state of any of their processes. For example, if one application +(e.g. Pidgin) was compromised, it would be possible for an attacker to +attach to other running processes (e.g. Firefox, SSH sessions, GPG agent, +etc) to extract additional credentials and continue to expand the scope +of their attack without resorting to user-assisted phishing. + +This is not a theoretical problem. SSH session hijacking +(http://www.storm.net.nz/projects/7) and arbitrary code injection +(http://c-skills.blogspot.com/2007/05/injectso.html) attacks already +exist and remain possible if ptrace is allowed to operate as before. +Since ptrace is not commonly used by non-developers and non-admins, system +builders should be allowed the option to disable this debugging system. + +For a solution, some applications use prctl(PR_SET_DUMPABLE, ...) to +specifically disallow such ptrace attachment (e.g. ssh-agent), but many +do not. A more general solution is to only allow ptrace directly from a +parent to a child process (i.e. direct "gdb EXE" and "strace EXE" still +work), or with CAP_SYS_PTRACE (i.e. "gdb --pid=PID", and "strace -p PID" +still work as root). + +In mode 1, software that has defined application-specific relationships +between a debugging process and its inferior (crash handlers, etc), +prctl(PR_SET_PTRACER, pid, ...) can be used. An inferior can declare which +other process (and its descendants) are allowed to call PTRACE_ATTACH +against it. Only one such declared debugging process can exists for +each inferior at a time. For example, this is used by KDE, Chromium, and +Firefox's crash handlers, and by Wine for allowing only Wine processes +to ptrace each other. If a process wishes to entirely disable these ptrace +restrictions, it can call prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...) +so that any otherwise allowed process (even those in external pid namespaces) +may attach. + +The sysctl settings (writable only with CAP_SYS_PTRACE) are: + +0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other + process running under the same uid, as long as it is dumpable (i.e. + did not transition uids, start privileged, or have called + prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is + unchanged. + +1 - restricted ptrace: a process must have a predefined relationship + with the inferior it wants to call PTRACE_ATTACH on. By default, + this relationship is that of only its descendants when the above + classic criteria is also met. To change the relationship, an + inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare + an allowed debugger PID to call PTRACE_ATTACH on the inferior. + Using PTRACE_TRACEME is unchanged. + +2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace + with PTRACE_ATTACH, or through children calling PTRACE_TRACEME. + +3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via + PTRACE_TRACEME. Once set, this sysctl value cannot be changed. + +The original children-only logic was based on the restrictions in grsecurity. + +============================================================== diff --git a/Documentation/security/keys-trusted-encrypted.txt b/Documentation/security/keys-trusted-encrypted.txt index c9e4855ed3d..e105ae97a4f 100644 --- a/Documentation/security/keys-trusted-encrypted.txt +++ b/Documentation/security/keys-trusted-encrypted.txt @@ -1,7 +1,7 @@ Trusted and Encrypted Keys Trusted and Encrypted Keys are two new key types added to the existing kernel -key ring service. Both of these new types are variable length symmetic keys, +key ring service. Both of these new types are variable length symmetric keys, and in both cases all keys are created in the kernel, and user space sees, stores, and loads only encrypted blobs. Trusted Keys require the availability of a Trusted Platform Module (TPM) chip for greater security, while Encrypted diff --git a/Documentation/security/keys.txt b/Documentation/security/keys.txt index 4d75931d2d7..a4c33f1a7c6 100644 --- a/Documentation/security/keys.txt +++ b/Documentation/security/keys.txt @@ -123,7 +123,7 @@ KEY SERVICE OVERVIEW The key service provides a number of features besides keys: - (*) The key service defines two special key types: + (*) The key service defines three special key types: (+) "keyring" @@ -137,6 +137,18 @@ The key service provides a number of features besides keys: blobs of data. These can be created, updated and read by userspace, and aren't intended for use by kernel services. + (+) "logon" + + Like a "user" key, a "logon" key has a payload that is an arbitrary + blob of data. It is intended as a place to store secrets which are + accessible to the kernel but not to userspace programs. + + The description can be arbitrary, but must be prefixed with a non-zero + length string that describes the key "subclass". The subclass is + separated from the rest of the description by a ':'. "logon" keys can + be created and updated from userspace, but the payload is only + readable from kernel space. + (*) Each process subscribes to three keyrings: a thread-specific keyring, a process-specific keyring, and a session-specific keyring. @@ -400,6 +412,10 @@ The main syscalls are: to the keyring. In this case, an error will be generated if the process does not have permission to write to the keyring. + If the key type supports it, if the description is NULL or an empty + string, the key type will try and generate a description from the content + of the payload. + The payload is optional, and the pointer can be NULL if not required by the type. The payload is plen in size, and plen can be zero for an empty payload. @@ -554,6 +570,10 @@ The keyctl syscall functions are: process must have write permission on the keyring, and it must be a keyring (or else error ENOTDIR will result). + This function can also be used to clear special kernel keyrings if they + are appropriately marked if the user has CAP_SYS_ADMIN capability. The + DNS resolver cache keyring is an example of this. + (*) Link a key into a keyring: @@ -668,7 +688,7 @@ The keyctl syscall functions are: If the kernel calls back to userspace to complete the instantiation of a key, userspace should use this call mark the key as negative before the - invoked process returns if it is unable to fulfil the request. + invoked process returns if it is unable to fulfill the request. The process must have write access on the key to be able to instantiate it, and the key must be uninstantiated. @@ -789,6 +809,23 @@ The keyctl syscall functions are: kernel and resumes executing userspace. + (*) Invalidate a key. + + long keyctl(KEYCTL_INVALIDATE, key_serial_t key); + + This function marks a key as being invalidated and then wakes up the + garbage collector. The garbage collector immediately removes invalidated + keys from all keyrings and deletes the key when its reference count + reaches zero. + + Keys that are marked invalidated become invisible to normal key operations + immediately, though they are still visible in /proc/keys until deleted + (they're marked with an 'i' flag). + + A process must have search permission on the key for this function to be + successful. + + =============== KERNEL SERVICES =============== @@ -828,15 +865,14 @@ encountered: calling processes has a searchable link to the key from one of its keyrings. There are three functions for dealing with these: - key_ref_t make_key_ref(const struct key *key, - unsigned long possession); + key_ref_t make_key_ref(const struct key *key, bool possession); struct key *key_ref_to_ptr(const key_ref_t key_ref); - unsigned long is_key_possessed(const key_ref_t key_ref); + bool is_key_possessed(const key_ref_t key_ref); The first function constructs a key reference from a key pointer and - possession information (which must be 0 or 1 and not any other value). + possession information (which must be true or false). The second function retrieves the key pointer from a reference and the third retrieves the possession flag. @@ -924,14 +960,17 @@ payload contents" for more information. the argument will not be parsed. -(*) Extra references can be made to a key by calling the following function: +(*) Extra references can be made to a key by calling one of the following + functions: + struct key *__key_get(struct key *key); struct key *key_get(struct key *key); - These need to be disposed of by calling key_put() when they've been - finished with. The key pointer passed in will be returned. If the pointer - is NULL or CONFIG_KEYS is not set then the key will not be dereferenced and - no increment will take place. + Keys so references will need to be disposed of by calling key_put() when + they've been finished with. The key pointer passed in will be returned. + + In the case of key_get(), if the pointer is NULL or CONFIG_KEYS is not set + then the key will not be dereferenced and no increment will take place. (*) A key's serial number can be obtained by calling: @@ -957,6 +996,23 @@ payload contents" for more information. reference pointer if successful. +(*) A keyring can be created by: + + struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid, + const struct cred *cred, + key_perm_t perm, + unsigned long flags, + struct key *dest); + + This creates a keyring with the given attributes and returns it. If dest + is not NULL, the new keyring will be linked into the keyring to which it + points. No permission checks are made upon the destination keyring. + + Error EDQUOT can be returned if the keyring would overload the quota (pass + KEY_ALLOC_NOT_IN_QUOTA in flags if the keyring shouldn't be accounted + towards the user's quota). Error ENOMEM can also be returned. + + (*) To check the validity of a key, this function can be called: int validate_key(struct key *key); @@ -1081,12 +1137,53 @@ The structure has a number of fields, some of which are mandatory: it should return 0. - (*) int (*instantiate)(struct key *key, const void *data, size_t datalen); + (*) int (*preparse)(struct key_preparsed_payload *prep); + + This optional method permits the key type to attempt to parse payload + before a key is created (add key) or the key semaphore is taken (update or + instantiate key). The structure pointed to by prep looks like: + + struct key_preparsed_payload { + char *description; + void *type_data[2]; + void *payload; + const void *data; + size_t datalen; + size_t quotalen; + }; + + Before calling the method, the caller will fill in data and datalen with + the payload blob parameters; quotalen will be filled in with the default + quota size from the key type and the rest will be cleared. + + If a description can be proposed from the payload contents, that should be + attached as a string to the description field. This will be used for the + key description if the caller of add_key() passes NULL or "". + + The method can attach anything it likes to type_data[] and payload. These + are merely passed along to the instantiate() or update() operations. + + The method should return 0 if success ful or a negative error code + otherwise. + + + (*) void (*free_preparse)(struct key_preparsed_payload *prep); + + This method is only required if the preparse() method is provided, + otherwise it is unused. It cleans up anything attached to the + description, type_data and payload fields of the key_preparsed_payload + struct as filled in by the preparse() method. + + + (*) int (*instantiate)(struct key *key, struct key_preparsed_payload *prep); This method is called to attach a payload to a key during construction. The payload attached need not bear any relation to the data passed to this function. + The prep->data and prep->datalen fields will define the original payload + blob. If preparse() was supplied then other fields may be filled in also. + If the amount of data attached to the key differs from the size in keytype->def_datalen, then key_payload_reserve() should be called. @@ -1102,6 +1199,9 @@ The structure has a number of fields, some of which are mandatory: If this type of key can be updated, then this method should be provided. It is called to update a key's payload from the blob of data provided. + The prep->data and prep->datalen fields will define the original payload + blob. If preparse() was supplied then other fields may be filled in also. + key_payload_reserve() should be called if the data length might change before any changes are actually made. Note that if this succeeds, the type is committed to changing the key because it's already been altered, so all |