/*
* Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef BR_BEARSSL_X509_H__
#define BR_BEARSSL_X509_H__
#include <stddef.h>
#include <stdint.h>
#include "bearssl_ec.h"
#include "bearssl_hash.h"
#include "bearssl_rsa.h"
#ifdef __cplusplus
extern "C" {
#endif
/** \file bearssl_x509.h
*
* # X.509 Certificate Chain Processing
*
* An X.509 processing engine receives an X.509 chain, chunk by chunk,
* as received from a SSL/TLS client or server (the client receives the
* server's certificate chain, and the server receives the client's
* certificate chain if it requested a client certificate). The chain
* is thus injected in the engine in SSL order (end-entity first).
*
* The engine's job is to return the public key to use for SSL/TLS.
* How exactly that key is obtained and verified is entirely up to the
* engine.
*
* **The "known key" engine** returns a public key which is already known
* from out-of-band information (e.g. the client _remembers_ the key from
* a previous connection, as in the usual SSH model). This is the simplest
* engine since it simply ignores the chain, thereby avoiding the need
* for any decoding logic.
*
* **The "minimal" engine** implements minimal X.509 decoding and chain
* validation:
*
* - The provided chain should validate "as is". There is no attempt
* at reordering, skipping or downloading extra certificates.
*
* - X.509 v1, v2 and v3 certificates are supported.
*
* - Trust anchors are a DN and a public key. Each anchor is either a
* "CA" anchor, or a non-CA.
*
* - If the end-entity certificate matches a non-CA anchor (subject DN
* is equal to the non-CA name, and public key is also identical to
* the anchor key), then this is a _direct trust_ case and the
* remaining certificates are ignored.
*
* - Unless direct trust is applied, the chain must be verifiable up to
* a certificate whose issuer DN matches the DN from a "CA" trust anchor,
* and whose signature is verifiable against that anchor's public key.
* Subsequent certificates in the chain are ignored.
*
* - The engine verifies subject/issuer DN matching, and enforces
* processing of Basic Constraints and Key Usage extensions. The
* Authority Key Identifier, Subject Key Identifier, Issuer Alt Name,
* Subject Directory Attribute, CRL Distribution Points, Freshest CRL,
* Authority Info Access and Subject Info Access extensions are
* ignored. The Subject Alt Name is decoded for the end-entity
* certificate under some conditions (see below). Other extensions
* are ignored if non-critical, or imply chain rejection if critical.
*
* - The Subject Alt Name extension is parsed for names of type `dNSName`
* when decoding the end-entity certificate, and only if there is a
* server name to match. If there is no SAN extension, then the
* Common Name from the subjectDN is used. That name matching is
* case-insensitive and honours a single starting wildcard (i.e. if
* the name in the certificate starts with "`*.`" then this matches
* any word as first element). Note: this name matching is performed
* also in the "direct trust" model.
*
* - DN matching is byte-to-byte equality (a future version might
* include some limited processing for case-insensitive matching and
* whitespace normalisation).
*
* - Successful validation produces a public key type but also a set
* of allowed usages (`BR_KEYTYPE_KEYX` and/or `BR_KEYTYPE_SIGN`).
* The caller is responsible for checking that the key type and
* usages are compatible with the expected values (e.g. with the
* selected cipher suite, when the client validates the server's
* certificate).
*
* **Important caveats:**
*
* - The "minimal" engine does not check revocation status. The relevant
* extensions are ignored, and CRL or OCSP responses are not gathered
* or checked.
*
* - The "minimal" engine does not currently support Name Constraints
* (some basic functionality to handle sub-domains may be added in a
* later version).
*
* - The decoder is not "validating" in the sense that it won't reject
* some certificates with invalid field values when these fields are
* not actually processed.
*/
/*
* X.509 error codes are in the 32..63 range.
*/
/** \brief X.509 status: validation was successful; this is not actually
an error. */
#define BR_ERR_X509_OK 32
/** \brief X.509 status: invalid value in an ASN.1 structure. */
#define BR_ERR_X509_INVALID_VALUE 33
/** \brief X.509 status: truncated certificate. */
#define BR_ERR_X509_TRUNCATED 34
/** \brief X.509 status: empty certificate chain (no certificate at all). */
#define BR_ERR_X509_EMPTY_CHAIN 35
/** \brief X.509 status: decoding error: inner element extends beyond
outer element size. */
#define BR_ERR_X509_INNER_TRUNC 36
/** \brief X.509 status: decoding error: unsupported tag class (application
or private). */
#define BR_ERR_X509_BAD_TAG_CLASS 37
/** \brief X.509 status: decoding error: unsupported tag value. */
#define BR_ERR_X509_BAD_TAG_VALUE 38
/** \brief X.509 status: decoding error: indefinite length. */
#define BR_ERR_X509_INDEFINITE_LENGTH 39
/** \brief X.509 status: decoding error: extraneous element. */
#define BR_ERR_X509_EXTRA_ELEMENT 40
/** \brief X.509 status: decoding error: unexpected element. */
#define BR_ERR_X509_UNEXPECTED 41
/** \brief X.509 status: decoding error: expected constructed element, but
is primitive. */
#define BR_ERR_X509_NOT_CONSTRUCTED 42
/** \brief X.509 status: decoding error: expected primitive element, but
is constructed. */
#define BR_ERR_X509_NOT_PRIMITIVE 43
/** \brief X.509 status: decoding error: BIT STRING length is not multiple
of 8. */
#define BR_ERR_X509_PARTIAL_BYTE 44
/** \brief X.509 status: decoding error: BOOLEAN value has invalid length. */
#define BR_ERR_X509_BAD_BOOLEAN 45
/** \brief X.509 status: decoding error: value is off-limits. */
#define BR_ERR_X509_OVERFLOW 46
/** \brief X.509 status: invalid distinguished name. */
#define BR_ERR_X509_BAD_DN 47
/** \brief X.509 status: invalid date/time representation. */
#define BR_ERR_X509_BAD_TIME 48
/** \brief X.509 status: certificate contains unsupported features that
cannot be ignored. */
#define BR_ERR_X509_UNSUPPORTED 49
/** \brief X.509 status: key or signature size exceeds internal limits. */
#define BR_ERR_X509_LIMIT_EXCEEDED 50
/** \brief X.509 status: key type does not match that which was expected. */
#define BR_ERR_X509_WRONG_KEY_TYPE 51
/** \brief X.509 status: signature is invalid. */
#define BR_ERR_X509_BAD_SIGNATURE 52
/** \brief X.509 status: validation time is unknown. */
#define BR_ERR_X509_TIME_UNKNOWN 53
/** \brief X.509 status: certificate is expired or not yet valid. */
#define BR_ERR_X509_EXPIRED 54
/** \brief X.509 status: issuer/subject DN mismatch in the chain. */
#define BR_ERR_X509_DN_MISMATCH 55
/** \brief X.509 status: expected server name was not found in the chain. */
#define BR_ERR_X509_BAD_SERVER_NAME 56
/** \brief X.509 status: unknown critical extension in certificate. */
#define BR_ERR_X509_CRITICAL_EXTENSION 57
/** \brief X.509 status: not a CA, or path length constraint violation */
#define BR_ERR_X509_NOT_CA 58
/** \brief X.509 status: Key Usage extension prohibits intended usage. */
#define BR_ERR_X509_FORBIDDEN_KEY_USAGE 59
/** \brief X.509 status: public key found in certificate is too small. */
#define BR_ERR_X509_WEAK_PUBLIC_KEY 60
/** \brief X.509 status: chain could not be linked to a trust anchor. */
#define BR_ERR_X509_NOT_TRUSTED 62
/**
* \brief Aggregate structure for public keys.
*/
typedef struct {
/** \brief Key type: `BR_KEYTYPE_RSA` or `BR_KEYTYPE_EC` */
unsigned char key_type;
/** \brief Actual public key. */
union {
/** \brief RSA public key. */
br_rsa_public_key rsa;
/** \brief EC public key. */
br_ec_public_key ec;
} key;
} br_x509_pkey;
/**
* \brief Distinguished Name (X.500) structure.
*
* The DN is DER-encoded.
*/
typedef struct {
/** \brief Encoded DN data. */
unsigned char *data;
/** \brief Encoded DN length (in bytes). */
size_t len;
} br_x500_name;
/**
* \brief Trust anchor structure.
*/
typedef struct {
/** \brief Encoded DN (X.500 name). */
br_x500_name dn;
/** \brief Anchor flags (e.g. `BR_X509_TA_CA`). */
unsigned flags;
/** \brief Anchor public key. */
br_x509_pkey pkey;
} br_x509_trust_anchor;
/**
* \brief Trust anchor flag: CA.
*
* A "CA" anchor is deemed fit to verify signatures on certificates.
* A "non-CA" anchor is accepted only for direct trust (server's
* certificate name and key match the anchor).
*/
#define BR_X509_TA_CA 0x0001
/*
* Key type: combination of a basic key type (low 4 bits) and some
* optional flags.
*
* For a public key, the basic key type only is set.
*
* For an expected key type, the flags indicate the intended purpose(s)
* for the key; the basic key type may be set to 0 to indicate that any
* key type compatible with the indicated purpose is acceptable.
*/
/** \brief Key type: algorithm is RSA. */
#define BR_KEYTYPE_RSA 1
/** \brief Key type: algorithm is EC. */
#define BR_KEYTYPE_EC 2
/**
* \brief Key type: usage is "key exchange".
*
* This value is combined (with bitwise OR) with the algorithm
* (`BR_KEYTYPE_RSA` or `BR_KEYTYPE_EC`) when informing the X.509
* validation engine that it should find a public key of that type,
* fit for key exchanges (e.g. `TLS_RSA_*` and `TLS_ECDH_*` cipher
* suites).
*/
#define BR_KEYTYPE_KEYX 0x10
/**
* \brief Key type: usage is "signature".
*
* This value is combined (with bitwise OR) with the algorithm
* (`BR_KEYTYPE_RSA` or `BR_KEYTYPE_EC`) when informing the X.509
* validation engine that it should find a public key of that type,
* fit for signatures (e.g. `TLS_ECDHE_*` cipher suites).
*/
#define BR_KEYTYPE_SIGN 0x20
/*
* start_chain Called when a new chain is started. If 'server_name'
* is not NULL and non-empty, then it is a name that
* should be looked for in the EE certificate (in the
* SAN extension as dNSName, or in the subjectDN's CN
* if there is no SAN extension).
* The caller ensures that the provided 'server_name'
* pointer remains valid throughout validation.
*
* start_cert Begins a new certificate in the chain. The provided
* length is in bytes; this is the total certificate length.
*
* append Get some additional bytes for the current certificate.
*
* end_cert Ends the current certificate.
*
* end_chain Called at the end of the chain. Returned value is
* 0 on success, or a non-zero error code.
*
* get_pkey Returns the EE certificate public key.
*
* For a complete chain, start_chain() and end_chain() are always
* called. For each certificate, start_cert(), some append() calls, then
* end_cert() are called, in that order. There may be no append() call
* at all if the certificate is empty (which is not valid but may happen
* if the peer sends exactly that).
*
* get_pkey() shall return a pointer to a structure that is valid as
* long as a new chain is not started. This may be a sub-structure
* within the context for the engine. This function MAY return a valid
* pointer to a public key even in some cases of validation failure,
* depending on the validation engine.
*/
/**
* \brief Class type for an X.509 engine.
*
* A certificate chain validation uses a caller-allocated context, which
* contains the running state for that validation. Methods are called
* in due order:
*
* - `start_chain()` is called at the start of the validation.
* - Certificates are processed one by one, in SSL order (end-entity
* comes first). For each certificate, the following methods are
* called:
*
* - `start_cert()` at the beginning of the certificate.
* - `append()` is called zero, one or more times, to provide
* the certificate (possibly in chunks).
* - `end_cert()` at the end of the certificate.
*
* - `end_chain()` is called when the last certificate in the chain
* was processed.
* - `get_pkey()` is called after chain processing, if the chain
* validation was successful.
*
* A context structure may be reused; the `start_chain()` method shall
* ensure (re)initialisation.
*/
typedef struct br_x509_class_ br_x509_class;
struct br_x509_class_ {
/**
* \brief X.509 context size, in bytes.
*/
size_t context_size;
/**
* \brief Start a new chain.
*
* This method shall set the vtable (first field) of the context
* structure.
*
* The `server_name`, if not `NULL`, will be considered as a
* fully qualified domain name, to be matched against the `dNSName`
* elements of the end-entity certificate's SAN extension (if there
* is no SAN, then the Common Name from the subjectDN will be used).
* If `server_name` is `NULL` then no such matching is performed.
*
* \param ctx validation context.
* \param server_name server name to match (or `NULL`).
*/
void (*start_chain)(const br_x509_class **ctx,
const char *server_name);
/**
* \brief Start a new certificate.
*
* \param ctx validation context.
* \param length new certificate length (in bytes).
*/
void (*start_cert)(const br_x509_class **ctx, uint32_t length);
/**
* \brief Receive some bytes for the current certificate.
*
* This function may be called several times in succession for
* a given certificate. The caller guarantees that for each
* call, `len` is not zero, and the sum of all chunk lengths
* for a certificate matches the total certificate length which
* was provided in the previous `start_cert()` call.
*
* If the new certificate is empty (no byte at all) then this
* function won't be called at all.
*
* \param ctx validation context.
* \param buf certificate data chunk.
* \param len certificate data chunk length (in bytes).
*/
void (*append)(const br_x509_class **ctx,
const unsigned char *buf, size_t len);
/**
* \brief Finish the current certificate.
*
* This function is called when the end of the current certificate
* is reached.
*
* \param ctx validation context.
*/
void (*end_cert)(const br_x509_class **ctx);
/**
* \brief Finish the chain.
*
* This function is called at the end of the chain. It shall
* return either 0 if the validation was successful, or a
* non-zero error code. The `BR_ERR_X509_*` constants are
* error codes, though other values may be possible.
*
* \param ctx validation context.
* \return 0 on success, or a non-zero error code.
*/
unsigned (*end_chain)(const br_x509_class **ctx);
/**
* \brief Get the resulting end-entity public key.
*
* The decoded public key is returned. The returned pointer
* may be valid only as long as the context structure is
* unmodified, i.e. it may cease to be valid if the context
* is released or reused.
*
* This function _may_ return `NULL` if the validation failed.
* However, returning a public key does not mean that the
* validation was wholly successful; some engines may return
* a decoded public key even if the chain did not end on a
* trusted anchor.
*
* If validation succeeded and `usage` is not `NULL`, then
* `*usage` is filled with a combination of `BR_KEYTYPE_SIGN`
* and/or `BR_KEYTYPE_KEYX` that specifies the validated key
* usage types. It is the caller's responsibility to check
* that value against the intended use of the public key.
*
* \param ctx validation context.
* \return the end-entity public key, or `NULL`.
*/
const br_x509_pkey *(*get_pkey)(
const br_x509_class *const *ctx, unsigned *usages);
};
/**
* \brief The "known key" X.509 engine structure.
*
* The structure contents are opaque (they shall not be accessed directly),
* except for the first field (the vtable).
*
* The "known key" engine returns an externally configured public key,
* and totally ignores the certificate contents.
*/
typedef struct {
/** \brief Reference to the context vtable. */
const br_x509_class *vtable;
#ifndef BR_DOXYGEN_IGNORE
br_x509_pkey pkey;
unsigned usages;
#endif
} br_x509_knownkey_context;
/**
* \brief Class instance for the "known key" X.509 engine.
*/
extern const br_x509_class br_x509_knownkey_vtable;
/**
* \brief Initialize a "known key" X.509 engine with a known RSA public key.
*
* The `usages` parameter indicates the allowed key usages for that key
* (`BR_KEYTYPE_KEYX` and/or `BR_KEYTYPE_SIGN`).
*
* The provided pointers are linked in, not copied, so they must remain
* valid while the public key may be in usage.
*
* \param ctx context to initialise.
* \param pk known public key.
* \param usages allowed key usages.
*/
void br_x509_knownkey_init_rsa(br_x509_knownkey_context *ctx,
const br_rsa_public_key *pk, unsigned usages);
/**
* \brief Initialize a "known key" X.509 engine with a known EC public key.
*
* The `usages` parameter indicates the allowed key usages for that key
* (`BR_KEYTYPE_KEYX` and/or `BR_KEYTYPE_SIGN`).
*
* The provided pointers are linked in, not copied, so they must remain
* valid while the public key may be in usage.
*
* \param ctx context to initialise.
* \param pk known public key.
* \param usages allowed key usages.
*/
void br_x509_knownkey_init_ec(br_x509_knownkey_context *ctx,
const br_ec_public_key *pk, unsigned usages);
#ifndef BR_DOXYGEN_IGNORE
/*
* The minimal X.509 engine has some state buffers which must be large
* enough to simultaneously accommodate:
* -- the public key extracted from the current certificate;
* -- the signature on the current certificate or on the previous
* certificate;
* -- the public key extracted from the EE certificate.
*
* We store public key elements in their raw unsigned big-endian
* encoding. We want to support up to RSA-4096 with a short (up to 64
* bits) public exponent, thus a buffer for a public key must have
* length at least 520 bytes. Similarly, a RSA-4096 signature has length
* 512 bytes.
*
* Though RSA public exponents can formally be as large as the modulus
* (mathematically, even larger exponents would work, but PKCS#1 forbids
* them), exponents that do not fit on 32 bits are extremely rare,
* notably because some widespread implementations (e.g. Microsoft's
* CryptoAPI) don't support them. Moreover, large public exponent do not
* seem to imply any tangible security benefit, and they increase the
* cost of public key operations. The X.509 "minimal" engine will tolerate
* public exponents of arbitrary size as long as the modulus and the
* exponent can fit together in the dedicated buffer.
*
* EC public keys are shorter than RSA public keys; even with curve
* NIST P-521 (the largest curve we care to support), a public key is
* encoded over 133 bytes only.
*/
#define BR_X509_BUFSIZE_KEY 520
#define BR_X509_BUFSIZE_SIG 512
#endif
/**
* \brief Type for receiving a name element.
*
* An array of such structures can be provided to the X.509 decoding
* engines. If the specified elements are found in the certificate
* subject DN or the SAN extension, then the name contents are copied
* as zero-terminated strings into the buffer.
*
* The decoder converts TeletexString and BMPString to UTF8String, and
* ensures that the resulting string is zero-terminated. If the string
* does not fit in the provided buffer, then the copy is aborted and an
* error is reported.
*/
typedef struct {
/**
* \brief Element OID.
*
* For X.500 name elements (to be extracted from the subject DN),
* this is the encoded OID for the requested name element; the
* first byte shall contain the length of the DER-encoded OID
* value, followed by the OID value (for instance, OID 2.5.4.3,
* for id-at-commonName, will be `03 55 04 03`). This is
* equivalent to full DER encoding with the length but without
* the tag.
*
* For SAN name elements, the first byte (`oid[0]`) has value 0,
* followed by another byte that matches the expected GeneralName
* tag. Allowed second byte values are then:
*
* - 1: `rfc822Name`
*
* - 2: `dNSName`
*
* - 6: `uniformResourceIdentifier`
*
* - 0: `otherName`
*
* If first and second byte are 0, then this is a SAN element of
* type `otherName`; the `oid[]` array should then contain, right
* after the two bytes of value 0, an encoded OID (with the same
* conventions as for X.500 name elements). If a match is found
* for that OID, then the corresponding name element will be
* extracted, as long as it is a supported string type.
*/
const unsigned char *oid;
/**
* \brief Destination buffer.
*/
char *buf;
/**
* \brief Length (in bytes) of the destination buffer.
*
* The buffer MUST NOT be smaller than 1 byte.
*/
size_t len;
/**
* \brief Decoding status.
*
* Status is 0 if the name element was not found, 1 if it was
* found and decoded, or -1 on error. Error conditions include
* an unrecognised encoding, an invalid encoding, or a string
* too large for the destination buffer.
*/
int status;
} br_name_element;
/**
* \brief The "minimal" X.509 engine structure.
*
* The structure contents are opaque (they shall not be accessed directly),
* except for the first field (the vtable).
*
* The "minimal" engine performs a rudimentary but serviceable X.509 path
* validation.
*/
typedef struct {
const br_x509_class *vtable;
#ifndef BR_DOXYGEN_IGNORE
/* Structure for returning the EE public key. */
br_x509_pkey pkey;
/* CPU for the T0 virtual machine. */
struct {
uint32_t *dp;
uint32_t *rp;
const unsigned char *ip;
} cpu;
uint32_t dp_stack[32];
uint32_t rp_stack[32];
int err;
/* Server name to match with the SAN / CN of the EE certificate. */
const char *server_name;
/* Validated key usages. */
unsigned char key_usages;
/* Explicitly set date and time. */
uint32_t days, seconds;
/* Current certificate length (in bytes). Set to 0 when the
certificate has been fully processed. */
uint32_t cert_length;
/* Number of certificates processed so far in the current chain.
It is incremented at the end of the processing of a certificate,
so it is 0 for the EE. */
uint32_t num_certs;
/* Certificate data chunk. */
const unsigned char *hbuf;
size_t hlen;
/* The pad serves as destination for various operations. */
unsigned char pad[256];
/* Buffer for EE public key data. */
unsigned char ee_pkey_data[BR_X509_BUFSIZE_KEY];
/* Buffer for currently decoded public key. */
unsigned char pkey_data[BR_X509_BUFSIZE_KEY];
/* Signature type: signer key type, offset to the hash
function OID (in the T0 data block) and hash function
output length (TBS hash length). */
unsigned char cert_signer_key_type;
uint16_t cert_sig_hash_oid;
unsigned char cert_sig_hash_len;
/* Current/last certificate signature. */
unsigned char cert_sig[BR_X509_BUFSIZE_SIG];
uint16_t cert_sig_len;
/* Minimum RSA key length (difference in bytes from 128). */
int16_t min_rsa_size;
/* Configured trust anchors. */
const br_x509_trust_anchor *trust_anchors;
size_t trust_anchors_num;
/*
* Multi-hasher for the TBS.
*/
unsigned char do_mhash;
br_multihash_context mhash;
unsigned char tbs_hash[64];
/*
* Simple hasher for the subject/issuer DN.
*/
unsigned char do_dn_hash;
const br_hash_class *dn_hash_impl;
br_hash_compat_context dn_hash;
unsigned char current_dn_hash[64];
unsigned char next_dn_hash[64];
unsigned char saved_dn_hash[64];
/*
* Name elements to gather.
*/
br_name_element *name_elts;
size_t num_name_elts;
/*
* Public key cryptography implementations (signature verification).
*/
br_rsa_pkcs1_vrfy irsa;
br_ecdsa_vrfy iecdsa;
const br_ec_impl *iec;
#endif
} br_x509_minimal_context;
/**
* \brief Class instance for the "minimal" X.509 engine.
*/
extern const br_x509_class br_x509_minimal_vtable;
/**
* \brief Initialise a "minimal" X.509 engine.
*
* The `dn_hash_impl` parameter shall be a hash function internally used
* to match X.500 names (subject/issuer DN, and anchor names). Any standard
* hash function may be used, but a collision-resistant hash function is
* advised.
*
* After initialization, some implementations for signature verification
* (hash functions and signature algorithms) MUST be added.
*
* \param ctx context to initialise.
* \param dn_hash_impl hash function for DN comparisons.
* \param trust_anchors trust anchors.
* \param trust_anchors_num number of trust anchors.
*/
void br_x509_minimal_init(br_x509_minimal_context *ctx,
const br_hash_class *dn_hash_impl,
const br_x509_trust_anchor *trust_anchors, size_t trust_anchors_num);
/**
* \brief Set a supported hash function in an X.509 "minimal" engine.
*
* Hash functions are used with signature verification algorithms.
* Once initialised (with `br_x509_minimal_init()`), the context must
* be configured with the hash functions it shall support for that
* purpose. The hash function identifier MUST be one of the standard
* hash function identifiers (1 to 6, for MD5, SHA-1, SHA-224, SHA-256,
* SHA-384 and SHA-512).
*
* If `impl` is `NULL`, this _removes_ support for the designated
* hash function.
*
* \param ctx validation context.
* \param id hash function identifier (from 1 to 6).
* \param impl hash function implementation (or `NULL`).
*/
static inline void
br_x509_minimal_set_hash(br_x509_minimal_context *ctx,
int id, const br_hash_class *impl)
{
br_multihash_setimpl(&ctx->mhash, id, impl);
}
/**
* \brief Set a RSA signature verification implementation in the X.509
* "minimal" engine.
*
* Once initialised (with `br_x509_minimal_init()`), the context must
* be configured with the signature verification implementations that
* it is supposed to support. If `irsa` is `0`, then the RSA support
* is disabled.
*
* \param ctx validation context.
* \param irsa RSA signature verification implementation (or `0`).
*/
static inline void
br_x509_minimal_set_rsa(br_x509_minimal_context *ctx,
br_rsa_pkcs1_vrfy irsa)
{
ctx->irsa = irsa;
}
/**
* \brief Set a ECDSA signature verification implementation in the X.509
* "minimal" engine.
*
* Once initialised (with `br_x509_minimal_init()`), the context must
* be configured with the signature verification implementations that
* it is supposed to support.
*
* If `iecdsa` is `0`, then this call disables ECDSA support; in that
* case, `iec` may be `NULL`. Otherwise, `iecdsa` MUST point to a function
* that verifies ECDSA signatures with format "asn1", and it will use
* `iec` as underlying elliptic curve support.
*
* \param ctx validation context.
* \param iec elliptic curve implementation (or `NULL`).
* \param iecdsa ECDSA implementation (or `0`).
*/
static inline void
br_x509_minimal_set_ecdsa(br_x509_minimal_context *ctx,
const br_ec_impl *iec, br_ecdsa_vrfy iecdsa)
{
ctx->iecdsa = iecdsa;
ctx->iec = iec;
}
/**
* \brief Initialise a "minimal" X.509 engine with default algorithms.
*
* This function performs the same job as `br_x509_minimal_init()`, but
* also sets implementations for RSA, ECDSA, and the standard hash
* functions.
*
* \param ctx context to initialise.
* \param trust_anchors trust anchors.
* \param trust_anchors_num number of trust anchors.
*/
void br_x509_minimal_init_full(br_x509_minimal_context *ctx,
const br_x509_trust_anchor *trust_anchors, size_t trust_anchors_num);
/**
* \brief Set the validation time for the X.509 "minimal" engine.
*
* The validation time is set as two 32-bit integers, for days and
* seconds since a fixed epoch:
*
* - Days are counted in a proleptic Gregorian calendar since
* January 1st, 0 AD. Year "0 AD" is the one that preceded "1 AD";
* it is also traditionally known as "1 BC".
*
* - Seconds are counted since midnight, from 0 to 86400 (a count of
* 86400 is possible only if a leap second happened).
*
* The validation date and time is understood in the UTC time zone.
*
* If the validation date and time are not explicitly set, but BearSSL
* was compiled with support for the system clock on the underlying
* platform, then the current time will automatically be used. Otherwise,
* not setting the validation date and time implies a validation
* failure (except in case of direct trust of the EE key).
*
* \param ctx validation context.
* \param days days since January 1st, 0 AD (Gregorian calendar).
* \param seconds seconds since midnight (0 to 86400).
*/
static inline void
br_x509_minimal_set_time(br_x509_minimal_context *ctx,
uint32_t days, uint32_t seconds)
{
ctx->days = days;
ctx->seconds = seconds;
}
/**
* \brief Set the minimal acceptable length for RSA keys (X.509 "minimal"
* engine).
*
* The RSA key length is expressed in bytes. The default minimum key
* length is 128 bytes, corresponding to 1017 bits. RSA keys shorter
* than the configured length will be rejected, implying validation
* failure. This setting applies to keys extracted from certificates
* (both end-entity, and intermediate CA) but not to "CA" trust anchors.
*
* \param ctx validation context.
* \param byte_length minimum RSA key length, **in bytes** (not bits).
*/
static inline void
br_x509_minimal_set_minrsa(br_x509_minimal_context *ctx, int byte_length)
{
ctx->min_rsa_size = (int16_t)(byte_length - 128);
}
/**
* \brief Set the name elements to gather.
*
* The provided array is linked in the context. The elements are
* gathered from the EE certificate. If the same element type is
* requested several times, then the relevant structures will be filled
* in the order the matching values are encountered in the certificate.
*
* \param ctx validation context.
* \param elts array of name element structures to fill.
* \param num_elts number of name element structures to fill.
*/
static inline void
br_x509_minimal_set_name_elements(br_x509_minimal_context *ctx,
br_name_element *elts, size_t num_elts)
{
ctx->name_elts = elts;
ctx->num_name_elts = num_elts;
}
/**
* \brief X.509 decoder context.
*
* This structure is _not_ for X.509 validation, but for extracting
* names and public keys from encoded certificates. Intended usage is
* to use (self-signed) certificates as trust anchors.
*
* Contents are opaque and shall not be accessed directly.
*/
typedef struct {
#ifndef BR_DOXYGEN_IGNORE
/* Structure for returning the public key. */
br_x509_pkey pkey;
/* CPU for the T0 virtual machine. */
struct {
uint32_t *dp;
uint32_t *rp;
const unsigned char *ip;
} cpu;
uint32_t dp_stack[32];
uint32_t rp_stack[32];
int err;
/* The pad serves as destination for various operations. */
unsigned char pad[256];
/* Flag set when decoding succeeds. */
unsigned char decoded;
/* Validity dates. */
uint32_t notbefore_days, notbefore_seconds;
uint32_t notafter_days, notafter_seconds;
/* The "CA" flag. This is set to true if the certificate contains
a Basic Constraints extension that asserts CA status. */
unsigned char isCA;
/* DN processing: the subject DN is extracted and pushed to the
provided callback. */
unsigned char copy_dn;
void *append_dn_ctx;
void (*append_dn)(void *ctx, const void *buf, size_t len);
/* Certificate data chunk. */
const unsigned char *hbuf;
size_t hlen;
/* Buffer for decoded public key. */
unsigned char pkey_data[BR_X509_BUFSIZE_KEY];
/* Type of key and hash function used in the certificate signature. */
unsigned char signer_key_type;
unsigned char signer_hash_id;
#endif
} br_x509_decoder_context;
/**
* \brief Initialise an X.509 decoder context for processing a new
* certificate.
*
* The `append_dn()` callback (with opaque context `append_dn_ctx`)
* will be invoked to receive, chunk by chunk, the certificate's
* subject DN. If `append_dn` is `0` then the subject DN will be
* ignored.
*
* \param ctx X.509 decoder context to initialise.
* \param append_dn DN receiver callback (or `0`).
* \param append_dn_ctx context for the DN receiver callback.
*/
void br_x509_decoder_init(br_x509_decoder_context *ctx,
void (*append_dn)(void *ctx, const void *buf, size_t len),
void *append_dn_ctx);
/**
* \brief Push some certificate bytes into a decoder context.
*
* If `len` is non-zero, then that many bytes are pushed, from address
* `data`, into the provided decoder context.
*
* \param ctx X.509 decoder context.
* \param data certificate data chunk.
* \param len certificate data chunk length (in bytes).
*/
void br_x509_decoder_push(br_x509_decoder_context *ctx,
const void *data, size_t len);
/**
* \brief Obtain the decoded public key.
*
* Returned value is a pointer to a structure internal to the decoder
* context; releasing or reusing the decoder context invalidates that
* structure.
*
* If decoding was not finished, or failed, then `NULL` is returned.
*
* \param ctx X.509 decoder context.
* \return the public key, or `NULL` on unfinished/error.
*/
static inline br_x509_pkey *
br_x509_decoder_get_pkey(br_x509_decoder_context *ctx)
{
if (ctx->decoded && ctx->err == 0) {
return &ctx->pkey;
} else {
return NULL;
}
}
/**
* \brief Get decoder error status.
*
* If no error was reported yet but the certificate decoding is not
* finished, then the error code is `BR_ERR_X509_TRUNCATED`. If decoding
* was successful, then 0 is returned.
*
* \param ctx X.509 decoder context.
* \return 0 on successful decoding, or a non-zero error code.
*/
static inline int
br_x509_decoder_last_error(br_x509_decoder_context *ctx)
{
if (ctx->err != 0) {
return ctx->err;
}
if (!ctx->decoded) {
return BR_ERR_X509_TRUNCATED;
}
return 0;
}
/**
* \brief Get the "isCA" flag from an X.509 decoder context.
*
* This flag is set if the decoded certificate claims to be a CA through
* a Basic Constraints extension. This flag should not be read before
* decoding completed successfully.
*
* \param ctx X.509 decoder context.
* \return the "isCA" flag.
*/
static inline int
br_x509_decoder_isCA(br_x509_decoder_context *ctx)
{
return ctx->isCA;
}
/**
* \brief Get the issuing CA key type (type of algorithm used to sign the
* decoded certificate).
*
* This is `BR_KEYTYPE_RSA` or `BR_KEYTYPE_EC`. The value 0 is returned
* if the signature type was not recognised.
*
* \param ctx X.509 decoder context.
* \return the issuing CA key type.
*/
static inline int
br_x509_decoder_get_signer_key_type(br_x509_decoder_context *ctx)
{
return ctx->signer_key_type;
}
/**
* \brief Get the identifier for the hash function used to sign the decoded
* certificate.
*
* This is 0 if the hash function was not recognised.
*
* \param ctx X.509 decoder context.
* \return the signature hash function identifier.
*/
static inline int
br_x509_decoder_get_signer_hash_id(br_x509_decoder_context *ctx)
{
return ctx->signer_hash_id;
}
/**
* \brief Type for an X.509 certificate (DER-encoded).
*/
typedef struct {
/** \brief The DER-encoded certificate data. */
unsigned char *data;
/** \brief The DER-encoded certificate length (in bytes). */
size_t data_len;
} br_x509_certificate;
/**
* \brief Private key decoder context.
*
* The private key decoder recognises RSA and EC private keys, either in
* their raw, DER-encoded format, or wrapped in an unencrypted PKCS#8
* archive (again DER-encoded).
*
* Structure contents are opaque and shall not be accessed directly.
*/
typedef struct {
#ifndef BR_DOXYGEN_IGNORE
/* Structure for returning the private key. */
union {
br_rsa_private_key rsa;
br_ec_private_key ec;
} key;
/* CPU for the T0 virtual machine. */
struct {
uint32_t *dp;
uint32_t *rp;
const unsigned char *ip;
} cpu;
uint32_t dp_stack[32];
uint32_t rp_stack[32];
int err;
/* Private key data chunk. */
const unsigned char *hbuf;
size_t hlen;
/* The pad serves as destination for various operations. */
unsigned char pad[256];
/* Decoded key type; 0 until decoding is complete. */
unsigned char key_type;
/* Buffer for the private key elements. It shall be large enough
to accommodate all elements for a RSA-4096 private key (roughly
five 2048-bit integers, possibly a bit more). */
unsigned char key_data[3 * BR_X509_BUFSIZE_SIG];
#endif
} br_skey_decoder_context;
/**
* \brief Initialise a private key decoder context.
*
* \param ctx key decoder context to initialise.
*/
void br_skey_decoder_init(br_skey_decoder_context *ctx);
/**
* \brief Push some data bytes into a private key decoder context.
*
* If `len` is non-zero, then that many data bytes, starting at address
* `data`, are pushed into the decoder.
*
* \param ctx key decoder context.
* \param data private key data chunk.
* \param len private key data chunk length (in bytes).
*/
void br_skey_decoder_push(br_skey_decoder_context *ctx,
const void *data, size_t len);
/**
* \brief Get the decoding status for a private key.
*
* Decoding status is 0 on success, or a non-zero error code. If the
* decoding is unfinished when this function is called, then the
* status code `BR_ERR_X509_TRUNCATED` is returned.
*
* \param ctx key decoder context.
* \return 0 on successful decoding, or a non-zero error code.
*/
static inline int
br_skey_decoder_last_error(const br_skey_decoder_context *ctx)
{
if (ctx->err != 0) {
return ctx->err;
}
if (ctx->key_type == 0) {
return BR_ERR_X509_TRUNCATED;
}
return 0;
}
/**
* \brief Get the decoded private key type.
*
* Private key type is `BR_KEYTYPE_RSA` or `BR_KEYTYPE_EC`. If decoding is
* not finished or failed, then 0 is returned.
*
* \param ctx key decoder context.
* \return decoded private key type, or 0.
*/
static inline int
br_skey_decoder_key_type(const br_skey_decoder_context *ctx)
{
if (ctx->err == 0) {
return ctx->key_type;
} else {
return 0;
}
}
/**
* \brief Get the decoded RSA private key.
*
* This function returns `NULL` if the decoding failed, or is not
* finished, or the key is not RSA. The returned pointer references
* structures within the context that can become invalid if the context
* is reused or released.
*
* \param ctx key decoder context.
* \return decoded RSA private key, or `NULL`.
*/
static inline const br_rsa_private_key *
br_skey_decoder_get_rsa(const br_skey_decoder_context *ctx)
{
if (ctx->err == 0 && ctx->key_type == BR_KEYTYPE_RSA) {
return &ctx->key.rsa;
} else {
return NULL;
}
}
/**
* \brief Get the decoded EC private key.
*
* This function returns `NULL` if the decoding failed, or is not
* finished, or the key is not EC. The returned pointer references
* structures within the context that can become invalid if the context
* is reused or released.
*
* \param ctx key decoder context.
* \return decoded EC private key, or `NULL`.
*/
static inline const br_ec_private_key *
br_skey_decoder_get_ec(const br_skey_decoder_context *ctx)
{
if (ctx->err == 0 && ctx->key_type == BR_KEYTYPE_EC) {
return &ctx->key.ec;
} else {
return NULL;
}
}
/**
* \brief Encode an RSA private key (raw DER format).
*
* This function encodes the provided key into the "raw" format specified
* in PKCS#1 (RFC 8017, Appendix C, type `RSAPrivateKey`), with DER
* encoding rules.
*
* The key elements are:
*
* - `sk`: the private key (`p`, `q`, `dp`, `dq` and `iq`)
*
* - `pk`: the public key (`n` and `e`)
*
* - `d` (size: `dlen` bytes): the private exponent
*
* The public key elements, and the private exponent `d`, can be
* recomputed from the private key (see `br_rsa_compute_modulus()`,
* `br_rsa_compute_pubexp()` and `br_rsa_compute_privexp()`).
*
* If `dest` is not `NULL`, then the encoded key is written at that
* address, and the encoded length (in bytes) is returned. If `dest` is
* `NULL`, then nothing is written, but the encoded length is still
* computed and returned.
*
* \param dest the destination buffer (or `NULL`).
* \param sk the RSA private key.
* \param pk the RSA public key.
* \param d the RSA private exponent.
* \param dlen the RSA private exponent length (in bytes).
* \return the encoded key length (in bytes).
*/
size_t br_encode_rsa_raw_der(void *dest, const br_rsa_private_key *sk,
const br_rsa_public_key *pk, const void *d, size_t dlen);
/**
* \brief Encode an RSA private key (PKCS#8 DER format).
*
* This function encodes the provided key into the PKCS#8 format
* (RFC 5958, type `OneAsymmetricKey`). It wraps around the "raw DER"
* format for the RSA key, as implemented by `br_encode_rsa_raw_der()`.
*
* The key elements are:
*
* - `sk`: the private key (`p`, `q`, `dp`, `dq` and `iq`)
*
* - `pk`: the public key (`n` and `e`)
*
* - `d` (size: `dlen` bytes): the private exponent
*
* The public key elements, and the private exponent `d`, can be
* recomputed from the private key (see `br_rsa_compute_modulus()`,
* `br_rsa_compute_pubexp()` and `br_rsa_compute_privexp()`).
*
* If `dest` is not `NULL`, then the encoded key is written at that
* address, and the encoded length (in bytes) is returned. If `dest` is
* `NULL`, then nothing is written, but the encoded length is still
* computed and returned.
*
* \param dest the destination buffer (or `NULL`).
* \param sk the RSA private key.
* \param pk the RSA public key.
* \param d the RSA private exponent.
* \param dlen the RSA private exponent length (in bytes).
* \return the encoded key length (in bytes).
*/
size_t br_encode_rsa_pkcs8_der(void *dest, const br_rsa_private_key *sk,
const br_rsa_public_key *pk, const void *d, size_t dlen);
/**
* \brief Encode an EC private key (raw DER format).
*
* This function encodes the provided key into the "raw" format specified
* in RFC 5915 (type `ECPrivateKey`), with DER encoding rules.
*
* The private key is provided in `sk`, the public key being `pk`. If
* `pk` is `NULL`, then the encoded key will not include the public key
* in its `publicKey` field (which is nominally optional).
*
* If `dest` is not `NULL`, then the encoded key is written at that
* address, and the encoded length (in bytes) is returned. If `dest` is
* `NULL`, then nothing is written, but the encoded length is still
* computed and returned.
*
* If the key cannot be encoded (e.g. because there is no known OBJECT
* IDENTIFIER for the used curve), then 0 is returned.
*
* \param dest the destination buffer (or `NULL`).
* \param sk the EC private key.
* \param pk the EC public key (or `NULL`).
* \return the encoded key length (in bytes), or 0.
*/
size_t br_encode_ec_raw_der(void *dest,
const br_ec_private_key *sk, const br_ec_public_key *pk);
/**
* \brief Encode an EC private key (PKCS#8 DER format).
*
* This function encodes the provided key into the PKCS#8 format
* (RFC 5958, type `OneAsymmetricKey`). The curve is identified
* by an OID provided as parameters to the `privateKeyAlgorithm`
* field. The private key value (contents of the `privateKey` field)
* contains the DER encoding of the `ECPrivateKey` type defined in
* RFC 5915, without the `parameters` field (since they would be
* redundant with the information in `privateKeyAlgorithm`).
*
* The private key is provided in `sk`, the public key being `pk`. If
* `pk` is not `NULL`, then the encoded public key is included in the
* `publicKey` field of the private key value (but not in the `publicKey`
* field of the PKCS#8 `OneAsymmetricKey` wrapper).
*
* If `dest` is not `NULL`, then the encoded key is written at that
* address, and the encoded length (in bytes) is returned. If `dest` is
* `NULL`, then nothing is written, but the encoded length is still
* computed and returned.
*
* If the key cannot be encoded (e.g. because there is no known OBJECT
* IDENTIFIER for the used curve), then 0 is returned.
*
* \param dest the destination buffer (or `NULL`).
* \param sk the EC private key.
* \param pk the EC public key (or `NULL`).
* \return the encoded key length (in bytes), or 0.
*/
size_t br_encode_ec_pkcs8_der(void *dest,
const br_ec_private_key *sk, const br_ec_public_key *pk);
/**
* \brief PEM banner for RSA private key (raw).
*/
#define BR_ENCODE_PEM_RSA_RAW "RSA PRIVATE KEY"
/**
* \brief PEM banner for EC private key (raw).
*/
#define BR_ENCODE_PEM_EC_RAW "EC PRIVATE KEY"
/**
* \brief PEM banner for an RSA or EC private key in PKCS#8 format.
*/
#define BR_ENCODE_PEM_PKCS8 "PRIVATE KEY"
#ifdef __cplusplus
}
#endif
#endif