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The function X509_verify_cert checks the value of |ctx->chain| at the beginning, and if it is NULL then it initialises it, along with the value of ctx->untrusted. The normal way to use X509_verify_cert() is to first call X509_STORE_CTX_init(); then set up various parameters etc; then call X509_verify_cert(); then check the results; and finally call X509_STORE_CTX_cleanup(). The initial call to X509_STORE_CTX_init() sets |ctx->chain| to NULL. The only place in the OpenSSL codebase where |ctx->chain| is set to anything other than a non NULL value is in X509_verify_cert itself. Therefore the only ways that |ctx->chain| could be non NULL on entry to X509_verify_cert is if one of the following occurs: 1) An application calls X509_verify_cert() twice without re-initialising in between. 2) An application reaches inside the X509_STORE_CTX structure and changes the value of |ctx->chain| directly. With regards to the second of these, we should discount this - it should not be supported to allow this. With regards to the first of these, the documentation is not exactly crystal clear, but the implication is that you must call X509_STORE_CTX_init() before each call to X509_verify_cert(). If you fail to do this then, at best, the results would be undefined. Calling X509_verify_cert() with |ctx->chain| set to a non NULL value is likely to have unexpected results, and could be dangerous. This commit changes the behaviour of X509_verify_cert() so that it causes an error if |ctx->chain| is anything other than NULL (because this indicates that we have not been initialised properly). It also clarifies the associated documentation. This is a follow up commit to CVE-2015-1793. Reviewed-by: Stephen Henson <steve@openssl.org>
129 lines
4.9 KiB
Plaintext
129 lines
4.9 KiB
Plaintext
=pod
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=head1 NAME
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X509_STORE_CTX_new, X509_STORE_CTX_cleanup, X509_STORE_CTX_free, X509_STORE_CTX_init, X509_STORE_CTX_trusted_stack, X509_STORE_CTX_set_cert, X509_STORE_CTX_set_chain, X509_STORE_CTX_set0_crls, X509_STORE_CTX_get0_param, X509_STORE_CTX_set0_param, X509_STORE_CTX_set_default - X509_STORE_CTX initialisation
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=head1 SYNOPSIS
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#include <openssl/x509_vfy.h>
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X509_STORE_CTX *X509_STORE_CTX_new(void);
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void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx);
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void X509_STORE_CTX_free(X509_STORE_CTX *ctx);
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int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *store,
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X509 *x509, STACK_OF(X509) *chain);
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void X509_STORE_CTX_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);
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void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx,X509 *x);
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void X509_STORE_CTX_set_chain(X509_STORE_CTX *ctx,STACK_OF(X509) *sk);
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void X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk);
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X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(X509_STORE_CTX *ctx);
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void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param);
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int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name);
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=head1 DESCRIPTION
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These functions initialise an B<X509_STORE_CTX> structure for subsequent use
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by X509_verify_cert().
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X509_STORE_CTX_new() returns a newly initialised B<X509_STORE_CTX> structure.
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X509_STORE_CTX_cleanup() internally cleans up an B<X509_STORE_CTX> structure.
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The context can then be reused with an new call to X509_STORE_CTX_init().
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X509_STORE_CTX_free() completely frees up B<ctx>. After this call B<ctx>
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is no longer valid.
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If B<ctx> is NULL nothing is done.
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X509_STORE_CTX_init() sets up B<ctx> for a subsequent verification operation.
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It must be called before each call to X509_verify_cert(), i.e. a B<ctx> is only
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good for one call to X509_verify_cert(); if you want to verify a second
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certificate with the same B<ctx> then you must call X509_XTORE_CTX_cleanup()
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and then X509_STORE_CTX_init() again before the second call to
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X509_verify_cert(). The trusted certificate store is set to B<store>, the end
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entity certificate to be verified is set to B<x509> and a set of additional
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certificates (which will be untrusted but may be used to build the chain) in
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B<chain>. Any or all of the B<store>, B<x509> and B<chain> parameters can be
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B<NULL>.
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X509_STORE_CTX_trusted_stack() sets the set of trusted certificates of B<ctx>
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to B<sk>. This is an alternative way of specifying trusted certificates
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instead of using an B<X509_STORE>.
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X509_STORE_CTX_set_cert() sets the certificate to be verified in B<ctx> to
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B<x>.
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X509_STORE_CTX_set_chain() sets the additional certificate chain used by B<ctx>
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to B<sk>.
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X509_STORE_CTX_set0_crls() sets a set of CRLs to use to aid certificate
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verification to B<sk>. These CRLs will only be used if CRL verification is
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enabled in the associated B<X509_VERIFY_PARAM> structure. This might be
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used where additional "useful" CRLs are supplied as part of a protocol,
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for example in a PKCS#7 structure.
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X509_VERIFY_PARAM *X509_STORE_CTX_get0_param() retrieves an internal pointer
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to the verification parameters associated with B<ctx>.
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X509_STORE_CTX_set0_param() sets the internal verification parameter pointer
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to B<param>. After this call B<param> should not be used.
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X509_STORE_CTX_set_default() looks up and sets the default verification
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method to B<name>. This uses the function X509_VERIFY_PARAM_lookup() to
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find an appropriate set of parameters from B<name>.
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=head1 NOTES
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The certificates and CRLs in a store are used internally and should B<not>
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be freed up until after the associated B<X509_STORE_CTX> is freed. Legacy
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applications might implicitly use an B<X509_STORE_CTX> like this:
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X509_STORE_CTX ctx;
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X509_STORE_CTX_init(&ctx, store, cert, chain);
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this is B<not> recommended in new applications they should instead do:
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X509_STORE_CTX *ctx;
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ctx = X509_STORE_CTX_new();
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if (ctx == NULL)
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/* Bad error */
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X509_STORE_CTX_init(ctx, store, cert, chain);
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=head1 BUGS
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The certificates and CRLs in a context are used internally and should B<not>
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be freed up until after the associated B<X509_STORE_CTX> is freed. Copies
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should be made or reference counts increased instead.
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=head1 RETURN VALUES
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X509_STORE_CTX_new() returns an newly allocates context or B<NULL> is an
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error occurred.
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X509_STORE_CTX_init() returns 1 for success or 0 if an error occurred.
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X509_STORE_CTX_get0_param() returns a pointer to an B<X509_VERIFY_PARAM>
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structure or B<NULL> if an error occurred.
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X509_STORE_CTX_cleanup(), X509_STORE_CTX_free(), X509_STORE_CTX_trusted_stack(),
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X509_STORE_CTX_set_cert(), X509_STORE_CTX_set_chain(),
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X509_STORE_CTX_set0_crls() and X509_STORE_CTX_set0_param() do not return
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values.
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X509_STORE_CTX_set_default() returns 1 for success or 0 if an error occurred.
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=head1 SEE ALSO
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L<X509_verify_cert(3)|X509_verify_cert(3)>
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L<X509_VERIFY_PARAM_set_flags(3)|X509_VERIFY_PARAM_set_flags(3)>
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=head1 HISTORY
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X509_STORE_CTX_set0_crls() was first added to OpenSSL 1.0.0
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=cut
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