source: libabac/abac_graph.c @ ebe824c

#include <assert.h>
#include <stdlib.h>

#include "abac_graph.h"

#include "abac_set.h"
#include "abac_util.h"

#include "uthash.h"

// vertex
struct _abac_vertex_t {
    abac_role_t *role;
    char *name;

    abac_list_t *edges;

    // only relevant to intersection edges
    abac_list_t *prereqs;

    UT_hash_handle hh;
};

// edge
typedef struct _abac_edge_t {
    abac_vertex_t *vertex;
    abac_credential_t *credential;
} abac_edge_t;

// derived edge
typedef struct _abac_derived_key_t {
    abac_vertex_t *head;
    abac_edge_t *tail;
} abac_derived_key_t;

typedef struct _abac_derived_t {
    abac_derived_key_t key;
    UT_hash_handle hh;
} abac_derived_t;

// graph
struct _abac_graph_t {
    abac_vertex_t *vertices;
    abac_derived_t *derived;
    int dirty;
};

// ugghhhghhhghh need this for intersections
abac_list_t *abac_credential_prereqs(abac_credential_t *);

/**
 * True iff a vertex is linking.
 */
static inline int _vertex_is_intersection(abac_vertex_t *vertex) {
    return vertex->role == NULL;
}

/**
 * Create a new graph.
 */
abac_graph_t *abac_graph_new(void) {
    abac_graph_t *graph = abac_xmalloc(sizeof(abac_graph_t));

    graph->vertices = NULL;
    graph->derived = NULL;
    graph->dirty = 0;

    return graph;
}

/**
 * Deep copy a graph.
 */
abac_graph_t *abac_graph_dup(abac_graph_t *graph) {
    abac_vertex_t *vertex;
    abac_edge_t *edge;

    abac_graph_t *clone = abac_graph_new();

    // copy the vertices edge by edge
    for (vertex = graph->vertices; vertex != NULL; vertex = vertex->hh.next)
        abac_list_foreach(vertex->edges, edge,
            // only copy non-derived edges
            if (edge->credential != NULL)
                abac_graph_add_credential(clone, edge->credential);
        );

    return clone;
}

/**
 * Add a vertex to the graph. Should only be called by abac_graph_add_credential.
 */
static abac_vertex_t *_get_vertex(abac_graph_t *graph, abac_role_t *role) {
    abac_vertex_t *vertex;
    char *string;
    
    string = abac_role_string(role);
    HASH_FIND_STR(graph->vertices, string, vertex);

    // add the vertex if it doesn't exist
    if (vertex == NULL) {
        vertex = abac_xmalloc(sizeof(abac_vertex_t));
        vertex->role = abac_role_dup(role);
        vertex->name = abac_role_string(vertex->role);

        // create the list of edges
        vertex->edges = abac_list_new();

        // for intersections, always NULL on normal vertices
        vertex->prereqs = NULL;

        // add it to the vertices
        HASH_ADD_KEYPTR(hh, graph->vertices, vertex->name, strlen(vertex->name), vertex);
    }

    return vertex;
}

/**
 * convert a list of prereqs to a string suitable for use as a hash key
 * format: role & role & ... & role
 */
static char *_prereq_key(abac_list_t *prereqs) {
    abac_role_t *role;
    char *string;
    int i = 0, size;
    size_t len = 0;

    // find the required size
    abac_list_foreach(prereqs, role,
        len += strlen(abac_role_string(role)) + 3;
    );

    string = abac_xmalloc(len);
    string[0] = '\0';

    size = abac_list_size(prereqs);

    // concat the names
    abac_list_foreach(prereqs, role,
        strcat(string, abac_role_string(role));
        if (i++ < size - 1)
            strcat(string, " & ");
    );

    return string;
}

/**
 * Find/create intersection vertex. Only called by abac_graph_add_credential.
 */
static abac_vertex_t *_get_intersection_vertex(abac_graph_t *graph, abac_credential_t *cred) {
    abac_role_t *role, *tail_role;
    abac_vertex_t *vertex;

    abac_list_t *prereqs = abac_credential_prereqs(cred);
    char *string = _prereq_key(prereqs);
    HASH_FIND_STR(graph->vertices, string, vertex);

    // add the vertex if it doesn't exist
    if (vertex == NULL) {
        vertex = abac_xmalloc(sizeof(abac_vertex_t));
        vertex->role = NULL;
        vertex->name = string;

        // create the list of edges
        vertex->edges = abac_list_new();

        // for intersections, will be populated first time it's created
        vertex->prereqs = abac_list_new();

        // add each prereq to the vertex
        abac_list_foreach(prereqs, tail_role,
            abac_vertex_t *tail_vertex = _get_vertex(graph, tail_role);
            abac_list_add(vertex->prereqs, tail_vertex);
        );

        // add it to the vertices
        HASH_ADD_KEYPTR(hh, graph->vertices, vertex->name, strlen(vertex->name), vertex);
    }
    else
        free(string); // already exists, get rid of useless memory

    return vertex;

}

/**
 * Add a credential to the credential graph.
 */
int abac_graph_add_credential(abac_graph_t *graph, abac_credential_t *cred) {
    abac_vertex_t *head_vertex, *tail_vertex;
    abac_edge_t *edge;

    assert(cred != NULL);

    abac_role_t *head = abac_credential_head(cred);
    abac_role_t *tail = abac_credential_tail(cred);

    // a valid credential must have a role for the head
    if (!abac_role_is_role(head)) return 0;

    head_vertex = _get_vertex(graph, head);

    // tail is a normal role
    if (tail != NULL)
        tail_vertex = _get_vertex(graph, tail);

    // intersection
    else
        tail_vertex = _get_intersection_vertex(graph, cred);

    // make sure we don't insert the same edge twice (ugh)
    abac_list_foreach(head_vertex->edges, edge,
        if (edge->vertex == tail_vertex)
            return 0;
    );

    // create the edge and add it
    edge = abac_xmalloc(sizeof(abac_edge_t));
    edge->vertex = tail_vertex;
    edge->credential = abac_credential_dup(cred);

    abac_list_add(head_vertex->edges, edge);

    // must re-derive edges
    graph->dirty = 1;

    return 1;
}

// find the principals that have a role
static abac_set_t *_find_principals(abac_graph_t *graph, abac_vertex_t *start_vertex) {
    abac_set_t *principals = abac_set_new();

    abac_list_t *traversal = abac_graph_postorder(graph, start_vertex->role);
    abac_vertex_t *vertex;

    abac_list_foreach(traversal, vertex,
        if (vertex->role != NULL && abac_role_is_principal(vertex->role))
            abac_set_add(principals, vertex->name);
    );

    abac_list_free(traversal);
    return principals;
}

// remove any derived edges from the graph
void _clear_derived(abac_graph_t *graph) {
    abac_derived_t *current;

    while (graph->derived) {
        current = graph->derived;

        HASH_DEL(graph->derived, current);

        abac_vertex_t *head = current->key.head;
        abac_edge_t *tail = current->key.tail;
        assert(tail->credential == NULL);

        // this can fail, but we assume the data structures are consistent
        abac_list_remove(head->edges, tail);

        free(current);
        free(tail);
    }
}

// add a derived edge
static void _derived_edge(abac_graph_t *graph, abac_vertex_t *head, abac_vertex_t *tail) {
    abac_edge_t *edge = abac_xmalloc(sizeof(abac_edge_t));
    edge->vertex = tail;
    edge->credential = NULL;
    abac_list_add(head->edges, edge);

    // add to list of derived edges
    abac_derived_t *derived = abac_xmalloc(sizeof(abac_derived_t));
    derived->key.head = head;
    derived->key.tail = edge;
    HASH_ADD(hh, graph->derived, key, sizeof(abac_derived_key_t), derived);
}

// find a vertex by name
abac_vertex_t *_find_vertex(abac_graph_t *graph, char *name) {
    abac_vertex_t *ret = NULL;
    HASH_FIND_STR(graph->vertices, name, ret);
    return ret;
}

void abac_graph_derive_links(abac_graph_t *graph) {
    abac_vertex_t *vertex;

    if (!graph->dirty)
        return;

    for (vertex = graph->vertices; vertex != NULL; vertex = vertex->hh.next) {
        // intersection
        if (_vertex_is_intersection(vertex)) {
            // for each prereq edge:
            //     find principals that have the edge
            // find intersection of all sets
            // for each principal B in intersection:
            //     add link

            char *name;
            abac_vertex_t *prereq;
            abac_set_t *principals = NULL;

            abac_list_foreach(vertex->prereqs, prereq,
                abac_set_t *cur = _find_principals(graph, prereq);

                if (principals == NULL)
                    principals = cur;
                else {
                    abac_set_intersect(principals, cur);
                    abac_set_free(cur);
                }

                if (abac_set_size(principals) == 0)
                    goto isect_done;
            );

            abac_list_t *prin_names = abac_set_elements(principals);
            abac_list_foreach(prin_names, name,
                abac_vertex_t *principal = _find_vertex(graph, name);
                _derived_edge(graph, vertex, principal);

                printf("adding edge from %s to %s\n", principal->name, vertex->name);
            );

            abac_list_free(prin_names);
isect_done:
            abac_set_free(principals);
        }

        // linking role
        else if (abac_role_is_linking(vertex->role)) {
            // linking roles take the form A.r1.r2
            char *A_r1 = abac_role_linked_role(vertex->role);
            char *r2 = abac_role_role_name(vertex->role);

            // find the linked role in the graph
            abac_vertex_t *A_r1_vertex;
            HASH_FIND_STR(graph->vertices, A_r1, A_r1_vertex);
            if (A_r1_vertex == NULL)
                continue;

            // find the principals that have A.r1
            abac_set_t *principals = _find_principals(graph, A_r1_vertex);
            char *B;

            abac_list_t *elts = abac_set_elements(principals);

            // and add a link for each B.r2 to A.r1.r2
            abac_list_foreach(elts, B,
                int B_len = strlen(B);
                int r2_len = strlen(r2);

                // create the string B.r2, thx C
                char *B_r2 = malloc(B_len + r2_len + 2);
                memcpy(B_r2, B, B_len);
                B_r2[B_len] = '.';
                memcpy(B_r2 + B_len + 1, r2, r2_len);
                B_r2[B_len + r2_len + 1] = 0;

                // add an edge if the principal's granted it to someone
                abac_vertex_t *B_r2_vertex = _find_vertex(graph, B_r2);
                if (B_r2_vertex) {
                    debug_printf("adding edge from %s to %s\n", B_r2, abac_role_string(vertex->role));
                    _derived_edge(graph, vertex, B_r2_vertex);
                }

#ifdef DEBUG
                debug_printf("    incoming edges for %s\n", abac_role_string(vertex->role));
                abac_edge_t *cur;
                abac_list_foreach(vertex->edges, cur,
                    debug_printf("        %s (%s)\n", abac_role_string(cur->vertex->role), cur->vertex->name);
                );
#endif

                free(B_r2);
            );

            abac_list_free(elts);
            abac_set_free(principals);
        }
    }

    graph->dirty = 0;
}

static void _order_recurse(abac_vertex_t *vertex, abac_set_t *seen, int preorder, abac_list_t *stack) {
    abac_edge_t *incoming;

    // don't revisit nodes
    if (!abac_set_add(seen, vertex->name))
        return;

    if (preorder)
        abac_list_add(stack, vertex);

    // recurse along the incoming vertices
    abac_list_foreach(vertex->edges, incoming,
        _order_recurse(incoming->vertex, seen, preorder, stack);
    );

    if (!preorder)
        abac_list_add(stack, vertex);
}

static abac_list_t *_order(abac_graph_t *graph, abac_role_t *start, int preorder) {
    debug_printf("%sorder at %s\n", preorder ? "pre" : "post", abac_role_string(start));

    abac_vertex_t *start_vertex = _get_vertex(graph, start);
    abac_set_t *seen = abac_set_new();

    // create the return list
    abac_list_t *stack = abac_list_new();

    _order_recurse(start_vertex, seen, preorder, stack);

    abac_set_free(seen);

    return stack;
}

abac_list_t *abac_graph_postorder(abac_graph_t *graph, abac_role_t *start) {
    return _order(graph, start, 0);
}

/**
 * Postorder traverse the graph and return all the credentials within.
 */
abac_list_t *abac_graph_postorder_credentials(abac_graph_t *graph, char *start) {
    abac_vertex_t *vertex;
    abac_edge_t *incoming;

    // get the postorder of vertices
    abac_role_t *role = abac_role_from_string(start);
    abac_list_t *order = abac_graph_postorder(graph, role);

    // go through the list and dup all the credentials
    abac_list_t *credentials = abac_list_new();
    abac_list_foreach(order, vertex,
        abac_list_foreach(vertex->edges, incoming,
            if (incoming->credential != NULL)
                abac_list_add(credentials, abac_credential_dup(incoming->credential));
        );
    );

    abac_role_free(role);
    abac_list_free(order);

    return credentials;
}

static void _query(abac_graph_t *graph, char *role_name, char *principal, abac_graph_t *return_graph) {
    abac_vertex_t *vertex;
    abac_edge_t *incoming;

    abac_role_t *role = abac_role_from_string(role_name);
    abac_role_t *prin_role = abac_role_from_string(principal);

    // give up on bogus roles
    if (role == NULL || prin_role == NULL) {
        free(role);
        free(prin_role);
        return;
    }

    abac_set_t *on_path = abac_set_new();
    abac_set_add(on_path, abac_role_string(prin_role));

    abac_list_t *traversal = abac_graph_postorder(graph, role);
    abac_list_foreach(traversal, vertex,
        abac_role_t *role = vertex->role;
        char *vertex_name = vertex->name;

        abac_list_foreach(vertex->edges, incoming,
            abac_role_t *incoming_role = incoming->vertex->role;
            char *incoming_name = incoming->vertex->name;

            if (!abac_set_contains(on_path, incoming_name))
                continue;

            abac_set_add(on_path, vertex_name);

            // get implying edges for intersection vertices
            if (_vertex_is_intersection(vertex)) {
                abac_vertex_t *prereq;
                abac_list_foreach(vertex->prereqs, prereq,
                    _query(graph, prereq->name, principal, return_graph);
                );
            }

            // recursively find linked roles
            else if (abac_role_is_linking(role)) {
                char *linked_role = abac_role_linked_role(role);
                char *principal = abac_role_principal(incoming_role);

                _query(graph, linked_role, principal, return_graph);
            }

            // add non-derived edges to the proof graph
            else
                abac_graph_add_credential(return_graph, incoming->credential);
        );
    );

    abac_list_free(traversal);
    abac_set_free(on_path);
    abac_role_free(role);
    abac_role_free(prin_role);
}

abac_graph_t *abac_graph_query(abac_graph_t *graph, char *role, char *principal) {
    abac_graph_derive_links(graph);

    abac_graph_t *return_graph = abac_graph_new();
    _query(graph, role, principal, return_graph);
    abac_graph_derive_links(return_graph);
    return return_graph;
}

/**
 * Get all the credentials (attribute/issuer cert pairs) from the graph.
 */
abac_list_t *abac_graph_credentials(abac_graph_t *graph) {
    abac_list_t *credentials = abac_list_new();

    abac_vertex_t *vertex;

    for (vertex = graph->vertices; vertex != NULL; vertex = vertex->hh.next) {
        abac_edge_t *edge;
        abac_list_foreach(vertex->edges, edge,
            if (edge->credential != NULL)
                abac_list_add(credentials, abac_credential_dup(edge->credential));
        );
    }

    return credentials;
}

void abac_graph_free(abac_graph_t *graph) {
    abac_vertex_t *vertex;
    abac_edge_t *edge;

    // kill derived edges
    _clear_derived(graph);

    // delete vertices
    while ((vertex = graph->vertices) != NULL) {
        HASH_DEL(graph->vertices, vertex);

        abac_role_free(vertex->role);

        abac_list_foreach(vertex->edges, edge,
            if (edge->credential != NULL)
                abac_credential_free(edge->credential);
            free(edge);
        );
        abac_list_free(vertex->edges);
        free(vertex);
    }

    free(graph);
}

abac_role_t *abac_vertex_role(abac_vertex_t *vertex) {
    return vertex->role;
}